I NASA NASA SP-8102 SPACE VEHICLE DESIGN CRITERIA (GUIDANCE AND CONTROL) SPACE VEHICLE ACCELEROMETER APPLICATIONS DECEMBER 1972 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GUIDE TO THE USE OF THIS MONOGRAPH The purpose of this monograph is to organize and present, for effective use in space vehicle de- velopment, the significant experience and knowledge accumulated in development and opera- tional programs to date. It reviews and assesses current design practices, and from them establishes firm guidance for achieving greater consistency in design, increased reliability in the end prod- uct, and greater efficiency in the design effort. The monograph is organized into three major sections that are preceded by a brief introduction and complemented by a set of references. The State of the Art, section 2, reviews and discusses the total design problem and identifies which design elements are involved in successful designs. It describes the current technology pertaining to these elements. When detailed information is required, the best available references are cited. This section serves as a survey of the subject that provides background material and prepares a proper technological base for the Criteria and Recommended Practices. The Criteria, shown in section 3, state clearly and briefly what rule, guide, limitation, or standard must be imposed on each essential design element to insure successful design. The Criteria can serve effectively as a checklist for the project manager to use in guiding a design or in assessing its adequacy. The Recommended Practices, as shown in section 4, state how to satisfy each of the criteria. Whenever possible, the best procedure is described; when this cannot be done concisely, appro- priate references are provided. The Recommended Practices, in conjunction with the Criteria, provide positive guidance to the practicing designer on how to achieve successful design. Both sections (Criteria and Recommended Practices) have been organized into decimally numbered subsections so that the subjects within similarly numbered subsections correspond from section to section. The format for the Contents displays this continuity of subject in such a way that a particular aspect of design can be followed through both sections as a discrete subject. The design criteria monograph is not intended to be a design handbook, a set of specifications, or a design manual. It is a summary and a systematic ordering of the large and loosely organized body of existing successful design techniques and practices. Its value and its merit should be judged on how effectively it makes that material available to and useful to the user. NASA experience has indicated a need for uniform criteria for the design of space vehicles. Ac- cordingly, criteria are being developed in the following areas of technology: Environment Structures Guidance and Control Chemical Propulsion Individual components of this work will be issued as separate monographs as soon as they are completed. This document, Space Vehicle Accelerometer Applications, is one such monograph. A list of all previously issued monographs can be found at the back of this publication. These monographs are to be regarded as guides to design and not as NASA requirements, except as may be specified in formal project specifications. It is expected, however, that the criteria sections of these documents, revised as experience may indicate to be desirable, eventuall; will be uniformly applied to the design of NASA space vehicles. This monograph was prepared for NASA under the cognizance of the Jet Propulsion Laboratory, California Institute of Technology. Graham W. Casserly of Champlain Technology, Inc. (CTI) was the principal investigator. The effort was guided by an advisory panel, of which Mr. Casserly was the chairman. The follow- ing individuals participated in the advisory panel and monograph review activities: G. J. Bukow MIT, C. Stark Draper Laboratory A. T. Campbell Jet Propulsion Laboratory A. Copeland Bell Aerospace Company B. M. Dobrotin Jet Propulsion Laboratory M. E. Jones NASA Manned Spacecraft Center C. R. Kochakian MIT, C. Stark Draper Laboratory G. Morrison Boeing Company, Seattle T. H. Phillips Honeywell, St. Petersburg H. Rogall SingerlKearfott Division K. M. Russ Jet Propulsion Laboratory J. 0. Salvatore Hughes Aircraft Company, El Segundo K. Shenfish IBM, Huntsville iii CONTENTS 1. INTRODUCTION ................................................................ 1 2 . STATE OF THE ART .......... ............................................ 2 2.1 Technical Introduction ........................................................ 2 2.1.1 The Physics of Accelerometer Applications .................................. 2 2.1.2 Accelerometer Principles ................................................ 4 2.1.2.1 Accelerometer Capture Loops ................................ 6 2.1.2.2 Linear Accelerometers ........................................... 12 2.1.2.3 Angular Accelerometers .......................................... 16 2.1.2.4 Tilt Sensors ................................................... 17 2.1.2.5 Other Accelerometers ........................................... 19 2.1.2.6 Summary ..................................................... 21 2.1.3 Space Vehicle Accelerometer Functions .................................... 21 2.1.3.1 Leveling ...................................................... 21 2.1.3.2 Guidance and Navigation ........................................ 23 2.1.3.3 Monitoring and Control ..................................... 24 21.3.4 Summary .... ......................................... 25 2.2 History of Applications ............................... ...................... 25 2.2.1 Specific Applications .............................................. 2.2.1.1 Guidance and Navigation ........................................ 30 2.2.1.2 Monitoring and Control .......................................... 34 2.2.1.3 Leveling ....................................................... 36 2.2.2 Mounting Considerations ........................................... 38 2.2.2.1 Body Bending .................................................. 38 2.2.2.2 Strapdown vs Gimballed Platform Considerations ..................... 38 2.3 Advanced Applications ........................................................ 39 2.3.1 Advanced Instruments .................................................. 39 2.3.2 Low-g Measurement .................................................... 40 2.3.3 Guidance and Navigation Applications ..................................... 41 2.3.4 Environmental Factors .................................................. 41 3. CRITERIA ................................................................. 41 3.1 Applications ................................................................ 42 3.2 Accelerometer Selection ....................................................... 42 3.2.1 Accelerometer Requirements ............................................. 42 3.2.2 Compatibility with Mission Requirements .................................. 43 3.2.3 Program Milestones and Component Specifications ........................... 43 V 3 . CR1TERI:f (rnntintlrd\ ............................................................ 41 3.3 Trndcoff Filctors ............................................................. 4'3 3.3.1 Perfnrmsnrr .......................................................... 44 3.3.2 Type- of Captiirr I.oop ............... ................................ 44 3.3.3 f{c*li:il)ilit y ......... ................................................ 4-1 3.3.1 cA)St ................................................................. 45 3.4 Testing and Evnliintion ........................................................ 45 3.4.1 >f;ijr>rTccting CXizcific.ntir1ll .............................................. 45 3.4.2 Test Pl.iriniiip and Siwc.ificatior1 .......... ............................. 45 3.4.3 Trst Tolrrnncr Pl~~iiiiing... ........................................... 4(3 3.41 Eva1tl;itiorl of Test 1Lt.i ... .................. ...................... 48 3.5 Crnrrnl Progrn1ii Cmirqidt.r;itioliz ....... ..................................... 46 3.5.1 Aligiin>rnt nnd Citliltr.ifior> ................ .................... ... 4R 3.5.2 Accrlrrnmrtcr Chi~ip~inriitIr*vr! Tvsts ...... ........................... 47 3.5.3 Siilicy~trrnsTest ... ................................................ 47 3.5.4 S!.strm Trstc .............................. ........................ 47 3.5.5 Tvd D.it.i Ev;lliIntin11 ................................................... 47 3.5.6 Prclniinrh C.)iccknirt arirt In-I%gl)t SIoniti)ririp ............................... 47 4 . RECO?r!S!ESI)EI) PR.\CTIC ES ................................................ 4.1 Applicntinn< ........... ............................................ 4$ 4.2 Accrlrrnmrfcr Srlrct iriii ............................................ 49 4.2. I Accrlrrnnirtrr 11qiiirrmrnt Ikfiriitinn ..................................... 49 4.2.2 Chriipatii>ilit!~V'itl~ Slizsinri Ih.rliiirc*mrnts ............................... 43 4.2.3 rrogrnrn %!ilrdfu1rsiintl Coriipnnrnt Sprcif im........................... 50 4.3 Triitlroff Factors ............................................................. 51 4.8.1 Pvrfonnnncr .......................................................... 51 4.3.2 Clroicr of Ciipttlrr Irmp ......................................... 59 4.3.3 Rc.lialdit! ............ ....................................... '60 4.3.4 Chf ................................................................