--------·--------·-·��-·-·-··11111111111 I .• NASA TECHNICAL NOTE NASA TN 0-6850 C!, I - -t ;;;;;;;;;;;;;;;- n m ==== :c === r- c_I:-'� ii ::u L.OAN CO PY: RETUJi � � AF WL (00UL> �- � KIRTLAND AFB, N, c=- _PI -=== z 3: APOLLO EXPERIENCE REPORT - LUNAR MODULE LANDING GEAR SUBSYSTEM by William F. Rogers Manned Spacecraft Center Houston, Texas 77058 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION • WASHINGTON, D. C. • JUNE 1972 TECH LIBRARY KAFB, NM llllllllliiiiiii0133650iiiU lllllllllll�ll lllllll G�vernment Accessio� No. 3. Recipient's Catalog No. 2. Report Date Title and Subtitle 5. APOLLO EXPERIENCE REPORTI I June 1972 4. LUNAR MODULE LANDING GEAR SUBSYSTEM l 6. Performing Organization Code Performing Organization Report No. 7. Author(s) 8. I MSC S-316 William F. Rogers, MSC . Work Unit No. 9. Performing Organization Name and Address I 914-13-20-13-72. 110 - Manned Spacecraft Center Contract or Grant No. Houston, Texas 77058 111. Type of Report and Period Covered 12. Sponsoring Agency Name and Address 113. Technical Note National Aeronautics and Space Administration Spons;rin� Agency Code Washington, D.C. 20546 114. Supplementary Notes The MSC Director waived the use of the International System of Units (SI) for this Apollo Experience Report, because, in his judgment, us e of SI Units would impair the usefulness of the report or result in excessive cost. 16. Abstract The development of the lunar module landing gear subsystem through the Apollq 11 lunar -landing mission is presented. The landing-gear design evolved fr om the design requirements, which had to satisfy the structural, mechanical, and landing-performance constraints of the vehicle. Ex- tensive analyses and tests were undertaken to verify the design adequacy. Techniques of the landing-performance analysis served as a primary tool in developing the subsystem hardware and in determining the adequacy of the landing gear for top pling stability and energy absorption. The successful Apollo 11 lunar-landing mission provided t he first opportunity for a complete flight test of the landing gear under both natural and indueed environments. Distribut ion Statement 17. Key Words (Suggested by Author(s)) 18. · Landing Gear ' Spacecraft Mechanisms • Lunar Module · Lunar Landing · Landing Dynamics · Landing Performance ·Landing-Gear Testing - - .. ecurity Classif. (of this r-;port) Security Classif. (of this page) No. of Pages None None 58 - t. - .,20._ j 21. 122. ;;c:�o " For sale by the National Technical Information Service, Springfield, Virginia 22151 -IIIIII IIIIIIIIIIIIIIIIIIIIIIIUr Ill I 11 1111 1-1 11111 ·-----------·-·---------·---·····1111 CONTENTS Section Page SUMMARY . 1 INTRODUCTION • 1 DESIGN REQUIREMENTS AND CRITERIA • 2 DEVELOPMENT HISTORY • • • • 4 CONFIGURATION DESCRIPTION . • 6 MAJOR PROBLEMS . • • . 9 Redesign of the 167-Inch-Tread-Radius Landing Gear 9 Statistical Landing Performance 10 Thermal Insulation . 12 Weight Summary 13 Failure History 14 APOLLO 11 FLIGHT-TEST RESULTS 16 CONCLUDING REMARKS . 20 REFERENCES •••.... 21 APPENDIX A-LANDING PERFORMANCE OF THE LM . 22 APPENDIX -HARDB WARE DEVELOPMENT AND CERTI FICATION TESTING •.••••...•••.•..•. 33 APPENDIX C-DETAILED CON FIGURATION DESCRIPTION •.•... 46 iii r 11 11 1-1 11111111 TABLES Table Page I SIGNIFICANT LANDING -GEAR DESIGN CONCEPTS • • . • • . 5 II LANDING -GEAR THERMAL-INSULATION WEIGHT HISTORY 12 ill APOLLO 11 LANDING -GEAR -COMPONENT WEIGHT SUMMARY . 14 IV LANDING -GEAR FAILURE HISTORY . 15 V APOLLO 11 (LM-5) STRUT-STROKE ESTIMATES. 19 A-I LANDING -PERFORMANCE HISTORY OF TH E LM 31 B-I LANDING -GEAR DEPLOYMENT-TEST SUMMARY 35 B-II LANDING -GEAR DROP -TEST SUMMARY . 36 B-ill CERTIFICATION SUMMARY OF THE LM LANDING -GEAR SUBSYSTEM ....................... 41 B-IV COMPARISON OF CERTIFIED AND FLIGHT-CONFIGURATION HARDWARE . • • . 42 iv -------- ···-···"''________ - ..... _.,_ ... , ""' FIGURES Figure Page 1 The LM configuration (contractor technical proposal) . 3 2 Stowed and deployed positions of the landing gear . 5 3 The LM supported in the SLA 7 4 The LM landing gear . • 7 5 Overall view of the LM with the landing gear deployed 8 6 Landing-gear primary strut 8 7 Primary -strut compression load as a function of compression stroke ..... 8 8 Landing -gear secondary strut 8 9 Secondary -strut compression and tension loads (a) Compression load as a function of compression stroke 9 (b) Tension load as a function of tension stroke 9 10 Final-landing-gear landing performance 10 11 Critical landing conditions .... ... 10 12 Apollo 11 attitude and motion touchdown conditions . 11 13 The LM weight history (a) The LM touchdown weight history . 13 (b) The LM landing -gear weight history 14 14 Apollo 11 LM (LM-5) on the lunar surface 16 15 Apollo 11 LM (LM-5) minus -Z (aft) footpad 16 16 Apollo 11 (LM-5) attitudes and attitude rates at touchdown (a) Pitch angle as a function of time . 17 (b) Roll angle as a function of time 17 (c) Yaw angle as a function of time • . 17 (d) Pitch rate as a function of time • . 17 (e) Roll rate as a function of time . 18 (f) Yaw rate as a function of time . 18 v 11111111.111 11111 Figure Page 17 Apollo 11 (LM-5} descent-engine skirt . .......•.. 20 A-1 Validation of touchdown-analysis mathematical model 22 A-2 Lunar-surface description (a) Slope profile . 25 (b) Protuberance profile .. 25 A- 3 One-sixth-scale drop-test model . 26 A- 4 One-sixth-scale model and drop-test equipment at the prime contractor facility . 27 A-5 One-sixth-scale-model test/analysis gross correlation for symmetrical drops . 27 A-6 One-sixth-scale-model test/analysis time-history correlation for symmetrical drops (a) Horizontal velocity as a function of time . 27 (b) Vertical velocity as a function of time 27 (c) Horizontal acceleration as a function of time 28 (d) Vertical acceleration as a function of time . 28 A-7 Simulated-lunar-gravity test vehicle and related equipment at the LRC ..•. ......... 28 B-1 Test summary of the LM landing gear 33 B-2 Landing-gear drop-test equipment ... 37 B-3 Landing gear configured for unsymmetrical drop test .. 37 B-4 Landing gear following drop into simulated lunar soil . 37 C-1 Landing-gear uplock mechanism .......... 48 C -2 Landing-gear deployment and downlock mechanism (a) Stowed position . 48 (b) Down and locked position . ... 48 C -3 Lunar-surf ace-s ensing-probe -deployment mechanism 50 C-4 Lunar-surface-sensing-probe switch 50 C-5 Landing-gear footpad . 51 C-6 Landing-gear-assembly test flow 52 vi APOLLO EXPERIENCE REPORT LUNAR MODULE LANDING GEAR SUBSY STEM By William F. Rogers Manned Spacecraft Center SUMMARY The development of the lunar module landing gear subsystem through the Apollo 11 lunar-landing mission is described in this report. Based on the design requirements, which must satisfy the structural, mechanical, and landing-performance constraints of the vehicle, the landing gear evolved from a fixed landing gear with five inverted tripod­ type legs to a four-legged deployable landing gear. Both extensive analyses and full-scale and model tests were undertaken to verify the design adequacy. The techniques developed for the landing-performance analyses served as a primary tool in the development of the subsystem hardware and in the pre­ diction of the lunar module touchdown-performance capability. A major portion of the analyses was devoted to determining the performance adequa cy of the landing gear for toppling stability and energy absorption. Landing-performance testing was used pri­ marily to verify the analyses. The successful Apollo 11 lunar-landing mission provided the first opportunity for a complete flight test of the landing gear under both natural and induced environments. INTRODUCTION The landing of the lunar module (LM) on the surface of the moon is one of the more crucial events of the Apollo mission. During the critical seconds at touchdown, the LM landing system brings the vehicle to rest while preventing toppling, absorbing the landing-impact energy, and limiting loads induced into the LM structure. The landing­ gear design is influenced significantly by the LM structural requirements, the LM con­ trol system, the lunar-surface topographical and soil characteristics, and the available stowage space. The landing gear also must provide a stable launch platform for lift-off of the ascent stage from the lunar surface. The design and development of the LM landing gear subsystem hardware from the time of ·1ts conception through the Apollo 11 lunar-landing mission are presented. Also presented is the interaction of the landing gear with other LM subsystems. The specific design requirements for the landing-gear development are discussed, followed by the development history, a brief configuration description, a discussion of major problems, 11111111-111 11111 and a summary of flight test results. Detailed information about the LM landing per­ formance, the hardware development and testing, and the landing-gear configuration is given in appendixes A, B, and C, respectively. DESIGN REQUIREMENTS AND CRITERIA The landing gear subsystem hardware design requirements may be divided into three general categories- structural, mechanical, and landing performance. Struc­ turally , the landing gear must withstand the loads and conditions imposed by the induced and natural environments defined in thetechnical specification (ref. 1) and in the report entitled "Design Criteria and Environments - LM" (ref. 2). The landing-gear strut loads must not exceed the LM structural-design requirements. Mechanically, the landing gear must deploy properly and lock down while in lunar orbit. This is accomplished before the undocking of the LM from the command and service module (CSM) . In the stowed position, the landing gear must physically clear the SaturnIVB (S-IVB) stage and the spacecraft/LM adapter (SLA) during the CSM/LM ejection maneuver, and landing -gear deployment must be controlled from within the LM cabin. The landing gear must provide sufficient energy-absorption capability and ade­ quate vehicle -toppling stability for the range· of possible touchdown conditions and for the lunar -surface characteristics defined in the technical specification.