CRa TER PDR Mechanical Design CRa TER Assembly
CRa. TER PDR Mechanical Design, CRa. TER Assembly and Electronics Assembly Preliminary Design Review Matthew Smith Mechanical Engineer (617)-252 -1736 matt@space. mit. edu Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Overview Instrument and Assembly Description Mechanical Environments and Requirements Mechanical Design Details Near Term Tasks Back-up slides Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Instrument and Assembly Description • Crater integrates two main sub-assemblies: The Telescope Assembly and The Electronics Assembly. – – The Telescope Assembly is being designed and built by The Aerospace Corporation The Analog Board is being designed by Aerospace. The Flight Analog Boards will be built by MIT The Digital Board and Electronics Enclosure Assembly are being designed and built by MIT will integrate the sub-assemblies and perform all functional, environmental and acceptance testing. Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Instrument and Assembly Description Cosmic RAy Telescope for the Effects of Radiation
Mechanical Environments • CRa. TER PDR Mechanical Design From 431 -RQMT-000012, Environments Section 2. Section Description Levels 2. 1. 2 Net cg limit load 12 g 2. 4. 2 Sinusoidal Vibration Loads Frequency: Protoflight/Qual: Acceptance: 2. 5 Acoustics • Enclosed box without exposed thin surfaces OASPL Protoflight/Qual: 141. 1 d. B OASPL Acceptance: 138. 1 d. B 2. 6. 1 Random Vibration See Random Vibration slide 2. 7 Shock environment 40 g at 100 Hz 2665 g at 1165 to 3000 Hz. No self induced shock. 2. 8 Venting Per 431 -SPEC-000091 LRO Thermal Subsystem spec. Cosmic RAy Telescope for the Effects of Radiation 5 -100 Hz 8 g 6. 4 g
Mechanical Requirements and Verification • CRa. TER PDR Mechanical Design From 431 -RQMT-000012, Verification Requirements Section 3. Section Description Levels 3. 1. 2. 1 3. 1. 2. 2 Stowed fundamental Hz Deployed fundamental Frequency Freq >35 >3 Hz 3. 2. 1 Factors of Safety See FOS table 3. 2. 2 Test factors See Test Factors table 3. 2 MEVR-10 Perform frequency verification test for Instruments with frequencies above 50 Hz. . MEVR-11 Report frequencies up to 200 Hz Low level sine sweep We will be above 50 Hz. 3. 3 Finite Element Model requirements We will be above 75 Hz and will not be required to submit an FEM of CRa. TER. Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design General Thermal Subsystem Requirements from 431 -Spec-000091 Section Description 4. 1 Exterior facing MLI blankets shall have 3 mil Kapton with VDA in outer Coating. 4. 2 MLI Blanket Grounding: All blankets shall be grounded per 431 -ICD-00018 4. 3 MLI Blanket Documentation: The location and shape documented in as-built ICDs. 4. 4 Attachment to MLI Blankets: All exterior MLI blankets shall be mechanically constrained at least at one point. Cosmic RAy Telescope for the Effects of Radiation
DESIGN DETAILS Electronics Assembly • CRa. TER PDR Mechanical Design Natural Frequency Estimates – Based from Steinberg Vibration Analysis for Electronic Equipment(Simply supported on 4 sides. ) • • Top Cover~ 199 Hz Bottom Cover ~ 159 Hz Analog Board~ 138 Hz Digital Board~ 149 Hz – From SOLID WORKS model of E-Box • frequency is 702 Hz at the middle plate that holds the two Circuit Card Assemblies. Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design DESIGN DETAILS Mechanical Environments, Random Vibration • • • Random Vibration will drive most of the analysis For resonances in the Random Vibration Spec, Miles’ Equation shows 3 sigma loading on the order of 75 -150 g Assume Q=10 Overall 14. 1 Grms 10. 0 grms Cosmic RAy Telescope for the Effects of Radiation
DESIGN DETAILS Stress Margins, Electronics Assembly Pieces • • • CRa. TER PDR Mechanical Design Load levels are superceded by random vibration spec Factors of Safety used for corresponding material from 431 -SPEC-000012. – Metals: 1. 25 Yield, 1. 4 Ultimate – Composite: 1. 5 Ultimate Margin of Safety = (Allowable Stress or Load)/(Applied Stress or Load x FS) – 1 Description Material Desc. MS Yield MS Ultimate Comments Top Cover Aluminum 6061 +14. 2 +19. 5 Note 1 Bottom Cover Aluminum 6061 +13. 4 +18. 4 Note 1 Digital Board FR 4 brittle +1. 5 Note 1 Analog Board FR 4 Brittle +0. 2 Note 1 E-box Structure Aluminum 7075 > +2. 8 >+3. 1 Note 2 Note 1. From Steinberg, Vibration Analysis for Electronic Equipment Note 2. From SOLID WORKS, COSMOS excluding top and bottom covers in the model. All components have positive Margin of Safety Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Details • The first fundamental frequency is estimated to be 149 Hz. – Not required to produce an FEM since our predicted first frequency is >75 Hz. • • • All positive margins of safety. Meet all factors of safety. No Fracture Critical Items. Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Internal Requirements for the Electronics Assembly • Derived Internal Mechanical Requirements for Electronics Enclosure – – – Have adequate contact area (. 5 in^2 min) to the spacecraft to support Thermal requirements. Provide safe structure, within Factors of Safety specified, to support Telescope Assembly. Provide for mounting 2 Circuit Card Assemblies. • – – – The Analog Board to provide direct linear path for electronics from the telescope interface to the Digital Board interface to reduce noise. Provide means to route cable from telescope to the Analog side of the Electronics Enclosure. Electrically isolate the electronics Enclosure from the Telescope, yet provide sufficient thermal conductance path. Provide adequate surface area for mounting electrical components. Interface to the Spacecraft to be on one side of the Electronics Enclosure. • – – The Analog Board and Digital Board must be separated by an aluminum plate. The interface connectors to be on the Digital side of the Electronics Enclosure (separate from the Analog side) Provide GN 2 purge interface inlet and outlet ports. Follow the octave rule for natural frequency of the PWAs to the Electronics Enclosure. The Electronics Assembly meets all internal requirements except for … – – Details need to be worked out for the GN 2 design. Electrical isolation of the E-box and Telescope needs more thought. Cosmic RAy Telescope for the Effects of Radiation
DESIGN DETAILS Electrical/Mechanical Interface CRa. TER PDR Mechanical Design Interface Connectors J 1 9 Pin D-Sub Male 311409 -1 P-B-12 J 2 9 Pin D-sub Female 311409 -1 S-B-12 J 3 1553, BJ 3150 J 4 1553, BJ 3150 Mounting Hardware - Six #10 -32 SHCS Surface roughness of 63 micro inches or better for interface surfaces. Mounting surfaces have Electrically Conductive finish (MIL-C-5541 Cl 3) PART OF MID DRAWING NUMBER 32 -02003. 02 Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design NEAR TERM TASKS – Update MICD to reflect latest configuration. – Further develop analysis on natural frequencies and stresses using SOLID WORKS and COSMOS on the complete CRa. TER Assembly. – Finalize interface between Telescope Assembly and Electronics Box Assembly. • Specify the electrical isolation material between the telescope and the E-Box. – Identify the GN 2 purge system (mechanical interface to the spacecraft, internal flow, pressure measurements…) – Complete the drawings for part and assembly fabrication. – Define attachment points and outline for thermal blankets. Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Backup Slides Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design Factors of Safety Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design BOARD ANALYSIS Analog Board Analysis 1 2 3 an 8. 429 x 5. 95 board separated into two parts 4 5 6 Polyimide modulus of elasticity E (lb/in sq 4. 21 E+05 Thickness h (inches) 0. 06 4. 21 E+05 0. 09 0. 11 0. 12 0. 15 u 0. 12 length a (in) 4. 215 width b (in) 5. 95 weight W (lb) 0. 65 0. 69 0. 71 0. 73 0. 79 in/sec. Sq 386 386 386 3. 14 D= 7. 69 25. 95 35. 60 47. 38 61. 51 120. 14 mass/area=W/gab 6. 19797 E-05 7. 13 E-05 7. 33 E-05 7. 54 E-05 8. 16 E-05 107 120 161 182 207 232 312 138 157 poisson ratio g pi D=E*h^3/(12(1 -u^2)) density p 4. 21 E+05 6. 7145 E-05 for a a simply supported board on 4 sides f=pi/2((D/p)^. 5)(1/a^2+1/b^2))^. 5 4. 21 E+05 Frequency=(Hz) 47 83 94 From Steinberg, vibration analysis for electronic equipment page 149 for a fixed beam on 4 sides 4. 21 E+05 Frequency=(Hz) 91 Average Frequency 69 160 121 Cosmic RAy Telescope for the Effects of Radiation 176 237
CRa. TER PDR Mechanical Design BOARD ANALYSIS Analog Board Analysis Cont’d STRESS Gin=peak load(g's)= 125 125 125 Q=transmisibility= 10 10 10 Gout=Gin*Q= W=board weight(lb)= 1250 1250 0. 65 0. 69 0. 71 0. 73 0. 79 q=load intensity=W*Gout/ab 13. 393 14. 509 15. 402 15. 848 16. 295 17. 634 My=bending moment at center= 6. 641 7. 195 7. 637 7. 859 8. 080 8. 744 3 3 0. 12 0. 15 10100 6995 DYNAMIC BENDING STRESS Kt= stress concentration factor h=height Sb=6*Kt*My/h^2= lb/in^2 3 3 0. 06 Stress due to bending 0. 09 33206 15988 FACTORS OF SAFETY 3 0. 11 13747 11691 FOS Yield FOS Ultimate 24000 psi 0. 7 1. 5 1. 7 2. 1 2. 4 3. 4 >10^8 0. 4 0. 6 1. 3 NUMBER OF CYLES BEFORE FAILURE check S-N curve for board type Ch 12 to determine if board will fail number of cycles before failure 10^4 >10^8 MARGIN OF SAFETY MOS=(Allowable stress/applied stress*FS)-1 3 >10^8 -0. 5 0. 0 For a composit Fs=1. 5 Ultimate Cosmic RAy Telescope for the Effects of Radiation 0. 2
CRa. TER PDR Mechanical Design BOARD ANALYSIS Digital Board Analysis 1 2 3 a 8. 562 x 7. 488 board two sections 6 E, psi 4. 21 E+05 h(inches) 0. 06 0. 09 0. 11 0. 12 0. 15 u 0. 12 length a (in) 4. 281 width b (in) 7. 488 weight W (lb) 0. 55 0. 57 0. 58 0. 59 0. 61 in/sec. Sq 386 386 386 3. 142857 143 3. 14285714 3. 142857 D= 7. 69 25. 95 35. 60 47. 38 61. 51 120. 14 mass/area=W/gab 4. 44492 E 05 4. 6066 E-05 4. 69 E-05 4. 77 E-05 4. 85 E-05 4. 93 E-05 113. 41 128. 14 177. 60 Thickness poisson ratio g pi D=E*h^3/(12(1 -u^2)) density p for a a simply supported board on 4 sides Frequency, HZ = 47. 32 85. 39 This is from an example by Steinberg, vibration analysis for electronic equipment page 149 for a fixed board on 4 sides 5 modulus of eleasticity Polyimide fiberglass f=pi/2((D/p)^. 5)(1/a^2+1/b^2))^. 5 4 99. 14 Frequency, HZ = 94. 79 171. 06 198. 61 227. 19 256. 69 355. 79 Average Frequency 71 128 149 170 192 267 Cosmic RAy Telescope for the Effects of Radiation
CRa. TER PDR Mechanical Design BOARD ANALYSIS Digital Board Analysis Cont’d STRESS Gin=peak load(g's)= 125 125 125 Q=transmisibility= 10 10 10 Gout=Gin*Q= 1250 1250 W=board weight(lb)= 0. 55 0. 57 0. 58 0. 59 0. 61 q=load intensity=W*Gout/ab 12. 277 12. 723 12. 946 13. 170 13. 393 13. 616 My=bending moment at center= 5. 782 5. 992 6. 097 6. 202 6. 307 6. 412 DYNAMIC BENDING STRESS Kt= stress concentration factor 3 3 3 0. 06 0. 09 0. 11 0. 12 0. 15 28908 13315 10974 9226 7884 5130 24 kpsi 0. 8 1. 8 2. 2 2. 6 3. 0 4. 7 >10^8 >10^8 1. 7 2. 0 3. 1 h=height Sb=6*Kt*My/h^2= lb/in^2 FOS Yield FOS Ultimate check S-N curve for board type Ch 12 to determine if board will fail MARGIN OF SAFETY MOS=(Allowable stress/applied stress*FS)-1 MOS 0. 6 1. 2 For a composite FS=1. 5 (Ultimate) Cosmic RAy Telescope for the Effects of Radiation 1. 5
E-BOX COVERS, ANALYSIS CRa. TER PDR Mechanical Design Top Cover Bottom Cover Elastic Modulus E(lb/in sq 1. 00 E+07 Thickness h(inches) 0. 063 u 0. 33 length a (in) 9. 343 9. 119 width b (in) 6. 623 8. 443 weight W (lb) 0. 41 0. 46 in/sec. Sq 386 3. 142857143 G 125 q 0. 828233449 0. 746833585 Poisson ratio g pi D=E*h^3/(12(1 -u^2) density p f=pi/2((D/p)^. 5)(1/a^2+1/b^2))^. 5 D= mass/area=W/gab frequency = 233. 837392 1. 71655 E-05 1. 54784 E-05 199 159 1. 9009 2. 0061 2874 3033 5. E+08 Bending moment at center My= q(u/a^2=1/b^2)/(pi^2(1/a^2+1/b^2)^2 dynamic bending stress Sb=6*My/h^2 Stress= Check S-N curve at Stress N= FOS Yield/Stress Ultimate/Stress Tensile yield, psi 35000 12. 18 11. 54 Tensile Ultimate, psi 42000 14. 6 13. 8 Tensile yield, psi 35000 14. 2 13. 4 Tensile Ultimate, psi 42000 19. 5 18. 4 Margin of Safety (allowable stress/applied stress *FOS)-1 Cosmic RAy Telescope for the Effects of Radiation
CURRENT BEST ESTIMATE, MASS PROPERTIES grams lbs Analog CCA 480 1. 05 Electronics Assembly Digital CCA 540 1. 19 Interconnect Cable, A/D 52 0. 11 Internal E-box Cables 122 0. 27 Mechanical Enclosure 1800 3. 96 Top Cover 250 0. 55 Bottom Cover 225 0. 49 Hardware 166 0. 36 Purge system 178 0. 39 3813 8. 38 Electronics Assembly Sub-Total Detector Assembly Circuit Board 138 0. 30 Telescope Sub-Assy 1398 . 87 Detector Mechanical Enclosure 525 1. 15 Detector Assembly Sub- Total 1061 2. 32 MLI and TPS Sub-Total 250 . 55 Mounting Hardware Sub-Total 40 . 09 5164 11. 34 CRa. TER CBE Total Cosmic RAy Telescope for the Effects of Radiation CRa. TER PDR Mechanical Design
CRa. TER PDR Mechanical Design Drawing List Drawing Number Drawing Title Rev. 32 -1000 CRa. TER Assembly 32 -10200 Electronics Assembly 32 -10201 Layout Complete Drawing Created Checked Released 0% - 25% Digital Electronics, PWA 02 50% 32 -10202 Analog Electronics PWA 02 50% 32 -10203 Electronics Enclosure 01 95% 32 -10204 Cover, Top Electronics Enclosure 01 95% 32 -10205 Cover, Bottom Electronics Enclosure - 95% Cosmic RAy Telescope for the Effects of Radiation
Material Properties 2 2 1. MIL-HDBK-5 J 2. Efunda materials list via efunda. com Cosmic RAy Telescope for the Effects of Radiation CRa. TER PDR Mechanical Design
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