Matthew Smith Mechanical Engineer (617)-252-1736 matt@space.mit.edu Mechanical Design, CRaTER Assembly and Electronics Assembly Preliminary Design Review Matthew Smith Mechanical Engineer (617)-252-1736 matt@space.mit.edu

Overview Instrument and Assembly Description Mechanical Environments and Requirements Mechanical Design Details Near Term Tasks Back-up slides

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. MIT will integrate the sub-assemblies and perform all functional, environmental and acceptance testing.

Instrument and Assembly Description

Mechanical Environments 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: 5-100 Hz Protoflight/Qual: 8g Acceptance: 6.4g 2.5 Acoustics Enclosed box without exposed thin surfaces OASPL Protoflight/Qual: 141.1 dB OASPL Acceptance: 138.1 dB 2.6.1 Random Vibration See Random Vibration slide 2.7 Shock environment 40 g at 100 Hz 2665g at 1165 to 3000 Hz. No self induced shock. 2.8 Venting Per 431-SPEC-000091 LRO Thermal Subsystem spec.

Mechanical Requirements and Verification 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 3.2.3.2 MEVR-10 Perform frequency verification test for Instruments with frequencies above 50 Hz.. MEVR-11 Report frequencies up to 200Hz Low level sine sweep We will be above 50Hz. 3.3 Finite Element Model requirements We will be above 75Hz and will not be required to submit an FEM of CRaTER.

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.

DESIGN DETAILS Electronics Assembly 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 702Hz at the middle plate that holds the two Circuit Card Assemblies.

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

DESIGN DETAILS Stress Margins, Electronics Assembly Pieces 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 +13.4 +18.4 Digital Board FR4 brittle +1.5 Analog Board Brittle +0.2 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

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.

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 and Digital Board must be separated by an aluminum plate. 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 interface connectors to be on the Digital side of the Electronics Enclosure (separate from the Analog side) Provide GN2 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 GN2 design. Electrical isolation of the E-box and Telescope needs more thought.

DESIGN DETAILS Electrical/Mechanical Interface Interface Connectors J1 9 Pin D-Sub Male 311409-1P-B-12 J2 9 Pin D-sub Female 311409-1S-B-12 J3 1553, BJ3150 J4 1553, BJ3150 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

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 CRaTER Assembly. Finalize interface between Telescope Assembly and Electronics Box Assembly. Specify the electrical isolation material between the telescope and the E-Box. Identify the GN2 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.

Backup Slides

Factors of Safety

BOARD ANALYSIS Analog Board Analysis 1 2 3 4 5 6 an 8.429 x 5.95 board separated into two parts   Polyimide modulus of elasticity E (lb/in sq 4.21E+05 Thickness h (inches) 0.06 0.09 0.1 0.11 0.12 0.15 poisson ratio u length a (in) 4.215 width b (in) 5.95 weight W (lb) 0.6 0.65 0.69 0.71 0.73 0.79 g in/secSq 386 pi 3.14 D=E*h^3/(12(1-u^2)) D= 7.69 25.95 35.60 47.38 61.51 120.14 density p mass/area=W/gab 6.19797E-05 6.7145E-05 7.13E-05 7.33E-05 7.54E-05 8.16E-05 for a a simply supported board on 4 sides f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5 Frequency=(Hz) 47 83 94 107 120 161 From Steinberg, vibration analysis for electronic equipment page 149 for a fixed beam on 4 sides 91 160 182 207 232 312 Average Frequency 69 121 138 157 176 237

number of cycles before failure BOARD ANALYSIS Analog Board Analysis Cont’d STRESS   Gin=peak load(g's)= 125 Q=transmisibility= 10 Gout=Gin*Q= 1250 W=board weight(lb)= 0.6 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 DYNAMIC BENDING STRESS Kt= stress concentration factor 3 h=height 0.06 0.09 0.1 0.11 0.12 0.15 Sb=6*Kt*My/h^2= lb/in^2 Stress due to bending 33206 15988 13747 11691 10100 6995 FACTORS OF SAFETY FOS Yield FOS Ultimate 24000 psi 0.7 1.5 1.7 2.1 2.4 3.4 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 -0.5 0.0 0.2 0.4 1.3 For a composit Fs=1.5 Ultimate

BOARD ANALYSIS Digital Board Analysis Average Frequency 149 1 2 3 4 5 6 a 8.562 x 7.488 board two sections   modulus of eleasticity Polyimide fiberglass E, psi 4.21E+05 Thickness h(inches) 0.06 0.09 0.1 0.11 0.12 0.15 poisson ratio u length a (in) 4.281 width b (in) 7.488 weight W (lb) 0.55 0.57 0.58 0.59 0.6 0.61 g in/secSq 386 pi 3.142857143 3.14285714 3.142857 D=E*h^3/(12(1-u^2)) D= 7.69 25.95 35.60 47.38 61.51 120.14 density p mass/area=W/gab 4.44492E-05 4.6066E-05 4.69E-05 4.77E-05 4.85E-05 4.93E-05 for a a simply supported board on 4 sides f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5 Frequency, HZ = 47.32 85.39 99.14 113.41 128.14 177.60 This is from an example by Steinberg, vibration analysis for electronic equipment page 149 for a fixed board on 4 sides 94.79 171.06 198.61 227.19 256.69 355.79 Average Frequency 71 128 149 170 192 267

BOARD ANALYSIS Digital Board Analysis Cont’d STRESS   Gin=peak load(g's)= 125 Q=transmisibility= 10 Gout=Gin*Q= 1250 W=board weight(lb)= 0.55 0.57 0.58 0.59 0.6 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 h=height 0.06 0.09 0.1 0.11 0.12 0.15 Sb=6*Kt*My/h^2= lb/in^2 28908 13315 10974 9226 7884 5130 FOS Yield FOS Ultimate 24kpsi 0.8 1.8 2.2 2.6 3.0 4.7 check S-N curve for board type Ch 12 to determine if board will fail >10^8 MARGIN OF SAFETY MOS=(Allowable stress/applied stress*FS)-1 MOS 1.2 1.5 1.7 2.0 3.1 For a composite FS=1.5 (Ultimate)

E-BOX COVERS, ANALYSIS Top Cover Bottom Cover Elastic Modulus E(lb/in sq 1.00E+07 Thickness h(inches) 0.063 Poisson ratio u 0.33 length a (in) 9.343 9.119 width b (in) 6.623 8.443 weight W (lb) 0.41 0.46 g in/secSq 386 pi 3.142857143 G 125 q 0.828233449 0.746833585 D=E*h^3/(12(1-u^2) D= 233.837392 density p mass/area=W/gab 1.71655E-05 1.54784E-05 f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5 frequency = 199 159 Bending moment at center My= q(u/a^2=1/b^2)/(pi^2(1/a^2+1/b^2)^2 1.9009 2.0061 dynamic bending stress Sb=6*My/h^2 Stress= 2874 3033 Check S-N curve at Stress N= 5.E+08 FOS Yield/Stress Tensile yield, psi 35000 12.18 11.54 Ultimate/Stress Tensile Ultimate, psi 42000 14.6 13.8 Margin of Safety (allowable stress/applied stress *FOS)-1 14.2 13.4 19.5 18.4

CURRENT BEST ESTIMATE, MASS PROPERTIES Electronics Assembly grams lbs Analog CCA 480 1.05 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 Electronics Assembly Sub-Total 3813 8.38 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 .55 Mounting Hardware Sub-Total 40 .09 CRaTER CBE Total 5164 11.34

Drawing List Drawing Number Drawing Title Rev. Layout Complete Drawing Created Checked Released 32-1000 CRaTER Assembly 0% 32-10200 Electronics Assembly - 25%   32-10201 Digital Electronics, PWA 02 50% 32-10202 Analog Electronics PWA 32-10203 Electronics Enclosure 01 95% 32-10204 Cover, Top Electronics Enclosure 32-10205 Cover, Bottom Electronics Enclosure

Material Properties MIL-HDBK-5J Efunda materials list via efunda.com 2 1 2 MIL-HDBK-5J Efunda materials list via efunda.com