Analysis of Structural Dynamic Data from Skylab August 1976 Volume I - Technical Discussion 6

E NASA CONTRA CTOR 8' ... " 2 REPORT E

h N h N I CIL U

ANALYSIS OF STRUCTURAL DYNAMICDATA FROM SKYLAB Volume I - TechnicalDiscussion

F"' - f" ~ATIONALAERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. c. . AUGUST 1976 " TECHNIC14L REPOF ~~ 1. REPORT NO. 2; GOVERNMENTACCESSION NO. NASA CR-2727 ~" ~ ~ -I== A TITLEAN0 SUBTITLE 5. REPORTDATE Analysis of Structural Dynamic Data from Skylab August 1976 Volume I - Technical Discussion 6. PERFORMINGORGANIZATION CODE ' .M-i76 7. AUTHOR(S) 8. PERFORMING ORGANIZATION REP0R.r U Leonard Demchak and Harry Harcrow ~ . ~~ 9. PERFORMINGORGANIZATION NAME AND ADDRESS ,O. WORK UNIT, NO. Martin Marietta Corporation P. 0. Box 179 I 1. 'CONTRACT OR GRANT NO. NAS8-31224 Denver,Colorado 80201 13. TYPE OF REPORT & PERIODCOVEREL .....=.- _~____ ~- ~~ 12. SPONSORINGAGENCY NAME AND ADDRESS Contractor Report Final National Aeronautics and Space Administration Washington, D.C. 20546 1.1. SPONSORINGAGENCY CODE

______"" .. ~ 15. SUPPLEMENTARYNOTES

I _.-.-- 1.~- 16. ABSTRACT

This report presents the resultsof a study to analyze data and document dynamic program highlights of the Skylab Program. Included are structural model sources, illustration of the analytical models, utilization of models and the resultant derived data, data supplied to organization and subsequent utilization, and specifications of model cycles.

This analysis is published in two volumes:

Volume I - TechnicalDiscussion - NASA CR-2727 Volume a -- Skyla$ Analyticaland Test Modal Data - NASA CR-2728

- ~~ . ~ ~~ 17. KEY WORDS 18. DISTRIBUTIONSTATEMENT

STAR Category 15

." - "= ~~~~ ~ ~-. ". ~~ ~ ~~~ 19. SECURITYCLASSIF. rmpcrt) 20. SECURITYCLASSIF. (of this psgq 21. NO. OFPAGES 22. PRICE Unclassified Unclassified 220 $7.25 - - .- - . . For sale by the National Technical Information Service, Springfield,.Virginia 22161

iii

CONTENTS

Introduction ...... X 1. Structural ModelDeployment ...... 1- 1 1.1 SkylabVibration Analysis Chronology ...... 1- 2 1.2Evolution of Structural Models ...... 1- 8 1.3 Conclusion ...... 1- 22 2 . SkylabAnalytical Methodologies ...... 2- 1 2.1Skylab Modal Characteristics ...... 2- 1 2.2Skylab Docking Response ...... 2- 2 2.3 Model Correlationto Vibration Testing ...... 2-6

3 . OrbitalCluster Interior Acoustics ...... 3- 1

3.1 AcousticAcceptance Criteria ...... 3- 1 3.2 Definition of Environment ...... 3- 2 3.3 Flight Measurement Results ...... 3- 3 3.4 AcousticEnvironment Mapping ...... 3- 5 3.5 Skylab Crew MissionAcoustic Evaluation ...... 3- 6 3.6 ArticulationIndex (AI)Analyses ...... 3- 11 3.7 Flight Anomalies ...... 3- 12 3.8 Conclusions ...... 3- 12 3.9 Recommendations ...... 3- 13

4 . General Test Program ...... 4- 1

4.1Vibro-Acoustic Test Overview ...... 4- 1 4.2Phase IIA PayloadAssembly Launch ConfigurationTests ...... 4- 3 4.3Phase IIB PayloadOrbital Configuration Modal Survey ...... 4- 20 4.4Phase I11 Additional IU Acoustic Tests ...... 4- 30 5 . Dynamic Structural Model Verification ...... 5- 1 5.1 Pre-Test Modal VibrationAnalysis ...... 5- 1 5.2Discussion of Test Modes ...... 5- 23 5.3Correlation of Test Modes withAnalytically Predicted Modes ...... 5- 25 5.4Correlation Improvement Methodology ...... 5-41 5.5 Correlation ImprovementProcedure ...... 5- 44 5.6 Postflight Model Verification ...... 5-65 iv

6 . Conclusions ...... 6-1 6.1Structural Modes ...... 6-1 6.2System Modal Characteristics ...... 6-1 6.3Structural Testing ...... 6-2 6.4General ...... 6-3 7.0Notes ...... 7-1 7.1Abbreviations ...... 7-1 7.2References ...... 7-3 7.3Additional Reference Material ...... 7-5

List of Tables

1.1 Model ComplexityHistory ...... 1-5

3.1Speech Interference Levels Due Individualto NoiseSources at 5.0 PSIA ...... 3-15 3.2 SkylabEquipment andExperiment List ...... 3-17

3.3 Experiment ERD's Reviewed ...... 3-18 3.4Noise Sources Located in MDA ...... 3-19 3.5 NoiseSources Located in AM/STS ...... 3-20

3.6Noise Sources Located in OWS ...... 3-21 3.7 MDA NoiseSource Power Levels ...... 3-32

3.8 MDA/STS NoiseSource Power Levels14.7 PSIA Atmosphere ...... 3-33

3.9 MDA/STS NoiseSource Power Levels 5.0 PSIA Atmosphere ...... 3-34 3.10 AM NoiseSource Power LevelsinDecibels ...... 3-35

3.11 OWS NoiseSource Power Levels (Pm's)14.7 PSIA Atmosphere ...... 3-36

3.12 Experiment M509 Nozzles SoundPower Levels at 5.0 PSIA Ambient Pressure ...... 3-37 3.13 Experiment TO20 Nozzles SoundPower Levels ..... 3-38 V

-Pas 3.14 Equivalent A-WeightedSound LevelsCaused by IndividualNoise Sources at 5.0 PSIA ...... 3-39 3.15 SkylabAcoustical Compartment Characteristics . . . . 3-40

3.16 Skylab Interior Noise Source SPL'sMeasured During SL-3 Mission ...... 3-48

3.17 SpeechInterference Levels Applicable to SL-2, SL-3 and SL-4 M487 Measured FlightData ...... 3-53

3.18 ModifiedSpeech Interference Levels Applicable to SL-2, SL-3 and SL-4 M487 Measured Flight Data ...... 3-53 3.19 Skylab Interior SPL'sMeasured During Coolant Loop NoiseInvestigation - SL-4 ...... 3-54

4.1 Skylab Payload Assembly Acoustic/IU Modal SurveyTest Summary ...... 4- 13

5.1 Identification of First Six Natural Frequencies Free-Free CSM on DTACSM SuspensionSystem . . . . . 5-14 5.2 Identification of First Six Natural Frequencies Free-Free ATM on DTA ATM SuspensionSystem . . . . . 5-15

5.3 Orbital Modal SurveyDegree of Freedom Table for Mode Shapeand Discrete Mass Matrix ...... 5-16

5.4 Orbital Configuration (DTA) CoupledAnalytical Modes...... 5-17

5.5 Orbital Configuration Analytical Modes GMC Summary ...... 5-21

5.6 Skylab Orbital Configuration Modal Survey Test, Valid Test Runs Arranged in AscendingOrder . . . . . 5-28 5.7 Summary of Test Modes OrthogonalityResults . . . . . 5-29

5.8 Description of Test Modes . . :...... 5-30 5.9 OrbitalConfiguration Test Modes GMC Summary . . . . 5-32 5.10 Summary of Testand Analytical Modes Correlation . . 5-33

5.11 Cross-Orthogonalityand GMC Least-Squares Fit Results...... 5-37 vi

.Pa e 5.12 Pre-Test Modal StrainEnergy Distribution ...... 5-51

5.13 OrbitalConfiguration Modal SurveyTest Modes Generalized Mass Contribution Summary ...... 5-52 5.14Frequency Correlation Summary ...... 5-53 5.15 CalculationofLeast-Squares DA ScalingFactor ... 5-54 5.16 CSM FlexibilityInfluence Coefficient Data ..... 5-55

5.17 Sunnnary of Test andAnalytical Modes Correlation . . 5-60 5.18 Modal DeflectionsAcross DA rigidizing Arms ..... 5-68

5.19Flexibility Influence Coefficients Across Rigidizing Arms ...... 5-69

List of Figures

1.1 AAP Wet Workshop Configuration ...... 1-1 1.2 Skylab CSM Axial DockingConfiguration ...... 1-3 1.3 CSM Radial Docking Configuration ...... 1-3 1.4 SkylabConfiguration 3.1 ...... 1-6 1.5 SkylabConfiguration 1.2 ...... 1-7 1.6 Nonlinear1.6 Force-Deflection Relationship ...... 1-8

1.7Skylab A OrbitalConfiguration (Configuration 6) Test Setup Modal Survey Tests ...... 1-10 1.8 Skylab Component Systems ...... 1-12 1.9 FAS/IU/OWS ...... 1-13

1.9a OWS SolarArray System ...... 1-14 1.10 MDA/STS/MDA Model ...... 1-16 1.10aAirlock Module ...... 1-17 1.10b MDA ...... 1-18 1.11 Axially Docked CSM ...... 1-20 vi i

.Pa gg 1. lla ApolloDocking Pr.obe Assembly ...... 1-21 1.12 Deployed ATM ...... 1-23 1.12a ApolloTelescope Mount ...... 1-24 1.12b ATM RackModel ...... 1-25

1.12c Flow Chart for Developing AT" Rack Flight LoadsModel ...... 1-26 1.12d SL ATM Retained GimbalRing Assemble Structural Model ...... 1-27 1.12e GRA RollerEffective Spring Rates ...... 1-28 1.12f SL ATM CanisterStructural Model ...... 1-29 1.12g Undeployed DA Model ...... 1-30 1.13 Graphic Summary of Model Evolution ...... 1-32 2.1 Chronologyof Modal AnalysisMethodology ...... 2-3 2.2 Chronologyof Docking Response Methodology ..... 2-7

2.3 Chronologyof Eigensolution Sensitivity to . Parametric Model Perturbations ...... 2-8

3.1 AcousticalNoise Limits Acceptable for ContinuousExposure ...... 3-14

3.2 Location of MDA and STS NoiseSources ...... 3-23

3.3 Locationof MDA and STS NoiseSources ...... 3-24

3.4 Locationof AM/STS NoiseSources ...... 3-25

3.5 Location of AM/STS NoiseSources ...... 3-26

3.6 Locationof OWS NoiseSources ...... 3-27

3.7 Location of Noise Sources in OWS Forward Compartment ...... 3-28

3.8 Location ofNoise Sources in OWS Forward Compartment ...... 3-29 viii

3.9 Location of Noise Sources in Experiment Compartment ...... 3-30 3.10 Location of NoiseSources in OWS Wardroom Compartment ...... 3- 3 1 3.11 Estimated MDA/STS ReverberationTimes at AtmosphericPressures of 14.7 and 5.0 PSIA . . . . . 3-41

3.12 Estimated AM Reverberation Times at Atmospheric Pressures of14.7 and 5.0 PSIA ...... 3-42

3.13 Estimated OWS Reverbera tion Times at Atmospheric Pressures of 14.7and 5.0 PSIA ...... 3-43 3.14 MeasurementLocations inthe OWS Aft Compartment . . 3-44

3.15 Measurement Locations in the OWS Forward Compartment ...... 3-45 3.16 MeasurementLocation inthe STS/AM ...... 3-46 3.17 MeasurementLocation inthe MDA ...... 3-47

3.18 Comparison of Predictedand Measured SPL's in MDA/STS at 5.0 PSIA ...... 3-49

3.19 Comparis,on of Predictedand Measured SPL's in AM at 5.0 PSIA ...... 3-50

3 -20 Comparisonof Predicted and Measured SPL's in OWS at 5.0 PSIA ...... 3-51

3.21 Comparison of MeasuredAcoustic Levels in Skylab ...... 3-52

4.1 PayloadAssembly Test Article Launch Configuration ...... 4-6 4.2 PayloadAssembly Test - Airlock Module ...... 4-7

4.3 PayloadAssembly Test - Multiple Docking Adapter , -Y Section ...... 4-8

4.4 PayloadAssembly Test - MultipleDocking Adapter, +Y Section ...... 4-9

4.5 MSC SpacecraftAcoustic Laboratory Payload Assembly Test Configuration ...... 4-10 ix

.Pa= 4.6 AcousticSystem for PA Testing ...... 4-11 4.7 DataAcquisition System for PA Testing ...... 4-12 4.8 ThrusterDriving Locations ...... 4-17 4.9 ShakerSuspension System ...... 4-18 4.10 BlockDiagram of Control System ...... 4-19 4.11 Modal SurveyTest Setup ...... 4-21

5.1 Skylab A Orbital Configuration (Configuration 6) Test Setup Modal Survey Tests ...... 5-9

5.2 Base Ring/OWS ForwardSkirt/IU/FAS Model for Configuration 6 ...... 5-10 5.3 MDA/STS/AM Model ...... 5-11

5.4 ATM RackModel ...... 5-12 5.5 Axially Docked CSM ...... 5-13

5.6 Component GMC Summaries vsFrequency ...... 5-38

5.7 Component QVIC Summaries vs Frequency ...... 5-39

5.8 Component GMC Summaries vs Frequency ...... 5-40

5.9 Test/Analytical Mode Comparison ...... 5-56 5.10 Test/AnalyticalModeComparison ...... 5-57 5.11 Test/Analytical Mode Comparison ...... 5-58 5.12 Test/Analytical Mode Comparison ...... 5-59

5.13 Rate Gyro Time History and Fourier Analysis ...... 5-70 X

INTRODUCTION ". .". __-~ ~ ."

The Skylabcluster is themost complex spacecraft structure thathas ever beenanalyzed, assembled, tested and flown. Skylab was anextension of the Apollo Applications Program (AAP) and was intendedto provide an experimental man ratedlaboratory in space utilizingprimary components and systems developed under the Apollo program.This report represents a compendium ofSkylab structural dynamics analytical and test programs.These programs are assessed to identifylessons learned from the structural dynamic predictioneffort and toprovide guidelines for future analysts andprogram managers of complex spacecraft systems. It is a synopsisof the structural dynamic effortperformed under theSkylab Integration contract and specificallycovers the development,utilization and correlation of Skylab Dynamic Orbit- al Models.

The ApolloApplications Program was initiatedin 1965, and continuedto 1969, when theprogram was officiallytitled Skylab. Earlyconfigurations included the LEM dockingsystems, MDA with fivedocking parts, boom systemsand consideration of rotating spacestation using S-IVb, CSM, LEM andS-I1 stages, to create artificialgravity environments. The primeconsideration always was the developmentof an orbiting space laboratory with self contained power topermit extended man exploration of his planet andsurrounding environment. Specifically, the developed space station was tobe designed utilizing, where possible, existing "offthe shelf" structural hardware from the Apollo program.

Skylab,therefore, represented an evolved structural design utilizingexisting space hardware except for specific manned laboratoryand experimental requirements. These included developmentof the Multiple Docking Adapter (MDA), deploymentassembly for a redesigned(inverted) lunar decent vehicle (Am) required tohouse the space telescopes, necessary solar array assemblies toprovide powerand modificationof the third stage, SI%, of theSaturn V toprovide for an Orbital Workshop (OWS).

The developmentof such an orbiting, manrated laboratory, requireddevelopment of significant dynamicmethodologies to pre- dictexpected response and load performances during orbital operation. These principallyconcerned the generation of advanced stateof the art technologies associated with: xi

o Docking responsestudies. o Modelingof complex structure. o Vibrationanalyses of large degree of freedomsystems. o Acoustic,vibration and shock criteria. o Testingof orbital structural assemblies.

As a summary ofthe detailed technical effort included duringthe development phases of Skylab, we representthree cyclesof developed structural models. These cycles represented:

o Initialor preliminary Skylab design model. o Modelsdeveloped and used toverify dynamic test. o Finalanalytical structural models, correlated with dynamic test andused to verify flight readiness and launchsupport activities.

The NASA Skylab structural test programconsisted of both static anddynamic test. Theseincluded structural tests on components,subsystems and major assemblies and were performed at contractor, NASA JSC and NASA MSFC test facilities.Static test includedinfluence coefficient, static load and tension test. These tests produceddata required in the early design phaseand necessary in the development of analytical structural models.Solar array and assembly deployment, performance and forcedresponse structural testing were completedbut are beyond thescope of this study and are not includedwithin the report. Extensivestructural dynamicpayload vibroacoustic tests were performed on bothlaunch and orbital payload assemblies, i.e., forward of vehiclestation 3200. The dynamic tests wereper- formed toverify/correlate vibration environments and derived structuralanalytical data. Of principalconcern, for this report, is theorbital payload assembly acoustic and modal survey tests. Analytical model test datacorrelation studies resulted in a more detailed zonal vibration criteria and minor modifica- tionin the deployment assembly analytical model. Significant testingphilosophies, procedures and instrumentationrequirements forfuture complex structural test weredeveloped during this test program.In fact, a large amount of test datarelating to structural andmodal damping, automatic test procedures, vibrationcriteria resolution, and test instrumentationrequirements were obtainedand as yetremains unused.

Programchanges during the last year of theSkylab project resultedin reduced structural flight instrumentation which xii

greatly hampered detail evaluation of the Skylab mission except for some phasesof ignition, liftoff and launch times. However, utilizationof the limited data available did provide some flight correlationdata with an insight in what data are requiredfor. futuresystems. Provided as a summary tothis report is a relativelydetail critical review ofthe Skylab program, decisions made and definitive recommendations for,future dynamicprograms of this nature.

' Interspacedwithin the report are structural model sources, illustration of the analytical models, utilization of models and theresultant derived data, data supplied to organizations and subsequentutilization, and specifications of modelcycles. 1- 1

1. STRUCTURALMODEL DEVELOPMENT

The Skylabprogram was anoutgrowth of the Apollo Application's Program (AAP), initiatedin 1965.Actually, the Skylab was a final configuration designation which hadevolved from numerous trade studies duringthe AAP program.

These studies fesulted in the preliminary design of theApollo Telescope Mount (ATM) andOrbital Workshop (OWS) SolarArrays, Multiple DockingAdapter (MDA), originationof the docking program, ATM and its telescopeconfiguration, GimbalRing Assembly, Space StructureTransi- tion Section (STS) , Airlock Module (AM) with the AM trussesand a preliminary OWS floorconfiguration. This configuration, presented in Figure 1.1 was referredto as the "wet workshop".

LHIATM ,, [ ,-ATM-SAS

Figure 1.1 - AAP Wet Workshop C.onfiguration

The Skylabprogram was officially inaugurated in 1969 withone configuration,but two concepts.These concepts were identifiedas wet or dry Orbital Workshops,which referred to a live or spent third stage, S-IVb, Saturn V workshop. 1- 2

The decision was made toreplace the Lunar Kodule (LM) and its dockingport with the Apollo Telescope Mount (ATM) andDeployment Arm (DA), which simplified the mission by deleting the LM dockingevent.

The Skylab orbital cluster consists of the Orbital Workshop (OWS), Instrument Unit (IU) , Fixed Airlock Shroud (FAS) , Airlock Module (AM), StructuralTransition Section (STS), DA truss,Multiple DockingAdapter (MDA), deployed ATM anddeployed SASS ofthe ATM and OWS.When the Command andService Module (CSM) docked to the axial port of the MDA, (Figure1.2), it resultedin the Axial Configuration. The rescue mis- sionrequired the use of another CSM docked to the MDA radial port; this was referredto as the Radial Configuration (Figure 1.3).

Latein 1969, thedry workshop was officiallyadapted as the Skylab configuration.This section documents thedevelopment and design of the structural modelsassociated with the Skylab DryWorkshop configuration.

1.1 SkylabVibration Analyses Chronology

The wet workshopmathematical models were represented primarily withequivalent beam stiffnesses.This "stick" model consistedof a mass springrepresentation of the modules which made up theconfigura- tion ofFigure 1.1. Only the ATM rackstructural model was a finite element.representation of the stiffness of the actual structure. The formulationof such a model involvedthe idealization of an actual structural member or assemblyof members into a series of discrete or orfinite elements. These elements were consideredto be connected at node points to form a networkor model from which stiffness char- acteristicscould be obtained for the structure, using a digital computerprogram. The MartinMarietta system of structural analysis programs utilizedthe direct stiffness method. A stiffness matrix was formed foreach discrete element (axial member,beam, plate,etc.) andthe element stiffness matrices were merged toform the overall stiffnessmatrix for the entire assembly represented by the model. To obtain good representativestiffness characteristics of this complexstructure, the original model was formed in more detail than that used in the dynamic model. The largestiffness matrix was thenreduced or collapsed to one of moremanageable proportions. The effectof all intermediate, or collapsed, stiffnesses was retained in the final stiffness matrix. B 1- 3

Figure 1.2 - Skylab CSM AxialDocking Configuration

Figure 1.3 - CSM RadialDocking Configuration

Themain cluster configuration was defined as shown in Figures 1.4 and 1.5. Duringthe initial phases of theSkylab cluster structural configuration redefinition from a docked ATM and "wet workshop" to the deployed ATM and"dry workshop" structural analytical modelsof the principalSkylab systems were in a state ofchange.

The mathematicalmodels became largerand more complicatedas the Skylabstructural design cycle progressed. Table 1.1 illustratesthe DOF andsubsequent mode increase.

In 1970, the NASA associate contractors provided better mass and stiffness matrices for the compo'nentswhich comprised Skylab configura- tionsthan those used in the original stick model wet workshop. Inthe new models,only the OWS, ATM solar panels, and MDA were represented with

I I

' '. 1- 4

beam elements (EI, AE, KAG, GJ). All othercomponents of the model were represented with free-free and fixed-free mass and stiffness matrices. The totaldegrees of freedom (DOF) which made up themodel, prior to any reduction,approached 20,000 DOF.

The technfqueused to compute the modeswas modal coupling(Reference 1) , with the modes ofthe various components being computed separately. Theseuncoupled modes were mathematicallycoupled and transformed to form a set of coupled modes.During thiscoupling process, a frequencycutoff criterion was definedfor the coupled mode set. The frequency limit then determinesthe number ofcomponent modes requiredin the coupled analysis.

It is known that some component modes are more importantthan others in modal coupling. The obviousplace to look forthe important component modes was in the ATM and OWS solararrays, since these two componentsac- countedfor approximately 80 percentof the total number of modes required. The method forselecting the important component modes involvedselecting the solar array modes whichhad the largest effect on the main beam re- sponseand discarding allothers in the vibration analysis. To calculate accurateloads on thesolar arrays, all panel modes had to beused. The methodemployed was to calculate the accelerations at the solar panel attachmentpoint on the model with the truncated panel modes and touse derivedaccelerations to base drive the solar array cantilevered modes.

In 1971, it was recognizedthat the vibration analyses used for the loadsanalyses were not necessarily sufficient for control system analyses. Theconcept of uniform frequency cutoff was usedfor the controls model. The concept was to retain all modes ofeach component to a specific frequencydetermined by thesize limitation of the computer program, which at that time was 115 DOF. The modal selectiontechnique did not guarantee maximum control moment gyro (CMG) orrate gyro motion. Of course,this limited the frequency definition in the controls model to slightly less than 5.0 cps. As onemight suspect, this was notadequate forloads calculations. Here again,the modal selectiontechnique was employed toincrease the frequency definition of theloads model above 10 cps.

In 1972,the decision was made toassess the accuracy of the loads versusthe controls modes, toassess the validity of solararray modal selectiontechniques, and to determine an acceptable frequency fidelity forvibration analyses. It was concludedthat all future vibration analyses would contain individual component frequencies equal to or greaterthan 15.0 cps. The solararrays used consecutive uncoupled modesup to 5.0 cps andused modal selection techniques for defining important modesup to 15.0 cps. A single model forboth loads and controlsanalysis, determined in accordance with the aforementioned criteria, was considered more accurate than previous vibration analyses based on consecutive modes andfrequency cutoff for a limited number of coupled modes.The mathematicalmodels were now so complex that the'final modalcoupling run using over 200 DOF requring a CDC 350K core storage capacity. Table 1.1 - Model ComplexityHistory

OWS SAS ATM SAS Main Beam - - Total Coupled Model Report Conf ig. Freq. -cps Freq. Modes Freq. Modes DOF Freq. Modes ED-2002- Date

Axial 27.2 10.5 224 2.8 100 19.0 85 790- 1 4- 15-69 Axia 1 28.8 19.5 7 32 .O 12 115 '28.4 100 7 90- 2 7-24-70 Axial 21.5 20 .o 14 20.5 11 114 23.6 105 7 90- 3 9- 23- 70 Axia 1 20.3 18.3 12 20.3 12 115 20.3 97 790- 4 I- 14- 7 1 Axia 1 19.5 18.3 12 20.3 12 115 19.6 96 7 90- 5 4-12-71 Axial 13.2 13.6 10 9.5 10 115 13.7 103 790-6 7- 16-7 1 Axi a 1 15.7 13.6 10 14 .O 11 133 15.5 118 7 90- 7 2-15-72 Axia 1 16.1 21 15.1 14.0 17 180 15.0 157 1444 5- 22- 72 Axia 1 15.3 17 .O 25 15.8 19 2 12 15.3 168 1564 12-20-72

Radia 1 24.5 10.5 224 2.8 100 19.1 91 790- 1 4-15-69 Radia 1 18.58 26.5 31.8 11 112 18.5 90 7 90- 2 7- 24- 70 Radia 1 18.5 10 16.6 17.7 10 112 18.6 96 790- 3 9- 23- 70 Radial 16.7 15.3 10 14.0 11 115 18.6 98 790-4 1- 14- 7 1 Radial 16.2 15.3 10 14.0 11 115 15.4 96 790-5 4-12-71 Radial 9.2 8.6 8 7.9 11 115 9.8 97 790-6 7-16-71 Radial 15.4 13.6 9 7.9 11 144 15.4 122 7 90- 7 2- 15-72 Radial 15.4 15.9 10 7.9 11 146 16.0 129 1444 2- 15-72 Radial 16.1 17 .O 25 15.8 19 221 15.1 173 1564 12-20-72 lu I h

1- 8

Figure 1.6 - NonlinearForce-Deflection Relationship

1.2Evolution of Structural Models

Throughoutthe 3 yeardevelopment program, hardware changes and raised mass and stiffness definition ofthe structure, required up- datingof the Skylab mathematical models. Three time periodshave been chosenas representative of the program to illustrate Skylab model evolution. The first or initial model was documented in July 1970, and was thefirst formulation of the"Skylab" cluster. The secondor pretest model,represented the Skylab configuration just prior to the Ground VibrationSurvey (GVS). Additionally, pretest modes were de- rivedusing a dynamic test configurationas shown in.Figure l. 7. The finalor preflight model was documented in December1972. It represented the final flight modeland containedstiffness scaling factors derived during GVS correlationstudies. This model was usedfor final flight readinessreviews, flight anomalies studies and flight evaluation. This reportdoes not document the Skylab anomalies studies. # PrimeSkylab mission configurations are shown in Figures 1.4 and 1.5. Structural model evolution is shown as a pictorialrepresentation inFigures 1.8 through 1.13. Thesefigures represent, in a similar manner,the mathematical modeling associated with the vibration studies (see Section 1-1). Thesecomponent systems/assemblies will beused to illustrate the detailed modeldevelopment of Skylab. 1- 9

An interestinglearning experience came to the surface in the field ofmathematical modeling. The Skylabmodels were developedfrom approximately 11 modules. Inthe modal couplingprocedure, several modulus were tiedtogether to form a main beam.The remainingmodulus were modally coupledto the main beam. Forthis example, the main beam consistedof the FAS, IU and OWS modules. The finiteelement models forthese structures were developed by NASA associatecontractors. Historically, in- terfaceloads had been required at the FAS/IU and IU/OWS, which made it desirableto have a centerlinepoint at each of these interfaces. There is a limitation to the number ofdegrees of freedom which can be retained in a dynamicsmodel. Another reason tomaintain a centerline node point is to make the main beam module compatiblewith the sizes of the other modules.However, thecenterline coordinates were not modeled inthe original model. To derive a centerline nodepoint, the radial degrees offreedom were first reduced out to allow radial motion to occur in a typicalbreathing mode manner. A geometrictransformation relating IU ringmotion of all tangential andlongitudinal coordinates in terms of motion at the IU centerline reduced further the number of IU ring inter- facecoordinates. Coupling which occurred between the radial and tangential degrees offreedom in effect constrained the IU ring motion radially. A visualanalogy of this phenomenon is toimagine that the IU centerline pointrepresents the motion of a radiallyslotted rigid plate. This causedthe OWS-SAS loadsto be conservativeto the point of exceeding publisheddesign limits. Inorder to alleviate this situation, all IU coordinates were collapsedout of the main beam model.This allowed the main beam stiffness model to reflect the OWS-SAS attach point flexibility as defined in the original IU finiteelement model, thus allevia- tingthe problem with the OWS-SAS loads.

A facet of modelingwhich had to beconsidered on Skylab was pro- vidingan adequate vibration analysis where it was known that a component ofthe configuration exhibited nonlinear behavior. This was trueparticu- larly in the ATM where thegimbal ring assembly (GRA) is suspendedwithin therack on a nonlinearspring. The springrate is highfor small deflections up tothe point where the preload in the spring is relievedand becomes softthereafter, until the GRA bottomsout on the rack stop. A simple illustration of this problem is demonstratedwith the load-def lec- tioncurve of Figure1.6. For a controlsystem vibration analysis, where vehicleforces are small, it is reasonableto use a GRA springconstant basedon the force deflection range which passes through the origin. The dockingand latching forcing functions cause GRA responsesand corres- pondingdeflections which operate in the nonlinear range. The cost and schedule impact ofperforming a nonlinearanalysis dictated the use of an iterative process in the vibration analysis using the spring constants and frequenciesdetermined from the dashed lines of Figure 1.6. Luckily, a few iterations of the GRA frequencyproduced a modelwhich provided loads consistent with the desired force-deflection relationship. .-

AIR SPRING AIR SPRING SUSPENSION SUSPENSION bl- 4 COMMAND AND SERVICE MODULE(CSM)

Figure 1.7 Skylab A OrbitalConfiguration (Configuration 6) Test Setup Modal Survey Teats 1- 11

1.2.1Orbital Workshop Assembly - The orbital workshopassembly analytical model evolved from.an Apollo launch configuration beam stiffness modelused inthe initial Skylab analyses. Principal changes to this model related to more detailedrepresentations of the Solar Array Sys tem, the backup structure which reflected motion of the arrays to a centerline model, and interface points for compatibility to the STS/ AM/AM-TRUSS subassembly.

Themodel was composedof threemajor subassemblies. These were the OWS structural model, OWS SolarArray System, and the FAS/IU assembly.(See Figures 1.8, 1.9and 1.9a)

1.2.1.1 OWS Structural Model - The initial model was represented by a six mass point, 6 DOF, centerline model.This model actually representedthe stiffness associated with a spentthird stage, S In, ofthe Apollo launch vehicle. The resulting 36by 36 free-free massand stiffnessmatrices were collapsedto 28 by 28 matrices. The primarycon- cernassociated with this assembly was upgradingthe stiffness matrix to reflect a dry workshop configuration.

Boththe pretest and flight modelsof thisassembly were represented by a six centerline point model resulting in 36by 36 massand stiffness matrices. The final model didreflect revised stiffness data associated withthe aft skirt section, but its effect to the overall modal characteristics were minor.However, changes inthe mass dataduring the three modelingperiods were significant.

1.2.1.2 OWS SolarArray System - Detailedmodels were utilizedfrom thestart to define the solar array system. The initial model reflected a 25grid point model resulting in overall 96 by 96 massand stiffness matrices.Modeling problems developed not because of limited size of the model butto inadequate definition of its response.Specifically, these includedirregular tip deflections, no effect of radialmotion (later definedas backup structure) , andno separate representation for near or far side arrays although their orientation was different (see Figure 1.9a) . The pretest and flight models,although similar in size (93 by 93and 99 by 99), were significant improvements.These models contained separate stiffness matrices for each array, inclusion of structural effects fromthe centerline model tothe OWS skin, and effectsof the beam fairing interface with the deployed arrays.

1.2.1.3 FAS/IU/OWS Forward Skirt - Thisassembly had been principally designedduring the APP developmentcycle. Remaining concerns to this assembly was associatedwith.interface responses, load paths, and attachment pointswith adjacent assemblies. The effects of AM trussdesign even withtruss realignment and bottle arrangement did not significantly influ- encethe systems response. The primarydesign driver was thedesign and developmentof the ATM deploymentassembly (DA). Recallthat, at the Skylabconfiguration designation, one substructure remained for major design.This was the A'I!M DA (see DA section). -B Figure i. 8. Skylab Component Systems

LOOKING AFT (POSITIVE 'X = ?'OWAED)

Figure 1.9a OWS Solar Array System 1- 15

The initial FAS/IU model was structured as a finite element model, usingpreliminary load path data of the ”I,-Beam” DA andconsidering only the mass affectsof bottle attachment. Later models included structural flexibilitiesassociated with the ECS and 02 bottles. The pretest model containedgrid points in the assembly so that direct attachment to the DA and AM was possible. The final model additionallyincluded flexibilities associatedwith the OWS forwardskirt. This was due torefinement of OWS SolarArray attachment points and upgrading load allowables on the beam fairing OWS skirt interface.

1.2.2Multiple Docking Adapter Assembly-- The multipledocking assembly analytical structural model evolved from the AAP programstudy. Actually, it was initially composed offive docking parts and a payload shroudconfiguration. With the dry workshop designation, the assembly was refinedto the MDA cylinderportion, STS/AM/AM-truss and two docking ports.Depending upon which orbital configurations were analyzed, the CSM was considered.(See Figures 1.8, 1.10,1.10a and 1.10b)

1.2.2.1 AM/STS Structure - Duringthe AAP developmentphase of the Skylabprogram, thisassembly was treatedas abeam model. At theini- tiation ofthe dry workshop concept, redesign of the trusses provided truss rearrangement for EVA missionsfrom the Air LockModule (AM). Actually, this was utilized to free the pinned OWS-Solar Array system anddeployment of the parasol configuration during mission operations.

Analyticalmodeling changes of this structural system occurred in only two models.These were theinitial and final models. The initial model was representedas a finite element, beam truss modelwith two nitrogen (N2) bottlesattached rigidly to the trusses. The final model includedeffects of the AM/OWS-dome bellowstorsional spring flexibility andarc assembly interface attachment for the N2 bottles.This model was combinedwith the MDA structuralassembly to yield the MDA/STS/AM modal coupling partition.

1.2.2.2 Axial -~and Radial MDA Port Structure - The initial model was completed by consideringthree degrees of freedom at each latch pointand considering the port models, axial or radial, independent ofthe MDA centerline beam model.Significant revision was made for the pretest modeldue tocompletion of the MDA static influence coefficient test and a more definitive modelof the MDA. Portstiffness ma- ,trices were definedfrom a model defined by elastic ports and an elastic MDA. By removingthe flexibilities associated with the MDA, theport stiffnesses were obtained. The final model was revisedonly for the radial port to reflect the 37.75 degreerotation of the CSM about its longitudinalaxis in order to place it intothe proper radial-dock orientation.

1.2.2.3 MDA Structure - Althoughthe MDA was consideredas a centerline beam model in all three modelingphases the pretest and final models were derived from a finite element modelwhich was collapsedto a centerline model of the MDA. The MDA was combinedwith the STS/A”truss model to yield the modalcoupling partition. 1- 16

Y 1- 17

Support Trues Assembly Tunnel And Shear Web8

Figure 1.10a Airlock Module SERVICEVALVES 1- 19

1.2.2.4 CSM Structure - An Apollo CSM model was usedthroughout theanalysis phase and remained significantly unchanged until after the test (see Figures 1.8, 1.11 and1.11a). Due to dynamic test correlation studiesthe CSM stiffness was modified by increasingthe torsional stiff- nessbetween the Command Module (CM) andService Module (SM) by a factor of 3.19.

1.2.3 ~Ipollo TelescopeMount Assembly - The ATM evolvedfrom a simple assemblyto be deployed from a SM service bay, to the mostcomplex structural component of theSkylab program. (See Figures 1.8, 1.12, 1.12a, b, c; d, e, f andg)

1.2.3.1 ATM SolarArray System - Severalmodels of the ATM-SAS had beendeveloped during the AAP program.These had been modeled, tested and revised.Therefore, the array system was completedprior to the Skylab designation. Changes made tothis structural assembly dealt with revising mass propertiesand incorporating, in the pretest and final models,accurate defiahtion of backup structure flexibilities.

1.2.3.2 ATM Rack,>parCanister and Gimbal Ring Assembly Structure - ThiB systemcreated the most concern and revision of any of the major structuralassemblies of the orbital assembly. These concerns were due to :

a. inadequacyof original lock system for the Spar Canister, re- quiringan additional lock assembly, launch lock, that did not totallyeliminate interface responses;

b. error in mass modeling with the failure to consider total effects ofthe ATM wire bundleswhich did not reflect actual CG offset problems ;

C. redesignof the EVA removablerack launch strut;

d. numerousproblems associated with ATM forcedresponse test and effects ofSpar modeling.

This structural system was the mostcomplex of. the structural systems and,therefore, was modeled indetail initially. The initial model was represented by 484 gridpoints using finite beam and shellelements. A flow chart for developing the ATM rack, as shown in Figure 1.12b is repre- sentedin Figure 1.1212. The ATM gimbalsystem was modeled as a substruc- turethen coupled to the rack model (Figure1.12d). The Spar/Canister was assumed to be a rigid subcomponent.

Themodel was not significantly changed during the pretest period. The final model resulted in a revised interpretation of the roller-spring stiffnessdata. Of principalconcern during the analysis, was the non- linearitiesof the roller-spring rates that affected the controls response. 1- 20

Figure 1.11 Axially Docked CSM 1- 21

ies 1- 22

The roller-spring rates were updatedby assembly bench tests to obtain deflection-load curves which were linearized (see Figure1.12e). The radial stiffness of the two type B ATM rack roller-springs were changed from 113 lb/into 37500 lb/in.Thus, all four(type A and B) .of the rackroller-springs, which connected the rack to the GRA had radial stiffnessof ,37500 lb/in. This was theonly change to the basic rack stiffnessdata. The Spar/Canister was consideredflexible instead of rigid and was modeled as depicted in Figure 1.12f.

1.2.3.3 DA Structure - At theSkylab configuration designation, onlyone substructure was left formajor design. This was the AT" DeploymentAssembly (DA) . Modelingproblems existed inthe definition of first primarybending frequency, attach point designation, and load pathdefinition. Due inpart to the major configuration change, removal of LEM docking, three radial MDA dockingports, and conversion to the dry workshopconcepts, requirements were established for immediateas- sessmentof control and load impacts due to the DA. Thisprecipitated numerous orbital cluster vibration analyses using varying models of the DA. However, since we havepreviously defined three modeling phases forSkylab, we will notdiscuss the "L-Beam'' andother preliminary DA mode Is.

The initial modelassumed structural members to bethin walled aluminum tubesand wasa truss-beamstiffness model (see Figure1.12g). Themodel was revised by the dynamic test correlationresults. This was accomplishedby scaling down the stiffness matrix by a factor of 0.6. Actually,as a resultof the dynamic test, remodelingshould have been performedprimarily atthe interface connection points. However,detailed models were notavailable from the prime contractor so thescaling was appliedto the entire DA. Later,in comparison of flight results, this correction had to be revisedand stands as theonly significant modelingerror made in the Skylab Orbital Dynamic Analyses.

1.3 Conclusions

Initially, modelchanges were broughtabout by the solidification ofthe Skylab design. Beam models were replaced bymore accuratefinite elementrepresentations of the substructures. Locations and size of instrumentationpackages were decidedupon, thereby requiring morede- taileddescriptions of the modal mass distributions.

Further modelchanges were required to obtain finer descriptions ofareas of interest, such as the ATM and OWS SolarArrays. This in- creasedthe number ofdegrees offreedom in critical areasrequiring reduction in the number of DOF in other substructures in order to stay withincomputer size limitations. Modal couplingand modal selection techniques were developed (see Methodologysection, 2.1) to help solve this problem. The GVS broughtto the surface modelinadequacies. Model correlationtechniques determined that CSM torsionalsprings and DA

1- 24

ATM Spar Assembly

ATM Rack Assembly

ATM Canister Amrembly

Figure 1.12a APOLLO Telescope .Mount I

1-25

X (UNDEPLOYED)

BAY 5

Y (UNDEPLOYED & DEPLOYED)

2 (DEPLOYED)

Figure 1.12b ATM Rack Model ...... _.

1-26

ATM Rack Thermal Shield Model "E" Cable Beam Assembly (Te s t) Assembly

Collapsed Collapsed Collapsed Stiffness Stiffness Stiffness Matrix Matrix Matrix I I b ATM Rack Model "F"

1. Assemble Stiffness Matrices

2. Generate Flexibility Matrix

ATM Rack Mode 1 "F"

1. Invert Flexibility Matrix

2.Subtract Ground Springs

ATM Rack Mode 1 "F" (Flight)

Collapsed Stiffness Matrix

FIGURE 1.12~- FLOW CHART FOR DEVELOPING ATM RACK FLIGHT LOADS MODEL I FiRur- 1,12d SL ATM Retained Gimbal Ring Assemble Structrral Model 1-28

~ ~~

1 MOTIONTOWARD IAL ROLLER BOTTOM AXIAL ROLLER

AxialRoller Effective Spring

501 I0

101 00

RadialRoller Effective Spring

Figure 1.12e GRA RollerEffective Spring Rates

~ SUN END -Y -Y

W -2 -+z +z X A

ut L"t +Y +Y -2 +Y +z -Y

% n u .I m a x, 71 71

SUN END

Figure 1.12f SL A!IM Canister Structural Mode 1 1- 30

Figure1.12g Undeployed DA Model 1-31

stiffnessscaling factors had to be added tothe models. Finally, the requirement of tolerance studies of the structure , generated additional modeling inthe form of perturbed stiffness and mass matrices. At the time, thisrequired reruns of the modal couplingand new solutionsof theeigenproblems. Figure 1.13 provides a graphic summary of the model evolution presented here. 1.3.1Recommendations -

a. Early definition of a final configuration can eliminate costly remodeling.

b. Prior to final configuration definition, inexpensive beam and stick models,with small numbersof DOF'S, shouldbe used whereverpossible.

C. The final configuration model interfaceareas should be modeled as fineas possible. Modal coupling andmodal selectiontech- niquesshould then be used to reduce the number of DOF'S to withinthe computer size limitations. This would haveeliminated the model discrepancies discovered during flight.

d. Afterthe design configuration is finalized, model perturbations canbe handled using an eigensolution sensitivity approach (see MethodologySection, 2.3). Thistechnique provides an economi- cal eigensolution for a perturbed model by circumventingthe necessityfor regeneration of the complete model.Major design changes,mass redistributions, test derivedscaling factors and tolerancestudies can be handled effectively by thistechnique.

e. If a GVS is to beperformed on a test article, the GVS should beperformed as early as possible to permit a thorough model evaluation. 1-32 I I FINITE ELEMENTMODEL

0 BEA"ST1CK MODEL I I

PWS-I SAS INITIAL MODEL I

1 AT" SASl PKI ~AR/CANISTERI lGRAI IDA I PWS-SAS I 2- 1

2.0 SKYLAB ANALYTICAL "HODOLOGIES

The ApolloApplications Program (AAP) whichevolved into the Skylab programpresented numerous dynamic problems which required significant analytical developments to cope with the complexity and sophistication of a manned orbitallaboratory. Principal concern in the structural dynamic areas were 1) a large flexible structural system requiring detailed modeling to define accurately modal characteristics for load and control studies, 2) subsequentrefinement in modal couplingand mode selection programs, 3) requirementfor a sophisticateddocking impact analysis due tostructural load modal sensitivity, 4) controlimpulse definition, com- plicated with the interaction of control sensors at variouslocations of the orbital structural to natural model characteristics and a requirement foraccurate definition of propellant and impulse requirements, and 5) structural model correlation and revision due to differences in analytical anddynamic test results.

Technical requirements and resulting analytical methodologies were originated early in the programand expanded throughout the Skylab program.During the program and inthe years hence,.these analytical tools havebeen refined and expanded into other areas/projects of application. Figures2.1 through 2.3 definethe chronological development of the principalSkylab structural dynamicmethodologies. Principal metho- dologiesdeveloped under the Skylab program were:

a.Skylab modal characteristics, b.docking response of flexible bodies, c. structural model correlationwith dynamic test.

2.1Skylab Modal Characteristics

Skylabrepresented the most complex structural assembly that had beenconsidered to date byany scientific organization and assuch pre- senteddistinct analytical problems to the analysts. Actually, the growth of modal characteristics beganunder the original AAF' studiesand their. concepts will beincluded.

2.1.1Early Assessment - Initial problemsfacing the analyst on the AAP andsubsequently the Skylab programs were size problemsassociated with existingor revised computer programs. These problems included:

a. MDA finiteelement modelsrequired to find a model todefine six degreeof freedom response at skin stations;

b.incapability of structural models from associate' contractors to define structural response adequately; 2- 2

c. modelstoo course to effectively answercontrol system design requireants;

d. difficultyin determining modal toleranceson a totallythree dimensionalstructural system;

In an attempt to retain sufficient accuracy of models and at the same time a rationalapproach to structural model sizelimitations, a If beamology" approachto mathematical modeling evolved. Primary consideration was given to detailed modeling of the interfaces and either direct mass point centerline models or detailed structural modelof systems which were later collapsed/reduced' to centerline point models for a compatible mass matrix on these centerline models were determined.

Even withthese considerations, the size and complexity of the structuralelements which comprised the Skylab configuration did not lendthemselves to efficient "direct" vibration analyses. This was primarilydue to computer size limitations associated with long com- puterrun times. Some programrun times were beyond the mean time to failure ofthe individual computer systems. This problem was partially resolved by applying a component mode substitution method(modal coupling). This method considersthe structural system to bean assemblage of sub- systemcomponents. The vibration modes foreach component aredetermined separatelythen a reducedor truncated set ofthese modes areused to synthesisthe total system.

The nextsection describes the chronology associated with the developmentof thistechnique with parallel methodology development.

2.1.2Methodology Development - Of mostconcern in theearly developmentof system modal characteristics was therequirement to obtain some modal fidelity limits on themodel. The Skylab was such a complexmodel that manymodes were present that had to beaccurately defined to complete designstudy requirements. Initially, this was resolved byassuming iso- latedstructural systems, i.e., due tostructural dampingmajor systems didnot significantly couple, therefore, these complex systems could be analyzedas "uncoupled systems". Such systems were assumed to be ATM dockingports, and OWS SolarArray System. As theseassumptions were not valid,the development of adequate methodologies followed.

It is not the intent of this report to republish all previously developedand published methodology. However, toassure the completeness ofthe report, Figure 2.1 illustrates the Skylab modal characteristic methodologydevelopment.

2.2 SkylabDocking Response

The dockingproblems of spacecraft, inthe past years, has been focused on thedocking requirements of the Apollo and Skylab missions. However, missionsof the future, in particular Space Shuttle, will require Vibration Report for AAP Beamology Model A description of inertial coupling of a systemof finite element and ED2002-414 beam or truss models. I 1 April 1968

Derivation of a loads modal selectiontechnique to assure model fidelity Report - ED-2002-790-2 and subsequentaccuracy of derived modes. 24 July 1970

The structuralsystem is consideredto be anassemblage of subsystemsor components. The vibration modes foreach component are determined separately and thenused to synthesize thesystem modes. Thenumber of component modes used may be truncatedto reduce the number Structures byComponent of generalizedcoordinates required for a vibrationanalysis. Only component vibration Mode Substitution modes are retained as generalizedcoordinates when thesystem modes areobtained; hence, AIM Journal, Vol.9, No. 7 the method is particularly suitable for structures vLth a large number of component inter- July 1971 facecoordinates, such asfinite-element shell models. The boundary conditions used for determining component vibration modes can be eitherfree-free constrained.or tw I w Complex structures that comprise the Skylab cluster configurations do notlend themeelver toefficient direct vibration analysis/eigenvector program. This is primarily due to computer size limitations and longrun time necessary to invert large size matrices. ED2002-1256 This document defines in detail a computerprogram which utilizes a modal couplingtech- 10 February1971 nique. Mi3DL3 is a programwhich is meant to perform modal inertial and/or modal stiffnerm coupling of structural components in order to determine the vibration modem of a cornplex structural system. It also produces inertialloads transformstionr fqr the coupled mymtcm.

A LinearStriinEvaluation of Modal HydroelasticMathematical TetrahedronElewnt With AnalysisTcchniques Model Spaceof Shuttle Boundary Compatibilityfor MCR-73-310 LiquidPropellant Tanks Fluids end Solids 1973 MCR-75-178, June 1975 D.M. 170, December 1973

Figure 2-1. Chronology of Modal Analysis Methodology 2-4 docking of space vehicles with space station satellites andnecessitate extensive dockinganalyses. The dockingmaneuver and its associated responses will affectthe design of these large, flexible structures. Additionally,definition of successful capture boundaries, spacecraft attitude control requirements, propellant utilization studies, and man/ machine interaction or the degree of automation are required.

One ofthe first studiesdealing with docking dynamics presented a generic analysis of rigid body dockingdynamics from initial physical contact of two spacecraftto final latching. The dockinginterval was specified in threephases - initialcontact, continuous maneuverand latching - andassumed that the first and thirdphases occurred over a finite time interval. The studypresented an analysis that revealed grosseffects of significantdocking parameters, including attitude misalignment, initial relative vehicle rates anddocking rate.

A two-dimensionalanalysis of the dynamics of'the probe and drogue dockingconcept was presented(Reference 2) in 1966.The mathematical simulationof the docking maneuverassumed thedocking vehicles were rigid bodies, but included a provisionwhereby the probe vehicle might bemodeled as a rigid structure with spring and dashpot attached masses. Probe rotation was constrained by a resisting moment, andprobe axial deformation was assumed to act in accordance with a prescribedenergy absorber. The restriction that the probetip mustremain in contact withthe drogue surface was notintroduced, and it was assumed that, when theprobe was not in contact, it returnedto its equilibriumposi- tion in a prescribed manner. This assumptionprecluded the necessity for an iterative solution if nonlinear shock attenuators were included. Latching was assumed tohave occurred when (and if) theprobe tip reached a designatedposition in the drogue socket. All postlatchanalyses were conductedwith the probe tip assumedpinned in thesocket.

In 1967,analyses were completedof the docking maneuver that con- sideredan Apollo docking mechanism (Reference 3). The primarygoal of thisanalysis was todetermine the nature of theloading on the two dockingvehicles caused by thedocking mechanism and to evaluate the internalelastic loads induced in the vehicle. The generalapproach to thedevelopment of the analytical method was to'solve the two-bodydynamics problem in which rigidbodies are subjected to loading from a model ofthe docking mechanism. These load histories were thenused in a generalized modalresponse analysis to determine the resulting elastic response of thedocking vehicles.

Additionalstudies were completed(Reference 4) based on impulse- momentum relationships and considered friction between probe and drogue, energylosses due to permanent deformation, attitude control of the chasevehicle, and thrusting of the chase vehicle following initial contact. All motion was consideredto take place in a plane,and the probetip was constrainedto lie on orwithin the drogue cone walls. Giventhe spacecraft mass propertiesand a set of initial conditions, I

2- 5

the simulation was able to predict whether a dockingmaneuver would be successful(capture) or fail (miss). The simulationalso provided an estimate ofthe contact loads that would occurduring the attempt. This simulation was used to obtain results for docking maneuvers of theSkylab spacecraft.

Skylab analysts completed an analytical study of the docking dynamics of two spacevehicles that were more generalthan the efforts of previous investigators. The equationsof motion, coupled with pertinent constraint equations and equations of momentum-impulse, were developed without regard toany particular docking mechanismconcept. Their equations resulted fromapplying Hamilton's principle of least action(Reference 5) as if the system under analysis were a conservative system subjected to auxili- ary,holonomic constraint conditions. They modifiedthe resulting equations to account for the possibility of unconservativeforces and non- holonomicconstraint conditions through application of the principle of virtual work.They showed thatif the mass properties(inertial forces) ofthe docking mechanism were negligible, the requirement for momentum- impulseequations disappeared.

The Skylabdocking event assumed the role as the most significant orbital dynamic loadproblem. As such, it precipitated a directphysical mating,docking response, test computerhybrid study at.NASA JSC which establishedinitial boundaries, rates and latchforces. In excess of 6000 physicaldockings were simulatedand basic formulation of the docking problem was accomplished.

The modelingof the drogue/probe assembly (see Figure l.lla) and resulting sliding motion coupled with control sensi'tivities, were initially consideredas the most significant problem area. Therefore, docking problems were considered in two ways,one thechanging ofmodal properties of thesystem during the docking event due to engagement, and two, being largenonlinearities being excited,eg. ,propellant slosh. The complexity ofthe docking problem was felt to bepredominantly in the description of theprobe neck as it contactedthe drogue. It is interesting.to note that at this time capture was notconsidered the significant event and, therefore,overall cluster response due todocking was considered small due to structural damping.

The initial loads methodology for the docking event considered general step and ramp buildupforces and utilized amodal acceleration method forresolving the transient responses.

As a result ofthe hybrid computer test results and films of orbital mating of the CSM/LEM, more detailed studies were initiated to resolve impactof latch forces to Skylab design.

The results of a study of theresponse of flexible space vehicles todocking impact have been detailed in Reference 6. This studyresulted 2- 6

in a comprehensive analytical development and digital computer program to investigate the dockingdynamic characteristics of elastic space vehicles. The analysisconsidered influence of one or more attitude control systems actingduring the maneuver.The resultingmathematical model wasprogrammed for numerical evaluation; primary program output consisted of time history plots of significant program variables, in- cludingvehicle velocities, probe deformation characteristics, probe/ drogueinterface forces and moments,and controlsystem parameters.

Note thatthis analysis and that of Reference 6 were the first in whichthe elastic properties of the two dockingvehicles were considered. The analysis also considered the effects of sliding friction between probeand drogue, internal binding friction caused by probedeformation, and the possibility of nonlinear stiffness and damping characteristics.

The developmentof a completeSkylab dynamic docking maneuver analysisprogram, from impact through the latching sequence was a sig- nif icant state of the art development.

Recentstudies utilizing those derived programs include general dockingmethods, propellant responses, spinning bodydynamics and response of flexible , rotating components.

Figure2.2 schematically depicts the docking study evolution.

2.3 . Mode 1 Correlation to Vi.bration Testing

Analyticalmodeling of complex test articles seldomagree with dynamic test results.Design changes, data tolerance effects, mathematical techniquesand engineering judgement impose uncertain constraints on the analytical model.

This section describes a rational methodology to correct the model discrepanciesdiscovered by dynamic tests which was developedon the Skylabprogram. The problem is approachedby formulating the eigenproblem in terms of perturbednominal model finite element data and nominal modal coordinates. The extentof coupling produced by elementalstiffness and/or mass matricesbetween the nominal modes determinesthe respective distri- butionsof modal strain energy and modal kinetic energy among the model elements. The extentof this coupling is limited by orthogonality of thenominal model eigenvectors with respect tothe unperturbed finite elementdata. This property is utilizedto decrease the size ofthe eigenproblem required to calculate modal perturbationsproduced by a givenelement perturbation. Thus, the sensitivity of a particular mode to perturbation of a specific modelelements can be determined economi- cally. The model sensitivityinformation is usedto define a set of test data that is mostapplicable for adjusting the analytical model to correlate with dynamic test results.

The chronologyof the development of this technique is depicted in Figure2.3. It shouldbe noted that at the time of thisreport, addi- tionaldevelopment is proceeding in this area. 2- 7

DockingDynamics for Rigid Body Spacecraft - AIM Journal, Vol. 2, No. 1, January 1964

Dynamic Analysesof the Probe and DrogueDocking Mechanism Journalof Spacecraft and Rockets May 1966 I Program to Derive Analytical Model Representationsof the ApolloSpacecraft and its Launch Vehicles,Docking Analysis Final Report D2-84124-3, May 1967 I A Method for Digital Computation of SpacecraftResponse in the Docking Maneuver Proceedings, ASME/AIAA log Structures, Structural Dynamicsand Materials Conference April 1969 I 1-MethodologyReport for DockingLoads ED-2002-595, August 1969 -~

to DockingImpact MCR-70-2. March 1970

Docking Probe Analytical Model ED-2002-770, August 1971 I I

NASA JSC Physical Mating Test of ApolloDocking Hardware 1969-1971

FIGURE 2.2 - CHRONOLOGYOF DOCKING RESPONSE METHODOLOGY 2- 8

DynamicModel Verification Report(Orbital Configuration) ED-2002- 1551, October 1972

Dynamic Test Reflected Structural ModelMethodology ED-2002- 1577, December1972

Laterderived methodology (Post Skylab)

Parametric Model Perturbations April 1975,R-75-48628-001

Parametric Model Perturbations 46G Shockand Vibration Bulletin

(Presentlybe developed)

FIGURE 2.3 - CHRONOLOGY OF EIGENSOLUTION SENSITIVtTY TO PARAMETRICMODEL PERTURBATIONS I

3- 1

3.0 ORBITALCLUSllER INTERIOR ACOUSTICS

The purposeof the Skylab Interior Acoustics contract was tocoor- dinatewith the National Aeronautics and Space Administration/Marshall SpaceFlight Center (NASA/MSFC) andequipment contractors to assure com- pliance with the acoustic requirements established by theMedical Research andOperations Directorate. The following are examplesof tasks which were performedand are sunsnarized in this section.

a. Identifyand locate noise sources in the Skylab. Determine the frequency of useand duration of operation of noise sources as a functionof mission profile time.

b. Updateanalyses as required to evaluate the effects of additive noisesources at crew work stations and rest stations.These analysesshall reflect nominal continuous levels and maximum levels resultingfrom equipment/experiment operation during the mission profile.

C. Coordinate with MSFC and MSC to establish measurementrequire- ments,locations and time/line schedule for obtaining noise levelmeasurements during the Skylab mission.

d. Analyze interiornoise level measurements obtained during the missionsand correlate results with predicted levels.

Prior to a presentation of theacoustic data measured during the SL-2, 3 and 4 missions, a discussionand description of theSkylab noise sources,the Skylab compartment characteristics and the acoustic metho- dologyutilized, are presented.

3.1 AcousticAcceptance Criteria 3.1.1 SkylabInternal Noise Levels - The MedicalResearch and OperationsDirectorate at JSC, recognizingthat the acoustic environment couldinfluence the astronaut's performance and ability to communicate,published a criteriafor the Skylab internal noise levels as shown in Figure 3.1.The criteria was applicable to any noise source or combinations of noisesources operating continuously in the Skylab interior. Of particularconcern was thedesire to insure adequate, unin- terrupted sleep periods for the astronauts.

The development of the criteria was based,in part, on experience gainedduring the Apollo program, where crew members hadobjected to thenoise output of the post-landing-ventilation (PLV) fans.These fans were plannedfor extensive application throughout the Skylab ven- tilationcontrol system. Consequently, MSFC conductedan extensive developmentprogram to provide mufflers for these fans-to reduce noise levelsto acceptable limits. 3- 2

3.1.2Speech Interference Levels - The preferredfrequency speech interference level (PSIL) was selectedto assess thespeech-interfering aspectsof the Skylab interior noise sources. ThePSIL is defined as the arithmetic averageof the sound pressure levels in each of thethree octave soundbands with center frequencies of 500, 1000 and 2000 Hz.

ThePSIL associated with the Skylab interior noise criteria in Figure 3.1 was 56.7 dB. Forthis PSIL value,face to face communications at 14.7 psiaambient pressure are possible using "a normalnoise" when a speaker . and listener are less than five feetfrom each other (see Reference7).

Anotherrating system, the modified speech interference level (MSIL) , includesthe higher frequency noise. MSIL is definedas the arithmetic average of thesound pressure levels in each of thefour octave bands with centerfrequencies of 500, 1000, 2000and 4000 Hz. The MSIL associated withthe Skylab interior noise criteria is 56.25 dB. PSIL and MSIL values in each Skylab section due to operation of the individual noise sources at 5.0 psiaambient pressure are presented in Table 3.1.

3.2Definition of Environment

3.2.1Noise Sources and Locations - Skylabequipment and experiments were reviewed todetermine noise sources. Tables 3.2 and 3.3 present a listing ofthe Skylab equipment and experiments; noise sources are indi-

catedwith an arrow or asterisk in these two tables.Originally, the , noisesources were groupedaccording to the contractor subdivisions. It was de.terminedthat grouping the noise sources according to acoustic space would provide moremeaningful results. The threeacoustic spaces chosen were the MDA,AM/STS and OWS. The noisesource, number, location, frequencyof operation and table number for its soundpower level are pre- sentedfor each compartment in tables 3.4, 3.5 and3.6. Figures 3.2 through 3.10 indicatethe locations of each of these noise sources. The soundpower levelsfor each compartment are delineated in Tables 3.7 through 3.13.

A-weightedsound levels (dBA) were calculatedfor the noise sources atan atmospheric pressure of 5.0 psia.Octave band sound pressure levels were convertedto the equivalent A-weighted sound level by ap- plyingthe relative response for the A-weightednetwork tothe estimated octave band levels andobtaining the overall level from the resulting octave band levels. Theseequivalent A-weighted sound levels are presentedin Table 3.14.

3.2.2Compartment Characteristics - Thevolumes and surfaceareas ofthe MDA, STS, AM and OWS were calculated.In addition to these, equipmentvolumes, surface areas and common wallareas between each compartment were calculated. The results ofthese calculations are presentedin Table 3.15, Skylab Acoustical Compartment Characteristics.

Reverberation times for the flight configuration were estimated fromthe Skylab mockup. Figures3.11 through 3.13 presentthe reverberation times for the MDA/STS, AM and OWS at pressures of 5.0 psia and14.7 psia. 3- 3

3.2.3 Acoustic Methodology - Sound pressure level estimates for each compartment, dueto noise sources in the same compartment, were calculated using the following equation for a reverberant sound field:

SPL = PWL - 10 .Log V .+ 10 Loglo ( P/PReF) f 10 10 Loglo T60 f 19.6 dB (1) where 3 V = volume of section containing noise source, ft

P = ambient pressure in the enclosure, psia,

Pref = reference ambient pressure= 14.7 psia,

T60 = reverberation time of enclosure, sec

To obtain estimates of the sound pressure levels in the compartment due to noise sources in other compartments, the following expression was used from Reference 7:

PWLl f 10 (SW/R1)Loglo - TL (2) pwL2 where

pwLl noise source PWL located in Room 1, PWL of noise source applicable to Room 2, pwL2 sw = area of common wall between Rooms1 and 2,

- room constant of Room 1 = S / (1 Z ) = .049V2/T60 R1 - - TL = transmission loss of common wall= 0 for an open passage

Combining equations (1) and (2) yields the PWL of the noise source applicable to.Room 2 in terms of the SPL in 1.Room

= (SW/4) PWL2 SPL1 + 10 Loglo - 10 Loglo (P/PRef) - TL (3)

From equation (2), the following definition ofT60 is applicable.

T60 = .049V/SZ (4) 3- 4 where

a = averageabsorption coefficient. (Reference 7 ) where

= surfacearea of the i2 wall si = absorptioncoefficient of the i2 wall d i

3.3Flight Measurement Results

3.3.1 NoiseMeasurements Durin-kylab Mission(Experiment M487) - The objectivesof experiment M487 were tomeasure, evaluate and report the habitability features of the crew quartersand working areas of the crews inengineering terms usefulto the design of future manned spacecraft. A portionof this experiment included the mea.surement of sound pressurelevels onSkylab using a portablesound level meter (Bruel + Kjaen,type 2203) and octave filter set (Bruel + Kjaen,type 1613). Eightmeasurement locations were selected and are shown in Figures 3.14 through3.17. These are the aft OWS area (4 locations),the forward OWS area (1 location),the STS/AM area (2 locations)and the MDA area (1 location). The soundlevel meter, usedto obtain these data, was ori- ented as follows:

a. OWS Wardroom - parallel to CDR foodtray, microphone pointed towards OWS (location 1’1);

b. OWS ExperimentCompartment - parallel to floor at LBNP, microphone pointedtowards sleep station (location #2) ;

C. OWS WasteManagement Compartment (WMC) - onfloor, microphone pointed towards +X (location f3) ;

d. OWS Sleep Compartment - in PLT compartment,on floor, microphonepointed towards +X (location 1’4);

e. OWS ForwardCompartment - parallel to floor located at locker ringarea, microphone pointed towards +Y (location 115); f. AM - parallel,with microphone pointed towards +X in middle of compartment (location 116) ;

g* MDA - at Experiment M512 station,microphone pointed towards -X (location #7);

h. STS - microphonepointed at Mole Sieve A (location #8). "

3- 5

3.3.2Flight Environmental Conditions for SL-2, SL-3 and SL-4 - The following ventilation system fan operational mode existed during the periodthe acoustic data were obtained on the SL-2 mission:

a. CSM portablefan in MDA was off; b.cabin fans 1 and 2 in MDA were onlow; c. OWS interconnectfan (STS ductfan) on hi; d.cabin heat exchange module (STS heatexchange fans (3)) on hi; e. OWS heatexchanger fans (4) in MDA were on hi; f . OWS ductfans (8) in OWS were on hi. Forthe SL-3 and SL-4 missions the following operation mode existed:

a. CSM portablefan in MDA on hi; b.cabin fans 1 and 2 in MDA were on hi; c. STS ductfan on hi; d. STS heatexchanger fans (3) on hi; e. OWS heatexchanger fans (4) in MDA were onhi; f. OWS ductfans (12) in OWS wereon hi.

In addition to the M487 acousticmeasurements obtained during the SL-3 mission,acoustic noise source measurements were also obtained. Thesemeasurements were made in the immediate vicinity of eleven noise sourcesin the Skylab interior. Specific information applicable to sound level meter (SLM) distanceand orientation to each noise source was notreceived so a distance of3 feet was assumed.The results of thesemeasurements are presented in Table 3.16.

3.3.3Comparisons of Predicted and Measured Skylab SPL's - A comparison of theSkylab measured SPL datafrom the SL-2, SL-3 and SL-4 missionswith previously predicted SPL's is indicatedin Figures 3.18 through3.20.

Figure3.18 compares the MDA/STS SPL'sand indicatethe MAX/MIN envelope of theSkylab flight data andthe composite of predicted con- tinuousnoise source in the MDA/STS. A comparisonof the data indicates thepredicted SPL's begin to exceed the measured data by3 to 6 dB, from 1000 to 4000 Hz. Below1000 Hz, thedata comparefavorably. A comparisonof acoustic data applicable to the Airlock module is indicatedin Figure 3.19.The predicteddata fall within the measured SPL envelope at thelower frequencies and begin to exceed the envelope above1000 Hz. A comparison,of acoustic data applicable to the OWS is indicated in Figure3.20. The predicteddata fall within the measured SPL envelope, especially in the mid-frequency range. 3- 6

levels were measured in the STS, influencing the MDA and AM SPL's to some extent.In general, the only areas to exceedthe acoustic criteria by 2 to 3 dB were the STS, AM and OWS waste management compartment.

Preferred .speech interference levels (PSIL'S)and modified speech interferencelevels (MSIL's) were calculatedbased on the M487SPL data.These PSIL and MSIL valuesare indicated in Tables 3.17 and 3.18,for eight locations in Skylab. These values do notexceed the acoustic criteria PSIL's and MSIL's in any area.

3.5Skylab Crew MissionAcoustic Evaluatioh

A reviewof the Skylab crew comments applicable to the acoustic environmentsthey were exposed to during the SL-2, SL-3 and SL-4 missions is discussedin the following paragraphs, and is based on data containedin Reference 8.

3.5.1. SL-2 Mission Acoustic Evaluation - Crew Acoustic evaluations aredescribed as follows:

a. verbalcommunications - "withinthe MDA you could holler at someone in the workshop,however, could not holler from workshop to MDA" ;

b. SIA communications - "terriblefor ground communications; have tokeep certain SIA's turned down";

C. experiment "509 - "when 509 thrusters fire, it is quite loud in OWS; I recommend everybody in OWS to wear earpro- tec tion (PLT) ";

d. pre-sleep - "veryquiet in sleep area;noisiest seems to be MDA/STS; canhardly hear fans running in OWS, butcan hearrefrigeration pumps, (CDR)"; 3- 7

e. post-sleep - "reportedthat both mouthsounds and snoring are as loud in zero G as they are at 1 G;

f. Crew SubjectiveEvaluation of Compartments:

Locat ion CDR SPT PLT

(3wS Wardroom excellent,ex- excellent very good tremely low ows WMC excellent adequate very good

OWS Sleep Area low exceptfor too high when very good noise from WMC others are mov- blower ing about, needssound proofing

OWS Exp. Compt . low ok very good

OWSFwd Dome excellent ok very good

Airlock low all right

FDA/ STS fine ok satisfactory; gets high during EREP runs

3.5.2 SL-3 MissionAcousticEvaluation - Crew acousticevaluations are described as follows:

a. CDR - "canhave duct fan heat exchangers turned off andcan't tell anydifference in noise level, they are so quiet" ;

b. PLT - "have toholler pretty loud to be heard from crew quarters up intothe dome. Voicesdo not transmit up throughthe airlock at all. Have touse intercom to talk to anyone in MDA/STS. SIA's keepsquealing all the time., Noise is definitelysatisfactory";

c. CDR - "noise,very nice, very good"; d.Environmental Noise Factors Causing Interference: PLT - "just SIA's; OWS is comparativelyquiet. No interference withability to sleep". SPT - "never,no interference with sleep". CDR - "sometimesnoises worry you, but after 3 or 4 daysyou get used to them".

' 3- 8

e. Habitability Improvements: PLT - "keep noise makers away from the sleep area, in the future. Portable fans run quiet, don't make any noise.''

f. Subjective Evaluation of Compartments:

Location CDR SPT PLT

i OWS Wardroom adequate noise very good, very good, noise level is ok, noise levels level is quite communications are satis- low, no objec- is good in factory every- tionable noise here ows WMC ok very good very good

OWS Sleep Area need to be looks reasona- very good able to de- bly good crease noise level from rest of vehicle as it is hard to sleep when somebody else isn' t asleep

OWS Expt. Coapt.ok (adequate) very good, very good, no satisfactory objectionable everywhere noise

OWS Fwd Dome ok (adequate) very good very good

Air lock ok (adequate) very good very good

MDA/STS ok (adequate) very good very good, higher in STS with fanson but its a very comfortable noise leve1 r

3- 9

3.5.3 SL-4 MissionAcoustic Evaluation - Crew acousticevaluations are described as follows:

a. Communications - CDR: "Squeal;verbal communications is possible in workshop area betweencompartments except WMC when door is closedand fan is on". SPT: "Squeal is ok if you are in same compartment,for verbalcommunications. If you try to gofrom one to anothercompartment, it is awfulhard. There's too much noiseor absorption of sound. If you are in experimentcompartment, then you can call up to some- oneabove you but it takes a fair amount ofvolume." PLT: Whenon the same level (Z plane),there is no . difficultywith verbal communications. Noise level increases as you go up and down (X axis). When separated by 10 to 15 feetalong the X axis, it is extremely difficult to communicate by shouting."

b.Environment - CDR: "Surprised at how little noise there is inspacecraft. MDA/STS is only place there's quite a bitof noise in. In OWS, it is extremely quiet. All thedifferentpumps and everything in MDA make all thenoise. It's aboutthe same orpossibly higher (slightly)then noise level in the command module." SPT: "There,'sjust a little too much noiseto get sound sleep, more thanI'd like to have." PLT: "It's good to have a little noise."

c. Environmentalchanges - CDR: "No changefrom noise patternmentioned earlier. Surprisinglyquieter than I expected.Noise in MDA/STS/AM is at a highlevel and it hasaffected our recordings. ATM C&D pumps are quitenoisy and noise as it comes down throughairlock is amplified by the dome for megaphone effects. Gets fairlynoisy by the time it gets down toexperiment compartment. Can turn pumps off at night so it won' t interferewith sleep." SPT: "Noise is highin MDA and at ATM console.Find it getsto me when I am tryingto concentrate or trying to use the speaker. Noiseof pump in airlock used to get to me when work- ingin MDA." PLT: "Can hearergometer right now quite well and ATM pumps are quiteloud. All the pumps are loud. Rate gyros are loud."

d.Subjective Evaluation of Compartments: 3- 10

Location CDR SPT PLT

OWS Wardroom Very low in wardroom as Great, no problem Really not that it is in entire OWS un- bad less you'vegot the EREPI ATM cooling loop running; then the dome takes the noise as it comes down the air lock and serves as a great big megaphone andsends it down slightly amplified.

ows WMC OK, but a little noisy Great Ok withseparators going. Not uncomfortable at all.

OWS Sleep Area Excellent,very quiet. Fine Noisepropagates Walls anddoors pretty into sleep com- well damp outnoise partment when any- as well as light attenua- one else is doing tors. something.Can' t rest. There is no noisecontrol in vehicle.

OWS Expt. Compt Fine Yo comments Very good

OWS FwdDome Adequate. Just a little Yo comments Adequate. Ok, ex- bit noisier than exp. cept it is reasonably comp t . because closer high.There is to MDA/STS soundfocusing up in dome area becauseof spherical nature.

Airlock No ratinggiven. Ex- ITM/EREP coolant Fairly high tremely noisy.Cool- ?ump noiseprob- ant pumps are noisy. lem is way too ligh.Should locatepotential loisesources away frommetal galls thatcan act likean lcousticalcan. .~

3- 11

d.Subjective Evaluation of Compartments (Continued):

Location CDR SPT PLT MDA/ STS Unacceptable.Highly Way too high. Both tFairly high unacceptable,biggest pump and rate gyros offender is rate gyro make a racket. Af- ter a while, you can tuneout the noise but can't think as clearly in there.

3.6 ArticulationIndex (AI) Analyses - The articulation index(A.I.) is a generalcriterion applicable for judging the effectsof noise on communication. The AI predictsthe intel- ligibilityof speech (i.e., the percentage of wordsor sentences which arecorrectly understood) for a specifiednoise environment One method available to determine the AI, and utilized herein, is the'weighted-octave-band (WOB) method, as describedin Ref- erence 9. The intelligibilitycriteria applicable to the AI is described as follows:

An A.I. of . .. . Providescommunications ...... 0.7 to 1.0 Satisfactoryexcellent to

0.3 to 0.7 Slightly difficult to satisfactory; up to 98% ofsentences are heard correctly.

0.0 to 0.3 Impossibleto difficult; special vocabulariesand radio-telephone voiceprocedures are required.

Articulationindices .have been calculated for the SIA/ATM data (SL-4 mission),the MDA "487 data (SL-3 mission),and the OWS Experiment "487 data (SL-3 mission). The AI values com- paredthe Skylab mission data to two speechspectrums, one applicableto a moderatevoice and one to a raisedvoice. The AI values are indicated as follows:

I 3-12

\ -Speech Reference SIA/ATM MDA Exp.Area - "OWS

M odera te VoiceModerate 0.550 0.054 0.048

Ra ised VoiceRaised 0.150 0.723 0.186

Thesedata indicate that communications in the OWS area shall be satisfactoryto excellent, while communications in the SIA/ATM and MDA/STS areasmight be quite difficult. These preliminary AI estimates tend to supportthe crew comments as described in paragraph 3.5.

3.7 Flight Anomalies

On Mission Day 33, the SL-4 crew noticed a "loudwhine, not quite a squeal, but a whiningnoise", when theyturned on the pumps.The pilot, on Mission Day 34, performed some acoustic.measurementsto in- vestigatethis noise source.

A tabulation of the SPL's measuredduring the coolant loop noise investigation is indicated in Table 3.19 andincludes -measured and calculatedoverall SPL's in terms of dBA, calculatedoverall SPL's andthe measuredoctave band SPL's.

The AM SPL's compare closely with each other and are a maximum of 9 dB higherthan the acoustic criteria at 1000 Hz. The STS/ATM SIA SPL's exceed the criteria at 500 Hz by 6 dB, and by 5 dB at 1000 Hz. The MDA CSM hatch SPL's exceedthe criteria by 2 dB at 1000 Hz. The OWS experimentcompartment SPL's are a minimum of 10 dB belowthe acoustic criteria.

3.8 Conclusions

3.7.1"487 FliPht Data - The datameasured inthe OWS indicated thisarea to be the quietest region of theSkylab cluster. The OWS data were 5 to 10 dB belowthe acoustic criteria specification, ex- c luding the lJMC area, and generally enveloped the predicted SPL's . The STS measureddata indicated this region to be the noisiest of the Skylabcluster, which tended to support previously predicted SPL's. The STS acousticenvironment tended to influence the MDA and AM en- vironmentsto a significantdegree. Both STS measuredand predicted SPL's exceededthe acoustic criteria specification. The MDA measured acousticdataagreed closely with predicted SPL's, anddid not exceed the criteria. The only MDA noisesource of a problemnature was therate gyros. Rate gyroacoustic data tended to exceed the MDA fandata by 5 to 10 dB.

3.7.2 NoiseSource Data - The noisesource data obtained in the OWS indicatethat the refrigeration system SPL's are 5 to 10 dB higher thanthe VCS fan SPL's, butdo not exceed the acoustic criteria. The 3- 13

AM duct fan muffler noise source SPL's are quite high in the lowfrequency region,exceeding the criteria'by as much as 11 dB at 250 Hz. TheMole Sievecompressor noise source data are quite noisy at 500 Hz, exceeding the criteria at 500 Hz. The MDA noisesource data are dominatedby the rate gyro SPL's, which exceed the criteria by as much as 7 dB at 500 Hz. AT" Coolant Loop acoustic data was obtained during the SL-4 mission by the PLT crew member. Noticableincreases in the SPL occurredin the Aft Airlockand Forward Airlock locations, where increases as high as 12 dB at 1000 Hz were measuredwith the pumps operating.

3.9 Recommendations

a. The acousticenvironment in Skylab was notunlike that of earth living in that the crew was able to obtain "rest" periodsfrom thehigher level noisein the work area (MDA/STS). Future manned long term missionsshould address noise control in the early designstages. Consideration of absorption material and more efficient suppression of noisy equipment in confined spaces such as the AM and MDA/STS should be incorporated into future programs.

b.The intercomdesign must be improved to a.lleviate feedback problemsand improve communications.

c. Sleepareas should be better isolated from the rest ofthe crew quarters in terms ofnoise and other extraneous disturbances.

d.Updated acoustic criteria should be defined; similar to that indicated in Figure 3.1.However, these criteria should be more detailed,and be broken down into sleep, work,normal connnuni- cationsintermittent, etc., criteria-.In other words, one criteria cannot satisfactorily meet the requirements for all condit,ions,especially in a long-exposureorbital application.

Table3.1. Speech Interference Levels Due toIndividual NoiseSources at 5.0 PSIA

MDA/ STS NoiseSource AM. ows and Location PSIL MSIL PSIL MSIL PSIL MSIL

Fan Muffler Assemblies Located in MDA 52.2 52.5 49.0 49.. 2 32.2 32.4

Cabin Heat Exchanger Located in STS 52.2 48 .O44.7 49.0 32.3 27.9

Interconnect Fans Located in STS 46 .O 43.440.1 42.8 26.1 23.3

Teleprinter(Print Speed) Located in STS 56.4 54.9 53.2 51.6 36.5 34.8

Mole SieveFans Located in STS 57.1* 54.7 53 .8 51.4 37.2 34.6

Tape Recorder(Playback Mode) Located in STS 30.7 31.528.2 27.5 Not Avail. Not Avail.

OWS Cooling Module Located in AM 44.0 40.747.3 50.5 33.8 30.5

Refrigeration System Located in OWS 31.4 28.531.9 37.8 45.1 42.5

Focal Collector Located in OWS 29.7 26.5 33.1 36.1 43.5 40.5

* Exceeds noise criteria of PSIL = 56.7 dB or MSIL = 56.25 dB Table 3.1 (continued)

MDA/STS NoiseSource and Location PSIL MSIL PSIL AM MSIL 1 PSIL OWs MSIL Odor Fan Located in OWS 18.4 19.9 26.3 25.0 33.6 32.4

Suit Drying Station Located in OWS 24.6 26.2 32.6 31.2 40 .O 38.6 PortableFans (3) Located in OWS 30.3 29.6 44.1 42.9 44.1 43.6

Ergometer Located in OWS 51.1 47 .O 57 .55(53.7 61.0* 64.8*

M509 Thrusters Located in OWS 84.7*80.5* 86.9 90.8*98.2* 94.3* TO20 Thrusters Locatedin OWS 67.7* 71.9 74.2* 78.6* 81.5* 86 .O*

* Exceeds noise criteria of PSIL = 56.7 dB or MSIL = 56.25 dB 3- 17 and Experiment Lirt

A. Cmnd b Servico Hcdule D. Inetrurnt Unit E. (Continued)

1. IPS Lnline None 81. Force l4eeeurinl Unit 2. Runninl Lishte (8 place.) 82. Interior Lilhtm 3. Scimitar Antenna 83. Hain AcC.8. 4. Dockins Lilht E. Orbital WorkehoD 84. Heat Filter ?en 5. PitchControl Enginme 85. Ewrpncy Accmea 6. Crew Hatch 1. QIS Hatch 86. Portable Weter Bottle 7. PitchControl Encinee 2. VC8 Hixinl Chamber 6 Filter 87. Interior Lichee 8. lendezvouaWindw 3. vcs Duct IL 88. VCS Fen Clueter 9. EVA HandHold. 4. Storale Lockere 89. Iood Container 10. EVA Li#ht 5. vcs Duct 90. Food Container 11. Side Wind- 6. Therm1Shield 91. Coronagraph Container (Experiwnt 12. loll Enliturn (2 plecee) 7. o2 Preea.Supply Liru 1025) 13. LPS Radiator ?anelm (6 place.) 8. MteoroidShirld 92. Scientific Airlock 14. Sn RCS Hodule (4 place.) 9. WaterContainere (10 plecea) 93. W X-lhy SOL-Photo (Experirnt 1s. LCS lhdietor 10. ?ood Storase (2 plecee) s02 0) 11. Storale Lockere 94 * Sample Array Symtem Container 12. Preu.Reguletorefor H20 Supply 95. Water Wicroblolo~ical Control Equip. B. MutultiDle Dockina Adapter 1). 3o.p Peetrainte 96. Utility Outlet 14. Intorca Ba 97. Photorter System Container 1. Docking Tarlet 15. 8torileLockerr Front 6 Back @xperL.nt T027) 2. Experinat -12 Facility 16. SleepRoatraint IL 98. Foot Controlled Mneuverinl Unit -3. ECS metto Port 5 17. SleepRemtreint (Pxparhnnt ~020) 4. Vacuum Vent Panel 18. Experfnnt n131 Equip. stwale IIC 99. Autoutically Subflired !Uneurer- 5. Frame Electrical Umbilicel Container in8 Unit (Experirnt M09) 6. Spare ?an Container 19. Storage Iacker 100. Intercom Box 7. SpareLllht Container 20. PrivacyCurtain 101. Food Containarm - 8. FilmVault No. 1 -21. Lxperirnt Hl3l Rotatins Chair 9. ECS9. met Control CoNoh -10. Experirnt SOOU Cennieter 22. Stonla bt.r 11. Flight Dnta File 23. Dryiru Arm 12. SpeakerIntercom 24. WaehDiepoaal Airlock 13. AIW ChD COMOh 25. Tf Cutlet 14.Vault Film No. 4 26. Utility Outlet. 1. ApolloTeleecow llount 15.Vault Film No. 3 27. rod Heater -16. Experiment SO09 SupportStructure 28. ?ropored Winda 1. Colrnd Antenna 17. M hue. notor (UC) 29. Interem Box 2. Iolmtry AntanM -18. Area Fan (2 placer) 30. Storage Lockare 3. All4 Solar Array Wing No. 1 19. Film Vault No. 2 31. Solar Array Ammy. 4. AR( Solar Array Win8 No. 2 20. M Structuro (AM) 32. Storale Cobirute 5. ATM Solar Array Viol No. 3 21. C9Abembere and Wim 33. Ion Source Shield 6. Cwnd Ante- 22. Dockina ?ort No. 3 94. Utility Outlet ?. Am Solar Array Wing No. 4 23. Experiwnt SO65 I)35. Refril./?reocer 8. Telmtry AntenM 24. Experimnt 9101 leeupply 36. Fire Extinlulaher 9. Charlac Batteryblulator Module 25. LxperirntSlOl 37. Food, Water Heeter L ChillerTable (6 placer) 26. lunnins Lllht (4 place.) 38. Cravlty Work Bench 10. Control motcfo (3 place.) 27. External Duct ;It 39. Lrlouter 11. ARI lhck 28. Vacuum VentConruetion forLxperfnnt 40. me AM1Jrar 12. CIG Inwetor No. 3 xs 12 41. Intercom Box 13. Cenieter 42. m1-t B= 14. AS= Aperture Door (Experbent 43. . Kxperirnt Support Syetn SO%) C.nodule Airlock 45. Carer Body?rer.D.vlee Nelativo 15. NRL-A FilmRetrieval Door 4). CWS Control 6 Dieplay Coamole (Expmrirnt SWU) 1. Windm (4 placer) 46. Interem Box 16. HE-2 Amrture Door .rC 2. nolecular Siwea (2 placer) 47. loteting Chnir 17. 3. Dimcone Antencam (2 placee) 48. PCB Duct 4. Thernl Bleakat 49. Crotch Aru 18. 5. 4 Tanke (6 pluee) SO. IlrteaoidIhiold lW2B) 6. Cabin ?rere. Relief Val- Sl. IharulShield 19. RL-A Aparturr Ooor (Cxperhnt Suft Storas.7. Suft Si. lunniq Lilht (4 pI.caa) SOSU) 8. Bio-Hod Cable SS. Weete Stores. Tank 20. HCO-A Aperture Dmr (Expriunt 9. Suit st or.^. S. AXS Ihruetere 805U) 10. Undefined Stmale Vol. SS. WteoroidShield 21. Fine Sun 8aruor Apartura Door 11. Cewra Equip. Itore#* 56. haeh Diapomal Separation &?no 22. Acquiaition Sun Sovorm 12. ITS cm ran01 57. An9 CN2.Spherer(15 place.) 23. Ho-1 Aparturo Door 13. 7MFilm Storela fa. Xunninl Lilht (4 place.) 24. HA0 Aporture Door (Experirnt SOS2) 14. Forward Airlock ktch S9. Solar Array Panel. 2s. CSrC Apertura Door (Lxperirnt 15. Tape Recorder 60. Acquimitioa Lilht S056) 16. Spar. PreeeureControl Unit 61. InteriorLilht 17. NA/IVA Umbilicele -62. IdStorale heermr 18. Am CooparWnt Control ?a~l 63. LLb Motion hey. Containor -19. HeatExchangere U. Hicrobiolo~ieelSpecimn heecer 20. Lilht Ammy. -65. Iody Mreurmont mici 21. A?I Airlock Hatch 66. Force WuuriryUnit 22. Lock Capartmnt EVA ?male -67. hopwed VC8 Duct 23. Runnhl Lilhtl (4 plaC..) M. Spare. Container 24. N2 Tanka (5 pluee) 69. Aatro Aide Container 25. EVA/IVA U.bilicalm 70. InteriorLilhta 26. %IN2 Panel 71.Airlock &ientific -27. Iuit HoduleCoolin& 72. Dnta 9yetn 28. Fermnent Storal. 73. Force Wuurlnl Unit 74. VCS Fan Cluater 7% Food Container 76. Intorca Box 77. Suit Containor 78. Lmrlency Acceee 79. W Stellar Artroo- Conteim 80. N2 Tank# (3 place.) ~PPIoII nm>+ ?wt Controlled Hamursring Unit m3 snfllgbt Aerosol An8IJmi.a To27 conteplinsticm Merrsuremnt TO13 Crew Vehicle Disturbances TO18 Precision Orbital Tracking n5= MaterIa3.a Rocerring irr Spsca a79 Zero Gravity Flaumblllty m74* Spechen Mass Xeasyr8ment.a ~131+ Hman Vestibular EFunctlon n133* Sleep norritorirrg Exper-nt ~151 Tima and Motion Study nip+ Body MBss Measurement x113 Blood Volme and Red Cell Liie Span Mill Cytogonetlc Studies of Blood MlI.2 Man'r Iasnurlty - Inviro Aspocta Hll4 Red Blood Cells Hog1 Ro-&Poet-Flight ISNP m1 Mineral Balance m73 Bioassay of Body Fluids -3 vectorcsrdiogFslr ~171* Xetabelic Activity Do21 gxpardsble Airlock Tschnobgy Do24 !rh.rPsl Control coatlngm Soog Huchar BmrIdon sol9 w Stellar Ibtroncmy (End 1- spec.) so63 UV Airglow Horizon Photogrsphr w* InfUght ImP M5W btrorrsut Maneuvering Equimnt Galactic x-Ray napplna S149 Fkrticla Collection 5020 X--/UV SO- phatogrcrphy Slgo Multispuctral photographic Facility s191 Infrd Spectramtsr SI92 II) Bard MultLpectral Sourcer SI93 Micravsvs Radiamebr m25 Coronagraph Contamlnatlam Memauement I!= Experiaunt Support-Symh ERGP Resourcer ExperWnt EXT TV External Television M4 15 Thermal ControlCoatings M487 Habitabillty/Crew Quarters Proton Spec Proton Spec SO7 3 Gegan8chein/Zodiacal Light S183 Ultra Violet Panorama S194 tBand Radiometer s195 Earth Terrain Camera TO02 Manual NavigationsSighting8

*Experiments Having Identified Noise Sources U

Table 3.4 - Noise Sources Located inMDA

Number of Location Shown Frequency of Sound Power Noise Source Noise Sources in Figure Operation ;eve 1 Estimates

MDA Fan Muffler Assembly 3.2,3.3 Continuous Table 3.7 SO09 Experiment: Nuclear Emulsion 3.3 Intermittent N/A Portable Vacuum Cleaner * "- Intermittent Table 3.11

S190 Experiment: Multispectral Photographic Facility 3.2 Intermittent N/A

S191 Experiment: Infrared Spectrometer 3.2 Intermittent N/A

S192 Experiment: 10 Band Multispectral Sources 3.3 Intermittent N/A

!; operates in AM/STS andOWS also Table 3.5 - NoiseSources Located in AM/STS

Number of Location Shown Frequencyof Sound Power 1 NoiseSource r NoiseSources in Figure Operation Level Estimates OWS Cooling Module 1 (4 fans) 3.5 Continuous Table3.10

CabinHeat Exchanger (CHE" 1 3.2,3.5 Continuous Table3.9

Interconnect Duct Fan/Muf f ler 1 3.3,3.4 Continuous Table3.9

CondensingHeat

Exchanger Module 2 """ Continuous Table 3.8

Teleprinter 3.3,3.4 Intermit tent Table3.8

Tape Recorder 3.5 Intermittent Table 3.8

Portable Vacuum Cleaner * ""- Intermittent Table3.11

* portable vacuum cleaner also operates in MDA and OWS Table3.6 - NoiseSources Located in OWS

Number of Location Shown Frequency of SoundPower NoiseSource NoiseSources in Figure Opera tion Level Estimates Ventilation Control Sys tem (VCS) Fan Cluster 3.6,3.7,3.8 Continuous Table 3.11

RefrigerationSystem 3.8,3.10 Continuous Table 3.11

PortableFans -" Continuousor Table3.11 Intermittent

Odor Fan 3.6,3.8 Intermittent Table3.11

Fecal Collector 3.6,3.10 Intermittent Table3.11

Suit Drying Station 3.7,3.8 Intermittent Table3.11

Portable Vacuum Cleaner * 1 "- Intermittent Table 3.11 Experiment M509: Nozzles-Astronaut Maneuvering Unit 1 3.6,3.7 Intermittent Table3.12

Experiment TO20 : Nozzles-Foot Controlled Maneuvering Unit 1 3.6,3.7 Intermit tent Table 3.13 Experiment M17 1: Ergometer 1 3.6,3.9 Intermit tent Table 3.10

* portable vacuum cleaner may be operated in MISTS and MDA Table3.6 - NoiseSources Located in OWS (continued)

~~~ Number of Location Shown Frequency of SoundPower NoiseSource NoiseSources in Figure Operation Leve 1 Estimates

Experiment M131: Revolving Chair 1 3.6,3.9 Intermittent N/A

Experiment M074: Specimen Mass Measure- ments 1 3.6,3.10 Intermittent N/A

Experiment M172 : Body Mass Measurements 1 3.8 Intermit tent N/A

3-25 Interconnect Duct Fan1

Teleprinter (Mole Sieve Fans)'

Figure 3.4 Location of AM/STS NoiseSources 3- 26

/-Cabin Heat Exchanger Module

Recorder Module

- (IWS Cooling Module

Figure 3.5 Location of AM/STS NoiseSources SATURN WORKSHOP

Figure 3.6 Location of OWS Noise Sources VCS Fan

Figure 3.7 Location of h’oise Sources in OWS Forward Compartment -

3-29

Refrigeration System

suit Drying Fan

Figure 3.8 Location of Nois.:! Sources in OWS Forward Compartment 3- 30

M131 Revolving

Figure 3.9 Location of ?bise Sources In ExTerfment Compartment 3-31

M0747; 3-32

3*7 MDA NoiseSource Power Levels

OCTAVE BAND FAN MUFFLER ASSEMBJ,Y FREQUENCY CRITERIA (3 FANS) (HERTZ PWL (DR)

62.5 64.8 1. 125 69.8 250 74.8 500 69.8 1000 69.8 2000 72.8 4000 72.8 8000 69.8 Table 3.8 MDA/STS Noise Source Power Levels 14.7 PSIAAtmosphere

I OCTAVE * TELEPRINTER CABIN HEAT EXCHANGERMODULE BAND PRINT I SLEW . FREQUENCY SPEED SPEED ONE FAN 3 FANS (HERTZ) (dB) (dB) (dB) (dB) 125 5.3 6 63.9 59.1 45.4 250 73.1 68.4 65.8 52.8 500 85.4 78.1 70.3 75.0 1000 78.3 86 .O 73.3 68.5 w 2000 77.0 85.3 67.2 72.0 I w 4000 60.9 56.1 84.2 76.5 w 8000 56.3 51.5 80.2 72.5

OCTAVE II I BAND CONDENSINGEXCHANGER.HEAT I TAPE RE DER FREQUENCY 11 12.1MODE VOLT I PLAYBACK RECORD (HERTZ) MODE (dB)

125 - 41.4 42.2 250 (82.3) 47.9 46.2 500 76.5 50.7 40.0 1000 79.5 51.5 44.9 2000 76.6 46.2 44.6 4000 73.7 53.4 53.0 8000 75.7 51.7 50.5 II Ii Table 3 09 MDA/STS Noise Source.Power Levels 5.0 PSIAAtmosphere

Y r OCTAVE TELEPRINTER CABIN HEAT EXCIWGER MODULE INTERCONNECTFANDUCT BAND PRINT SLEW FREQUENCY SPEED SPEED FAN ONE THREE FANS ONE FAN (dB) (dB) (dB) (dB) (dB) (dB) (dB) (dB)(HERTZ) (dB)

125 49.3 125 " 64.3 69.0 250 51.9 250 70.8 60.364.1 75.5 500 76.0 500 71.7 65.785.9 76.5 1000 68.5 75.7 66.484.3 73.2 2000 73.8 2000 58.4 62.180.9 63.2 4000 69.9 4000 50.0 55.176.8 54.8 8000 65.0 8000 45.0 53.773.3 49.8

w I w OCTAVE CONDENSINGEXCHANGER HEAT TAPE RECORDER .P BAND FREQUENCY 12.1 VOLT MODE MODERECORD MODE PLAY BACK (dB) (dB)(HERTZ) (dB) (dB)

125 42.2 " 41.4 250 70.2 47.9 46.2 47.9 70.2 250 500 72.5 500 50.7 40.0 1000 44.9 75.4 51.5 2000 70.5 46.2 44.6 4000 64.0 53.0 53.4 8000 50.5 69.7 51.7 3-35

Table 3 ,lo AM Noise Source Power Levels in Decibels

OCTAVE OWS COOLING MODULE BAND (4 FANS) FREQUENCY (HERTZ) 14.7 PSIA 5.0 PSIA

125 60.5 " 25072.7 70.0 50067.7 66.3 100067.5 67.5 200062.8 64.7 400053.7 60.7 800048.2 55.3 Table 3.11 OWS Noise SourcePower Levels (PWL's) 14.7 PSIAAtmosphere r 1 -a

OCTAVE PORTABLEFANS *ODOR FECAL COLLECTOR VCS FAN CLUSTERS BAND FAN BLWR, +1 SEPARATOR 1 CLUSTER 3 CLUSTERS F REQUENCY 1 FAN 3 FANS (HEXTZ) (dB) (dB) (dB) (dB) (dB) (dB)

63 65.7 70.5 67 .O 64.0 73.0 68.2 125 67.562.7 67.0 65.0 75.5 70.7 250 70.565.7 67.0 67 .O 78.0 73.2 500 72.067.2 69.0 64.0 70.7 75.5 1000 76.0 66.2 71.0 2000 65.260.2 65.070.0 1 !%; 60.0 58.7 63.5 4000 62.7 67.5 54 .o 57 .o 55.2' 60.0 8000 57.552.7 52.0 50.0 52.2 57 .0 L

OCTAVE REFRIG. SUIT DRYING PORTABLE VACUUM * SIIOWER M171 ' BAND SYSTEM STATION CLFMER (PLYS UN- ERGOMETER FREQUENCY KNo\ms 1 4- (HERTZ) (dB) (dB) (dB) (dB) .(dB)

63 64.0 " " 72.6 "- 125 54.0 54.5 (72.0) 72.0 86.3 250 53.0 69.0 81.0 81.0 92.6 500 66.0 67.0 80.0 80.0 93.4 1000 55.0 63.5 77.0 87.0 93.1 2000 53.0 58.0 72.0 86.0 82.6 4000 44.0 60.0 72.0 83.4 75.1 8000 46 .O 55.5 69.0 73 .o 69.4 Table 3.12 Experiment M509 Nozzles Sound Power Levels at 5.0 PSIAAmbient Pressure

OCTAVE BAND OCTAVE BAND SOUND POWER LEVEL, dB CENTER 2..35 PO~"-q 2.15 POUNDS 1 1.25 POUNDS 1 MULTI-NOZZLE FREQUENCY, THRUSTNOZZLE THRUST NOZZLE CONFIGURATION- HERTZ I I THRUST I 15.8 FOUND THRUST I

~ ~~ ~ ~~~~ ~ ~~ ~ ~~~~~ ~~~ ~ w 125 (88) (81.4) (8 1) "" (90 -6) w 250 97 05 90 04 90 83 -7 100 .1 500 107.4 99 -8 99 -4 92.9 109.8 1000 116.2 109 .4 109 .o 102.6 .118.9 2000 125 9 118.6 118.2 128.4 111.8 4000 131.8 126.5 126.1 121.3 135.4 8000 136.5 131.6 131.2 140.4 127.1 Table 3.13 Experiment TO20 Nozzles Sound PowerLevels

~~ ~~ ~ ~~~~ ~ ~~_____~~~~ ~ ~ ~~~~ ~~ OCTAVE BAND SOUND POWER LEVEL dB OCTAVE BAND 5.0 PSIA AMBIENT PRESSURE 14.7 PSIA AMBIENT PRESSURE CENTER 1.3 POUNDS 1 .O POUNDS 0,3 POUNDS 1.3 P0UM)S lT0 POUNDS . 0.3 POUNDS FREQUENCY, HZ THRUST THRUST THRUST THRUST THRUST THRUST

250 83.7 81.9 67.9 70 .O 68.8 59.9 500 93 .8 78.9 92.9 82.6 82.O 69 .O 1000 102.3 102.1 88 .O 92.5 91.8 77 .5 2000 .O 99.2 112.9 102.5113 102.1 89.4 40 00 121.5 108.5 120.8 112.1 111.4 99 *7 8000 128 .7 117.8 127.8 120 .o 120 .o 110 .o w w 16000 13 5 .O 133.3 123.4 125.5 127 .O 116.8 03 3 1500 140.1* 131.1* 138.9* 133.5* 133.5* 120 .o*

*One-thirdoctave band data at 40,000 Hertz was extrapolatedand used in 31500 Hertz octave band estimate. Table 3.14 Equivalent A-Weighted Sound Levels Caused by Individual Noise Sourcesat 5.0 PSIA

NOISE SOURCE NOISE SOURCE EIGHTED SOU 1 LEVEL dBA LOCATION AM ows

MDA Fans (3) MDA 59.7 56.4 39.4

Cabin Heat Exchanger Module (3 Fans) STS 58.2 55.0 OWS Int. Conn. Duct Fan STS 50.8 47.6 Mole Sieve Fane(2) STS 62.7 59.4 Teleprinter (Print) ST,S 61.3 58.0

I Tape Recorder (Plybk) STS 39.0 35.3

OWS ' Cooling Module(4 Fans) AM 49.9 55.8 39.2 VCS Fan Clusters(3) ows 37.7 44.1 51.5 w w Refrigeration System ows 20.5 27.0 34.5 u) Portable Fans (3) ows 36.0 42.9 52.0 Odor Fan ows 26.4 32.9 40.3 Fecal Collector ows 38.5 44.6 51.9 Suit Drying Station ows 33.3 39.5 46.8 Portable Vacuum Cleaner ows 43.3 49.7 57.1 Shover ows 52.5 59.1 66.4 Ergometer ows 57.1 63.4 70.8 M509 Nozzles (15.86) ows 102.0 108.4 115.8 TO20 Nozzles (2.6#) ows 91.9 99.1 106 .5 3-40

Table3.15 Skylab Acoustical Compartment Characteristics

Compartment/Equip.

MDA STS 301 ft3 AM .293.5 ft3 ows 8000 ft3 MDAISTS Equip. 160 ft3

MDA/ STS To ta 1 1300 ft3

Compartment/Equip. SurfaceArea

MDA 549 ft2 ST S AM 217175.9 ft $t2 ows 4895 ft2 MDA/STS Equip. 600 ft2

Compartment Common Wall Interface SurfaceArea

STSIAM 23 ft2 AMIOWS 8.9 ft2 3-41

10 I

10 100 1000 10K Frequency - Hertz

Figure 3.11 Estimated MDA/STS Reverberation Times at Atmospheric Pressures of 14.7 and 5.0 3-42

10 100 1000 1OK Frequtncy - Hertz

Figure 3.12 Estimated AN Reverberation Times at Atmospheric Pressures of 14.7 and 5.0 PSIA 3-43

.10

10 100 Frequency - Hertz

Figure 3.13 - Estimated OWS Reverberation Times at Atmospheric Pressure of 14.7 and 5.0 PSIA Ill - +x

i-X

Figure 3.14 MEASUREMENT LOCATIONS IN THE OWS AFT COMPARTMENT 3-45

-X

Figure 3.15 MEASUREMENT LOCATION IN THE OWS FORWARD COMPARTMENT

I 3-45

I-x

Figure 3.16 MEASURj2MEKC LOCATION IN THE STS/AM 3-47

i-x

Figure 3.17 MEASUREMENT LOCATION IN THE MDA Table 3.16 SKYLAB INTERIOR NOISE SOURCE SPL's MEASURED DURING SL-3 MISSION

Octave Band CenterFrequencies in Hertz Overall Overall SPL - - - - - SPL in in dB -1000 -2000 -4000 -8000 -16000 Loca tion/Description dBA :Calculated) 7% (dB) *- (dB) (dB) (dB) (dB) !leas ' d. - Ca LC, ------MDA Rate Gyro 72 .O 66.5 69.5 61.0 59.5 67 .O 60.5 57.5 50 .O 49.5 42 .O

MDA Fan No. 1 66 .O 58.3 62.2 58 .O 56 .O 55 .O 54.0 51 .o 45.0 41 .O 29 .O

MDA Fan No. 2 67 .O 59.7 64.3 60 .O 57 .O 58 .O 55.0 50 .O 48 .O 45.0 34.0

MDA CSM Fan 67 .O 57.5 63.7 61.0 56.0 56 .O 52 .O 49 .O 43 .O 41 .O 28 .O

STS Circ. Fans 71.0 63.6 70.1 67 .O 62 .O 64.5 57 .O 50 .O 45.5 45.5 35.0

Mole SieveCompressors 75.5 70.5 73.2 56.0 61.0 72 .O 60 .O 59 .O 62 .O - -

STS Panels 71.O 65.8 70.5 65.0 60 .O 68 .O 57 .O 52 .'O 45.0 43 .O 33 .O

AM Duct Fan/Muffler 61.0 57.3 60.7 52 .O 52 .O 58.5 34 .O 50 .O 44.5 44.5 35.3

ows cod. Module (AM) 77 .O 65.1 75.4 73.0 71.0 61.O 55 .O 48 .O 42 .O 40 .O 30 .O (all 4fans operating

OWS Refrig. System 63.5 57.3 62.7 59.0 50.5 .59.0 51.O 42 .O 34 .O 32 .O 22 .o

OWS VCS DuctFans 56.5 49.0 52.5 45.0 46 .O 48 .O 45.0 39 .O 29.0 32 .O 24.0 h - - - - -

* Data is questionable,since all values exceed calculated O.A. SpL's

u I Ln 0

loo 1w FREaEKY - HERTZ

.. 20 50 100 1000 10K 50 100 1000 1OX

Figure 3.21 Cornparkon of Measured Acoustic Levels in Skylab. 3- 53

Table 3.17 SPEECHINTERFERENCE LEVELS APPLICABLE TO SL- 2, SL- 3, AND SL-4“487 MEASURED FLIGHT DATA

- -. -. . , - -. - - -. - - ” .. .

Location SL- 2 SL- 3 SL- 4 Noise Criteria (dB) (dB) (dB) (dB) - -___ MDA 47.2 53 .O 52.8 56.7

ST S 55.8 58.3 ” 56.7 AM 51.3 52.7 55.7 56.7 OWS Wdrm. 40.5 41.0 37.7 56.7 OWS Exp. 41.7 42.2 46.6 56.7 ows WMC 43.8 55.5 -- 56.7 OWS Sleep 38.3 34.3 33 .O 56.7 OWS Fwd 40.7 44.5 44.0 56.7

Table 3.18 MODIFIED SPEECHINTERFERENCE LEVELS APPLICABLE TO SL-2,SL-3, AND SL-4“487 MEASURED FLIGHT DATA

. ~ 4

Location SL- 2 SL- 3 SL- 4 Noise Criteria (dB) (dB) (dB) (dB)

~~ ~__ MDA 44.6 51.4 50.4 56.25

STS 51.3 55.5 ” 56.25 AM 47.5 50.3 52.3 56.25 OWS Wdrm. 35.8 36.8 34.3 56.25 OWS Exp. 36.1 37.9 42.7 56.25

ows mc 37.9 48.4 ” 56.25 OWS Sleep 33.3 31.0 28.6 56.25 OWS Fwd. 42 .O 40.6 40.6 56.25

~~ -- . .. ~~ ~_____ 3*19 SKYLAB INTERIOR SPL' s MEASURED DURING COOLANT LOOP NOISE INVESTIGATION - SL-4.

Overall Overall SPL Octave Band Center Frequencies in Hertz SPL in in dB - - 500 1000 2000 4000 Loca tion/kscription dBA (Calculated) - - - -7% (dB) (dB) (dB) (dB) Meas'd. -Ca lc. - -AU Pugp-Og : .tc Exp. Compt. (A) 52 .O 49.1 53.1 42 .O 43 .O 47 .O 49.0 45.0 36 .O 29.0 23.0 e Exp.Compt. (B) 55 .O 47.8 52.4 41 .O 44.0 46 .O 49.0 41.0 35 .O 31.0 26.0

CSM Hatch 59.5 60.2 65.2 55.0 59.5 60 .O 57.0 57.0 49 .O 45 .O 40 .O ATM SIA 64 .O 68.1 69.1 56 .O 62 .O 60 .O 66.0 60.0 52 .O 45.0 42 .O AM Aft Airlock 63 .O 65.1 70.4 63 .O 64 .O 65 .O 60.0 63.0 53 .O 45.0 38 .O AM Fwd Air lock 68 .O -66 .O 70.1 -65.0 -61.0 -60.0 63.0 64.0 52 .O 50 .O -41.0 -Aa puEp-O&fi Exp. Cornpt . 55 .O 47.6 51.9 41.0 44.0 45 .O 48.0 43.0 34.0 28 .O 22 .o CSM Hatch 60 .O 55.6 61.7 52 .O 60 .O - - .52.0 50 .O 45 .O 41.0

ATM SIA 64 .O 62.9 68.8 59 .O 64.0 61.0 64.0 55.0 52 .O 45 .O 42 .O

AM Aft Air lock 60 .O 60 .O 68.8 62 .O 65.0 63 .O 56.0 55.0 48 .O 43 .O 36 .O

I All Fwd Air lock 60 .O 60 .O 68.1 65.0 60 .O 59 .O 52.0 61.0-49 .O 43.0 -40.0

* >:NOTE: EXPERIMENT COMPARTMENT (A) AND (B) SPL'S ARE APPLICABLE TO BEGINNING AND END OFMEASUREMENT ACQUISITION TIME PERIOD. 4- 1

4.0 GENERALTEST PROGRAM

The purposeof this section is topresent the experience and knowledge gainedfrom the Skylab Vibro-Acoustic Test Program. Includedin this section are descriptionsof test hardware, test setup,instrumentation requirementsand data acquisition requirements. Each major test phase was evaluated and constructive criticism is supplied in a form that may be helpful in future test programs.

4.1 VibroAcoustic Test Overview

The vibro acoustic test programwhich was performedon the Skylab Structural Model Vehicle included the Orbital WorkshopLaunch Confi- guration,Payload Launch Configurationand Payload Orbital Configuration Test Series.Separate Acoustic and Vibration Tests were conductedon these test configurations primarily to verify major stmcture and/or verify the analytical model. 4.1.1 InitialTesting Plan andRevisions - The initial test plan requiredacoustic and low frequency,vibration tests on the Orbital Workshop, as well as, Acoustic,Vehicle Dynamics, and modal survey vibration tests on thePayload Assembly (PA) Launch Configuration. A modal survey vibration test of the payload assembly orbital configuration was alsorequired in the initial test plan.This test plan was later revisedto include an Instrumentation Unit (IU) Acoustic Test and the ATM/CMG AcousticQualification Test for the Apollo Telescope mount.

4.1.2 VibroAcoustic Test Objectives - The vibroacoustic test objectives were dividedinto three phases. Phase I Beingthe Orbital Workship Tests; Phase I1 beingthe Payload Assembly Tests; andPhase I11 being the instrumentation unit and Apollo Telescope Mount Acoustic Tests. The objectivesof the Phase I Tests were as follows:

a. Verifystructural integrity of primaryand secondary structure when exposed to dynamicenvironments.

b, Verify dynamic designand test criteria for componentsand subassemblies.

c. Obtainmodal response data for analytical model verification.

The PayloadAssembly Tests, Phase I1 Objectives were as follows:

a. VerifyStructural Integrity of the Payload Assembly tothe Dynamic Environment

b. QualityFlight HardwareComponents

c.Obtain modal response data for an analytical model verification 4- 2

d. Verify Dynamic Design and Test Criteria for components and sub-assemblies

The objectives of the PhaseI11 tests were as follows:

a. Verify IU Dynamic Behavior

b. 'Verify Dynamic Design and Test Criteria for Components and Sub-assemblies

c. Verify Prototype FCC (IU) response characteristics

d. Full dynamic qualification of the ATM/CMG

4.1.3 - Generalization of Test Accomplishments - All the Test Objectives were accomplished for the PhaseI, Orbital Workshop Tests. One component was qualified as a resultof tests, with no requalification tests required.

The Phase IIA, Payload Assembly Launch Configuration Tests, accomplished all test objectives. This phase qualified four components' with the requirement for six requalification tests.It also established the requirement for additional IU Acoustic Tests and additional ATM/CMG Acoustic Qualification Tests (Phase111).

The Phase I1B, Payload Assembly Orbital Configuration Tests, accomplished all Test Objectives. Twenty-five unique test modes were acquired, which represent all identifiable major structural resonances in the zeroto twenty hertz frequency range. These twenty-five test modes were determined to be comprisedof nine major components. The quality of the test modes were excellent with only one mode exhibiting poor orthogonality characteristics.

All test objectives were accomplished €or the Phase 111, IU and Apollo Telescope Mount Acoustic Tests.The CMG was requalified due to tests and twenty-three requalification test were required forIU the components.

4.1.4 Test Anomolies and Criteria Surmnary- There were no test anomalies in the PhaseI Tests. Six levels of environmental sub zones were raised, thirty-three were lowered and fourteen remained unchanged. Forty-seven additional environmental sub zones were addedfc special component criteria.

In the Phase A,I1 Payload Assembly Tests a decision was reached to conduct additionalIU Acoustic Tests due to a ST-124 exceedance and a FCC excedance.

The Dynamic criteria assement for the major components of the Launch Configuration Payload Assembly were as follows: 4- 3

MDA

a. Delete sinusoidal evaluation criteria, all zones

b. Change weight specification for 2 environmental sub zones

c. Add 9 new environmental sub zones

AM (Including PS, DA, and FAS)

a. Raise 11 environmental sub zones

b. Add 3 new environmental sub zones

c. Special environmental criteria for 7 components

a. Acoustic criteria increased by a factorof2 db on the power spectral density (70-2000HZ range)

ATM

a. Raise 2 environmental sub zones 4.2 Phase.lII A Payload Assembly Launch Configuration Tests Acoustic and Vibration Tests were conducted on the Skylab Payload Assembly from 08 September through 08 October 1971. The Test Program for the Launch Configuration was comprised of the following major activities :

Payload Assembly- Lift-off Acoustic Environment Payload Assembly - Boundary Layer Acoustic Environment Acoustic Absorption Test IU Acoustic Test IU Modal Survey

4.2.1 Acoustic Tests

4.2.1.1 Test Requirements - The following conditions are sum- marized from the Acoustic Test Plan,S + E-ASTN-ADD-71-69

4.2.1.1.1 Test Objectives - The primary test objectivesof the Payload Assembly Test Program wereto:

a. Verify the structural integrity of the assembly

b. Verify the dynamic design and test criteria for components and sub-assemblies

c. Qualify flight hardware components 4- 4

4.2.1.1.2 Specimen Configuration - The test specimen consists of an Instrument Unit, Fixed Airlock Shroud, Payload Shroud. Airlock Module, Multiple Docking Adapter, Apollo Telescope Mount, and Deploy- ment Assembly. These items were assembledon an s-IV B OWS/Forward Skirt and Tank Dome Assembly as shown in Figure4.1. Flight type components which were installed during the acoustic tests and denoted in figures4.2, 4.3, and 4.4 are asfollows:

a. PLV Fan Motor Assembly located in the Cabin Head Exchanger Module of the STS.

b. Film Vaults 3 and4 located in theMDA.

c. H a 1 Camera located in Film Vault4 of the MDA.

d. AS & E Camera located in Film Vault3 of the MDA.

e. SO56 Experiment Camera located in Film Vault 3 of the MDA.

f. PLV Fan Motor and Muffler Assembly located in the Cone Section of the MDA.

All other components and assemblies were either prototype or mass simulated models.

4.2.1.1.3 Facilities Description- All the tests described in this document were conducted in the acoustic test facility, building 49, Manned Spacecraft Center, Houston, Texas. The test specimen was located in a reverberation chamber with a volume of approximately 169,000 cubic feet as shown in the sketch in 4.5. Figure

4.2.1.1.5 Control and Data Systems- The acoustic test spectra were controlled byan automatic closed loop system capableof adjusting the test environment to within_+ 2 db of prescribed values. Simulation limitations inherent in environmental acoustic testing were minimized by use of vibroascoustic transfer functions which were derived and used to adjust spectraso that selected test article responses in the OWS and IU would correlate with available flight data. Simplified block diagrams of the Acoustic Excitation/Control and Data Acquisition System are presented in Figures4.6 and 4.7.

4.2.1.2 Test Summary - The Acoustic Testing, conducted in the NAW reverberent chamber, consistedof exposing thePA Test Article to both lift off and aerodynamic environments for a prescribed time. A Test Summary is presented in Table 4.1, which is a chronological listing of the Test Sequence, run number, description, Test reference, Test parameters, duration, data, overallSPL, data reference and remarks.

4.2.1.2.1 Test Procedure - The performance of each acoustic exposure, identified in Table4-1 by run no.'s PA-A-002, 003,006, 009, 010, 011, 012,040, 041, 043, 044, and 045 was implemented by following the steps described in the detailed test procedure, DTP-SKY-7. 4- 5

Table4-1 run no.'s PA-A-046 and 047 sinewavesweeps were performed as required by reference 11.

4.2.1.2.2 Instrumentation - A total of 360measurements, consisting of 285 accelerometers, 43 microphones,and 32 strain gages, were recorded duringtesting. The dataacquisition system provided capabilities for recording 264 channels;therefore, a secondrun at each test condition with a repatchof 96 channels was required to obtain data from all 360 measurements.

No test was started with more than three data sensors in an inopera- tive condition. The test spectra were controlledto 10 surface mounted microphones.

The indicatedtotal accounts for all instrumentationlocations changes andadditions as described in the Volume I InstrumentationPlan, ED-2002-1255, Revision A, dated 31 December 1976.

4.2.1.2.3 Data Summary - Data from theacoustic test canbe found inreferences (12), and (13). Datanot presented in these references are availablefrom stored magnetic tapes. Measurement number versus run numberand recorder channel number information are presented in Table I1 of the instrumentation plan noted in 4.2.1.2.2.

4.2.1.2.4 Test Description - The followingcontains summaries of Test Problem Areas andsolutions to these problems. In addition, circumstancesresponsible for aborted test runs are tabulated by nature of error and frequency of occurrence.

PROBLEM: Lackof Acoustic Power in HighFrequency bands (above 500 Hz)

CORRECTION: Air modulator/HornConfigurations were changed to to EPT-200 modulators, which have greater acoustic outputin the upper frequency range.

PROBLEM: Data from PA-002 and PA-003 indicatedthat vibration inputs to the IU Componentswould exceed specification levels if the full lift-off spectrum was applied to the Test Article.

CORRECTION: An additional Low Level Test was run. A review of the data resulted in a decis.ion to use an alternate lift-off spectrum which was based on the IU Data alone,since transfer functions computedfrom the S-IV B forwardskirt measurements exhibited signifi- cantdeviations from corresponding flight measurements. 4- 6

WOLLO TELESCOP

MULTIPLE DOCKING

DEPLOYMENT ASSEMBLY

PAYLOAD SHROUD STRUCTURAL TRANSITION

SECTION +z 11

02 TANKS (TYF' FIXED AIRLOCK

INSTRUMENT.- " UNIT

-X

-__"" " ." . " Figure 4.1 - Payload Assembly Test Article Launch_" Configuration.- 4- 7

CP.BIN HEAT EXCHANGER MODyLE, VENTILATION DUCTS TO MDA XPLV Fan Motor Internal)

MOLECULAR ATM TANK MODULE F'LRMANENT STOWAGE FLIGHT SPARE STOWAGE CON-

-I CONDENSATE:

HZ0 TANK MODULE

STS IVA STATION TAPE RECORDER MODULE ATM FILM TREE SUPPORT PORTABLE TIMER AND ASSOCIATED BATTERIES CABIN PRESSURE RELIEF VALVE UMBILICAL END STOWAGE EVA HATCH EVA PANEL NO. 1 LSUSTOWAGE (310) CENTER INSTRUMENT

EVA PANEL NO. 2 LSU STOWAGE (31 1) 10 WATT LIGHT AFT INSTRUMENT PANEL HANDRAIL ASSY 1 MUFFLER ASSY FOR CROSSOVER DUCT TO OWS OWS(HINGED) MODULE

Figure 4.2 Payload AssemblyTest - Airlock Module

t ~~~ ~~ 4.3 PayloadAssembly Test-Multiple Docking-Adapter, -Y S ection ~- I

Figure 4.4 Payload Assembly Test-Multiple ‘DockingAdapter, +Y Section rSPACECRAF'T ACOUSTIC LABORATORY

-REVERBERANT CHAMBCF

-ACOUSTIC SEAL - (1/2" ALUMINUM PLATE: WITH DUCT SEAL)

I I --PAT/DTA I I -1 Iu

"COMPRESSOR- - - - .- " ROO-M.--/-. - I

4500 HPAIR COMPRESSOR

I WAS-3000 AIR “b MODULATOR (TYPICAL) A AIR 4b ACOUSTIC CONTROL + AIR MODULATOR I EPT-PO0 AIR ELECTRICALDRIVE MODULATOR SIGNALSYSTEM f (TYPICAL) F (TYPICAL) F COMPUTER CONTROL t t L ’/‘ TACP DRIVE SUPPLY

TACP FIELD CONTROL s UPP1.Y t

AIR MODULATOR COOLING SYSTEM (EPT-200 ONLY)

SIGNALS PROCESSED IN DATA SYS I’EMS AREA

Figure 4.6 AcousticSystem for PA Testing. 4COUSTIC TEST DATA CONTROL ROOM CHAMBER "I" - r PATCH PATCH PATCH M PA TCH TA PI? - h4bi'!l- - -' LOW NOISE fk PANEL PANEL PANEL RECORDER PLEXER C4BLES

1 .o - 2.5 KHz

24 CHANNELS OSCILLO- DC AMP

PATCH - /k PANEL VOILX

10 - 10 KHz 3 i. COUSTIC CONTROL 1 Ah'D MONITOR

I'IMING 11 J - BOX PATCX CALIB PATCH F?d PATCH TAPE - MULTI - EXCITA- PANEL PANEL - PLMER RECORDER ;TRAIN GAGES DC - 2.5 KHz t VOICE I

'MEASUREMENT LOCATIONS

Figure 4.7 Data Acquisition System for PA Testing.

4- 14

Malfunctions responsible for aborted Test Runs. FREQUENCY OF NATUR E OF NATURE ERROR OCCURRENCE

Was-300modulatorinsufficient had 1 Acoustic Power in upper frequency range.

Chatteringof Air Modulator Cooling System 1 Control relay

Test ControlComputerTestMalfunction 3

Power output switch in "Dummy Load" 1 Position resulting in no Acoustic Power Output

Microphone damaged when scaffolding 1 was removed prior to testing

The total number of Test Malfunctions is small compared to the total number of tests these malfunctions had no major detrimental effect on the Total Test Program.

4.2.2 IU Modal Vibration Test- The Skylab Payload assembly acoustic test data showed that vibration responses of the Flight Control Computer (FCC) and the ST-124 package were significantly higher than vibration qualification criteria, as previously reported in "Skylab Payload Assembly Acoustic Testing." Marshall Space Flight Center's assessment of this problem led to the conclusion that any requalification program on the FCC would have a serious impact on the Skylab Program. In an effort to obtain a better understandingof the modal characteristics of theIU which were contributing to the excessive vibration of these components, a vibrationwas test conducted on theIU.

4.2.2.1 Test Requirements - All'testing was conducted in accordance with MSFC Test Program S Plan+E - ASTN-ADD- (71-69), "PA Vibroacoustic Test Plan, Phase 11". Minor modifications to the Program were incorporated through Test Control Board Directives(TCBD).

'4.2.2.1.1 Test Objectives - The tests were conducted to define the mode shapes, resonance frequencies, and dampfing characteristics associated with the measured responseof the Flight Control Computer (FCC) and the ST-124 stabilized platform mock-ups observed during the PA Acoustic Testing. 4.2.2.1.2 Test Specimen - The test configuration consisted of the Instrumentation Unit with a mass simulated FCC mock-up. Force controlled sweeps, resonant dwells and decays were performed. Following this activity, a prototype FCC was installed replacing the mass mock up, and subsequent tests were performed. 4-15

4.2.2.1.3 Test Facilities- Refer to Section4.2.1.1.3 of this report for description.

4.2.2.1.4 Testing Apparatus- At each of the four exciter locations (Figure 4.8), a LingA280 shaker was suspended from the facility crane by cables, thus forming a low-frequency pendulum (resonance 2.0 below Hz). The shaker was positioned with a mounting assembly and attached to the IU through a "stinger" with a load-cell force link.A typical shaker suspension system is shown in Figure4.9. At three of the test locations,. aluminum plates (which had been drilled and tapped for the force link) were bonded to the test article to provide shaker attachment points. At the fourth location, the force link was attachedby drilling and tapping one of the ST-124 mounting bolts. 4.2.2.1.5 Control and Data Systems- The control system for the electrodynamic shaker consisted of a frequency synthesizer, its associated programing unit, andan amplitude-servo device for maintaining a constant input force over the frequency range. The electrical signal developed in these instruments was amplified by a solid state direct-coupled power amplifier to provide the necessary drive current for the shaker.A strain-gage load cell was installed between the shaker and the vehicle drive-point to provide force measurement for servo feedback.A block diagram of the control system is shown in Figure-4.10.

The readout system for phase tuning consisted of oscilloscopes with the force signal driving the horizontal axis and the referehce accelerometer driving the vertical, thus providing a Lissajous ellipse. All accelerometer and force signals were filtered through a 10-Hz bandwidth tracking filter whose center frequency was tuned to the synthesizer drive signal frequency.

4.2.2.2 Test Summary - The PA/IU was subjected to low-force levels which were varied sinusoidally over a frequency range 70of Hz 5 atto four different locations. Then resonant dwell tests were conducted based upon resonant frequencies observed and selected during the sine- sweep tests. In addition, the FCC mock-up was replaced withan FCC prototype, and subsequent tests were performed to determine the IU vibration characteristics with FCC prototype installed.

4.2.2.2.1 Test Procedure - Five sine-sweep tests were initally conducted over a frequency range from 705 Hzto during which data from 61 fixed measurements were recorded. Following completion of the sine- sweep testing, the data were processed and plotted in the form of g(peak)/lb versus frequency and phase angle (relative to force) versus frequency. The data review team examined the processed data and selected frequencies for further investigation. At each frequency of interest, a survey of the vibration accelerations normal to the external surface was made by means of acceleration probes. Personnel manning the probes were directed to grid positions on the structure by test engineers located at a central instrumentation point. At each location of interest, acceleration values and phase (relative to either force or a reference accelerometer) were measured and logged. In addition, numerous frequencies 4- 16 were selected,tuned, and acceleration data recorded for post-test examination.

Damping characteristics were determined by abruptly terminating power to the thruster and recording the vibration decay as measured by all accelerometers.

4.2.2.2.2 Instrumentation Summary - A totalof 64 fixedservo accelerometers were recordedduring the subject vibration tests, and a forcetransducer was usedto control the forceinput to the specimen. Details concerningspecific instrumentation locations are described in the Volume I InstrumentationPlan, ED-2002-1255 Revision A, dated 31 December 1971.

4.2.2.2.3 Data Summary - Tabulateddata from the modal survey dwell tests arepresented in reference (14). Data notpresented are availablefrom stored magnetic tapes. Information regarding recordeddata is presented in Appendix E, Table I1 ofthe Instrumentation Plan,noted 4..2.2.2.2.

4.2.2.2.4 Test Description - Although,no major equipment problem were encountered,several test reruns were requiredfor the followingreasons.

FmQUENCYOF CAUSEOF RERUN OCCURRENCE

Power supply 60 Hz noise;data 1 unreadable

P oorly defined Poorly mode 1

Repeatfor better log 6 decremintdata

ANOMALIES: The responseofthe FCC Prototype was significantly lowerthan the response of the mass mock-up for a giveninput force above 40 Hz. Inparticular, no significant 55-Hz responses were measured after installationof the prototype FCC. Acoustic test data previously obtained indicate that a 55-Hz mode contributed significantly to the FCC problem (FCC vibration levels greater than qualification levels). As a result ofthis disclosure, more testing was authorizedto determine the effect of prototype installation on the IU responseto random acousticexcitation.

4.2.3Alternate Test Approach + Recommendation'-Instrumentation recordinglimitating caused test turnarounddelays. 4- 17 +Z

Driving

A SPHERICAL BEARINGS

Driving Point

Figure 4.8 ThrusterDriving Locations

I 4-18

Figure 4.9 Shaker Suspension System Figure 4.10 Block Diagram of Control System 4- 20

CORRECTION: Scopeinstrumentation requirements within facility capability. This wouldrequire a pre-testanalysis as a basis for identifying minimum requirements.

4.3 Phase I1 B - PayloadOrbital Configuration Modal Survey - This modal survey was performedduring the periodextending from 23 May through 23 June1972 at the Manned SpacecraftCenter in Houston, Texas underthe direction of Marshall Space Flight Center, Huntsville, Alabama. Data was acquiredfrom this test whichidentified 23 elastic and 2 rigid body modes.

4.3.1 Test Requirements - The followingreported conditions are standard modal survey test requirements.

4.3.1.1 Test Objectives - The Skylabmodal survey test was performed to obtain the characteristic vibrationalfrequencies, mode shapes, damping coefficients,and generalized mass ofthe normal modes. Data derived from the test was used to evaluate the analytical results obtainedwith a mathematical structural model; and to further refine designload modeling techniques.

4.3.1.2 Test SpecimenConfiguration - Test configurationhardware consistedof the instrumentation unit (IU), fixedairlock shroud (FAS), the structural transition section (STS) , theairlock module (AM) , the multipledocking adapter (MDA), the ATM deploymentassembly @A), the Apollotelescope mount (ATM) , and the command andservice module (CSM) . The aforementionedsubassemblies were stacked upon the S-IVB configuration orbital workshop (OWS) forwardskirt/tank dome assembly(see Figure 4. n). The ATM includedsemi-deployed solar arrays, two ofwhich contained mass simulatedpanels.

Flight type componentswhich were installed during the test were as follows:

a. PLV FanMotor Assembly locatedin the Cabin Heat Exchanger Module of the STS;

b.Film Vaults 3 and 4 locatedin the MDA;

c. PLV FanMotor and MufflerAssembly located in the cone section ofthe MDA.

All othercomponents were eitherprototype or mass simulatedmodels.

4.3.1.3 Test Facilities - The tests described were conductedin theSpacecraft Vibration Laboratory (SVL) ofthe Vibration and Acoustic TestFacility (VATF), building 49, MSC, Houston,Texas. MDA

STS =

AM-

FWD. SKIRT

Figure 4.11 MODAL SURVEY TEST SETUP 4- 22

4.3.1.3.1 Test SuspensionSystem - The PA describedin para- graph4.3.1.2 was stackedin the orbital configuration on the 12,000 pound basering fixture. The CSM and ATM were supported fromabove by oneairspring each. Three additional airsprings attached to the outerperiphery of the base support ring fixture by means ofsingle attachpoint load cell linksspaced 120 degrees apart. Suspension spring rates anddamping characteristics were controlled by the regulation of air pressureto tk plenumchambers of the five pneumatic springs. Air pressure was maintainedto provide suspension resonance and damping characteristics at values where minimum interference with specimen modal resonanceproperties were realized,and the constraints of static sta- bility were still observed.Protection against possible catastrophic failure of thesuspension system was provided by automaticinterlock system and by positioningeight static support stands in sufficient dim- ensionalproximity to prevent any possible destructive translational or rotationalmotions reacting upon the test system.

4.3.1.3.2Shaker Positioning, - The excitationof predicted analytical modes demanded theplacement and activation of the vibration exciters at precisegeometrical positions and in exact forcelphase combinations. In some cases,mechanical accessibility prevented realization of dimen- sionalpositioning. Twenty-one shakers were attachedto the test specimen. Of these21 shakers, 12 werecontrolled simultaneously. During this test series, theshakers at 18 locations were subsequentlyutilized for modal tuning.

The shakers employed in this test were rated at 150 force poundsand were Unholtz-Dickie Model 28 exciters. Of the21 exciters emplaced, 14 were hard mounted to majorbuilding structural members,and seven were suspended upon spring yoke supportsystems. The exciterswere connected tothe structure by stringersdesigned to resonate at frequencies well abovethe upper frequency limits oftest. No stringeror suspension problems were encounteredduring conduct of this test series.

4.3.1.4Control and Data Systems - All test control and data operations were automated. The GAC 18/30digital computer and its ass- ociatedperipherals performed all facets of test control,data ac- quisitionlreduction,and data display under the supervision of Automatic Modal Tuningand Analysis System (AMTAS) softwarefor all phasesof the test programwith the exception of the wide band sweeps.Data emanating fromthe wide band sweeps were recorded on analog tapes forsubsequent digitalprocessing and graphic presentation.

Throughoutthe narrow band modal tuningand modal dwells, AMTAS operatedin the automatic digital mode.

4.3.2 Test Summary - In orderto accomplish the stated test objectives,the program was conductedin five distinet phases. These were:

a. An Automatic Modal Tuningand Analysis System (AMTAS) checkout andend-to-end calibration was conducted prior to initiation of thewide band sinusoidal sweeps. Thisassured the operational readinessand accuracy of the AMTAS system prior to commencement ofactual testing. ~ ~ ~~~~ ~ ~ ~

4- 23

b. Wide band sinusoidal sweeps were conductedusing both single and pairedshakers. For structurally mounted shakers,the frequency intervalextended from 0.8 to 20 Hz. When pendulummounted shakers were employed,the lower frequency limit was determined by theshaker suspension system isolation frequency. Single and pairedshakers connected at each of 13 separate vehicleexcitation stations were steppedover the test frequencyrange in increments of 0.1 Hz. The dwellduration at each0.1 Hz frequency increment was adjusted to assure a minimum of 12 cycles per increment. The outputsof 62 preselected servo accelerometers were recordedon analog magnetic tape. Thesemagnetic tapes were subseqeuntlyprocessed by theComputation and Analysis Division (CAD) yieldingCospectrum, Quadrature spectrum, Cross spectrum,and phase angle plots and alphanumeric tabulations for eachof 12 sweeps. Examinationof these records afforded an insight into the number andregions of significant resonances, thepresence of modal coupling,and the most efficient locations for the excitation of specific modes.

C. The rigid bodymodes ofthe specimen and suspension system were checked. Due tothe physical asymmetryof thestructure/support system, a highdegree of modal coupling was observed. Onlytwo rigid body (suspension) modes were acquireddue to schedule limitations.These data are essentialin determination of the effectsof suspension constraints upon the modaldamping.

d. Narrowband modal tuning was accomplished using multiple shaker installations at eachfrequency where resonant conditions were indicated by thewide band coincident-quadratureresponse plots. Coincident-quadratureplots were digitallyproduced for one force and threeselected accelerometers. Force distributions andphasing relationships were adjusted among thevarious exci- tationstations to achieve fine tuning of the mode. Achievement of final tuning was determined by examinationof both Lissajous patternsand the Coincident-Quadrature plots.

e. Afterfine tuning was accomplished,modal decay traces for 16 preselectedaccelerometers were recordedon oscillographs. In addition,12 selected decay accelerometers were recordedon analogmagnetic tape. Ifthese modal decaysproved free from beating,the narrow band force distributions were reestablished for purposes of data acquisition.

4.3.2.1 Test Procedure - A test procedure was generated by the test agencywhich reflected the requirements of the test planand pro- videdthe procedural steps toaccomplish wide band sweeps, finetuning, narrowband sweeps, etc. 4- 24

4.3.2.2Instrumentation Summary - The types,quantity, location and identification of all dynamicinstrumentation required during the test are presented in Martin Marietta Corporation (MMC) document ED- 2002-1532, Volume 111, dated 30September 1972. In summary, transducers which were required for this test were ofthe following types and quan- tities.

Type Quantity Servo Accelerometers 200 ForceTransducers 21 Strain Gages 20 Rate Gyros -9 Total 250

4.3.2.3Data Summary - Coincidence-quadrature (CO/QUAD) plots and tabulations were obtained for all wideband sweep tests and CO/QUAD plots were obtainedfor narrow band sweep tests. CO/QUAD tabulationsand two dimentional mode shapeplots were obtainedfor all dwell tests and time amplitudetraces were obtainedfor all decay tests. Referto the follow- ingsections for further details.

4.3.2.3.1 Test Techniques Wide Band Modal Tuning Sweeps - The computerprovided, through the Synchon interface, the required frequency and sweep rate parameters. Forcecontrol and abort exceedance supervision employed digital methods. The outputsof 62 preselected servo accelero- meterswere reocrded using the vidar multiplex system.This system multiplexed six channels of dataonto each analog magnetic tape track using carriers of differentcenter frequencies. The centerfrequencies anddeviations for each channel were as shown below:

DataChannel 1 62.5 KHz + 10 KHz Data Channel 2 100 KHz 10 KHz Data Channel 3 137.5 KHz t 10 KHz Data Channel 4 175 KHz 2 10 KHz Data Channel 5 212.5 KHz 2 10 KHz Data Channel 6 250 KHz 2 10 KHz ReferenceChannel 287.5 KHz 2 10 KHz

The62 accelerometers were recordedon 11 datatracks. An IRIG "B" time code was recorded on Channel 6 oftrack 13. The tape recording speed was 60 inchesper second (ips). A full scale 25 Hz calibration signal was recordedon each data channel preceding each data acquisition run.These tapes were deliveredto CAD forprocessing. The finaldata emanated inthe formof cospectrum, quadrature spectrum, cross spectrum, andphase angle plots and alphanumeric tabulations.

Normal turaround time from sweep test toprocessed data was 24 hours.These data were examinedand analyzed inorder to determine optimum frequenciesand effective excitation stations for subsequent narrow bandmodal tuningand modal dwell tests. I

4- 25 4.3.2.3.2 TestTechniques Narrow Band Modal Tuning - Wide band sweep data were examined for selection of a resonantfrequency, and an optimum shakerconfiguration (based uponobserved efficiency in the wide bandsweeps). The largestquadrature value governed the selection of the reference exciter and its associatedinput accelerometer. The reference exciter was brought up to a preselectedforce value. The forcingfunction was thentuned over a narrowfrequency band in order to obtain the desired 90 degreephase shift between force and the local input acceleration as indicated by a Lissajousfigure display. When the master shaker force-accelerationrelationship had been optimized, a secondshaker was energized.This procedure was repeateduntil all shakersof the pre- selectedarray had been activated. Frequency tuning, and adjustments offorce and phase relationships among the.various shakers were repeated until the optimum force-acceleration relationships were obtainedfor all ofthe Lissajous patterns (up to twelve were displayedon three oscilloscopes).Concurrent with the Lissajous pattern tuning procedures, three computercontrolled Houston Instrument (HI)Model DP-1 digital plotters describedthe accelerometer co-quad response curves for three preselected accelerometersin real time. Iterativeadjustments of force, phase, and frequency among all of the shakers were continued until a maximum quadrature combined withthe best co-quad relationship was obtained.

The multipleshakers were sweptacross a two or three hertz band centeringabout the resonant frequency. Co-quad plots were producedfor variouscombinations of forces and accelerometers to assure optimummodal tuning.

When the force distribution was judged to indicate a conditionof modalresonance, the forcing array was abruptlyterminated. The decaying outputsignals of 16 preselectedaccelerometers were recordedon oscillographrecords. Twelveof the 16 accelerometers were recorded on analogmagnetic tape for later dataprocessing atM"M.

Ifexamination of the modal decaysrevealed freedom from frequency beating,the forcing distribution was reinstated andthe AMTAS data acquisitionfunction initiated. Once activated, AMTAS collected all pertinentdata, stored these data on disk andproduced these data on punched cards. AMTAS computed raw co-quaddata for 200 servo-accelerometer positions,and provided these on tabular printout. Raw datawere transformedto the modelnode points,normalized, and the generalized mass was computedand listed.Normalized deflections were computedand planar deflection plots digitally produced for all ofthe 200 accelerometer locations. Modal orthogonalities were computedand listed.

Examinationof the decays, deflection plots, and orthogonality listingprovided an assessment of the degree of modal purity attained. Basedupon this evaluation, a decision to retune or move on to another frequency was effected. I

4-26

4.3.2.3.3Specimen Protection - The MASexhibited an extensive capabilityto. protect the vehicle from excessive force or motion conditions. A 16 channelforce and 32 channelaccelerometer summing detector monitoredactive exciter forces and 24 critical accelerometerlocations. Exceedance of predeterminedforce or acceleration levels during test resultedin automatic reduction of input forces. In addition, 20 strain gageslocated at critical loadpoints on the DA and MDA dockingtunnel were continuallysampled to detect excessive stress. When any strain gagechannel exceeded preselected strain limits, automaticabort occurred. In addition, 14 ofthe 20 strain gages were recordedon an oscillograph during modal dwells,thus providimg a basisto identify the magnitude andlocation of any over stress inducedduring test. Vertical overtravel inexcess of 1.5 inchesin any of the five t.est article suspension air springs also triggered an automatic abort.

4.3.2.4 Test Description - The following test descriptiongives a detailedaccounting of other test activities,problems and solutions.

4.3.2.4.1 AMTAS Checkout - Priorto test, and at frequentintervals throughoutthe test program,the AMTAS system was exercisedto reveal anyinconsistencies of a hadwareor software nature. Hardware and softwareanomalies revealed during these system checks and-corrected were :

a. Problem:Narrow band digitallycontrolled/acquired sweep co-quad plotsdisplayed spikes at 0.1 Hertzintervals. Correction:Loose connection within a module ofthe synthe- sizercontroller was identified andcorrected, resultant co- quad plots were free from0.1 Hertz repetive spikes.

b. Problem: On the1.43 Hertz run planar plots, several singu- larities inconsistentwith the data trend appeared. Correction:Sequence numbers 56, 62, 109 and 116 were checked fororientation of axes of sensitivity and calibration. Se- quence number 109 (SE 536-900-X) onthe service module (SM) forwardbulkhead was found to bereading 20% higher.This accelerometer was replaced.

C. Problem:The unityco-quad plots indicated a polarityreversal forsequence number 138. Correction: Thepunched carddata deck was inspected. It was determinedthat a negativeinstead of plus sign had been punchedon thesequence number 138card. The card was repunched withthe correct sign.

d. Problem: A number ofdwells were aborteddue to exceedance ofthe various strain gage limits. Correction: A DC offset was detectedin the signal conditioning equipmentwhich caused erroneous triggering of the force acceleration summing detector. The signalconditioning devices were corrected. 4- 27

4.3.2.4.2 O.therObserved Test Malfunctions - As is natural in a programof this size, both human andmachine malfunctions will occur. The-followingcircumstances were responsible foraborted test runsduring this problem.

Frequencyof Nature of Error Occurrence

ComputerCore Dump Causedby Software or Peripheral Error 3 AMTAS Control (AMC) Error 2 Tektronix Beehive Mod MI Alpha Crt Malfunction 12 DataChannel Dropout 2 Air Spring Assembly Electrical Failure 1 Strain Gage Malfunction 1 Wrong Accelerometer Selected 2 Transducer Malfunction on ATM Air Spring Assembly 1 DC Offset in NEFF Amplifier 1 MispatchedFalse Accelerometer Limits 1 PlotterScaling Factor Incorrect 4 IncorrectAccelerometer Identifica- tion Numbers on Plotters 3 Datanot Retrievable from Core 2 Incorrect Computer Inputs 5 FrequencySynthesizer Failure 2 StingerResonance 04H 1 Master AttenuatorOperator and Functional Malfunction 4 Synchon Errors or Malfunctions (Selectionof Incorrect Channels) 1 Loose Ground Wire onShaker 04H OvertravelSwitch 1 ProgramUpdate Problem - Computer Software 1 LinePrinter Failure 1 ScannerChannel Interpretation Malfunctions 3

Inconsideration of the scope and complexity of the overall project, both human errors andequipment malfunctions represented a veryminiscule fraction of the overall testing process.

4.3.3 AlternateTest Approach - Thefollowing test outlinefor future test application is submittedfor review andrepresents some refinementfrom the Skylab test. Each test activity is preceededby a statementof the purpose of the test, which is thenfollowed by the necessarydata requirernencs. 4- 28

Purpose: To determinethe force and phase distribution necessary to fine tune preselected modes.

Activity: Wide band sweeps shouldbe conducted without restricting the number ofsimultaneous shakers or requiring constant force input. The followinginformation is requiredfrom pretest analysisfor each wide band sweep

(1) frequencyrange

(2) number ofshakers, location and phasing requirements

(3) selected mode frequencies

(4) mode shapes

(5) maximum inputforce distribution and reference force

(6) minimum instrumentationrequirements for selected mode shapeidentification

Minimum Data Requirements: (1) CO/QUAD plotsand tabulations

(2) forceamplitude plots and tabulations

Notes: 1. Iflinearity data is required,additional wide band sweeps shouldbe conducted using constant amplitude control.

2. Ifselected modes are notidentified by thistechnique, it may be necessaryto change shaker locations and/or selectadditional shakers to suppress coupledmodes.

FINE TUNING MODES

Purpose: To finetune selected modes;and toacquire data identifying each test mode for correlation with the analytical model.

Activity: Performfine tuning by quadraturepeaking and acquire dwell, narrowband sweep, anddecay data for each mode.The followinginformation is requiredfrom wide band sweep datafor each mode prior to tuning

(1) shakerforce distribution and phase

(2) mode frequency

(3) decaymeasurements

(4) general mode shape 4-29

Thefollowing verifications should be made for each mode acquired.

linearity check

forceamplitude and frequency drift

Minimum Data Requirements: (1) dwell CO/QUAD tabulations

(2) decaydata

(3) narrowband CO/QUAD plotsand tabulations for each mode required

Notes : 1. If mode verification is negative it may benecessary to retune the mode, usingconstant amplitude control and/or frequency control.

4.3.3.1 TestComparisons and Conclusions - The foregoing test outline representsan attempt to refine test requirements,without affect- ingdata quality. These refinements could result in reduced cost and minimum scheduleimpact on similar test programs.

Specificdifferences in the foregoing outline and the Skylab payload tests are as follows:

1. moreemphasis is placedon the analytical model in the formof pre-test requirements;

2. wideband sweeps of individual shakers can bereplaced with multipleshaker wide bandsweeps;

3. fine tuning time canbe reduced since wide band data would be more representative of actualtuning conditions and also, requires less datainterpretation than the single shaker dataapproach;

4. theneed for a totallyautomated control and data acquisition1 reduction system can be optional;

5. data reduction requirements can be kept to a minimum. 4- 30

4.4 PHASE I11 ADDITIONAL IU ACOUSTICTESTS

Due to differences in the response of the FCC mass mock up when comparedwith the FCC Prototype, MSFC authorized additional Acoustic testingon the IU. Thissection will discussthe objectives, summarize the tests and make some conclusionbased on the test results.Descrip- tionsof test requirements, test facilities;Control andData'Systems, andInstrumentation summary will beomitted since they have not changed fromthe previous IU AcousticTests. Test descriptions have also been previouslysummarized and appear in Table 4.1 as PA-042 through PA-047.

4.4.1 TestObiectives - The followingobjectives were decided upon for these tests:

a. determinethe effect of the 25 Hz horn upon IU vibration responses;

b. determine if thesubstitution of a prototype FCC inthe IU for a mass mock-up FCC significantly changed vibration response levels measuredduring the previous acoustic testing. Inaddition, conduct sine-sweep tests toassess the modal densityof the reverberant chamber.

4.4.2 Test Summary - Threerandom acoustic runs were conducted duringthis investigation. The first run was conductedfor the purpose ofobtaining IU responsedata with a prototype FCC installed in this IU. Datafrom thisrun, along with previously obtained data, allowed a comparisonof the FCC-prototype response data to the mass mock-up response data. RunPA-A-043 subjectedthe test articleto an environment representingthe local IU liftoffenvironment. Control instrumentation and horn/modulatorselection and programing duplicated that used during the previous IU liftoffacoustic test (PA-A-040).

The secondrun was conductedfor the purpose of obtaining a set of IU responsedata with the 25 Hz horndeactivated. After deactivating the 25 Hz horn, two 50 Hz horns were programmed toproduce the low fre- quencyenvironment normally produced by the 25 Hz horn. PA-A-044 also subjectedthe test articleto the IU liftoffenvironment. Comparison ofthe data obtained during this run to data obtained during PA-A-043 enabled data analysts to assess any effect of the 25 Hz horn upon FCC andother IU responses. The thirdrun (PA-A-045) was conductedto obtain IU responses to theaerodynamic environment. The horn/modulatorselection and programming duplicatedthat used during the previous IU aerodynamicnoise run (PA-A- 041) with the minor exception that 2-W- 100 replaced 1-W- 100 in the horn selection. Althoughslightly higher low-frequency sound levels were produced in this run series (PA-A-043 through PA-A-045) thanobtained in the previouscomparable run series (PA-A-040 and PA-A-041), thediffere.nces arewithin prescribed tolerances and allowable limits. However, responsedata comparisons from these two run series required careful adjustmentsto eliminate variations resulting from these differences. 4- 31

In order to assess the reverberation chamber characteristics with the test articlein place, two sine-sweepruns were conducted. A special closed-loopsystem (very similar to that used for modal vibration excitation) was used to control the SPL at the throat of the 25-Hz horn.to a constantlevel. An initial sweep was made toobtain instrument ranginginformation. The sinusoidalsound pressure at the 25-Hz horn throat was varied over a frequencyrange of 19.98 to 99 Hz, and data from all microphonesand accelerometers were recordedon run PA-A-047. Subsequently,data processing was perfowed to obtainplots ofg’s (peak) versus frequency or sound pressure inpsi (peak) versus frequency.

4.4.3 Conclusionson Additional IU Testinq -

a. Assessmentof the sines weep Acoustic Data didnot indicate thepresence of any unusual reverberant chamber characteristics

b. FCC responsedata obtained after the installation of She Prototype FCC showed a significant decrease in response at 55 Hz with lesser changes at otherfrequences below 100 Hz.

c.Data assessment indicated that no significantchange in ST-124 responses were produced by the Prototype FCC installation or horn selection (25-Hz versus 50” horns)

I 5- 1

5. DYNAMIC STRUCTURALMODEL VERIFICATION

5.1Pre-Test Modal Vibration Analy&

This section presents the results of the final pre-test modal analysisfor the Configuration 6 (Orbit) modal survey test. Config- uration 6 is definedas consisting of the OWS Forward Skirt and Dome, IU, FAS, MDA, STS, AM, CSM, deployed DAY deployed ATM withfolded ATM solararrays and laboratory suspension systems with associated test fixtures. Themodal datapresented herein represent the best available mass and stiffness representation of the Configuration 6 Dynamic TestArticle (DTA). Thesedata were generatedprimarily for the purpose of providing a final mass matrix for use in on-site orthogonality checksduring modal surveytesting. In addition, these modal data will also beused inon-site mode shapecomparisons during testing. Figure 5.1 shows thecomponents of this configuration.

5.1.1 BaseRing and Base Ring Suspension System Structural Models - The BaseRing Suspension System model is based on geometryand weight dataprovided informally by NASAIMSC. Three air springs are locatedat 120 degreeintervals around the Base Ring. Axial spring rates for each air spring are based on a naturalfrequency of 0.5 Hz andthe suspended weight. The weightsuspended by the three Base Ring airsprings does notinclude the ATM orthe CSM sincethey are each supported by their own independentair suspension systems. Portions of the deployed DA weight were allocatedto two suspensionsystems, per informaldiscus- sionswith NASAIMSC. Seventypercent of the deployed DA weight was allocatedto the Base Ring Suspension System and the remaining 30 percent was allocatedto the ATM SuspensionSystem. The total suspendedweight acting at the Base RingSuspension System was 78,458pounds, divided among threesprings. The lateral pendulum springs were calculated usingthis weight and a pendulum lengthof 104 inches. The finalspring rates were assembledinto three 3x3grounded stiffness matrices, which were thenrigidly transformed to the aft OWS Forward Skirt centerline collocation point at station 3100,using a radiusfrom the centerline tothe Base Ring suspension points of 154.73 inches. Finally, a negative spring constant of -16.8118 x lo6 inch-poundlradian was added directly to the Qy and 8, degreesof freedom at station 3100 to ac- countfor the inverted pendulum effectof the weight supported by the BaseRing Suspension System. This negative spring constant was calculated using an estimated CG location at station 3314.28 for the supported weight.

5.1.2 OWS Forward Skirt, Dome and IU Structural Models - The OWS Forward Skirt Structural Model (see Figure 5 .2) is based on the OWS stiffnessdistribution taken from the NASA memorandum, "Change to AAP-1 StructuralCharacteristics," J. H. Farrow, 31 August1970, No. S&E-ASTN- ADS-70-33. The OWS Forward Skirt is modeledusing three centerline 5- 2

collocation points resulting in an 18x18 free-free stiffness matrix. The OWS Forward Skirt massmodel was supplied by the MMC Weights Group andconsisted of three 6x6 matrices andcombined to forman 18x18 mass matrix. The IU Structural model is basedon the IU stiffnessdistribu- tionsupplied by NASA-MSFC in May 1970.The IU is modeledusing two centerline collocation points resulting in a 12x12 free-free stiffness matrix. The IU mass model was supplied by the MMC Weights Group in the formof two6x6 mass matriceswhich were combined toform a 12x12 IU mass matrix. All mass data reflects DTA weightsand c.g.'s provided by NASA/MSFC . 5.1.3 FAS Structural Model - The basic FAS mass and stiffness data used in this analysis was provided byMcDonnell-Douglas Corpora- tion inTransmittal Memorandum 646-E236-061471. In orderto be compatible with the IU model, ,an equivalent centerline collocation point was generated at the IU interface by rigidlytransforming the skin- linepoints provided in the original mass and stiffness at the IU interface. The skin-linepoints at the Payload Shroud interface on the FAS were reduced out for this vibration analysis because they will notexperience any dynamic loads other than their own mass loading.

'5.1.4 AM/STS/Truss Structural Model - Updated mass and stiffness data were provided by McDonnell-Douglas. The AM/OWS dome bellowstorsional spring was added and the stiffness matrix relieved to yield a 61x61free-free stiffness matrix. Corresponding mass data appears in ED-2002-1326.The model consists of 4 AM tunnelcenterline nodes and the MDA/STS interface at 6 degreesof freedom each, plus 6 truss N2 bottlesand the 4 Truss/FASinterface points at 3 degreesof freedom each. Thebellows/OWS-dome interface is representedas one torsional degreeof freedom at MMC Station2320.0 (see Figure5.3).

5.1.5 MDA Structural Model - The MMC Stress Group supplied a 144x144 constrainedflexibility matrix for the MDA. After inverting theflexibility matrix to obtain a stiffnessmatrix, the stiffness matrix was collapsedto a 48x48 stiffnessmatrix. The48x48 matrix was reducedto a 12x12 matrix by useof rigid body transformations toobtain a centerline modelof the MDA. The 12x12 matrixrepresents two gridpoints (MMC stations 3605and 3545) with six degreesof freedom each. The12x12 matrix was thenrelieved with respect to MMC station 3441.765,resulting in an 18x18 free-freestiffness matrix.

The MDA mass reflects actual DTA weightand CG as determined by the MMC WeightsGroup. The mass propertiesfor the STS/AM were up; dated to reflect data provided in an informal memo fromPaul Heaton, MDAC-East , to Wayne Ivey, NASAIMSFC, dated 30December 197 1. 5.1.6 AxialPort Structural Model - The axialport structural model is masslessand consists of a 42x42 free-free stiffness matrix .which was added to the CSM to interface with the MDA stiffness model. . . I

5- 3

5 .1.7 Axially Docked CSM Structural Model - MMC received a92x92 stiffness matrix of the total CSM fromNorth American (see Figure 5.4). However, the DTA uses a CSM whichhas been modified in two respects: 1) the flight SM engineand bell wasremoved and replacedwith a spaced stack of steel plates whichapproximately duplicates the weight and CG ofthe SM engineand engine bell; 2) the DTA SM is a stripped down ver- sionof the flight hardware. Extensive ballast was added tothe SM and Cormnand Module in order to match the flight. CSM total mass, CG and roli inertia. It is not known whetherthe yaw and pitch inertias of the DTA CSM are significantly different fromthe CSM Structural Model used for thisanalysis. It is alsonot known whetherthe DTA ballast was attached so asto increase the overall stiffness of the SM. Since time andfunds did not allow generating a new DTA CSM mass and stiffness model, the flight CSM mass and stiffness model was usedwith one change. The stack ofspaced steel platesused on the DTA to represent the SM engineand bell are much'stiffer than the equivalent flight engine hardware. Therefore , a rigid transformation wasmade to lump the SM engine IILilss and stiffness formerly collocated at station 3929.16 to the aft struc- turalcollocation point onthe SM structure, located at station 3921.50 (see Figure 5.4).

5.1.8 ATM Spar/CanisterStructural Model - The ATM Spar/Canister stiffness model was generated by the MMC Stress Group (see Figure 5 .5). The mass model was generated by the MMC WeightGroup based on DTA weight datasupplied by NASA/MSFC in document %E-ASTN-SAE(71-48).

5.1.9 ATM GimbalRing Assembly GRA Structural Model - The ATM GRA sti,ffness is included in the ATM Rack stiffness model,described in a latersection. The mass matrixfor the GRA structural model was calculated by the MMC Weightsgroup to reflect actual DTA weightand CG. This 6x6 CG mass matrix was transformed in a least-squared best fit manner tothe 12 translationdegrees of freedom assigned to the four launchlock nodes on the ATM Spar/Canister mass model.

5 .1.10 ATM SolarArray5,- Stowed (ATM-SAS) Structural Model - The ATM-SAS structural model was updatedfrom a reduced 52x52 stiffness matrixsupplied by Sperry Rand SpaceSupport Division in transmittal memorandum SP-232-0579. A corresponding 52x52 diagonal mass matrix was alsosupplied. The ATM-SAS model includedthe ATM-SAS backup structure.

One vibration analysis of the ATM-SAS structural model was performed, inthe ATM-SAS localcoordinates. Then theresulting mode shapesand inertia loading matrices were transformed by geometrical transfonnations to the four bays of the ATM Rack.Thus , the DTA vibration modelassumes thatthe four ATM-SAS panelsare identical. However, the DTA hasone flight version panel, oneprototype flight panel,and two mass simulated ATM-SAS panels. By definition,the AT" SAS vibration analysis structural model shouldrepresent the flight and prototype ATS-SAS panelsused on the DTA. However, the two mass simulated panelsused on the DTA ATM wili naturally exhibit a different dynamic responsethan predicted by this vibration analysis. 5- 4

5.1.11Deployed ATM Rack Structural Model - The deployed ATM Structural Model is basedon a 160x160 free-free stiffness matrix provided by the MMC Stress Group inJanuary 1971. This stiffness matrix was collapsedto a 96x96 free-free stiffness matrix. The rollers and locks stiffnesses were addedand the entire Gimbal Ring Assembly stiffness matrix was reducedto six degrees-of-freedom at the center. The spar/canister is consideredto be rigid. The fourundeployed solar arrays were alsoconsidered to be rigid. The ATM mhss model was provided by the MMC WeightsGroup and formed into a 96x96 mass matrix. The masses .forthe four undeployed solar arrays were rigidly transformed to the six collocation points on theappropriate ATM bays resulting in four 18x18 solar array mass matriceswhich were added to the 96x96 ATM mass matrix. The ATM Rack mass model was updated by the MMC WeightsGroup to reflect actual DTA weightand CG data.

5.1.12 .Deployed DA Structural Model - The deployed DA structural model is based on a 63x63 mass and stiffness matrix provided by McDonne11- Douglas Corporation Transmittal Memorandum 646-E236-070771.

5.1.13 ATM SuspensionSystem Structural Models - Configuration 6 is suspended by air springs in the axial direction at five locations. Threeof these are located at 120 degreeintervals around the Base Ring. The CSM is suspendedfrom the aft SM structure while the ATM is suspended at Bay 2. The pointof suspension on the ATM was consideredto be directly overthe ATM centerof gravity. Axial spring rates for each of the five suspensionlocations are based on a naturalfrequency of 0.5 Hertz andthe suspended weight. In addition to the axial springs, restoring forcesdue to pendulum action were simulated by adding lateral springs inboth lateral axes at the points ofsuspension. For small deflections, thelateral spring rates are equal to the suspended weight divided by the pendulum lengthof each individual suspension point. The finalspring rates were assembledinto five 3x3grounded stiffnessmatrices. The stiffnessesfor the three BaseRing suspension points were rigidlytrans- formed to the aft OWS Forward Skirt centerline collocation point at station 310Q.O.The ATM suspensionstiffness was transformedin a leastsquares mannerand added to the ATM stiffnesses at the four corners of Bay 2.The CSM suspensionsystem was added to the CSM stiffness at centerlinestation 3921.5.Since adequate suspension system data were notavailable at the time ofthis analysis, the pendulum lengthof each suspensionpoint was assumed to 180 inchesand the radii from the centerline to the BaseRing suspension points, were assumed to be 150 inches. SuspensionSystem Structural Modelwas updated. The ATM updatedweights andgeometry data were suppliedinformally by NASA/MSC. The ATM suspensionsystem was modeled as a doublependulum similar to the basic concept usedfor the CSM suspensionsystem. The upperpendulum consists of only a single pendulum barwhich is 134.6inches long and weighs 90 pounds. The lowerend of the bar interfaces at a tie pointnode located at X 3668.10, Y = 0.0, Z = -219.20,which is abovethe CG of the corn- bined ATM Rack, SparCanister, GRA andthe four ATM-SAS panels.

From the ATM SuspensionSystem tie point,four turnbuckles (2 short and 2 long)and associated shackles and adapter plates carry the suspension 5-5

systemload to the four corners of the ATM Bay 2.Local 2x2 stiffness matrices for each of the four turnbuckles were calculatedassuming that each wasa steel barwith an area of0.50 square inches. Direction cosinetransformations were thenused to add each local turnbuckle stiffness matrix tothose degrees-of-freedom of the ATM Rack stiffness matrix correspondingto the appropriate corners of Bay 2.

The upperend of the pendulum bar is pinnedto the ATM air spring beam and air cylinders. The ATM air spring beam andcylinders are only allowed to move vertically andhave an approximate m.ving weight of 500 pounds. The remainderof the ATM suspensionhardware is involvedin the lateral pendulum spring calculations, with 491.3 poundslumped at the tie point node at station 3668.10and another 121.35 pounds is spreadout to the four corners of Bay 2 on the ATM Rack.

The 0.5-Hz ATM vertical air spring is basedon a vertical moving weightof 25,390.8 pounds, which includes 1185.9 pounds to represent 30 percentof the weight of the deployed DA, sinceonly 70 percent is supported by theBase Ring Suspension System. The upper pendulum lateralsprings, acting at the tie pointnode, are based on the 491.3 poundsupper pendulum weight, lumped at the tie point,plus 24,399.5 pounds forthe lower pendulum.

The lowerpendulum springs, acting at the combined CG ofthe ATM/30 percent DA/lower part of ATM SuspensionSystem, are basedon 24,399.5 poundsand a lowerpendulum length (tie point to CG) of122.77 inches. There is no substantial ATM rack structure at the combined CG location (X = 3545.33, Y = 0.0, 2 = -219.20) so the lateral lower pendulum springs were transformedin a rigid body manner tothe lateral degrees-of-freedom at the four corners of Bay 2 andof Bay 6.

A check vibration analysis was also made of the free-free ATM rack, mass loadedwith the ATM SparICanister, GRA andfour ATM SolarArrays, andgrounded by the ATM suspensionsystem mass and stiffness models. The resulting first six rigid bodymodes are tabulated in Table 5.1.

5.1.14 CSM SuspensionSystem Structural Model - The CSM Suspension SystemStructural Modelwas updated. The basicsuspension system model was changedfrom a single pendulum analysis with a masslesssuspension systemto amore realistic double pendulum analysiswhich included the weightand inertia addedby the CSM SuspensionSystem. Weight and geo- metrydata were suppliedinformally by NASA/MSC. The CSM Suspension Systemconsists of two 100 pound rigid bars 95.8inches long which are eachpinned to 100 pound fittings on the SM aft end.These fittings act at station 3939.2and are considered to be located at +Y = 75.0, Z = 0.0. The upperend of each of therigid bars is pinnedto a 150 inch long crossbeam which rests on the CSM plenumchamber air cylinders. The beam plus the moving air cylinders weighapproximately 600 pounds, witheach of the six aircylinders weighing 23pounds. A single 0.5 axial air spring acts at the center ofthe crossbeam, with a total SUS- pendedweight .of 30,772pounds, of which29,772 is the CSM. Because the 5-6

six air cylinders are interconnected to a common plenumchamber, there is no air spring restraint due tothe crossbeam rocking about the 8, axis. The mass and inertia effects ofthe crossbeam and aircylinders was accountedfor by lumpingthe beam and air cylinders to mass collocation points at the center ofeach air cylinder plus the center and endsof the crossbeam. The verticallinks and SM fittings were collo- catedat the ends of thecrossbeam and at the pivot point of the fittings.Finally, a rigid body transformation was writtento transform all ofthe suspension system mass collocation points to the aft end of the CSM, at station 3921.50.

Lateralupper pendulum springs,based on a pendulum lengthof 95.8 inches, were assumed to act at each outboard suspension fitting ofthe CSM. The endsof the crossbeam were assumed fixedin the 2 direction. Eachupper lateral pendulum spring carried one halfof the CSM weight plus a SM suspension system fitting plus a load cell plusone-half of thevertical support bar.

The lower lateral pendulum was consideredto extend from the suspension fitting pivot, at station 3939.2, tothe CG of the CSM, at sta- tion3791.64, for a lowerpendulum lengthof '147 -56inches. The lower pendulum weight was the CSM weight. The lateral lowerpendulum springs were rigidly transformed to act at the two closest SM centerline s truc- turalnodes, located at stations 3921.5and 3766.50. A similarrigid body transformation was used to transformthe upper lateral pendulum springs,acting at the outboard SM suspensionfittings, to the centerline SM node at station 3921.5.

A check vibration analysis wasmade of the free-free CSM grounded by theair spring andthe double pendulum springs. The first six modes andfrequencies of this check run correspond to a rigid CSM restrained by its suspensionsystem. These frequencies for the CSM suspension systemare listed and identified in Table 5.2.

5.1.15Discussion of Pretest Model - The vibrationanalysis reflects,as closely as possible, the properties ofthe actual DTA. However, some deficienciesin the model are known to exist and are notedas follows:

a. The flight CSM structuralmodel, modified in this analysis to reflect use of a simulated SM engineand engine bell, wouldbe a reasonablesimulation of the actual DTA if flight typeequipment and bracketry is usedthroughout the DTA CSM. However, unlesssufficient care is exercisedin the locations andmethod of attachment of all ballast used in the DTA CSM, the detailed dynamicresponse of the vibration analysis model andthe DTA can be expected to differ, primarily at higher frequencies.

b. Thisvibration analysis assumed thatall four ATM-SAS panels are identical and arerepresentative of flight hardware. 5- 7

However, the DTA uses two ATM-SAS panelswhich are mass simulated butnot stiffness simulated. Again the local response of the DTA andthe analytical models can be expected to differ womewhat, especially at higher frequencies.

c. The ATM Ra-ck stiffnessmatrix includes the stiffness effects of allfour outriggers. However, the outriggeron Bay 2 on the DTA is removed to make room for the ATM SuspensionSystem hardware. The stiffnesseffect of the removed outrigger was not subtractedfrom the ATM Rack stiffness matrix becausethe necessary free-free stiffness matrix for a single outrigger was not provided.In addition, the stiffening effect of the outriggers in the Orbit Configuration are probably not significant compared to the main structureof the ATM Rack.

The total vibration model contains 630 netdiscrete degrees of freedom.Briefly, the coupled modes analysis was performedas follows: The CSM and CSM suspension system were modally coupled to the MDA/STS/AM which in turn was modallycoupled to the !Main Beam" consisting of the Base RingSuspension System, Base Ring, OWS Forward Skirt, IU and FAS. In addition, the ATM SparlCanisterand the four ATM SolarArrays were modallycoupled to the ATM Rack and GRA. The ATM Rack was modallycoupled tothe DeploymentAssembly which, in turn, was modallycoupled to the "Main Beam" atthe FAS interface. (It shouldbe noted that the FAS 02 tanks stiffness or mass were notchanged as a result of theLaunch Configuration modal test which showed thatthese tanks respond analytically at higher frequenciesthan the test article).

The final coupled modes analysiscontained 208modal degrees of freedombased on thefollowing component modes andcut-off frequencies:

Component No. Modes Cut-OffFrequency, Hz. "

Main Beam 39 44.80 MDA/STS/AM 29 43.80 C SM 16 49.00 DA 19 41.96 ATM Rack/GRA 31 44.97 ATM SAS, Bay 1 13 38.53 ATM SAS , Bay 3 13 38.53 ATM SAS , Bay 5 13 38.53 ATM SAS,Bay 7 13 38.53 ATM Spar/Canister 22 43.84

The abovecomponent cut-offfrequencies insure accurate coupled modes forthe test range of 0 to 20 Hz. Degrees-of-freedomand location coordinatesfor the ten modally coupled branches are shown in Table 5 .3. A. description of the first 78 modes ofthe analytical model is provided inTable5.4 . The generalized mass contribution (GMC) forthe total analytical model is presented in Table5.5.

I II 5- 8

Prior- to commencing the study to correlate the analytical and test modes, thecoupled analytical modes were reducedto the 193 degrees of freedom shown inTable 5.3. The resultinganalytical modes were then re-normalized in the same fashionand with the same mass matrix as the test modes.The re-normalizedanalytical modes were plotted (two-dimensional)and GMCs were determined.Table 5-4 containsbrief descriptions of thefirst seventy-eight coupled analytical modes. The columnheaded "Generalized Mass". in Table 5.4 provides an indication of the adequacy ofthe representation of the original model by thereduced modes and reduced mass matrix.That is, ifthe representation were entirelyade- quate,the generalized masses wouldbe unityfor each mode. As canbe seen, modes involvingthe ATM components are not well represented by the reducedsystem. This is attributableto a basiclack of ATM instrumentation, resulting in an insufficient number of DOF's in the ATM components. 5- 9 .- ..

AIR SPRING AIR SPRING SUSPENSION SUSPENSION x tnl- COMMAND AND SERVICE MODULE (CSM)

MULTIPLEDOCKING ADAPTER(MDA)

DEPLOYMENT ASSEMBLY

AIRLOCKMODULE (AM) 9OLLO TELES MOUNT (ATM) FIXED AIRLOCK SHROUD(FAS)

INSTRUMENT UNIT AIR SPRING (IU) SUSPENSION

I I 1 \ ORBITAL WORKSHOI BASE iUNG FORWARD(OWS) SKIRT \ AIRSPRING SUSPEN SION

Figure 5.1 Skylab A OrbitalConfiguration (Configuration 6) Test Setup Modal Survey Teatr . ,.,. ."_, ""_.,, ""_. ..-.,.- ."". ""

5- 10

& U

AIRSPRING AIRSPRING NO, 1 NO. 2

AIR SPRING N0.3-

Figure 5.2 Base Ring/OWS Forward Skirt/IU/FAS Model for Configuration 6 5- 11

I a 22

MDA

c 0.21- I I STS 1

Figure 5.3 MDA/STS/AM Model

111 I 31 I' ~~

5- 13

e 84 81

Figure 5.5 ' Axially Docked CI;M 5- 14

Table5.1

IDENTIFICATION OF FIRST SIX NATURAL FREQUENCIESFREE-FREE CSH ON DTA CSM SUSPENSION SYSTEM

Mode No. Frequency, Hz Comments

.1863 1s t simple pendulum mode, mostly Y motion. .1867 1st simple pendulummode, mostly 2 motion .4363 8 rotation, mode, due pairto of lgteral pendulum springs at outer skin. 4 .4997 Axial mode, on 0.5 Hz airspring 5 .692nd 25 pendulum mode, Y direction (primarily 8 rotationabout nearly stat tonarycE) 6 .70 21 2nd pendulummode, 2 direction (primarily 8 rotationabout nearly stationary cE) 5- 15

Table5. 2

IDENTIFICATION OF FIRST SIX NATURAL FREQUENCIESFREE-FREE ATM ON DTA ATM SUSPENSION SYSTEM

M ode No. Mode Frequency ,Hz Comments

1 0 .oooo 0 rotationwith no restraint 2 .1984 16t simple pendulum mode, primarily Y motion. 3 .2033 1st simple pendulum mode, primarily Z motion. 4 .5190 Axial mode, on 0.5 Hz air spring.* 5 .7546 2nd pendulum mode, Y direction (primarily 0 rotationabout nearly stationary cE) 6 .7749 2nd pendulum mode, Z direction (primarily 0 rotationabout nearly T, tat ionarycE>

*NOTE : Thischeck run was made withoutany weight from the deployed DA. However the CSM SuspensionSystem airspring is based on a suspendedweight which includes 30 percent of the DA. Note thatthe 4th coupled mode forthe total DTA is anaxial suspensionsystem mode at 0.489 Hz.

I 5- 16

Table 5.3

ORBITCONFIGURATION MODAL SURVEY OEGREE OF FREEDOM TABLE FOR MODE 'SHAPES AND DISCRETE MASS MATRIX

NODE DEGREES~ OF FREEDOM LOCATION NO. DX DT DZ TX TY TI X Y z- DESCRIP TIOY

1' 1 2 3 4 5 6 3100.00 c.coc OmOOC BASE RNGrCUS SKIRT 27 8 9 10 11 12 3223 000 0 000 0.000 OYSIIUINTERFACE 3 13 19 15 17 16 1e 3258.555 @.OOC OmOOC IUIFAS XNTERFACE 4 19 :?0 21 3316.555 81.473 16.683 FAS 02 BOTLlr+Y +Z 5 22 2 3 29 3316.555 46.683 '81.973 FAS 02 BOTLZI+Y +2 6 25 2 6 27 3316.555 -46.683 81.473 FAS 02 BOTL3i-Y +Z 7 28 2 9 30 3316.555 -81.472 46.683 FAS 02 Bolt4r-Y +2 8 31 32 33 3316 555 -81.473 -06.685 FAS 02 00TL51-Y -2 9 39 35 36 3316 -555 -96.68' -81.473 FAS 02 B0Tt6r-Y -2 10 37 33 39 3391.615 116.050 0.000 FASIAMZDA IFi +Y 11 90 41 92 3341.615 CoMC 116m06C FAS/AV;/OA IF, +2 12 43 49 45 3391.615 .. *116mfl60 0.000 FAS/AM/DA IF, -Y 13 46 47 46 3355.700 -62.346 -81.1988 FAZIDA XFI -Y -Z 14 49 511 51 3341 0615 O-OUO -116.060 FASIAM TFI -2 15 52 53 54 3341 -615 a3.01.4~ -83.~143 FASIDA IF* +Y -z 16 55 60 5956 58 57 3282 -165 0 .ooe 0.000 AM TUNNELISHEIR YB 17 61 6562 69 63 E6 3399.615 c.0oc 0.000 AM TUNNEL /STS IF I8 61: 726871 70 69 3941.765 0 .ODR 0.000 MDIISTS XNTERFICE *9 73 74 75 76 78 77 3605 .COO 0.coc OoDOO MOA CONE/CYL ITRFC 20 79 80 81 3297.665 69 mO5P 0-OCO N2 TANK, +Ye LOYER 21 82 83 89 ?348.365 69.C5C OdOC N2 TANK, +Y e UPPER 22 85 85 87 3237.665 0.ODO. 63.350 N2 TANK# +ZI LOUER 23 88 e9 90 '398.365 C-TPC '69.050 N2 TANK. +Zr UPPER 24 91 92 93 3297.665 0-ODI? -69.950 N7 TANK -ZD LOUER 25 94 95 96 3348.3E5 CoCOC -69.050 N2 TANK, -2, UPPER 26 97 98 99 100101102 3678.000 o .ouo C-300 CM. FUD BULKHEAD 27 103 1c4 1051C61C7 1CB 3751 -600 cmcoc OmOOC CHI AFT BULKHEAD 29 109 110 111 112 113 11W 3756.500 Om000 OmOOQ SMr FYD BfJLKHE4D 29 315 116 117 118 119 12C 3921 500 C.QO@ 0-OOG SPr AFT BULKHEAD 30 121 122 123 3454 .765 o.ooo -9Q.oon LOYER D L~TCH, DA 31 12Q 125 126 3532.915 113.50C -11m85C LOYER +YTRUNNI@N 32 127 128 129 3532m.915 - 113o500 -11.850 LOYER -Y TRUNYION 33 130 131 132 3418.765 0-ODC IOOmOOO EREPPACKAGE CmGm 34 133 134 135 3479.099 27.399 -252.500 ATH PN 6~7IFIOUTR 35 136 137 138 3517.701 -65.906 -252.500 ATH PN 4rE IFrOUTR 38 139 140 141 5572.299 65.905 -252.500 ATM PM 8rl IFIOUTR 37142 19J 144 3ElC.906 -.27.29? -252.500 ATM PN 3.2 IFrOUTR 38145 146 147 3479.094 27-79? -158.ClOO ATM PN 6r7 IFIINNR 39198 149 150 3517.701 -65.906 -158mOOC ATH PN 4~5IFlINNR 40 151' 152 153 3572.299 . 65.906 -15P.000 ATH PN 991 IFIINNR 91154 155 156 361C. 906 -27.299 -.158.DOC ATM PN 2~3IFvINNR 42 157 158 159160161 162 3545 000 -65.906-1a1.9925 CMG, -Y SIDE 93163 164 165166167168 3545.000 E7mA39-181.995 CPGI +Y SIDE 44- 169 170 171172173 174 3610 906 0.000-182.000 CMGI +% fIOE 415 175 176 3599.9303 59.9301-207.490 ATH SASI PN I 46 177 178 3599.9301 -54m93C1-2r!7.490 ATM SASI PN 3 47179 18f 399C-0699 -54m9301-207m490 ATM SAS, P:: 5 48 181 182 349010699 59.~3c1-2cvm~9oATM saS1 PN 7 4R 183 184 185 18G 1871R3 3545.000 CmCflC -290.709 SPARCENTER 50 188 189 190191192 193 3545.000 O-OOr! -2!40.709GRAICAN CENTER Table 5.4 OrbitalConfiguration (DTA) Coupled Analytical Modes 'OWLED FREQUENCY, GENERALIZED a DESCRIPTION MASS 1.o SuspensionSystem (rigid body) Modes. 7 1.37 1.o First X-Z plane bending about MDA/CSM I/F, ATM rocking in X-Z plane out of phase with CSM. 8 1.57 .98 First X-Y planebending about MDA/CSM I/F, ATM rocking in X-Y plane outof phase with CSM. 9 1.96 .95 First X-Y planebending about MDA/CS.M I/F, ATM rocking in X-Y plane in ihase with CSM. 10 1.99 .99 First X-Z planebending about MDA/CSM I/F,ATM rocking in X-Z plane in phasewith CSM. I1 2.66 .99 Vehicle roll and first torsion coupled with X-Y plane first bending about MDA/CSM I/F, ATM X-Y planerocking in phasewith top of CSM. 12 3.25 .98 Vehicle first torsion with CSM,MDA/STS/AM out ofphase with FAS/IU/ OWS. Vehicle X-Y planebending. 13 3.52 .99 First X-Z planebending with ATM 2 motion in phasewith top of CSM. 14 4.93 .50 ATM rigid rotation about X-axiscoupled with some vehicle X-Y plane second bending. 15 5.32 .26 ATP1 rigidrotation about X-axis coupled with vehicle X-Y planesecond bendingabout CSM/MDA and STS/AM I/Fs. 16 5.76 .48 Vehicle X-Y planesecond bending about CSM/MDA and STS/AM I/Fs, ATM X and Z rotations, GRA/Can Z rotation out of phase with ATM. 17 6.03 .95 ATM Rack rotation about Y axis with vehicle X-Z planesecond bending. 18 6.79 .86 ATM Rack rotation about X axis with vehicle X-Y plane and some X-Z planesecond bending. 19 7.04 -96 Vehicle X-2 planesecond bending about CSM/MDA and STS/AM I/Fs. Significant DA-EREP Z motion. 20 7.70 .99 DA-EREPmode in Z directionwith some X motion.Small vehicle second bending in bothplanes. 21 8.03 .3 I GRA/Canister centertorsion (rotation about 2). 22 8.51 .51 ARI SolarArrays mode (out of planemotions of all four arrays). 23 8.62 .98 DA-EREP mode in Y direction coupled with Y and Z motionsof FAS tanks. 24 8.69 .54 ATM SolarArrays mode (outof plane motions of all fourarrays). 25 8.89 .68 ATM Solar arrays out of plane motions coupled with DA-EREP Y motion and FAS Tanks Y and Z motions. 26 8.95 .57 ATM SolarArrays mode (largelyout of plane motions of panels 1 and 2 arrays).

i Table 5.4 OrbitalConfiguration (ETA) CoupledAnalytical Modes (Continued)

FREQUENCY , GENERALIZED HZ. MASS DESCRIPTION - "" 9.03 .99 MDA/STS/AM and CSM rock?.r;lg and tramlation (largely in X-Y) about AM trusses with CSM bending about MDA/CSM I/F. 9.10 .88 FAS Tanks Y' and Z motions, DA-EReP Y motionwith some out of plane motionsof all four ATM Solar Arrays. 9.27 .97 FAS Tanks Y and Z motions (largely Tank 3 in Y and Tank 4 in 'Z) 9.38 .64 Vehicle first axial mode (largestmotions in CSM). 9.40 .38 Similar to Mode 30 with slightly smaller axial responses. 9.59 .99 FAS Tanks Y and Z motions(largely Tanks 1, 3 and 4). 9.71 .99 FAS Tanks Y and 2 motions(largely Tanks 2 and 6 in Y andTanks 1 and 5 in Z). 9.90 .24 GRAfCanisterTorsion (rotation about Z) , some FAS Tanks motions in Y and Z. 9.95 .92 FAS Tanks Y and Z motionscoupled with some rockingand translation of MDA/STS/AM about AM trusses in both planes. 10.28 .99 Vehiclesecond torsional mode with FAS tanks Y and Z motions (some X)

10.66 .01 Largely rigid translatlonal motion of ATM in Z direction relative to I/F with DA. 12.63 .94 Rocking,translation, bending (X-Y plane)and torsion of CSM, MDAfSTSf AM about AM trusses coupled AM Tanks Y motionsand FAS Tanks Z, Y and X motions. 12.75 .89 Vehicle third torsional mode WitL sane AM tanks Y motionsand FAS tanks X, Y and Z motions.

12.91 .98 Largely AM Tanks (+Z upperand lower tanks) with some FAS tanksmotion inall three directions. Some DA trunions Y and Z. 13.01 .19 Largely Y motionsof AM Tanks (+Y upper a'nd lowertanks) , FAS tanks in allthree directions with local deformations of ATM Rack.Out of phaserocking of GRA/ean andSpar about Y axis. 13.28 .20 AM Tanks Y and Z motions,Vehicle .third bending in X-Z plane. Out of phaserocking of GRA/Can andSpar abcut Y axis; 13.40 .89 Vehicle X-2 planethird bending with large X-Z planeshear motion at CM/SM I/F. 13.52 .02 ATM rockingabout Y axis with respect to DA interface, GRlblCa?:. and Sparout of phase X translation and Y axisrocking. MODE 1 FREQUENCY, 1 GENERATATZEDI I ??O. I Hz. MASS DESCRIPTION 45 I 13.70 .06 ATM rockingabout Y axiswith respect to DA interface, GRA/Can. I rockingabout Z axis(torsion). 46 13.78 .14 ATM rocking about X and Y axes, AM Tanks Y motions, some vehicle X-Z planethird bending, GRA/Can rockingabout Z. 47 13.97 .82 Vehicle third bending in both planes (largely X-Y) , AM Tanks Y and Z motions(largely Y) complex torsion of entire vehicle, DA trunnions Y and Z motions. 48 14.08 .73 Largely DA trunnion Y and Z motions(mostly Z) with X-Y plane vehicle third bending, some AM Tanks Y and Z motions. 49 14.47 .99 Largely AM Tanks Z motions. 50 14.52 -30 AT" SolarArrays out of plane motions of all four arrays. 51 14.61 .30 ATM SolarArrays out of plane motions of all four arrays. 52 14.62 .31 ATM SolarArrays out of planemotions of panels 1 and 5 arrays. 53 14.64 .32 ATM SolarArrays out of plane motions of panels 3 and 7 arrays. 54 14.97 .98 AM Tanks Y motions(largely +Y upper and +Z lowertanks) with vehicle X-Y planethird bending. 55 15.56 .55 ATM rocking with respect to DA about Y axis with some ATM translation in X direction. GRA/Can andSpar out of phase Y axisrocking. 56 15.57 .99 AM Tanks Z motions (largely. +Z upperand lower and -Z uppertanks) . 57 15.64 .98 AM Tanks Y motions (largely +Y upper a-,? lowertanks) . 58 15.69 .98 AM Tanks Z motions(largely +Z and -Z upperand lower tanks). 59 16.15 .99 AM Tanks Z motions(largely +Y and -Z lowertanks). 60 16.57 .37 ATM rockingabout X axis, translation in Y. GRA/Can andSpar rocking out of phaseabout X axis. 61 16.80 .14 ATM rockingabout X and Y axes, GRA/Can. andSpar rocking out of phase about X axis. 62 16.95 .99 AM Tanks Y motions(largely +Z lowertank). 63 17.17 .17 ATM SolarArrays out of planemotions of all fourarrays. 64 17.20 .16 ATfl SolarArrays out of plane motions of panels 1 .and 5 arrays. 65 17.27 .17 ATM SolarArrays out of plane motions of all four arrays. 66 17.31 .25 ATM SolarArrays out of phase motions of panels 3 and 7. Some GRA/ Can. andSpar out of phase X and Y rotations. 67 17.54 .98 Largely AM Tanks Z motisns(mostly +Y lowertank). 68 18.01 .95 FAS Tanks motions(mostly X), some AM Tanks Y motions. Table 5.4 ()rl bital Configuration (DrA) CoupledAnalytical Modes (Continued)

FREQUENCY, GENERALIZED xo. MAS DESCYIPTION ; Hz. s "- 69 18.32 .93 FAS Tanks X motions, AN Tanks Y motions(mostly -2 lowertank). : 70 18.35 .70 GRA/Can. and Spar nut of phasetranslations in ii and rotationsabout i Y. ATM Rack and CMGs X translation.

, 71 1.8.65 .96 FAS Tanks X motionscoupled with AM Tanks Y motions (largely rZ lower I tank) . i 72 18.75 .04 +Y and -Y CMGs Y motions, +XCMG X motion, -Y CMG rotation about X, i FAS Tanks X motions, AM Tanks Y motions. 73 18.80 .o 1 GRA/Can. andSpar out of phaserotations about Y and translations in X and Y. -Y CMG Y motion, +X CMG rotationabout 2. 74 18.82 .o 1 X motionsof ATM Rack and CMGs, out ofphase rotations about Y. of GRA/Can. andSpar. " I3 18.85 .oo ATM rackrotations about X and 2 withtranslation in 2. GRA/Can. and Sparout of phase rotations about Y and 2. 76 18.88 .99 AM Tanks Y motions(almost all -2 uppertank). 77 19.51 .94 Vehiclesecond axial mode. 78 19.53 .30 ATM rack rotation about Y with Y deformations. GRA/Can andSpar out of phase Y translationsand rotations about Y. Some vehiclesecond axia 1 mode, 5-21

Table 5.5

ORBITALCONFI6URATION ANALYTICAL HOOES GMC SUflMARI

UODE FREQI GM C CMC GMC GflC GHC G flC NO a HZ. (OX) (DY) (DZ) tfX) (TY) (12)

1 a 28 a 0048 99 19 a0002 a 0006 a 0000 a 0025 2 a 29 a 5055 a a0 21 a 9887 a 0015 a 0021 m~OOU0 3 a 36 a 0032 a5771 a 1128 a 3062 a 0001 a'0007 4 a 48 a 877 3 a0334 a0811 a 0001 a0053 a 0028 5 a 50 a 0596 a 6076 a 2807 a 0009 a 0165 a 0 345 6 a 51 a 2126' a 2 849 a4598 aoooo a 0271 a 0156 7 1.37 a 307 b moo20 a 6548 a 0019 a 0335 a'O000 8 la57 a I170; a7103 a0309 a 0761 0 0000 a'0657 9 la96 a 2668 a 47 74 a1136 a 0794 a 0034 a'0594 10 la99 a 4851 a 0569 a4053 a 0078 a 0385 a 0059 11 2.66 a 8116 a 2920 a0265 a 6490 a0002 a 0 205 12 3.25 a 0048 a 3387 a 1054 a 5412 a 000 0 a !O 0 99. 13 3.52 a 0135 a 0200 a9190 a 0042 a 0.431 a 0001 14 4. 93 a 0508 a 48 31 a 1396 0830 0006 a 2430 15 5.32 a 1210 a6200 a 1121 a 0581 0045 a 0843 16 5.76 a 1186 a 5725 a 0077 a 0116 a0003 a2895 it 6.03 3245 a 0541 a 4456 a 0011 a 1740 a 0006 18 6.79 a 1435 a 5559 a 1390 a 0911 a 0065 a!O 640 19 7.04 a 117 5 a 06 39 a 6948 0053 a 1167 a 0017 20 7.70 a 1286 a 0191 a 8331 a 0013 a 0178 a10001

21 ' 8.03 a 052T a 05 29 a0013 a 0045 a 0009 a 8878 22 8.51 a 49841 a5012 a0002 a 0001 a 0000 a 0032 23 8.62 0293 a 7239 a 2074 a 0387 .0003 a 0004 24 8.69 a 4612 a5004 a 0377 a 0005 a 0002 a'0000 25 8.89 a 2604 a 5858 a 1219 a 0263 a0028 a 0028 26 8a95 a 5106, a 42 34 a 0324 a 0036 a 0290 0 0011 27 9.03 a 0194' a 2259 a 1620 a5923 a 000 3 a 0002 28 9.10 a 0 865 a5011 a 3482 a 0454 00121 a 0067 29 9.27 0 243 a 4857 04782 a 0014 a 0078 a.00 26 30 9.38 9286' a 0297 a 0320 a 0002 00%3 a 0053 31 9.40 a 8793 a 0402 0346 a 0000 a 0043 0415 32 9.59 0590 a 4410 a4807 a 0167 ama8 0 06 33 9-71 a 0319 a 50 53 a 460 2 a 0019 0003 a'0004 34 9.90 11511 a 23 29 a 1993 a 0108 0006 a'4407 35 9.95 0646 a 4980 a 3705 a 0522 a0021 a'0126 36 10.21 a 0721 a 2458 a 247 3 a4332 0013 0003 37 10.66 a 03871 a 1059 a 8491 a 0033 a0028 a'O001 38 12-63 a 055 0s a 5142 a 1274 a 27 93 a 0062 a 0178 39 12.75 a 0520' a 3825 a 1231 a 4164 a0130 a 0131 44 12.91 a O70T a I815 a6398. a 0784 a0278 a 0018 41 13.01 a 1319 a 6245 a 1475 a 0166 a 0556 a!0242 42 13.28 a 1126 a 2655 a 4298 a 0212 a1376 a a333 43 13.40 a 017 3 1296 a 7433 a 0434 a 0574 a 0091 44 13.52 a 4343 a 1821 a 0936 a 0532 a 1350 a 1018 45 13.70 a 3048 a 2764 a 2319 a 0312 a 0459 a'lO99 46 13.78 a 2541 a 3719 a 2477 a0154 a 0179 a 0870 47 13.97 0108 a 5582 a 2820 a 1315 a 0037 a'0144 48 14a 08 0329 a 50 79 a4104 a 0294 0 0028 a10166 49 14ob7 027 a a 0559 a 6911 a 0031 a 0226 a40 02 50 14a52 a 4989 a 4973 a 0022 0 0008 a 0003 a 0006 51 14.61 a5001 a 4999 -a 0005 a0000 a 0005 0000 52 14a62 a 5109 a 45 91 -a0002 a 0006 a 0285 a 0010 5- 22

Table 5.5 (CONTINUED)

ORBITAL CCNFIl3URATIONANALYTICAL MODES GHC SUHHARV

HOD€ FREQ9 GMC G MC G HC GMC GMC NO . HZ (OX, iOY, (DZ) (TX) (TZ)

53 14.64 b L795 b5158 boo08 0014 .90002 54 14.97 0348 0 8703 00395 0 0148 0'0 354 55 15.56 b 3457 b 1372 1141 00079 00027

56 15.57 0 0090 0 0015 9815 0 0005 0 0001 !if 150 64 b 0096 0 9246 b 0567 0007 olOO24 58 15.69 0 9117' 0 0440 b 9345 0 0006 0 9002 59 16.15 bo155 0 0169 b'3587 .a034 .0000 60 16.57 0 0499 0 42 26 0 0417 0 4187 OC92 61 16.8C b 1571 b 4574 0 0315 0 3053 .r1034 62 16.95 0251 b 9211 e 0247 0 0205 0'0084 63 17.17 0 4974 0 4998 0 0004 0005 0017 61) 1702c b5001 0 5001 -b602@ 0007 0 0002 65 17.27 .4712 b 4773 051Q 0003 .10001 6(> 17.31 b 3233 b 4216 00393 1614 00023 67 17.54 0 0 241 0 0181 b 9198 b 0030 .0001 6 CI 18.01 b 5485 2859 1594 b 0037 0 OGO2 69 18.32 0 3614 5521 0761 b 0030 0 0030

70 18.35 3412 0 2319 0 0608 b 0657 0312 71 18.65 0 3569 05409 0 0979 b 0048 :0010 7:' 18075 0 4512 0 4217 rn 0725, 0 0444 0'0013

73 18080 0 2167' 0 33 07 b 0360 1014 0 0297 74 18.82 0 3766 b 9407 0 0208 00098 0'0166

75 18085 b 5164 2746 b C112 0 0629 .-0349 76 18088 0114. e 9506 e0153 0 0204 .00 21 77 19051 e 9851 .0 347 a 9702 0034 0'0004 78 19.53 0 260 0 0 2667 0395 0 1390 0 036 79 200 07 0724 0 0931 e 8106 0139 0:0018 80 20.19 0117 8638 00863 0256 0 0116 81 20.46 250 I 3762 0 0836 2265 0,0192 82 20.57 0 3175' 0 4221 bo203 b 2289 0057

83 20.58 0 3738 0 4254 0 0441 0 1220 OC15 84 20.61 0 3582 b 4156 Q781 0 1317 0034 85 20.65 0 3655 4123 e 0592 1494 00 31 86 21.25 b 7431 0 0892 0 0657 0 0990 010026

87 21.47 4724 0 20 38 01017 0 2133 0025 08 21.68 b 2485 0 1948 0463 0 0837 .3545 89 21.78 0 3213 0 1547 lL30 0 1510 2331 90 22. 06 b 430 6 0 2477 0 1009 0 0728 e 1124 91 22.22 0 057 3 1747 b 0138 b 0799 6322 92 22.35 0 3732 0 3150 0 1810 0 0892 0065 93 22.65 0 2957 30 32 b 0331 s 3055 b 0067 94 23.09 0 3976' 1329 0 0761 0899 0 2193 95 23.19 7053 m 1414 b 1334 0 0043 0'0031 96 23041 b 1286 0 26 15 b 0956 2697 0.0443 97 23.63 b 2485 b 5337 b1523 0 0567 00'56 98 24.02 0 857t 0 0200 bo873 0 0174 0 0008 99 24.21 0 3978 4 3210 .0168 1030 .'00?1 100 24.29 0 U659 b 0761 0 00 82 b 0253 0 0049 101 24. nz 0 tT72 0 ss 19 b 0675 2563 0519 1c2 250 15 0 0475 b 0897 0266 8200 0 0043 103 25.60 0 5 0441 2117 0561 0248 b 1998 104 250 67 .7959 0 1060 0409 b 0111 0'0496 5- 23

5.2Discussion of Test Modes

Thirty valid test modes were acquired during the Orbital Configura- tion modal survey. A list ofthese modes arrangedin order of ascending frequencies is presentedin Table 5 .6. It will benoted that test run no. 400 hasbeen deleted because it contained invalid data in the ATM areaof the structure.

It can be seen in Table 5.6 that twenty-five unique modes were ob- tainedranging in frequency from 0.31 Hz through 17.01 Hz whichrepresent all themajor resonances which could be identified in the 0 to 20 Hz test range. The remainingfive modes representthe results of efforts to retune someof the original modes to yield better orthogonality between modes.The reductionand normalization of data, modal characteristics and purity of the Table 5 .6 modes are discussed below.

5 .2.1Reduction of Data - Reductionof data consisted of "trans- lating"the acquired quadrature data for each test mode tospecific collocation points using rigid body or"least square" mathematical tr.ansformations. The specificcollocation points correspond to points selectedfrom the pretest modal vibrationanalysis. The degreesof freedomcorresponding to the reduced data and identical to the model DOF'S are shown in Table 5 .3. It will benoted that the Table 5 .3data define193 reduced degrees of freedom but the original quadrature test data were for 200 degreesof freedom. This is explainedas follows: The six accelerometerslocated on theoutboard ends of the ATM outriggers were deletedfor purposes of defining mode shapes. The primarypurpose of theseaccelerometers were toprovide reference accelerations for the sixforce shakers located on theoutriggers. The outriggeraccelerometers couldnot be utilized in a manner which would provide useful additional shapeinformation. In addition, data from the five accelerometers located on the ATM Canister were deleted (three on thesun end , two on the MDA end).Instead of .definingCanister motion separately, a new six degreeof freedom collocation point was defined at the same geometrical location as theSpar Center. This point was definedas the GRA (Gimbal RingAssembly)/Canister Center with motion given by the six accelerometers locatedon the GRA. The SparCenter point has five degrees of freedomdefined by thefive accelerometers located on thetop and bottom ofthe Spar. The datadeletions mentioned above total eleven resulting in 189 basicdegrees of freedom. Since the ATM solararray uniaxial accelerometers were mounted in the plane of eachfolded array, trans- formationof each accelerometer to launch vehicle coordinates (X and Y) was necessary resulting in an additional four degrees of freedom bringing thetotal for reduced data to 193.

5.2.2 Normalizationof Data - Afterreducing the data as described above,the results were normalizedto a 193 by 193 discrete mass matrix. The normalization was performed in a manner which yielded unity generalized

mass for each mode. ' Thisnormalization technique is convenientfor orthogonalitycalculations, determination of generalized mass contributions (GMCs) andcomparison with analysis. The 193 by 193 mass matrix was derivedfrom 5- 24

analytical mass matrices which were available for each of the various structural componentscomprising the analytical model. The method for .derivingthe mass matrix consisted of static collapse of the component matrices tothe 193 degrees of freedom contained in Table 5 .3. The results were merged toform the final 193 by 193matrix. Subsequent calculationsinvolving this matrix and the mode shapedata has shown it to haveinadequate definition in the area of the ATM. This is at- tributed to a basic lack of definition of A’SM motioncaused by thelimited number ofaccelerometers available for use on the ATM duringtesting. Since it is anextremely complex structure,the instrumentation required to define ATM motionadequately would havegone beyond practical limita- tionsor resulted in sacrifices in other important areas of the structure.

5 .2.3Orthogonality of Test Modes - Inorder to determine the relative purity ofeach test mode anddetermine if a re-tuned mode yields a purer mode thanthe original tuned mode, orthogonalitycalculations were performed. The resultsrepresent the standard triple matrixproduct of normalized modes andthe kernel mass matrix described above. This triple matrix product yields a 30 by 30 symmetricalorthogonality matrix containing a unitydiagonal with the off-diagonal terms representingthe amount of inertial coupling between modes as a fractionof the unity generalizedmasses. When multiplied by 100.0,the numbers inthis matrix can be thought of aspercentages. A summary ofthe data is shown in Table 5.7. The Table 5.7 dataindicates generally excellent orthogonality betweenmodes. Mode 15A exhibitsexcessive coupling with other modes (particularly Mode 14A) and is obviouslynot well isolated enough to be consideredfor use in correlation studies. Mode02A (suspension system mode) containsapparent bad data at two accelerometerson the Base Ring/OWS interface(sequence nos. 1 and3) causing apparent coupling withother modes.However, Mode02A is a well-tuned mode. It should also benoted that mode20A was not well isolated from mode 19A (32.4% coupling).

In thefive cases of re-tuned modes, theorthogonality results show:

a. mode06B is a purer mode than 06A, b. mode10A hasslightly higher average coupling but slightly lowerstandard deviation than mode 10B, and is therefore slightly more well tuned, c. mode13B is purer than mode 13A, d. mode 18A is purer than mode 18B, e. mode22B is purer than mode22A.

Therefore, modes 06B, 10A, 13B, 18A and 22B will beused forcorre- lation studies.

5.2.4Characteristics of Test Modes - There are twenty-fiveunique modes containedin the thirty test runsgiven in Table .6. The unique modes arebriefly described in Table 5.8. Most of the modes arehighly I ..

5- 25

cdupled modes involvingmotion throughout the structure while a few do havedominant local motions. CXCs basedon the 193 by 193 discrete mass matrix were determined for each of the 193 degrees of freedomcontained in Table 5.3 forevery test mode. Inaddition, GMCs forthe major com- ponentscomprosing the configuration were calculated. The major compo- nentsare considered to be the following:

a. Base Ring/OWS Skirt/IU/FAS, b. 6-FAS 02 Tanks, c . MDA/STS/AM, d. 6-AM N2 Tanks, e. Counnand/ServiceModule, f. DeploymentAssembly, g. ATM Rack with CMGs andSolar Arrays , h. ATM Spar, i . ATM GRA with Canister.

Table 5.9 shows a summary of GMCs foreach of the thirty test modes as anaid in determining the general nature of the test modes. It should benoted that the GMCs for Mode02A aredistributed improperly due to the bad accelerometerdata previously noted. A redistribution would show mostof the MC concentratedin the X-Y Plane.Two-dimensional plots for each ofthe thirty mode shapesare presented in Volume 11. The Volume I1 plotsrepresent the translated and normalized test quad- ra ture data. As opposed to the Launch Configuration test modes, theOrbital Configuration test modes donot exhibit local motions relative to the various component centerlines. However, these modes doexhibit characteristic large relative deflections in most degreesof freedom in the CSM fromthe MDA interfaceforward through the CM/SM interface. Thesedeflections occurred in the suspension system modes (Modes01A and 02A) as well asthe highsr frequency modes.

5.3 Correlationof Test Modes withAnalytically Predicted Modes

The following'paragraphspresent the methods, supporting data and theresults of thestudy to correlate the test modes.

5.3.1Methods of Correlation - Test,andanalytical GMCs and two- dimensional mode shapeplots were compared. HOwever, sincethe Orbital Configuration test modes did not indicate significant local deformtion which were notmeasured (as was not the case for the Launch Configuration) two supportingcorrelation techniques became available:the first of these is thecross-orthogonality check in which a triple matrix product is formedusing the transpose of the normalized test modes asthe pre- multiplier andthe reduced set of normalizedanalytical modes as the post-multiplierof the 193 x 193 mass matrix. The resultsof this triple productcontains elements equal to or less thanunity, indicating the degreeof similarity between the analytical modes andthe test modes. If a 5-26

givenanalytical mode tendsto correlate with a given test mode, the cross-orthogonalitycheck will indicate this byshowing a cross GMC approachingunity. The secondadditional method consistsof. determining a best fit ofanalytical and test GMCs over the entire mode shapein a least-squaressense. This is done by finding,for a given test mode, the sum ofthe squares of the differences between the. test and analytical GMCs forevery degree of freedom. The analytical mode for which this sum is a minimum will bethe mode which best fits the test mode GMC distribution. It shouldbe 'noted that the latter methods are employed only as a guideto correlation and must be used inconjunc- tionwith direct shape comparisons and engineering judgement.

5.3.2Correlation Results - Usingthe methods outlined above, twenty-fourof the twenty-five unique test modes were correlatedwith analytical modes. Mode 15A is notcorrelated due to poor orthogonality characteristicsdiscussed in Section 5.2. In general, the correlations are quite clear except for modes which contain significant FAS tanks responseswhich tend to make thecorrelation uncertain due to the known differencesbetween the analytical and MIA FAS tanks.Table 5.10shows a summary of thecorrelation results for the twenty-four unique test modes. Table 5 .ll presentsthe cross-orthogonality and least-squares GMC fit results. The lattertable shows boththe "best" and ''next best" correlationsusing these methods. It canbe seen that the two methods agree in many cases.

5.3.3 Discussionof Correlation Results - In mostcases, mode shapecorrelations are excellent. However, asTable 5.10 shows, the test and analyticalfrequencies vary in agreement. That is, in some cases,frequency differences are significant while in other cases they arenot. For first vehicle bending modes, theanalytical frequencies varyfrom 4.6 percentto 18.1 percenthigher than test frequencies. The first vehicle axial mode analyticalfrequency is 6 percenthigher than test whilethe second vehicle axial mode analyttcalfrequency is 14.7 percenthigher. The firstvehicle torsional mode analyticalfrequency is almost21 percent lower than test. All the modes mentioned aboveinvolve significant motions throughout the entire structure. Hence, it is difficult to determine with certainty at this point which individual components contain modeling deficiencies which would.result inthe abovefrequency differences. In most of the modes thereare significant relative motions across the CSM axial port area andacross the CM/SM interface. Hence, theseareas are suspect.

The FAS oxygentanks exhibit response characteristics similar to thoseobserved during the Launch Configuration test. That is, the tanksrespond analytically at frequencies higher than test frequencies (seeFigures 5.6 through5.8).

The ATM model appears to correlate well with test althoughthere werenot significant local deformations of the ATM inthe test frequencyrange. 5- 27

It canbe seen in Table 5.10 thatthe vehicle second torsional mode obtainedduring test (Mode 18A) is correlated with analytical mode 39 which is actually a thirdtorsional mode. The analyticalsecond torsional mode is mode 36 whichoccurs at 10.28 Hz. However, the mode 39 correlation with mode 18A is the best correlation which could be found. The shapediscrepancy leads one to suspect that the torsional stiffnessacross the CM/SM interface is modeled toosoftly. The correlation of the vehicle first torsional mode also indicates this apparent modeling deficiency.

5.3.4 Conclusions - As a resultof evaluating the Orbital Configura- tion modal survey test data and correlating these data with the best availablecorresponding analytically derived data, the following con- c lusions were reached :

a.twenty-five unique test modes were acquiredwhich represent all identifiable majorstructural resonances in the 0 to 20 Hz test frequencyrange;

b: thequality of the test modes is excellentwith only one mode exhibiting poor orthogonality characteristics;

c. correlations of the test and analytical mode shapesare excellent. However, some significantdifferences in test andanalytical frequencies were notedand required further, more detailed, studiesin order to pinpoint the sources of thesedifferences. Stiffnessmodeling in the areas of the CSM axial port and the CM/SM interfaceare suspected to be deficient, however,due to thenature of the test modes, otherstructural areas may be involved. I .I I,.. . ,. ,

5- 28

Table 5.6

SKYLAB ORBITALCONFIGURATION MODAL SURUEY. TEST

VALID TEST RUNS ARRANGED IN ASCENDING FREQUENCY ORDER

HODIS MODE RUN FREQm v NO. N AHE NO. HZ. COMMENTS "-.- "" "- """ -"_"""""-.~""-""~"" 1 01A 333 0. 31 2 02A 3 36 0 m31 3 038 614 1. 31 9 04a 37 8 1.43 5 05 A 3 96 1.66 6 06A 4 34 1a72 7 G6B 610 1.79 RE-TUNE OF MODE 06A 8 07A 432 2.51 9 C8 A rr 52 3. @6 10 09A 443 4 -10 11 10 A 48 2 4.50 12 1OB 619 4.55 RE- TUNE OF HODE 10A 13 11A 5 36 5.03 14 12A 574 5.86 15 13A 991 60 25 16 138 667 6.36 RE-TUNE OF MODE 13a 17 14 A 479 6. 73 18 1SA 600 7.59 19 16 A 347 8.85 20 17A 549 11.59 21 18 A 526 12.65 22 18B 663 12.87 RE-TUNE OF MODE 18A 23 19 A 586 13.30 24 204 627 13.68 25 21A 633 19.55 26 220 654 15040 RE-TUNE OF MODE 224 27 22 A 506 15.78 28 23A 695 16.20 29 24 A 638 16.53 30 2SA 499 17.01 ~ c

Table 5.7 Summary of Test Modes Orthogonality Results

NO. OF MODES NO. OF MODES AVERAGE STANDARD RANGE OF COUPLING [ODE MODE 2 10% > 10% COUPLING DEVIATION, r PERCEN': 'MODE -10. NAME COUPLING COUPLING PERCENT PERCENT MAX. MIN . 1 OIA 25 4 3.95 3.78 12.612% 0.210% 2 02A 23 6 5.66 6.U 20.511% 0.2118B 3 03B 29 0 2.05 2.61 9.4113A 0.1112A 4 04A 28 1 3.02 4.67 24.211% 0.1117A 5 0 5A 26 3 I 4.24 7.09 35.8106~ 0.2109A 6 06A 26 2 4.70 6.74 35.810% 0.011% 7 0 6B 26 2 3.10 4.15 19.610% 0 .O 117A 8 0 7A 28 1 2.83 2.84 10.8115A 0.1117A 9 08A 28 1 2.77 2.55 11.5113A 0. 111a 10 0 9A 27 2 3.47 3.34 13.711OA 0.210% 11 1OA 26 2 4.29 8.61 45.511% 0.2123A 12 10B 26 2 4.43 8.49 45.211% 0.2105A 13 lIA 29 0 1.97 1.77 6.4106B 0.012% 14 1% 26 3 3.64 5.14 24.2115A 0.0123A 15 13A 24 4 4.48 4.75 20.510% 0.31064 16 13B 27 I 1 2.69 3.68 17.5/0% 0.011% 17 14A 27 2 5.72 11.53 63.8115A 0.1124A 18 15A 22 7 10.38 15.83 63.8114~ 0.0/13B 19 16A 28 1 2.49 3.27 15.910% 0.1108A 20 17A 28 1 3.56 3.52 15,1122A O.O/06B 21 18A 25 3 4.21 5.80 27 e5122B OelIllA 22 18B 25 3 5-32 9.12 48.1119A 0.210% 23 19A 25 4 7.37 11.06 32.412OA 0.5/10B 24 20A 25 4 5.68 6.79 20.312lA 0.2/03B 25 21A 24 5 5.26 7.79 32.512% 0.3/03B 26 22B 22 6 6.10 8.57 32.01236 0.3/13B 27 2% 21 7 8.13 9.86 37.1123A 0.OlllA 28 23A 25 4 6.31 8.49 37.112% 0.011% 29 24A 26 3 4-95 4.11 16.612% 0.1114A -30 2% 27 2 3 063 3.83 16.. 6 1242~ 0.2110A Table 5.8 Descriptions of Test Modes

" MODE FREQUENCY 1 NO u;iE -a. DOMINANT CHARACTERISTICS 1 OlA 0.31 Suspensionsystem mode - largely X-Z plane translation of the vehicle. 2 0% 0.31 Suspensionsystem mode - largely translation and rotation of the vehicle in the X-Y plane. 3 0 3B 1.31 First vehicle X-Z plane bending about the MDA/CSM interface with ATM X-Z planerocking out ofphase with CSM. 4 04A 1.43 First vehicle X-Y plane bending about the MDA/CSM interface with AT" X-Y planerocking out of phase with CSM. 5 0 SA 1.66 First vehicle X-Y plane bending about the MDA/CSM interface with ATM X-Y plane rocking in phase with CSM. 7 0 6B 1.74 First vehicle X-Z planebending about the MDA/CSM interface with ATM X-Y plane rocking in phase with CSM. 0 7A 2.51 Vehicle roll and first torsion coupled with X-Y plane first bendingabout MDA/CSM interface and ATM X-Y plane rocking in phase with top of CSM. 9 08A 3.06 First vehicle X-Z planebending about the MDA/CSM interface with ATM Z , motion in phase withtop of CSM. 10 0 9A 4.10 First vehicle torsional mode with CSM andm/STS/AM out of phase with OWS/ I .* IU/FAS. Largetorsional motion of CSM relativeto MDA. i 11 10A 4.50 ATM rotation about X axis with vehicle X-Y planesecond bending about the MDA/CSM and STS/AM interfaces. I l3 1lA 5.03 ATM rotation about Y axis. I' 14 1% 5.86 Vehiclesecond X-Y planebending about MDA/CSM and STS/AM interfaces with some FAS tanksmotions in Y and Z directions. 16 13B 6.36 Ve'ii.*cle second X-Z planebending about the MDA/CSM and STS/AM interfaces. ~ 17 14A 6.73 FAS Tanks Y and Z motionscoupled with OWS/IU/FAS rockingabout the Base Ring in the X-Z plane. 19 16A 8.85 Vehicle first axial mode.

~ 20 17A 11.59 FAS tanks Y and Z motions, MDA/STS/AM X-Y planemotion. Some Y motionsof I1 both +$ AM tanks. 21 18A 12.65 Vehiclesecond torsional mode. 23 19A 13.30 Large Y motion of one AM tank (+Y, lower tank)with vehicle X-Y plane third bending. /I 24 20A 13.68 Large Y motionof +Y, upper AM tank and some Z motion of -Z, lower AM tank coupledwith vehicle X-Z planethird bending. i- i- Table 5.8 Descriptionsof Test Modes (Continued) - NODE FREQUENCY 1 NO. NAME Hz. DOMINANT CHARACTERISTICS 25 21A 14.55 Large Y motion of +Y, upper AM tank coupled with vehicle X-Y plane third bending. 26 22B 15.40 FAS tanksmotions in all three directions, AM tanksmotions in Y coupled with vehicle third bending in the X-Y plane. 28 23A 16.20 FAS tanksmotions in all three directions (dostly X) AM tanks Z motions, fourth vehicle X-Z planebending. 29 24A 16.53 FAS tanks X motions with AM tanks Y motions. 30 2% 17.01 Vehiclesecond axial mode. 5- 32

Tab le 5.9 ORBlT AL CONFIGURATION TEST HOOES GflC SUtlHARY

WD DE FRE Q, CM C CHC GHC G HC 6 HC GflC NO. HZ . cox 1 (OY 1 (DZ 1 tT)o (TY) (TZ) OlA 31 00106 mol71 09553 .0009 e0062 00 92 02B 031 202 7 22 19 .3995 00018 00702 .10 40 038 1.31 356 7 a 00 26 ~6142 .0004 00247 00 13 ObA 1.63 .220 5 .6L85 0641 05 24 .oaf0 a Ob 34 05A 1. 66 1138 06374 e0946 .1222 e00 15 e 0605 06A 1.72 3625 01600 32 10 .0299 00292 em74 068 1.74 .4395 0245 e4927 .00 11 o038b A038 O7A 2. 51 033 1 os621 a 0983 25 73 .0001 .Ob 93 08A 3.06 00596 00182 .86 30 a0003 mO46Z 00 26 09A G. 10 021 5 05 34 00401 .8755 .0001 a 00 94 1OA c.5; 152 8 .&?52 184C 1449 .0910 .Ob 20 108 4.55 1528 a 47 72 187t: 1394 .o >O€ 04 30 lid 5.03 a 3596 00176 4199 .0002 .ZOO7 .w21 12A 5.86 .C339 a6240 a 20 16 *025* .0011€ a0969 13A 6.25 G73 7 .os la o697C 0137 16 30 a OC 17 138 60 36 G3b i 04 15 76 15 00 96 01307 00 07 14A 6.73 034 1 e1890 3666 a 0457 000 35 00611 15A 7.59 C315 04499 .33 34 .:.? 12 00023 a 01 47 166 8.85 8781 00139 04 27 00012 00 0 29 00613 17A 11.59 oI.333 58 31; 3638 0195 .0050 0055 18A 12.65 C32 0 00723 .G7 39 .6192 '0 0 13 00013 188 12.87 0276 .26 59 .0812 06278 00 J 29 00147 19A 13.30 e Ob7 5 .75 73 a1922 J081 a0107 e 0262 ZOA 13.69 014 8 os335 49 36 uGb9 00475 0056 ZlA 16.55 007 9 8269 10 88 5273 00061 .Ot 39 228 1504i rn 150 3 0468 1 02327 air957 00 0 88 00445 22A 15. 78 270 3 03949 2322 .5352 00395 e0379 23A 16.2G 194 6 00932 06228 ,239 00591 O@65 24b 16053 282 4 a5388 0792 .ill9 .0210 01 66 25A 17. 3 1 825 7 00568 0952 30 32 00 OU .014u L

Table 5.10 Summary of Test and hrlalytical Modes Correlation II- &!.LYTICAL MODE 1 l- "- I' FREQ. Hz, DOMINANT "TION D(R4INANT MOTION .31 Suspensio'nsystem mode, Rigid body Suspension system mode. Rigid body , translaiion in ille X-Z plane. translation in the X-Z plane. .31 Suspension sys temmode. Rigid body Suspensionsystem mode. Rigid body ' translation in the X-Y plane. transla tion in the X-Y plane. 3(38)1 1.31 First bendingabout the MDA/CSM First bending about the MIlA/CSM interface in-X-Z planewith ATM interface in-X-2 plane with ATM rockingin X-Z planeout of phase rockingin X-Z planeout of phase with CSM. with CSM. 1.43 First bendingabout the MDA/CSM First bending 'about the MDA/CSM interface in X-Y plane with ATM interface in X-Y plane with ATM rocking in X-Y planeout ofphase rocking in X-Y planeout of phase with CSM. with CSM. First bending about the MDA/CSM 9 1.96 First bendingabout the l?DA/CSM interface in X-Y plane with ATM interface in X-Y plane with ATM ! rocking in X-Y plane in phase rocking in X-Y plane in phase -. -. with CSM. with CSM, 7(6B) 1-74 First bendingabout the MDA/CSM 10 1.99 First bendingabout the MDAICSM interface in X-Z planewith ATM interface in-X-Z planewith ATM rockingin X-Z planein phase rocking in X-Z plane in phase - with CSM. with CSMI 8(7A) 2.51 Vehicle roll and first torsion I1 2.66 Vehicle roll and first torsion coupledwith X-Y plane first coupledwith X-Y plane first bendingabout MDA/CSM interface bending about MDA/CSM interface and ATM rocking in Y-Z plane in and ATM rockingin Y-Z plane in Dhase w5- top of CSMr phasewith the top of CSM. First bendhg about theMDA/CSM First bendingabout the MW/CSM interface in X-Z plane with ATM interface in X-Z plane with AIM Z motion in phase with the top Z motion in phase with the top of CSM, CSM. Vehicle first torsional mode with Vehicle first torsional mode with CSM,MIk4/STS/AM ,out gf phase with CSM out of phase with MIA/STS/AM FAS/N/ORS. Largetorsional motion and FAS/IU/OWS. Largetorsional of CSM relative to MDA. motionof CSM relative to MDA. Table 5.10 Summarv of Test and Analvtical Modes Correlation(Cont'd)

EST M( E NAZ,Y11( LL MODE T NO. RFIQ. Hz. DOMINANIM6,TiON NO. FREQ. HZ, DOMINANT MOTION, ll(l0A) 4.50 9TM rotation mostly about X axis - 15 5.32 ATM rotation mostly about. X axis withvehicle second bending about withvehicle second bending about the MDA/CSM and STS/AM interfaces the MDA/CSM and STS/AM interfaces "_ in X-Y plane. in X-Y plane. 13(11A) 5 .oa ATM rotation about Y axis. 17 6.03 ATM rotation about Y axis. 140 5.86 Vehiclesecond bending about the 16 5.76 Vehiclesecond bending about the MDA/CSM and STS/AM interfaces in MDA/CSM and STS/AM interfaces in X-Y planewith some FAS tank X-Y plane coupled with ATM motion in Y-Z plane. rotations about X and Z axes, GRA/ CAN center rotation about 2 axis out ofphase with ATM rack. 16(1313: 6.36 Vehiclesecond bending about the 19 7.04 Vehiclesecond bending about the MDA/CSM and STS/AM interfaces in MDA/CSM and STS/AM interfaces in the X-Z plane, the X-Z plane. 17 (14A: 6.73 FAS 02tanks motion in Y-2 plane 28* 9.10 FAS 02tanks' motion in Y-Z plane, coupled with OWS Skirt/IU/FAS Y motion of EREP. rockingabout the base ring in X-Z plane, -19 (la: 8.85 Vehicle first axial mode. 30 9.38 Vehicle first axial mode. 20 (17A: 11 r59 FAS 09 bottle Y and Z motion, 38 12.64 m/AM Y motion, AM N? tanks-math- MDA/Ai Y motion, AM N2 2anks- ematical model point 'io and21 mathematical model point 20 and motion in Y direction. FAS bottle 21 motion in Y direction. motion does not correlate with test mode17A. FAS O2 tankmotion in test mode17A haselements of analytical modes 29(9.266 Hz.), 32 (9.593 Hz.), 33(9.710 Hz.), and35 (9.95 Hz.) all beingpredauinately FAS tank modes. Vehiclesecond torsional mode 39 12.75- Vehicle third torsional mode .**

*Correlation not clear. **ldcnticalin shape as test mode exceptfor CSM phase. 5*10 Summary of Test andAGalytical Modes Correlation(Cont'd) E T ' coAY9L MODE 1 REQ.,.! DOMINANT MOT ION FREQ.; DOMINANT MOTION 13a3 Y motionof AM N tank math.model 41 13.01 Y motion of An N2 tank math.model point No 20, vehicle2 third bending point No 20, vehicle. third bending predominately in X-Y plane. does not correlate well. Vehicle bending correlates closer with analytical modes 47(13.970) and 48 (14.084) . 13.68 AM N2 tanks Y and Z motion,vehicle 42 13.28 AM N? Tanks Y and Z motions, thirdbendings predominately in vehicle third bending predomina telJ X-Z plane.This mode was notwell in X-Z plane. separated from test mode lgA(13.3 Hz) as shown by largecoupling in orthogonalitycheck. 14.55 AM N2 tanks Y motion and vehicle 47 13.97 Vehicle third bending in X-Y plane: third bending in X-Y plane, AM tanksmotions do not correlate well. 54 14.97 AM N, tanks Y motion,vehicle bendrngdoes not correlate. cn 15.40. Vehiclethird bending predominately 47 13.97 Vehiclethird bending predominate11 I w in X-Y plane, AM N2 tanks Y and 2 in X-Y plane, AM N2 tanks and DA cn motions, FAS 02tanks X, Y and Z trunions Y and Z motion. motions.. 16.20 Z motion of AM N2 tanks coupled No single mode correlates well. with X, Y, Z motions of FAS 02 Analytical modes inthe 18-19 Hz tanks (X motion is largest) , rangeresemble FAS tanksmotions fourthbending of total vehicle but the FAS tanksmotions are in X-Z plane. Coupled with Y motions of AM tanks andnot Z motion as it occurs in test mode 23A. 67 17.54 AM N2 tanks Z motion.Note: Analytical mode67 onlyapprox- imatescorrelation. Table 5.10 Summary of Test and Analytical Modes Correlation (Cont'd) " I I CORRELATING I 1 , TEST MODE ANALYTICAL MODE , NO. 'FREQ. HZ. DOMINANT MOTION NO. FREQ. HZ.' DOMINANTMOTION 29(24A) 16.53 FAS 02 tanks X motioncoupled with 69 18.32 FAS 02 tanks X motions and AM N2 1ai.r N3 tanks Y motion. tanks Y motion. 30(25A) 17.01 !Vehiclesecond axial mode, 77 19.51 Vehiclesecond axial mode. J A . Table 5.11 Cross-Orthogonality and GI!C Least-Squares Fit Results

CORRELATING ANAWICAL MODES CORREIATING ANALYTICAL MODES , BASED ON CROSS-ORTHOGONALITY- I TEST 1: BEST NEXTBEST MODE KEF TEST i FREQ., ~ FREQ .,, MODE HZ. NO. , COUPLING ' HZ. NO. COUPLING HZ. T u-31 2 9 64 31 0.29 3 66 2(02A) 0.31 1 .445 0.28 6 .245 0.51 1 ""- , 3 (03B) 1.31 7 .894 1.37 37 .3107 10.66 1.37 4 (O=W 1.43 8 .876 1.57 751.96 .4059 18.85 5 (0%) 1.66 9 .809 1.96 1.578 ,4688 1.57 6 (OW 1.72 10 .766 1.99 37 .32610 10.66 7 (0 6B) 1.74 10 .831 1.99 37 .403 10.66 10 1.99 * I ""- ! 8(07A) 2.51 11 .704 2.66 12 .490 3.25 15 5.32 i 12 j 3.25 : 9 (OW 13 3.06.959 3.52 37 .502 10.66 13 3.52 * ""- 10 (0 9A) 4.10 12 .740 3.25 11 .601 2.66 11 2.66 1 12 I 3.25 I ll(l0A) 4.50 14 .756 4.93 15 .738 5.32 18 6.79 ' 15 5.32 12(10B) 4.55 14 .764 4.93 15 .744 5.32 18 6.79 15 13 (1lA) 5.03 17 .709 6.03 45 .416 13.70 17 I 6.03 * ""-

14(12A) 5.86 18 .650 6.79 16 .635 5.76 15 ~ 5.32 18 6.25 19 .820 7.04 17 .3 24 6.03 19 * 15(13A) ~ 7.04 ""- cn I 16(13B) 6.36 19 7.04 .83317 .377 6.03 19 1 7.04 * ""_ w 17 (14A) 6.73 18 .441 6.79 16 .343 5.76 35 9.95 18 U ~ 6.79 1 18(15A) 7.59 18 .636 6.79 60 .246 16.57 18 6.79 15 : 5.32 19(164) 8.85 30 .899 9.38 31 .874 30 9.409.38 31 ' 9.40 ' 20 (17A) 11.59 ' 38 .606 12.63 $1 .525 13.01 32 9.59 38 12.63 21 (18A) 12.65 39 .SO8 12.75 27 .404 9.03 39 12.75 * ""- 22 (18B) 1.2.87 39 .631 12.75 38 .429 12.63 39 12.75 38 12.63 23 (19A) 13.30 43 .49 1 13.40 42 .476 13.28 41 13.01 12.63 38 24 (20A) 13.68 . 47 .465 13.97 49 .455 14.47 41 42 13.0113.28 25 (2U) 14.55 57 .552 15.64 47 .525 13.97 54 14.97 57 15.64 26 (22B) 15.40 43 .297 13.40 67 .292 17.54 38 12.64 47 13.97 27 (22A) 15.78 43 .363 13.40 48 .299 14.08 47 13.97 15 5.32 28 (2%) 16.20 67 .569 17.54 87 .251 21.47 18 6.79 46 13.78 29 (244 16.53 54 .403 14.97 69 .384 18.32 90 22.06 72 18.75 30 (25A) 17.01 77 .777 19.51 78 .345 19.53 77 19.51 92 22.35 . I 1 \ asterisk (") indicatesthe second best fit was too poor to consider. 5- 38 I 1

I I

I i:!...... I iil ... iil. ...

U 0 U 0 ni 4 c

Figure 5.7 CWOWNT GK WIESVS. FREQENCY 5- 40 5-41

5.4 CorrelationImprovement Methodology 5.4.1 GeneralApproach - A list ofthe literature reviewed in searchof a suitable metliod to improve correlationbetween experimental and theoretical results is presentedin the Reference Section of this report. Mostof thereferenced methods involve computations using meas- uredamplitude data and result in a model limited in size to the number ofdegrees offreedom measured in test. They alsoi-equire the existence of a compatable mass matrix that is orthogonalto the measured data. Hall* proposed a methodof modifying existing detailed analytical models toachieve the desired correlation, but his approach also requires direct computationsusing measured amplitude data. It was felt that valid Sky- lab modeling results could not be obtained using any methodwhich depends onmeasured modal amplitude for the following reasons:

a. 630 degreesof freedom (DOF) inthe analytical model were judged necessaryfor good fidelityin loads calculations. Only 200 DOF were measured;

b. it was notpossible to derive a test c.ompatablemass matrix that adequatelyrepresented the Skylab Launch Configuration kinetic energy distribution in all areas of the analytical model;

c. much ofthe measured amplitude data contained local effects which could not be properly accounted for.

Inorder to minimize these shortcomings, a method to improvecorrelation betwe,enthe Skylab experimental results and the theoretical model was developedwhich relies heavilyon measured frequency data. A de- taileddescr'iption of this method is presentedin "Dynamic Test Reflected Structural ModelMethodology Report", published in December 1972. The methodologypresented in this section is limitedto a briefdiscussion ofthe frequency algorithm that has been developed and to discussion of its applicationto the Skylab Orbit Configuration test results.

5.4.2 The FrequencyAlgorithm - Theoretical mode shapesand frequencies of the pretest model were obtainedfrom the solution of the generaleigenproblem,

wheresubscript i refers to the ith mode.

* Linear Estimation of Structural Parameters from Dynamic Test Data 5-42

It is assumed that theoretical mode shapesand frequencies of a model that correlates with test results can be obtainedfrom the solu- tionof the eigenproblem,

where the matrices ImJ and lk] arethe mass and stiffness of subcomponent elements whose respective sums produce [M] and [KJ . (6] are scaling factors whichmust be determined in order to obtain both eigenvector and eigenvaluecorrelation with test results. It was shown inthe Dynamic Test Reflected Structural Model Methodology Report that scaling factors which produce eigenvalue correlation in all modes would alsoproduce eigenvectorcorrelation. This phenomenon ledto the development of a Taylor’s series expansionof the theoretical eigenvalues about the pretest valuesas a functionof the scaling factors to obtain an expression fromwhich those factors can be determined. The first order approxima- tionof this expansion is,

where subscript (e 1 refers to experimental data and subscript CO) refers tothe initial, or pre-test, data. Eachrow of the matrix of equations represents a theoretical mode for which is assumed thatcorresponding experimentaldata is availableand the derivative with respect to each requiredscaling parameter may be determined.Ideally, when subcomponent detail is sufficientto produce as many scalingfactors as there are modes, thesolution from Equation (3) is

Inpractice, this requirement will not be satisfied,nor will experimental data be determinedfor all modes.However, a least-squaressolution for { s} is possible when Equation (3) contains more modes than scaling factors. Or, ifthe Taylor’s series expansion of the i& theoreticaleigen- value is dominated by a single scaling factor, Sj, anapproximation of that factor may be obtainedfrom, 5-43

Because of thefirst order approximation of the Taylor's series expansion, an iterative application of the algorithm is requiredwhereby each set of parameters is usedto-calculate an updated modelwhose eigenvalue and eigenvalue derivatives are used to calculate new parameters until the differencein successive parameters is arbitrarily small.

5.4.3Calculation of Eigenvalue Derivatives Foxand KapoorJC provided an expression for the partial derivatives of an eigenvalue with respectto a structuralparameter. The generalexpression is statedas a functionof the derivatives of the mass and stiffnessof the eigen- problemwith respect to that parameter as

If the mass and s tiffnecs matrices are defined as linear functions of their subcomponent elements,as in Equation (2), where thestructural parametersare regarded scaling factors on theoriginal modeling, as opposed toreal hardware changes that would alter both mass and stiffness,Equation (6) produces two derivativeterms of theform,

Equations (7) and (8) bybe recognized as expressions for the kinetic andpoten.tia1 energy of the ith mode contained in the subcomponent ele- mentsdefined by [m] and [k] respectively.Since the sum ofthe sub- componentsequals the total system, the sum ofthe eigenvalue derivatives with re'spect to the mass scalingfactors equals the total kinetic energy ofthe system, and the sum ofthe eigenvalue derivatives with respect to thestiffness scaling factors equals the total potential energy of the system.Thus, dividing both sides of Equations (7) and (8) by theeigen- value, aia, yieldsthe fractional parts of the respective totalenergies containedin a particular subcomponent. Thisobservation allows Equation (3) totake the form,

* R. L. Foxand M. P. Kapoor, "Rates ofChange ofEigenvalues and Eigen- vectors", AIM Journal, Vol. 6, No. 12, December 1968, pp. 2426-2429. Where element ci ofmatrix [I-] is the fractional part of the total kinetic or potential energy contained in the ith test correlatedanaly- tical mode that is contributed by the jth subcomponent.

5.5 Correlation ImprovementProcedure

Priorto the initiation of thisstudy,tlie Skylab Orbit Configuration Dynamic Test.Article (DTA) vibrationanalysis modelhad been constructed. Eachcomponent of this model consistedof mass and stiffness data representingthe combination of many subcomponents.Information concerning thedetails of thesesubcomponents was notavailable for use in this study.This condition limited the scope of the effort to the determina- tionof component, rather than subcomponent, scaling factors that would improvethe correlation between experimental and theoretical results. Also, it was assumed at theoutset of thestudy that the mass of all components was adequatelyrepresented in the pre-test model so thatthe determination of mass scaling factors was not required.

5.5.1 The Pre-Test Model StrainEnergy Distribution - The strain energydistribution in the components of theOrbit DTA pre-test model was calculatedfor each of the analytical modes by the method defined inparagraph 5.4.3. The results of thesecalculations in the modes that arecorrelatable with test resultsare presented in Table 5.12. A review of thecorrelation revealed that analytical mode 14correlated with test mode 10A aswell as analytical mode 15did. Also, analytical mode 18 correlatedwith test mode 12A as well asanalytical mode 16did. These two additional modes arealso included in Table 5.12 with an asterisk. Although GMC dataindicated apparent correlation between test mode 18A and analytical mode 39,the actual vehicle second torsional mode occurred analyticallyas mode 36 at 10.285 Hz. Strainenergy for both mode 36 and 39 areincluded in the table, but the correlation is shown asexisting between analytical mode 36 and test mode 18A. Analytical mode 47 appears twice inTable 5.12; once with each of the test modes withwhich it was correlated .

The strain energy in analytical modes 41and 42 is contained pri- marilyin the Solar Arrays. Frequency correlation of the pre-test model with test results is very good in these modes andwould notbe affected by changesto other components due to the lack of strain energy in other components inthese modes. Similarly,all other analytical modes listed inTable 5.12 havevery little strainenergy in the Solar Arrays and would notbe affected by changesto Solar Array components. Since no changesto the Solar Array components can be made in this 'study, strain energycontribution for these components is notincluded in Table 5.12. 5- 45

Forconvenient reference, the experimental and analytical modal frequenciesare repeated in Table 5.12 asare the frequency differences expressedas a fraction ofthe experimental frequencies. The squareof thefrequency ratios minus one thatare required for the solution of the frequencyalgorithm defined by Equation(9) in paragraph 5.4.3 also are presentedin Table 5.12.

Ingeneral, the tabulated strain energy values reflect six degree offreedom motion of an entire component so that it is not possible, by review ofTable 5.12 alone,to determine the specific locations, if any, in a particular componentwhere thestrain energy is concentratednor thedirection of motion with which it is associated.Motion in many of the test modes is dominated by the FAS Oxygen Tanks or the AM Nitrogen Tanks.Determination of scaling factor for local support structure for thesetanks is required for improvementof correlation in those modes. Examinationof Table 5.12 shows that a CSM component scalingfactor large enough to improvecorrelation with the first torsional mode, test mode 09A, would have a largedetrimental effect on the existing good correlation between analytical mode 11 and test mode07A due to the very large CSM strainenergy contribution in analytical mode 11. Many other exam- ples can be citedfrom Table 5.12 to show that.the lack of subcomponent detaildisallows application of theidealized methodology for correlation improvement. However, theessence of the methodology was appliedwithin the limits ofthe available data to determine required changes to the deployed DA andthe CSM by therationale discussed in the following paragraphs.

5.5.2 The Deployed DA Component Model - Analytical mode 9 has70.8 percent of thetotal strain energy concentrated in the DA (see Table 5.12). The generalized mass contributions (GMC) of its corresponding test mode, Table 5.13, were in the ATM Rack in the X, Y, and 2 directions. Review ofthe plotted data in volume .I1 forthis mode shows very little relativemotion in the lower DA betweenthe trunnions and .the FAS interface.This type of motionsuggests that the upper DA, betweenthe trunnions and the ATM interface,contains the full 70.8 percent of strainenergy with a fairlyuniform distribution. The data inTable .12shows thatan increase in DA stiffness is requiredto .im- provefrequency correlation between analytical mode 9 and test modeOSA. It was concludedthat, since part of the DA was alreadytoo stiff tobe involvedin the motion of analytical mode 9 andthe remaining parts con- tributedequally, a scalingfactor applied to the entire DA component should result in a stiffness matrix that approximates one which would resultfrom adjustment of individual DA truss members had thedata requiredto do so beenavailable. An estimate ofsuch a scalingfactor was calculatedusing Equation (9) inparagraph 5.3.3 and thedata of analytical mode 9 andexperimental mode05A in Table 5.12 by,

6 DA = - .282/.70774 = -.398 5- 46

the McDonne11 DouglasCorporation model with a Deployed DA stiffness modeldeveloped by Martin Marietta Corporation (MMC) for use in stress analyses..Frequency data from a SkylabOrbital Configuration MIA coupled system vibration analysis using the MMC DA component stiffness modeland therevised GSM componentmodel discussedbelow in paragraph .5.3 is presentedin Table .14 as '"MC DA + CSM Eigensolution".Only data for the first few modes is presentedto support credibility of the least squaresscaling factor and no attempt was made to correlate the modes thatare not presented. A comparison of theflexibility influence coefficient data for both DA models showed that the MMC model is only 85 percent as stiff as the &Donne11 Douglasmodel overalland only 58 percent as stiff in the Z direction at the upper rigidizing armsand 58 percent as stiff in the X directionat the lower rigidizing arms.

Thisconcluded the procedure for improvement of correlationbetween theoreticaland experimental results by perturbationof the theoretical DA componentmodel.

.5.3 The CSM ComponentModel - Experimental modes 09A and 18A were identifiedrespectively as the first and second torsional modes of.the Skylab Orbit Configuration DTA. The correlatinganalytical modes, arelisted in Table ,12. The dataof Table .12 shows thatan increase in stiffness somewhere in the DTA was requiredto improve frequency correlationwith test results. The firstanalytical torsion mode, mode 12 in Table .12 has 36.2 percent of thestrain energy in the CSM component and 43.7 percentin the DA component. The remainingenergy is contained ininsignificant amounts inthe other components.Although a DA change producesthe largest frequency change in this mode, the DA changecalcu- latedin paragraph .5.2 to improve correlationin other modes is inthe wrong direction.Table -14 shows thefirst analytical torsion mode frequencydecreased to 2.995 W as a result of theleast squares DA component scalingfactor. The secondanalytical torsion mode, mode 36 inTable .12 has59.4 percent of thestrain energy .in the FAS/IU/OWS component,28.2 percent inthe CSM component,and the remainder spread ininsignificant amounts inthe other components. Although GMC data for analytical mode 36 was notreported because it was not correlated withtest data, GMC datafor that mode was calculatedand it showed large FAS Oxygen Tanksmotion. Due tothe lack of FAS subcomponent stiffness data the strain energy associated with Oxygen Tanksmotion could not be separatedfrom the total FAS/IU/OWS component contribution. A total FAS/ IU/OWS component scalingfactor calculated to improve correlation in the secondtorsional mode would produce a comparabledecrease in correlation betweenexperimental mode24A and analytical mode 69 which,as Table .12 shows , has 50.8 percentof the strain energy in the FAS/IU/OWS component and requiresscaling in the opposite direction. A total CSM component scaling factor to improve correlation in either torsion mode was also disallowed by the detrimental effects it would have on existing. good correlationin other modes.However, examination of thefirst andsecond analyticaltorsion modes asplotted data suggested that the addition of torsionsprings between the Command Module forwardand aft bulkheadsand 5- 47

The effect of this scaling factor on all other analytical modes listed inTable 5.12 was determined by usingEquation (3) ofparagraph 5.4.2 tosolve for the new eigenvalues,{we 1, thatare produced by theabove value of DA when thescaling parameters for all other components are set equalto zero. The resultsof these calculations are presented in Table 5.14 as "Mode 9 Estimation"data. The differencesbetween these frequenciesand experimental results, expressedas a fractionof the experimentalfrequencies, also are included in Table 5.14. Experimental andpre-test model analyticaldata are repeated in Table 5.14 for con- venientcomparison. A comparison shows significant improvement or no effect in all modes except the first torsional mode, correlatedwith experimental mode 09A, and analytical mode 47which correlates with experimental modes 21A and 22B, bothof which are strongly tank modes. This result ledto the examination of those analytical modes which showed thegreatest improvementfrom applicationof the DA scalingfactor. The examinationrevealed that the same type ofmotion occurs in those modes as in analytical mode 9; that is, multi-directional ATM activity on theupper DA and relativelystiff lower DA. It was then decidedthat a DA scalingfactor, that satisfies the frequency algorithm (Equation(9) of paragraph 5.3.3) in a leastsquares sense, for all test correlated modes which are clearly associated with uniform strain inthe upper DA, would producethe best correlation improvement possible withinthe limits ofavailable data. All datainvolved in the determina- tionof the least squares scaling factor are presented in Table 5.15. A question regarding which analytical modes best correlated with test modes 10A and 12A was raisedpreviously. Analytical modes 14and 18 were chosen forthis calculation because of their higher DA strain er,ergycontributions. Correlationin these modes is nottoo important since calculation of the leastsquares scaling factor was dominated by analytical modes 9 and 17.

The effect of theleast squares scaling factor on all other analytical modes listedin Table 5.12 was determined by usingEquation (3) in the same manner as was done for '!Mode 9 Estimation". The results of thesecalculations are presented in Table5.14 as "LeastSquares Esti- mation". The correspondingfrequency ratio data also are included. Figures 5.9 and5.10 compare pre-testand perturbated analytical mode shapesto test mode shapesin the X-Y and X-Z planes.Improved correlation between tests mode shapesand analytical mode shapes was obtained fromthe least square DA scaling factor.

Comparisonof these results with test andthe 'bode 9 Estimation" dataled to the decision to calculate the coupled modes ofthe system usingthe least squares scaling factor on the DA component stiffness matrix. The frequencydata for the first few modes fromthis vibration analysis is presentedin Table 5.14 as"Least Squares Eigensolution". No attempt was made to correlate the modes not shown.

Althoughthe results obtained by scalingthe Deployed DA component stiffnesslend confidence in the methodology by whichthe scaling was determined,an independent check on these results was made by replacing 5- 48

betweenthe Command Module aft bulkheadand Service Module forwardbulkhead wouldimprove torsional correlation without disturbing motion in non-torsion modes ifsprings of the proper magnitude could be determined. An estimate ofthe proper torsional spring magnitude was made usingthe data of analytical mode 12 inTable 5.12 andthe least squares DA component scalingfactor determined in paragraph 5 e 5.2 in Equation (9) from paragraph 5.3.3 by,

.36221 $ CSM + .43725 (- .4664) = + .591

gCsM= 2.19

This meant thattorsional springs 2.19 times themagnitude of those in the CSM Component model should beadded to the existing springs to improvecorrelation. Such a largechange questioned the credibility of theestimate. At thispoint, flexibility influence coefficient data for theApollo CSM was obtained by teleconfrom Jack Nichols of NASA, Hunts- ville.Table .16 presentsthis data and the corresponding Skylab CSM component flexibilityinfluence coefficient data. The ratiosof relative deflectionacross the ports in question, also presented in Table 5.16 shows thedifference in these models is greaterthan indicated by the scalingfactor estimated above. This result is consistentwith the methodologysince the calculation of thescaling factor involves division by the total CSM component strainenergy which is larger than that undeterminableportion associated with torsion alone.

With theApollo CSM datain hand, it was decidedthat the best Skylab CSM componentmodel improvement would result from the addition of torsional springsthat reflected the flexibility influence coefficient ratios shown inTable 5 .16.Calculations of these springs are included in Table 5.16. The coupled modes of theSkylab Orbit Configuration MIA were thencalcu- latedusing the CSM component withthe alterations discussed above the theDeployed DA component with stiffness increased by the least squares scalingfactor determined in paragraph 5..5.2. The frequencydata from this vibration analysis is presented in Table 5.14 as "Test VerifiedEigen- solution"data. Figures 5.11 and5.12 show theimprovements obtained over the pretest analytical modes by theinclusion of torsionalsprings and DA scaling factors.

Thisconcluded the procedure for improvement of correlation between theoretical and experimentalresults by perturbation of thetheoretical CSM componentmodel.

No other componentchanges were made in this study.

5..5.4 Results - Table 5. 17presents a summary ofthe correlation results.This table provides the basis for acceptance of the modeling changesdiscussed in the previous paragraphs. Supporting data for the statements made .in Table 5 .17 are provided in. Volume 11. Volume I1 I "

5-49

containplots for both test andanalytical results. The analytical modes were calculatedusing 198 component (uncoupled)modes, It was observed that many of those component modes hadno effect on thecoupled modes of interestin this study. To improveefficiency in conducting the analysis, those ineffective component modes were deleted.

5.5.4.1 The DA Component ScalingFactor Resul.ts - The primary effect of scaling the DA component stiffness matrix was to improve the correlationof experimental and theoretical frequency data. The mode shapecorrelation between the experimental results andthe pre.-test theoretical model results was satisfactory in those modes which may be categorizedas coupled main beam bendingand ATM activity. This good correlation was essentially unchangedby the DA scalingfactor. The pre-test model exhibitedstrong coupling between the first torsional mode andan X-Y plane first bending mode. Thismotion was notobserved in test. The applicationof the DA component scalingfactor eliminated thiscoupling in the analytical model. However, it alsodecreased the torsional mode frequencyto 2.995 Hz prior to the CSM componentmodel alterations. Correlation of FAS Oxygen and AK Nitrogentank modes and of longitudinal modes was unaffected by the DA component scaling factor

5.5.4.2 The CSM Component Torsional Sp-gs Results - The effect of theaddition of the two torsional springs to the CSM componentmodel was improvement of mode shapeand frequency correlation between experi- mentaland theoretical results in the first two torsional modes.

Inclusion of thesprings decreased the difference between experimental and analytical frequencies of the first torsional mode from20.7 percent of theexperimental frequency to 13.9 percent. The pre-test analytical model produced a largerelative torsional deflection between the command and service module bulkheadswhich resulted in the nodeof the first torsional mode beinglocated in the MDA conestructure whereas the node was observed to be at the AM trussesin the test results. As a result ofthe CSM componentchanges the analytical node was shifted aft to the STS/AM component. The differencebetween experimental and analytical frequencies of the secondtorsional mode decreasedfrom 18.7 percent of the experimental frequency to 4.6 percentas a result of the CSM componentchanges. A si.gni- ficant improvement inthe second torsional mode shapecorrelation in the CSM component also was produced by thesechanges.

Correlation of FAS Oxygen and AM Nitrogen tank modes andof longitudinal modes was unaffected by the CSM componentchanges.

5 .5.5Conclusions -

a. A valid methodology forperturbating a theoretical dynamicmodel to improve correlation with experimental results has been developed aspart of thisstudy.

b. The changesincorporated into the Skylab Orbit Configuration DTA model produce acceptable primary modal characteristics correlation of that model with test results in all planes ofmotion. 5- 50

C. Whilecomplete correlation of all test datawith analytical results was notachieved, further effort to produce total agree- men.t is unwarrantedbecause DTA mode1 changes required to do so would not necessarily be applicable to the flight article. d. Component models resultingfrom this study are technically acceptablefor use in the test verified dynamicmodel. Table 5.12

Pre-Test Model Strain Energy Distribution l- EXPEI ANALY'TICAL F,-F, COI flLLQmJ.iuzmL MODE MODE Fa FAS / IU / MDA/STS / MDA PORT DA ATM RACK SPAR/CAN F,l ows AM t- - 03B 1.31 7 1.372 .047 .02702 .18745 .26758 .20826 .13026 .00448 .00021 - .008 04A 1.43 8 1.566 .095 .00548 .12829 .26984 .21496 .21567 .00508 .OOO 23 -.166 0 5A 1.66 9 1.959 .180 .02482 .01484 .07753 .07425 .70774 .01064 .00100 -.282 0 6B 1.74 10 1.994 .146 .13517 .01564 .O 6044 .05708 .64632 .01258 .00088 -.239 0 7A 2.51 11 2.663 .061 .02514 .08675 .08761 .47598 .28279 .00601 .00044 -.112 08A 3.06 13 3.519 .150 .14959 .28163 .08181 .la949 .27271 .00720 .00037 - .244 0 9A 4.10 12 3.251 .207 .03898 .06468 .05558 .36221 .437 25 .00841 .00090 +.590 14+c 4.933 .096 .02038 ,14496 .00641 .03776 .23315 .23 250 ~0389 168 1OA 4.50 -. 15 5.319 .182 .01378 .11146 ,00387 .02766 .09902 .00808 .7 2599 - .284 1lA 5.03 17 6.029 .199 .05687 .12028 .00490 .02923 .61267 .09363 .00797 - .304 16 5.757 .018 .02587 .19523 .00579 .04979 .05104 .267 14 .39074 +.018 12A 5.86 18?t 6.791 .159 ,08704 .14616 .00446 .05054 .43898 .08520 ,07523 -.255 13A 6.36 19 7.043 .lo7 .20097 .15848 .00457 .05046 .43079 .06846 .00449 -.185 14A 6.73 28 9 .lo1 .352 .49526 .02542 .00087 .01829 .la583 .01697 ,01193, - .453 16A 8.85 30 9.381 ,060 .07336 .25603 .1473 2 .13 667 .01091 .00597 .35817 -.110 17A 11.59 38 12.635 .090 .27705 .25149 .03032 .16828 .03737 .01739 .0047 1 -.159 18A 12.65 36 .10.285 .187 .59394 .03747 .02377 .28230 .0343 6 .00172 .00027 +.513 NONE ""_ 39 12.746 "" .16536 .468 54 .03473 .17765 .01982 .03057 .007 29 ""- 19A 13.3 41 13.007 .022 .04304 .oa742 .oo 100 ,00325 .02189 .09288 .03606 +.046 20A 13.68 42 13.282 .029 .00777 ,06620 .01246 .05193 .01006 .OS249 .15686 +.061 47 13.970 .040 .05453 .28277 .05235 .23121 .31787 .00313 .00046 .085 21A 14.55 - 54 14.966 .029 .lo289 .6881j .03927 .13489 .01154 .01055 .00357 - .055 22B 15.40 47 13.970 .093 .05453 .28277 .05235 .23121 .3 1787 ,00313 .00046 +.215 23A 16.20 67 17.541 .083 .07183 .84068 .01306 .06179 .OO 248 .00454 .00221 -.147 24A 16.53 69 18.319 ,108 .507 65 .39711 ,00302 .01844 .01288 .00893 .04595 -.186 2% 17.01 77 19.508 .147 .27097 .3 6148 .14509 .16776 .00205 .00971 .04 104 - .240 . -l- . ..

5- 52

Table 5-13 ORBITALC~NFIGURAT ION n004C SURVEY

TEST MODES GEF!FWLXZFD MASS CONTQIRUTION SUHHARY

TOTLL CH CONTQTBUTIOY FO9 E4CH COHPONENT

PCjOYS SKIRT/TU/FAS 5-FAS 02 nYKS MDG/STS/AH 6-AM N2 TAWKS COHMANO/SERVICE HOD 9EPLOYHENT ASSEYPLY ATH-RACKICWGSI~~SAS BTM-SPAS CENTER ATPf-GPA/CAH CENTER D

Table 5.14 Frequency Correlation Summary " - " i .I Fa Fa Fa " " "

038 I 1.31 1.372 ', ,047 ~ 1.336 ,020 1.330 .015 1.278 .024 1.279 f ,024 1.348 ,029 ,

04.4 ~ 1.43 I .566 .(I95 1.497 .047 1.485 ,038 c ,037 I: 1.377 1.377 i .037 2.053 .436 I 05A 1.66 1.959 I ,180 I: 1.660 .o 1.603 .c34 1.667 .004 1.670 ' ,006 1.554 06B ' 1.74 1.994 1 .146 1 1.719 .012 1.667 ,042 1.643 .056 1.643 .056 1.868 *064.074 I,; 0 7A 2.51 2.663 /. .Ob1 '1 2.509 .o 2.481 ,012 2.310 .080 2.338 ,069 2.435 .030 .' 08A 3 .o 6 7.519 ,150 7.323 .086 3.288 .075 3.164 .031 3.151 .030 3.281 .072 09A 4.10 'I. 251 ,207 I 2.955 .279 2.901 .292 2.995 ,270 3.532 .139 3.546 .135 5.933 ,096 1 4.699 .044 4.657 .035 1OA 4.50 4.313 .0$2 4.323 ,039 5.293 5,319 .I82 5.213 ,158 5.195 ,154 .176 1lA 5.03 6.029 .199 5.243 .042 5.095 .n13 4.858 .OM 4.868 .03 2 5.861 .165 5.757 .018 5.698 .028 5.688 ,029 12A 5.86 5.698 .028 5.706 .02h 5.739 6.791 .159 6.169 .053 6.056 .033 .021 13h 6.36 7.043 .lo7 6.411 .008 6.296 .o 10 6.544 .o 2'1 6.552 ,030 h.fi02 .038 14A 6.73 9.101 .352 8.758 .301 8.698 .292 9.192 .366 16A 8.85 9.381 .060 9.361 .058 9.357 .057 4.405 ,063 17A .1.59 12.635 .090 12.541 ,082 12.524 .081 18A .2.65 10.285 .187 10.214 .193 10.202 ,194 12.072 .046 12.072 -04I' .2.029 .049 NONE 12.746 12.696 12.687 19A .3.3 13.007 .022 12.950 .026 12.940 ,027 12.568 .055 20A .3.68 13.282 ,029 13.255 .031 13.251 .031 13.323 .026 13.970 .040 13 .056 .lo3 12.893 .114 13.323 .084 21A .4.55 . 14.966 .029 14.931 .026 14.926 .026 14.855 .021 22B .5.40 13.970 .093 13.056 .152 12.893 .163 14.855 .03 5 23A .6.20 17.541 .083 17.532 .083 17.531 .082 17.552 .083 24A .6.53 18.319 .lo8 18.272 .lo5 18.264 ,105 18.361 .111 -25A .7.01 19.508 & 19.500 -.146 -1 9.499 .146 19.644 .155 Pre-Tes t Mode 9 L east Squares Least S lares Test Vel f ied [Mc w CSM Mode 1 Estimation E s tima t ion Eigensc 1t ion Eigensolution ,igensolution I Table 5!_15

Calculation of Least Squares DA Scaling Factor

Ir ~~ ~ ENTAL -ANAL? CCAL DA STRAIN DA STRAIN * COLUMN 5 MODE -Fe -MODE Fa ENERGY ( ENERGY X COLUMN 6 0 3B 1.31 7 1.372 .13025 - .088 -.0115 .0170 04A 1.43 8 1.566 .2 15.67 -.166 - .0358 .0465 Notes : 0 5A 1.66 9 1.953 .70774 -.282 - .1996 .5009 0 6B 1.74 10 1.994 .6463 2 -.239 -.1525 .4177 Leastsquare.s 07A 2.51 11 2.663 .28279 -.112 -.0317 .0 800 equation is , 0 8A 3.06 13 3.519 .27271 - .244 - .0665 .0744 0 9A 4.10 12 3.251 1st Torsion mode 14* 4.933 .23315 168 .0392 .O 544 10A 4.50 -. - 15 5.319 .09902 - .284 +.0281 .0098 1lA 5.03 17 6.029 .61267 - .304 -.1863 .37 54 16 5.757 .05104 +.018 +.0009 .0026 1% 5.86 18f: 6.791 .43898 -.255 - .1119 .1927 13B 6.36 19 7 .043 .43079 - .185 - .0797 .1856 14A 6.73 28 9.101 Oxygen tanks mode la 8.85 30 9.381 1st Axial mode 17A 111.59 38 12.635 Nitrogentanks mode 18A 12.65 36 10.285 2nd Tors ion mode None 39 12.746 3rd Torsion mode 19A 13.3 41 13.007 Nitrogentank: mode 20A 13.68 42 13.282 Nitrogentank: mode 47 13.970 21A 14.55 = -.4664 54 14.966 Nitrogentank: mode 228 15.40 47 13.970 Repeated data 23A 16.20 67 17.541 Nitrogentank! mode 24A 16.53 69 18.319 Oxygen ana Nitrogel tanks mode 25A 17.01 77 19.508 2nd Axial mode

m .9127 Zr: 1.957 i

L Table 5.16

CSM Flexibility Influence Coefficient Data (Angulardeflections due to applied unit moments)

DEFLECTION AT SKYLAB MODELAPOLM MODEL SKYLAB RELATIVE ABSOLUTE RE TAT IVE ABSOLUTE kELATIVE APOLLO REIATNE

CM Forward Bulkhead .307 (10) -' 1.03 (10) -' .057 (10) .253 (10) -8 4.44 CM Aft Bulkhead -' .777(10)'8 .250 (10) .2086(10)'8 ,7332(10)'8 3.52 SH Forward Bulkhead .0414(10)'8 .043 8 (10) -8

Note:Models areconstrained. at the aft endof the SM andunit moment is applied at thedocking port . Calculation of incrementaltorsional springs: 1. Between CM forwardand aftbulkheads, 1 1 1 11 1 cn

=K + K =K I ApolloSkylab S kylab + Skylab cn 3e44 cn

K1 = 3.44 (e~53(lo)'B) = 1.36(10) 9

2. Between C?f aft bu,lkhead and SM forwardbulkhead, 2 2 22 2 =K + K =K

Apo llo SkylabApollo Skylab + 2*52 Skylab -2 8 a K = 2.52 ( 1 ) =.3.42(10) .7332(10)'8 5- 56 Figure 5.9 TesdAnalytical Mode Comparisons TEST MODE 5 , 1.66 HZ ANALYTICAL MODE 9 * 1.959 HZ 5

PRETESTRESULTS 1.0

2/"_"" - I 0,0 0 "0 0 0 0 0 0 v) p1 0 n 0 n n 4

-1.0 /

TEST MODE 5 , 1.66 HZ ANALYTICAL NODE 10 , 1.670 HZ 5- 57

Figure 5.10 Test/Analytical Mode Comparisons

TEST MODE SA , 1.66 HZ ANALYPICAL MDE 9 , 1.959 kz

1 .o PRETESTRESULTS

/ / - -

-X

0 0 0 0 0 0 0 0 0 0 0 (D m 0 5 :: a 0 U (1 (1 (1 (1 (1 (1 u, (1 (1 -1.0

Y TEST MODE 5A , 1.66 HZ ANALYTICAL MODE 10 , 1.670 HZ

PERlWBATED RESLILTS

-1.0 5- 58 Figure 5-11 Test/Analytical Mode Comparisons TEST WWUE 9A , 4.10 le .ANALYTICAL MDE 12 , 3.251 ie 8 /”“” ,c -/ PRLTEST RESLlLTS / 1.0

/ ”””” ” -X

-1.0

TEST MODE 9A , 4.10 Hz ANALYTICAL MODE 13 , 3.532 h2 ex .“”

PERTURBATED RESLETS WITH TORSION SPRINGS ADDED 1.0

”_”” ”- / -x

0 0 0 0 0 0 O 0 0 8 0 0 0 0 0 N n .f “7 .n r. m a. 0 I? 0 0 n n (? (7 n (? U 5- 59

Figure 5.12 Test/Analytical Mode Comparisons , . .Lhsr .. FIOUP; 18~ ,_1~.20-I& - - ANALYTICAL MODE 38 , 12.625 in r es c \ / J r- \ PRETEST RESULTS I \

1.a

"---tx

0" 0" 'a 0 0 0 0 0 0 - .o 0 0 0 0 0 4 N I? U m m m 0 PI I? I? Fl I? 0 -m"" I? U

-l.t

TEST MODE 18A , 2Z262 Hz ANALnICAL MODE 38 , 12.072 kZ e /

PERTURBATEDRESULTS WITH TORSION SPRINGS ADDED 1.0

I -x 0 0 0 0 0 %---g" 0 :: 0 0 0 N Fl U z m 0, 0 0 0 n n 0 4- - "_ 0 U

-1.0 Table 5.17

Summary of Test and Analytical Modes Correlation

TEI ' MODE - ANALY tCAL )DE FREQ . G MC PLOT DESCRIPTION/COMMENTS MODE FREQ . GMC PLOT DESCRIPTION/COMMENTS Hz. rmus NO. NO. Hz. rmxs NO. 1.31 A-5 B-1 X-Z plane 1st bending in 7 1.279 c-1 D-1 Good agreement with test, A-6 MDA cone with AT" Y axis c-2 GMC andplotted data in rotation onupper DA all planes. trussout of phase with CSM. (Spurious TH Z motion at Node 28. suspected) . - - 1.43 A-7 B-2 X-Y plane 1st bending in 8 1.377 c-3 D-2 Good agreementwith test, A-8 MDA cone with ATM X axis c -4 GMC and plotteddata in rotation on upper DA all planes. truss in phasewith main beam, outer ATM Y motion in phasewith CSM.

~~ ~ ~~ - 1.66 A-9 B -3 X-Y plane 1st bending in 10 1.670 c -7 D -4 Combination of 0% and A-10 MDA cone with ATM X axis C-8 06B motion,predominately rotation on upper DA 05A. trussout of phasewith main beam, outer ATM Y motionout of phase with CSM. (Spurious TH Z motion at node 28 sus- pec ted .). 1.74 A-13 B -5 X-Z plane 1st bending in 9 1.643 c-5 D-3 Combination of 0%and A-14 MDA cone with ATM Y axis C-6 06B motion,predominately rotation on upper DA 06B. truss in phasewith CSM. - - Table 5.17 Continued

Summary of Test and Analytical Modes Correlation

Th. -r- ANALY ICAL I )DE XODE VIODE FREQ. GMC PLOT DESCRIPTION~OMMENTS ! so. 'NO. NO. Hz. :AB LES NO. i-" - - 0 711 2.51 A-15 B-6 1 X-Y plane 1st bending in 11 2.338 c-9 D-4 Good agreementwith test

11-16 I/ FDA cone with ATM X asis c- 10 GMC data in all planes .) rotation on upper DA and with plotted data in I trussout of phasewith X, Y, Z and TI1 X. ' main beam, outter Ah1 Y I motion in phasewith CSM, i 1 (TI1 Y and TH Z data in- I consistent with Y and Z - results .) - - 0 ai 3.06 I A-17 12 3.151 c-11 D-5 Good agreementwith test FDA cone with Ahf Y axis c-12 GMC datain all planes ! rotation on upper DA andwith plotted data in I trussout of phasewith X, Y, 2 and TH Y. CSM, and ATM Z axis ~ translation on upper DA

~ I trussin phase with CSM. - 0 9A €3-8 1 1st torsional mode with 13 3.531 C-13 D-6 Good agreementwith test CSM. FDA/STS/AM outof C-14 GFlC datain all planes phase with FAS /IU/OWS. andwith plotted data in Large torsionaldeflec- Y and TH X. tion across MDA cone. - - 10A B-9 X-Y plane 2nd bending in 14 4.323 C-15 D-7 Good agreement with test MDA coneand STS/AM C-16 GMC data in all planes coupledwith 1st tor- andwith plotted data in sional mode, and ATM X X, Y, 2 and TH X. axis rotation on upper ?)A out of phasewith CSM.

I Table 5.17 Continued

Summary of Test and Analytical Modes Correlation ANALY XAL- 1 IDE FREQ. GMC PLOT DESCRIPTION/COMMENTS ODE FREQ. GMC PLOT DESCRIPTION~OMMENTS Hz. TABLES NO. NO. HZ. - cmms -NO. 5.03 A-25 B-11 X-Z plane 2nd bendingin 15 4.868 C-17 D-8 Good agreementwith test A-26 MDA coneand STS/AM with c-18 GMC andplotted data in large ATM Y axis rotation allplanes (when spurious onupper DA truss in phasc test TH Z is ignored) . with CSM. (Spurious TH Z data at Node 28 suspected: 5.86 A- 27 B-12 X-Y plane 2nd bendingin 18 5.706 c-19 Good agreementwith test A-28 MDA cone and STS /AM c- 20 GMC dataexcept for coupledwith 1st tor- Oxygen tanksmotion and sional mode and ATM X withplotted data in X, axis rotation onupper Y and TH Z. DA outof phase with CSM (Similarto 10A except TH X and Y motionphase reversed). Also FAS Oxygen tanks Y and Z rno tion.

~~ 6.36 A-3 1 B-14 X-Z plane 2nd bending in 21 6.552 c-21 Good agreementwith test A-3 2 MDA coneand STS/AM with c-22 GMC andplotted data in ATM Y axis rotation on allplanes. upper DA trussout of phasewith CSM. 6.73 A-33 B-15 FAS Oxygen tanks Y and Z C-23 FAS Oxygen tanks Y and Z A-34 motion. C -24 motion,no shape correlation. Table 5.17 ' Continued

Summary of Test and Analytical Modes Correlation

- TE I ' MODE - LNALYT ZAL MC ,E $ODE FFSQ. GMC PLOT DESCRIPTION/COMMENTS IODE FREQ. GMC PLOT DESCRIPTION -NO Hz. TABES NO. NO. Hz. 'AB LE S NO. L6A 8.85 A-37 B-17 1st axial mode with node 9.405 C-25 D-11 Good agreementwith test A-38 point in AM. C-26 GMC datain all planes andwith plotted data in axialplanc (except CSM X deflection is larger - - in test than analysis .) L 7A 11.59 A-39 B-18 FAS Oxygen tanks Y and "" No truecorrelation. A -40 Z motion. L 8A 12.65 A-41 B-19 2nd torsional mode with 12.07 2 C-28 D-12 Good agreementwith test

I A-42 nodesbetween CM and SM C-29 GMC datain all planes bulkheadsand across AM andwith plotted data in - trusses. torsionalplane. L 9A 13. SO A -45 B-21 AM Nitrogentank Y 39 12.568 C-29 AM Nitrogentanks Y A-46 motion (model point 20) C-30 motion (Model points 20 andvehicle 3rd bending and 21) noshape corre- predominately in X-Y lation. - plane. !OA 13.68 A-47. B-22 AM Nitrogentanks Y and 41 13.323 C-3 1 D-13 Good agreementwith test A -48 Z motion with vehicle C-32 mode19A plotteddata in 3rdbending predomi- Y and TH Z. Good agree- nately in X-Z plane. ment with test mode20A This mode was not well plotted data in 2 and separated from test mode TH Y. 19A as shown by large couplingin orthogonality check.(Ref. ED-2002- 1522). Table 5.17 (Concluded )

Summary of Test and Analytical Modes Correlation

II :AL M )E MODE FREQ. DESCRIPTION/CO”ENTS MODE PLOT DESCRIPTION/COMMENTS Hz. Eq-F NO. -NO. 14.55 A-49 B-23 AM Nitrogentanks Y 45 D-14 Good agreementwith test motion and vehicle c-34 mode 2lA CMC data in Y 3rd bending in X-Y plane plane.Shapc correlation is onlyfair. (Shape of 15.4 Predominately vehicle analytical mode 41 A-52 3rdbending in X-Y correlates better with plane. AM Nitrogentanks test mode 2lA).Poor Y and 2 motions, FAS agreementwith test mode Oxygen tanks X, Y, and 22B GMC databut shape Z motions. - - correlation is fair. 16.20 AM Nitrogentanks Z 56 17.553 C-35 Large AM Nitrogen tanks mokion with FAS Oxygen 1 C-36 Z motions. No shape tanks X,Y, and 2 I correlation. motion 4th vehicle I bending in X-2 plane.

16.53 AM Nitrogentanks Y ~ 58 18.361 C-37 Fairagreement with test motionwith FAS Oxygen I I C-38 GMC datain all planes. tanks X motion. No shapecorrelation. 17.01 =“Tz3A-59 2nd Axial mode with node 19.644 C-39 D-15 2nd axial mode with node points between SM and C -40 points at port and CM bulkheads and across across AM trusses (CSM AM trusses. X deflection is larger than analysis). 5- 65

5.6 Postflight Mode 1 Verification

This is a good time to show how theanalyst can be trapped into altering a component stiffnessproperties without sufficient knowledge of thecomponents structural detail. A fourieranalysis of the AT" rack rate gyroflight measurements provides frequency data representing the ATM supported by the DA.

5-6.1Flight Results - Duringmaneuvers performed at 149:10:25:10 in SL-2 flight,the rate gyros displayed the data presented in Figure 5.13 forthe x, y and z axes. Thesampling rate of thegyro .data is 12 samplesper second. A Fourieranalysis wasperformed to identify thefrequency of the recorded signal. The period analyzed was 512 sampleswhich corresponds to 42.66 seconds. The frequency content is plotted also in Figure 5.13 with a frequencyresolution of 0.0234 (12/ 512) Hz. The'dominant frequencies are listed by axisin the following table.

DominantFrequency - Hz Axis 1 2 3 - - - X 1.027 0.8767 --

1 .60 1.35 1.80 1.35Y 1.60

21.027 0.876 "

The principalfrequency content is 0.88 Hz aboutthe x and z axesand 1.6 Hz aboutthe y axis. Reviewof vibration analyses of the Skylab configurationindicates the following correlation with orbital data.

Pre-GVS AnalysisConfig. Post-GVS AnalysisConfig. Flight 1.2 (Ref.ED-2002-790-4, 1.2 (Ref. ED-2002- 1562-2 , D ata January 197 January Data 1) November 1972)

.88 Hz .888 Hz ATM/DAl (81%) .594 Hz DA (DEPL)l (77%)

1.60 Hz 1.655 Hz ATM/DA4 (72%) 1.275 Hz DA (DEPL)2 (25%)

The low frequencyanalytical modes yere selectedon the basis of their correlation of AT" slopes in the x and z axis with 9, and Q2 flight rategyro data at .88 Hz. Similarly,the high frequency analytical modes exhibited ATM By correlationwith the 1.60 Hz rategyro data. ATM/DA4 is theessentially same mode as DA(DEPL)2. Thenames and uncoupled mode numbers differdue to a change in component definitionsbetween the two ana lyses. 5- 66

Thedifferences in the pre and post-GVS results reflect the DA stiffnessscaling factor. A scalingfactor to decrease the DA stiffness was determinedwhich improved correlation between experimental andanalytical frequency data in a leastsquares sense. Unfortunately thisscaling factor decreased correlation with flight results. A rigor- ousexplanation for these conflicting results wouldrequire extensive reanalysis. However, it is theorizedthat the source of the discrepancy arises fromthe fact that individual DA truss member adjustmentsrequired to improve experimentaljtheoretical correlationcould not be made dueto lackof component modeling detail information at MMC. A review ofthe type of motion in the modes ofconcern and comparison of MDAC and MMC flexibilitydefinition of the DA truss were made tosupport this theory asfollows.

The on-orbitconfiguration vibration analysis was rerunusing the original(unscaled) MDAC DA trussstiffness model. This analysis produced a .785 Hz and a 1.497 Hz mode whichcorrelate respectively with the .88 Hz and1.6 Hz flightdata. Examination of the mode shapesof the modes ofinterest (Table 5.18 ) shows therelative deflection across the DA rigidizing arms is verylarge in the directions associated with theprimary motion of theoverall mode shape.That is, large A X and A Y motionsoccur in the .784 Hz mode which is primarily 8, of the ATM, and large & X motionsoccur in the 1.497 Hz mode which is primarily X, QY of the ATM. Thisobservation suggests that increasing the stiffness modeling of the DA rigidizingarms alone wouldimprove correlation of these modes withflight data. It alsosuggests that the stiffness of the DA betweenthe ATM supportframe (excluding rigidizing arms) and the trun- nionscould be decreased as required to improve cor,relation with GVS results withoutgreatly affecting the frequency of the modes observed from flight data.

A comparisonof MDAC and MHC DA truss flexibility influence coef- ficientdata (Table 5.19) shows thatthe MMC model is considerablysofter than MDACs betweenthe ATM supportframe and the FAS interface. The fact thatthe MMC modelproduced lower frequency GVS correlatable modes than the MDAC model was pointedout and supported the DA scalingfactor that was defined.Table 5. 19 also shows that MMC modelrepresents the rigidizingarms to be stiffer than the MDAC model by a factor of 2 at DOF 13 and19 and a factorof 1.5 at DOF 14 and 20. Althoughthe MMC DA model hasnot Seen used in an on-orbit configuration vibration analyses with whichto compare the modes ofinterest, these differences in DA modeling inan area that strcngly affects the flight data modes indicatesthat local DA truss member modelingadjustments are required for theoretical correlation with both flight and GVS results.

Sincethe only significant structural response observed from on-orbit flight data was containedprimarily in the .88 hzand 1.6 Hz .modes,the DA scaling factor was abandoned.

Configuration 1.3N1/ was revisedto incorporate the unscaled MDAC trussstiffness model. 5- 67

.6.2 Recommendations - a. In futureapplications of themethodology developed under this taskto other vehicles, assure the availability of subcomponent modeling detail. b.Develop a method todetermine the type of test resultsthat will be. most suitable for theoretical/experimental correlation studies on a particularvehicle, and improve testing techniques to assure that such data will be obtained. Table 5.18 Modal DeflectionsAcross DA Rigidizing Arms

25th Mode .784 Hz DA(DEPL)l 40th Mode 1.497 Hz. DA(DEPLI2 A"I Attach ATM SupportAttach Point/ ATH Attach ATM Support AttachPoint/ D irqc tionDirqc DOF Point DOF Frame Support Frame !)OF Point DOF Frame SuDoort Frame

X 1 -4.587(10)-* -2.546(10>'231 1.81 1 5.318(10)'2 1.646(10)'2 31 3.25

Y 2 5.101(10)-2 32 3.584(10>-2 1.42 2 -3.958(10)'3 32 -3.045(10)'3 small ampl.

2 3 -2.422(10)'2 33 -2.629(10)'2 .92 3 -1.989(10)" 33 -2.082(10)'2 .95 X 7 4.644(10)" 34 2.581(10)'2 1.80 7 4.627(10)'2 34 1.064(10)'2 4.34 c: Y'5.097(10)-2 8 35 3.585(10)'2 1.42 8 -4.698(10)-3 35 -9.236(10)'~ small ampl. 6

9 2.427(10)'22 9 36 2.630(10)-2 .93 9 -2.573(10)'2 36 -2.733(10)'2 .94

X 13 1.952(10)-2 28 1,059(10)-2 1.85 13 4.872(10)" 28 1.230(10)'2 3.96

Y -1.430(10)'2 14 29 4.394(10)'3 -3.25 14 1.351(10>-4 2.293(10)'4 29 small ampl.

2 1.004(10)'2 15 30 5.960(10)'3 1.68 15 -6.110(10)^2 30 -5.956(10)'2 1.03

X -1.888(10)'2 19 25 -1.024(10)'2 1.84 19 5.170 25 1.554(10)'* 3.33

Y 20 -1.432(10)'2 26 4.395(10)'3 -3.26 20 -1.685(10)'5 26 2.633(1Olm4 small ampl.

2 -l.058(10)'2 21 27 -6.461(10)'3 1.63 21 -6.216(10)" 27 -6.024(10)'2 1.03

0 0 A A 19- 2 1 13- 15 25-27 28- 30 DOF Locations :

y-L 0 X 0 A X A 1-3 7- 9 31-33 34- 36 A?M Attach Point AIM Support Frame Table 5.19 FlexibilityInfluence Coefficients Across Rigidizing Arms

MDAC DA Model MMC DA Model AM Attach ATM Support ATM Attach ATM Support Point Frame Attach Point/ Attach Frame Point Point/ Attach Frame Point Direction i/j DEfl i/load j i/j Dcfl i/load j SupportFrame i/j Defl i/Load j i/j Defl i/load j SupportFrame

X 111 3.340(10)'4 31/1 1.322(10)-4 2.53 1/1 4.378(10)-~31111.605(10)-4 2.72 Y 2/2 3.707.(10>'4 32/2 1.840(10)'4 2.02 2/2 4.818(10)'4 32/2 2.126(10)'4 2.27 Z 3/3 1.175(10)'~ 33/3 1.091(10)-~ 1.075 1.877(10)-43/3 33/3 1.874(10>'4 1 .o X 7/7 3.333(10)'4 34/7 l.Xl(10)'4 2.52 7/7 4.385(10)'4 34/7 1.610(10)'4 2.72 Y 8/8 3518 1.843(10)'4 2.01 8/8 4.823(10)-4 35/8 2.128(10)-4 2.26 CT 3.?15(10)'4 cn w Z 919 1.155(10)'4 36/9 1.071(10)-4 1.07 9/9 1.838(10>-4.3619 1.836(i0)'~ 1.0 X 13/13 3.659(10)'4 28/13 1.136(10)'4 3.22 13/13 3.211(10)-4 28/13 1.937(10>'4 1.66 Y 14/14 3.707(10)'4 29/14 1.607(10)-4 2.31 14/14 3.516(10)-4 29/14 2.297(10)-4 1.53 Z 15/15 7.127(10)'5 30/15 5.823(10)-5 1.22 15/15 7.362(10)'5 30/15 7.337(10)" 1 .o X 19/19 3.654(10)'4 25/19 1.137(10)-4 3.21 19/19 3.213(10>'4 25/19 1.938(10)'4 1.66 Y 20/20 3.706(10)'4 26/20 1.606(10)-4 2.31 20/20 3.516(10)'4 26/20 2.298(10)'4 1.53 Z 21/21 7.277(10)-5 27/21 5.956(10)'5 1.22 21/217.073(10>-5 27/21 7.049(10)'51.0

0 0 A A 19-21 13-15 25-2728- 30

DOF Locations : - "7 yJ. X X 0 0 A A 1-3 7-9 31-33 34- 36 A'OI Attach Point AIM SupportFrame X AMPLITUDE - DEGREESISECONO

- E

FOURIER AMPLITUDE COEfFIClEM - DECREES I 6- 1

6 .O CONCLUSIONS

Detailedconclusions andsubsequent recommendations are included withineach section. However, onan overview of the Skylab program, severaldistinct points are obvious. In the process of completing a particular difficult project both on a logistics and a technical basis shortcuts are taken, baseline costs are trimmed,programs aredelayed or ignored, all ofwhich normally have to be repeated at a much larger cost.These items areparticularly true in structural analyses.

As a resultof this summary of theSkylab project, the following recommendations arepresented for evaluation in the areas of importance and on a chronological basis.

6.1 Structural Models

It is imperativethat detailed plans be established initially in theprogram to define sensitive structural areas. These areas refer to eitherresponse, which affects modal characteristics and resultant sta- bility studies, or load which affectsstructural design, material properties andsizing.

Sincethe problem is one of integration in a design beam or stick models will alwaysbe required, initially. However, evenwith beam models careshould be exercised with modeling, in some detail, "all" structural systeminterfaces. "All" shouldbe literally interpretated if possible and at a minimum shouldinclude any interface between separate system modeling,contractors or centers.

Aftercompletion of detailed analytical studies, using the derived beam models,resulting load and responsedata should be integratedin the structuraldesign. This should culminate in finite element models of all sensitivestructures and will remain"frozen" until completion of the subject dynamic test. Obviously, allsensitive structure will complete, at a minimum, static inf hence coefficient tests.

6.2 System Modal Characteristics

Accuratevibration analyses must be completed for both load, response and controlstability studies. However, thesestudies should be completed in an orderly mannerand in sufficient detail so as to satisfy modal fidelity, andmodal characteristics for the data users.

Initial studies should be limited to the structural beam models. There is a strongtendency in projects and the customer to require in- stantaneousvibration analysis. This results in a continuedupdate of thedata at great expense. In reality, programs should be planned to 6- 2

follow four periods of structural modeling and derivation of modal characteristics ofthe Structural System.These are:

a. initial beam models, b. preliminaryfinite element models, c. modelsgenerated at completionof static test and initialdesign reviews , d.models generated at completionof dynamic test andsystem design reviews.

6.3 S truc tural Testing

Static, dynamic andacoustic test seems toalways be completely plannedon a projectthen revised continually throughout the program. Initially, in the program a strongcommitment should be made on structuraltesting andwhat areas are to be completed. This includes pre- liminaryinstrumentation, support system and data retrieval programs.

If a test is worthcompleting, and considering the associated cost of just initiating anystructural test, it= have a strongcommittment fromthe project. It should be plannedand frozen well in advanceof scheduledtesting and completed in a timely manner so as to affect design andreduce costly analysis requirement.

Structuraltesting should not be considered only as ground tests. As a post mortemon theSkylab program, it seems ridiculousthat such limitedstructural data was retrievedfrom flight. Mega dollars were spentduring the study to resolve array response, gimbal ring response, dockingloads and beam fairing loads yet limited if. any flight data was retrievedto verify design decisions, loadlresponse criteria, or as a guideto future projects. Additionally, dynamic test datarelating to acousticenvironment (a noted problem in orbit) and structural damping data(a significant problem in structural design) remains to be analyzed.

Specificaily,the following reconmendations are made for structural testing :

a. influencecoefficient test shouldbe completed for all interface structural systems ;

b. automatic modal tuningprograms should be devisedto speed up testing and assureaccurate and timely results;

C. detailed pretest analysesshould be completed;

d. adequateinstrumentation must beprovided to assure accurate results especially in resolving structural damping;

e. detailed correlation studies should be plannedand completed in a timelymanner; 6- 3

f.results of all tests should beimplemented inthe analysis schedule.

6.4 General

Control and loads studies are generally analyzed in sufficient detail. However, emphasisshould be placed on limitingthese studies to the four periods of structural modelingand in completing the final response and load studies with test verified models.

The abandoned child in mostmajor projects is theadequate mission evaluationstudies for structural systems. Therefore, it is imperative that project directors assure there is adequate flight evaluation and correlation of structural design decisions andmodels, based on sufficient flight instrumentation. 7- 1

7 .O NOTES

7.1 Abbreviations

-a Average Absorption Coefficient AM Airlock Module ATM Apollo Telescope Mount CDR Commander CG Centerof Gravity CMG Control Moment Gyro C SM Command andService Module DA DeploymentAssembly dB Decibels dBA Sound levelmeasured with A-weighting network M: Dircc t Current DTA Dynamic Test Article FAS Fixed Airlock Shroud FCC IU Flight Control Computer FS S-IVB Forward Skirt ft Feet GRA GimbalRing Assembly GMC Generalized Mass Contribution Hz Hertz(cycles per second) IMC IMC Magnetics Corporation in Inches IU Instrumentation Unit

Log10 Logarithmto the base 10 MDA Multiple DockingAdapter MDAC- E McDonne11 DouglasAstronautics Company - EasternDivision MDAC- W McDonne11 DouglasAstronautics Company - WesternDivision Microbar A pressureof one dyne per squarecentimeter "c Martin Marietta Corporation MSC Manned SpacecraftCenter 7- 2

MSFC MarshallSpace Flight Center MST Modal Survey Test (s) MSIL Modified Speech Interference Level

N2 GaseousNitrogen NAR NorthAmerican Rockwell Corporation NASA NationalAeronautics andSpace Administration

02 Gaseous Oxygen OB Octave Band ows Orbi ta1 Workshop P Pressure PA Payload Assembly PLT Pilot PLV Post Landing Ventilation PSI Pounds PerSquare Inch PSIA Pounds PerSquare Inch, Absolute PSIL PreferredSpeech Interference Level PRI Primary Mole SieveFans PS PayloadShroud PWL Acoustic Power Level, dB R Room Constant Ref. Reference S Areaof Room SAS SolarArray System SAT SystemsAssurance Test Sec Secondary Mole SieveFans SIA Speaker Intercom Assembly SIL Speech Interference Level SMEAT Skylab Medical Experiment Altitude Test SPL Sound PressureLevel, dB SPT Science Pilot STS Structural Transition Section sws Sa turn Workshop T60 Reverberation Time, Seconds TCBD Test Control Board Directive 7- 3

TL Transmission Loss, dB TVIS TV StationInput V Volume vc s VentilationControlSystem WMC Waste ManagementCompartment WDB Weighted Octave Band

7.2 References

\ .Thefollowing documents are referenced inthe foregoing sections $y numbers only.

1. W. A. Benfieldand R. F. Hruda: VibrationAnalysis of Structures by Component Mode Substitution, AIAAIASME ll& Structural Dynamics andMaterial Conference, Denver,Colorado, April 22 - 24,1970.

2. W. D. Brayton, "Dynamic Analysisof the Probe and DrogueDocking Mechanism", Journal of Spacecraftand Rockets, May 1966.

3. David W. Malone: A Program toDerive Analytical Model Representa- tionsof the Apollo Spacecraft and ITSLaunch Vehicles, Docking AnalysisFinal Report. D2-84124-3.The Boeing Company, Space Division,Seattle, Washington, May 1967.

4. R. 3. Ravera:Docking Dynamics Simulationfor AAP. Technical Memorandum T"69-1022-6. Bellcomm, Inc.,Washington, D.C., July 1969.

5. C. Lanczos: The VariationalPrinciples of Mechanics.University ofToronoto Press, 1966.

6. C. S. Bodleyand A. C. Park:Skylab Docking Response Program. ED-2002-770. MartinMarietta Corporation, Denver, Colorado, April 1970.

7. J. Gremel (Personal Communication) , McDonne11 DouglasAstronautics Company- East : 1972 .

8. Caldwell C. Johnson:T"X-58163, Skylab M487 Habitability/Crew Quarters,dated October 1975

9. AFSC Design Handbook, Series 1-0,Personnel Subsystems, DH 1-3,. January1969.

10. Acoustic Absorption." Data Internal to Shroud, MSC TCBD No. OWS/PA- 52, Houston,Texas, 26 August1971. 7-4

11. Additional Acoustic Test for IU Anomaly Investigation, MSC, TCBD No. OWS/PA-57, Houston,Texas, 6 October1971.

12. VibrationAcoustic Data from the Skylab Phase IIA PayloadAssembly VibroacousticTest for the Liftoff Condition, Data Book for: -Runs Enclosure PA-A-008 & 009 3 PA-A-040 5 PA-A-043 7 PA- A- 044 8 MSFC Document No. S&A-ASTN-ADD-72- , Huntsville, Alabama, Release DatePending.

13. VibrationAcoustic Data from the Skylab Phase IIA PayloadAssembly VibroacousticTest for BoundaryLayer Condition, Data Book for: -Runs Enclosure PA-A-011 & 012 4 PA-A-041 6 PA-A-045 9 MSFC Document No.%E-ASTN-ADD-72- , Huntsville, Alabama, Release DatePending.

14. Phaseand Amplitude Data from the Skylab Phase IIA PayloadAssembly Special Modal Survey Test Performed on theInstrument Unit, Data Book for:

-Runs Enclosure

PA-V-012, 015,014, 019, 10 021,026, 027, 029, 031, 033,034, 036, 038, 040, 041and 044 MSFC Document No.S&E-ASTN-ADD-72- , Huntsville, Alabama, Release DatePending.

15. W. P. Rodden, "A Method forDeriving Structural Influence Coefficients from Ground Vibration Tests", AIAA Journal,Vol. 5, No. 5, May 1967, pp. 991- 1000.

16. A. Breman and W. C. Flannelly, "Theoryof Incomplete Models of Dynamic Structures", AIAA Journal, Vol.9, No. 8, August 1971, pp. 1481-1487.

17. R. G. Ross Jr. , "Synthesisof Stiffness and Mass Matricesfrom Experi- mentsVibration Modes", SAE Preprint710787, pp. 1-9. I

7- 5

18. A. E. Galefand D. L. Cronin,"Determination of Structural Proper- ties fromTest Data", TheShock and Vibration Bulletin, Bulletin 41, Part 7, December 1970, pp. 9-18.

19. B. M. Hall and E; D. Calkin,"Linear Estimation of Structural Parametersfrom Dynamic TestData", AIAA/ASME 11G Structures, Structural Dynamics,and MaterialsConference, Denver,Colorado, April 22-24,1970.

20. R. L. Fox and M. P. Kapoor, "Rates of Change ofEigenvalues and Eigenvectors", AIM Journal, Vol. 6, No. 12, December 1968, pp. 2426-2429.

7.3 Additional Reference Material

Thissection provides a listing of the date, report number and title ofSkylab documents that are applicable to the dynamics effort. Much of theinformation in this report was developedfrom these documents, therefore,persons requiring additional information or specific data may find thisreference section useful.

Report No. Date ED- 2002- Title

10127167 181 AAP DockingLoads Analysis 04/15/68 445- 1 DockingLoads Report 06/15/68 445- 2 DockingLoads Report 08/01/68 580- 1 Cluster DockingReport 08/15/68 445- 3 DockingLoads Report 05/30/69 827- 1 AAP Cluster DockingResponse Report 06/30/69 847 ControlImpulse Methodology Report 08/23/69 595 MethodologyReport for DockingLoads 09/25/69 908 CSM/MDP (Axial)Latch Loads 10/20/69 924 Latch Loads Evaluation Report 04/06/70 770 DockingProbe Analytical Model 09/23/70 1190 ATM DeploymentLoads Report 09/23/70 1197 Evaluation of Solar Array Deflection Model 10/15/70 120 1 Pre-TestStatic Influence Coefficients 11/02/70 1136- 1 Latch Load Evaluation Report 11/16/70 827-2 Skylab Cluster Docking Loads Report 03/29/71 1279 Orbital Workshop Solar Array System Sensitivity Analysis 7- 6

Vibration Modal Analye

Report No. Date ED- 2002- Title

06/30/67 137 VibrationAnalysis of the AAP Orbital Workshop 07/01/67 141 Vibration and Acoustic Analysis for AAP Flight Configuration 4. 12/18/67 300 VibrationAnalysis of the AAP Orbital Workshop 03/15/68 384- 1 Cluster Modal Vibration Report 0410 1/68 4 14 Vibration Report for AAP BeamologyModel 04/15/68 384- 2 Cluster Modal Vibration Report 05/15/68 384- 3 Cluster Modal Vibration Report 06/15/68 384-4 Cluster Modal Vibration Report 06/18/68 539- 1 AAP Vibration Analysis Report 07/22/68 384- 5 Cluster Modal Vibration Report 08/15/68 539-2 AAP VibrationAnalysis Report 12/15/69 960 Cluster Vibration Analysis Mass Properties 07/24/70 790-2 Vibration Modal Analysis Report 09/23/70 7 90- 3 Vibration Modal Analysis Report 01/14/71 7 90-4 Vibration Modal Analysis Report 02/10/71 1256 Modal CouplingProgram and Report 04/12/71 7 90- 5 Vibration Modal Analysis Report 06/30/71 1325 Pre-Test Vibration Analysis Report 07/16/71 790-6 Vibration Modal Analysis Report 07/19/71 1355 Modal ToleranceReport 09/01/71 1326 Vibration Modal Analysis Mass Properties 09/23/71 1355 Modal ToleranceReport 09/30/71 1338 Vehicle Dynamics Mechanical Vibration Modal Survey Test Plan 01/31/72 1433 Modal Property Data Report,Configuration 7 02/15/72 7 90- 7 Vibration Modal Analysis Report 02/26/72 1446 Modal Property Data Report,Configurations 9 & 10 03/31/72 1459 Modal Property Data Report,Configuration 6 04/20/72 1433 Modal Property Data Report,Configuration 7 Rev. A 7-7

Report No. Date ED- 2002- Title

04/15/71 1263 MDA Influence Coefficient Test Evaluation Report 04/19/71 827-3 Skylab Cluster DockingLoads Report 04/19/71 1281- 1 Orbital ManeuverLoads Report 05/21/71 1136-2 Latch Load Evaluation Report 05/15/71 1309- 1 ATM/SA DeploymentLoads Report 06/30/71 1324 Pre-TestStructural Response Report 07/30/71 1350- 1 ControlImpulse Response Report (Preliminary) 08/09/71 1339-2 ApolloTelescope Mount SolarArray System Sen- sitivity Analysis 08/23/71 1333- 1 Skylab Cluster DockingILatching LoadsReport (Preliminary) 11/22/71 1350- 2 ControlImpulse Response Report (Preliminary) 11/22/71 1395 SkylabDocking Maneuver Simulation Mathematical Model Report(Final) 02/23/72 1350- 3 ControlImpulse Response Report (Final) 02/23/72 1403 SkylabControl System Simulation Report 02/23/72 1309-2 Deployment Loads Report 05/22/72 1480 Skylab Cluster Radial Docking/La tching Loads Report 06/23/72 130 9- 3 DeploymentLoads Report 06/23/72 1487 OWS-SAS LoadsEvaluation Report 03/19/73 1333-3 SkylabCluster DockingjLatching Loads Report (Final) 06/18/73 1689 Docking/La tching Loads ATM Undeployed Orbital Configuration Report 07/23/73 1333- 2 SkylabCluster Docking/Latch Loads Report (Final) 08/23/73 1695 SkylabPremission Support of SL-2 OrbitalLoads 08/27/73 1704 Skylab Rescue Mission Latching Loads Report 09/20/73 1706 SL-2 Mission Evaluation Report 11/16/73 17 14 SL-3 Mission Evaluation Report 03/15/74 1720 SL-4 Mission Evaluation Inputs 7- 8

Report No. Date ED-2002- Title

06/21/72 14 94 Vibro-Acoustic Modal Survey Test Evaluation Report (Launch Configuration) 09/15/72 1544 Modal PropertyData Report, Configuration 7 09/15/72 1522 Vibro-Acoustic Modal Survey Test EvaluationReport (Orbital Configuration) 09/29/72 1525 Cluster Modal Properties for Control Analysis Interim Report 10/16/72 1546 DynamicsModal Verification Report (Launch Con- figuration) 10127172 1551 DynamicsModel VerificationReport (Orbit Con- figuration) 10/31/72 1554 Modal PropertyData Report, Configuration 6 11/14/72 1562-1 Modal PropertyData Report, Configuration 3.2 11/14/72 1562-2 Modal Property Data Report,Configuration 1.2 11/14/72 1562-3 Modal Property Data Report , Configuration 2.1 11/21/72 1563-1 Cluster Modal Properties for Control Analysis, Configuration 1.3/Nom 11/21/72 1563-2 Cluster Modal Properties for Control Analysis, Configuration 1.31-67.5O 11/21/72 1563-3 Cluster Modal Properties for Control Analysis, Configuration 1.31112.5' 12/19/72 1577 Dynamic Test Reflected Structural ModelMethodology Report 12120172 1564 Final Vibration Modal Analysis Report

ATM Systemand Subsystem Dynamic AnalyG

04/01/70 948-1 InterimReport, Spar Canister Modal Datafor Control Loop Analysis 101 15/70 1168 InterimReport, Spar Canister Modal Datafor Control Loop Analysis 04/01/71 1265 InterimReport, Spar Canister ModalData for Control Loop Analysis 05/15/71 1303 ATM Rack andSparlCanister Boost ConditionVibra- tional Transfer Function 09/15/71 1303 ATM Rack andSparlCanister Boost Condition Vibra- Rev. A tionalTransfer Function 10/20/71 1380 SparlCanister Modal Data forControl Loop Analysis II "

7-9

Report No. Date ED-2002- Title

03/31/721280- 1 Spar/Canister Modal Data forControl Loop Analysis

SWS Subsystem-InteriorAcoustic Levels - Orbital Conditions

10/30/70 1200- 1 Skylab Interior Acoustic Environment Report 01/31/71 1200-2 SkylabInterior Acoustic Environment Report 04/30/71 1200-3 Skylab Interior Acoustic Environment Report 07/31/71 1200-4 Skylab Interior Acoustic Environment Report 11/30/71 1200- 5 SkylabInterior Acoustic Environment Report 02/29/72 1200-6 SkylabInterior Acoustic Environment Report 06/30/72 1200- 7 SkylabInterior Acoustic Environment Report 12/31/72 1200-8 SkylabInterior Acoustic Environment Report 08/31173 1200- 9 SkylabInterior Acoustic Environment Report 03/31/74 1200- 10 SkylabInterior Acoustic Environment Report

Vibro-AcousticTest

03/31/71 1255 Dynamic InstrumentationPlan Volume I Acoustic Test 06/30/71 1255 Chg. 1 09/30/71 1338 Vehicle Dynamic MechanicalVibratiodModal SurveyPlan 12/31/71 1255 Rev. A 05/31/72 1255 Rev. B 01/31/72 140 9 Acoustic Test Summary Report 05/31/72 1479 Acoustic Test Summary Report Volume I 05/31/72 147 9 Acoustic Test Summary Report Volume I1 09/30/72 1516 Modal Survey Test Summary Report 09/30/72 1532 Dynamic Instrumentation Plan

Skylab Payload Boost Flight Analye

09/15/71 1366Skylab Boost Flight Phase Modal Properties 10/31/71 1396 Modal Property Data Configuration 8 11/21/71 1388 SkylabPayload Base Motion Analysis Report 7- 10

Report No. Date ED-2002- Title

12/17/71 1417 Modal Property Data Report S-IC FlightConfigura- tion 1, Part 2 12/17/71 1418 Modal Property Data Report S-IC Flight Configura- tion 2 12/19/71 1424 Skylab Boost Flight Phase Model Properties Report 01/10/72 1420 Modal Property Data Report, S-IC FlightConfigura- tion 4 01/10/72 1421 Moda 1 Property Data Report, S-I1 FlightConfigura- tion 1 01/10/72 1422 Modal Property Data Report , S- I1 Flight Conf igura- tion 2 01/10/72 1423 Modal Property Data Report, OWS Flight Configura- tion 1 01/10/72 1419 Modal Property Data Report, S-IC FlightConfigura- tion,Part 2 01/15/72 1431 Skylab Boost Flight LoadsAnalysis Report 02/18/72 1435 SkylabBoost Flight Loads Me thodology Report 03/31/72 1459 Modal PropertyData Report Configuration 6 05/19/72 1431- 2 SkylabBoost Flight LoadsAnalysis Report 04/20/72 1433 Modal Property Data ReportConfiguration 7 Rev. A 10/20/72 1555 SkylabPayload Base Motion Vibration Analysis Report 10123172 1556 Modal PropertyData Report , Base Motion Config- ura tion 11/06/72 1421- 2 Modal PropertyData Report,S-I1 Flight Config- uration 1 11/13/72 1420- 2 Modal PropertyData Report, S-IC FlightConfig- uration 4 11/15/72 1422- 2 Modal PropertyData Report,S-I1 Flight Config- uration 2 11/20/72 1424- 2 SkylabBoost Flight Phase Modal Properties Report 12/18/72 1431- 3 Skylab Boost Flight LoadsAnalysis Report 12/18/72 1388- 2 SkylabPayload Base Motion Analysis Report 03/19/73 1388-3 SkylabPayload Base MotionAnalysis Report 09/20/73 1700 InformalFlight Loads Data for Inclusion to SkylabMission Support 7-11

"SPS- cluster Reorientation Studies

Report No. Date ED-2002- Title

.. ._ -~~ .. . . -~" - - " - ~ ~ ~

03/26/73 1658 InformalLoads/Response Data SWS DeorbitFeasibility Study 06/29/73 1694 SPS ClusterReorientation Loads - Preliminary 08/15/73 1694 SPS ClusterReorientation Loads - Final Volume I 08/15/73 1694 SPS ClusterReorientation Loads - Final Volume 11 08/15/73 1694 SPS ClusterReorientation Loads - Final Volume I11 08/15/73 1694 SPS ClusterReorientation Loads - Final Volume IV

TaskMiscellaneous Special Studies

10/04/68 643 AcousticTest of Multiple Docking Adapter (MDA) Pane 1 07/01/70 1055 PreliminarySaturn Workshop AcousticalEnvironmental Mapping 04/19/71 1281- 1 Orbital ManeuverLoads Report 06/15/71 1131 SubsystemDesign Load Factors Due to Shock,Acous- tic andVibration 08/09/71 1339- 2 ApolloTelescope Mount SolarArray System Sensi- tivity Analysis 08/31/71 1356 CSM/MDA DockingShock Final Test Report 08/31/71 1357 EPCS Orbital Cluster Modal Properties and ATM Boost 09/14/71 1365 ATM Alignment Modeling 11/19/71 1281-2 Orbital ManeuverLoads Report (Final) 01/31/72 1432 Recommended SpecificationRevisions and Equipment ExceedanceStudy for MDA 02/15/72 1444 Skylab RCS-DAP Vibration Analysis 05/22/72 1444 Skylab RCS-DAP Vibration Analysis for Configurations sup. 1 1.3 and 3.2 05/07/73 1687 ReducedDynamic Test Damping DataAnalysis Report 08/23/73 1695 SkylabPremission Support of SL-2 OrbitalLoads

NASA-Langley, 1976