C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Mechanical Design, CRaTER Assembly and Electronics Assembly Preliminary Design Review Matthew Smith Mechanical Engineer (617)

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Overview Instrument and Assembly Description Mechanical Environments and Requirements Mechanical Design Details Near Term Tasks Back-up slides

C osmic R Ay T elescope for the E ffects of R adiation CRaTER 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. –MIT will integrate the sub-assemblies and perform all functional, environmental and acceptance testing.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Instrument and Assembly Description

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Mechanical Environments From 431-RQMT , Environments Section 2. SectionDescriptionLevels 2.1.2Net cg limit load12 g 2.4.2Sinusoidal Vibration LoadsFrequency: Hz Protoflight/Qual: 8g Acceptance: 6.4g 2.5Acoustics Enclosed box without exposed thin surfaces OASPL Protoflight/Qual: dB OASPL Acceptance: dB 2.6.1Random VibrationSee Random Vibration slide 2.7Shock environment40 g at 100 Hz 2665g at 1165 to 3000 Hz. No self induced shock. 2.8VentingPer 431-SPEC LRO Thermal Subsystem spec.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Mechanical Requirements and Verification From 431-RQMT , Verification Requirements Section 3. SectionDescriptionLevels Stowed fundamental Hz Deployed fundamental Frequency Freq >35 >3 Hz 3.2.1Factors of SafetySee FOS table 3.2.2Test factorsSee Test Factors table 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. 3.3Finite Element Model requirementsWe will be above 75Hz and will not be required to submit an FEM of CRaTER.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design General Thermal Subsystem Requirements from 431-Spec SectionDescription 4.1 Exterior facing MLI blankets shall have 3 mil Kapton with VDA in outer Coating. 4.2MLI Blanket Grounding: All blankets shall be grounded per 431-ICD MLI Blanket Documentation: The location and shape documented in as-built ICDs. 4.4Attachment to MLI Blankets: All exterior MLI blankets shall be mechanically constrained at least at one point.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design 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.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER 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 g Assume Q=10 Overall 14.1 Grms 10.0 grms

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design 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 –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 DescriptionMaterial Desc.MS YieldMS UltimateComments Top CoverAluminum Note 1 Bottom CoverAluminum Note 1 Digital BoardFR4brittle +1.5Note 1 Analog BoardFR4Brittle +0.2Note 1 E-box Structure Aluminum 7075> +2.8>+3.1Note 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

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design 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.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER 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 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.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design DESIGN DETAILS Electrical/Mechanical Interface Interface Connectors J1 9 Pin D-Sub Male P-B-12 J2 9 Pin D-sub Female S-B-12 J3 1553, BJ3150 J4 1553, BJ3150 PART OF MID DRAWING NUMBER 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)

C osmic R Ay T elescope for the E ffects of R adiation CRaTER 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 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.

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Backup Slides

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Factors of Safety

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design BOARD ANALYSIS Analog Board Analysis an x 5.95 board separated into two parts Polyimide modulus of elasticityE (lb/in sq4.21E+05 Thicknessh (inches) poisson ratiou0.12 lengtha (in)4.215 widthb (in)5.95 weightW (lb) gin/secSq386 pi3.14 D=E*h^3/(12(1-u^2))D= density pmass/area=W/gab E E E E E E-05 for a a simply supported board on 4 sides f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5Frequency=(Hz) From Steinberg, vibration analysis for electronic equipment page 149 for a fixed beam on 4 sidesFrequency=(Hz) Average Frequency

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design 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)= q=load intensity=W*Gout/ab My=bending moment at center= DYNAMIC BENDING STRESS Kt= stress concentration factor h=height Sb=6*Kt*My/h^2= lb/in^2Stress due to bending FACTORS OF SAFETY FOS Yield FOS Ultimate24000 psi NUMBER OF CYLES BEFORE FAILURE check S-N curve for board type Ch 12 to determine if board will fail number of cycles before failure10^4>10^8 MARGIN OF SAFETY MOS=(Allowable stress/applied stress*FS) For a composit Fs=1.5 Ultimate

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design BOARD ANALYSIS Digital Board Analysis a x board two sections modulus of eleasticity Polyimide fiberglassE, psi4.21E+05 Thicknessh(inches) poisson ratiou0.12 lengtha (in)4.281 widthb (in)7.488 weightW (lb) gin/secSq386 pi D=E*h^3/(12(1-u^2))D= density pmass/area=W/gab E E E E E E-05 for a a simply supported board on 4 sides f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5Frequency, HZ = This is from an example by Steinberg, vibration analysis for electronic equipment page 149 for a fixed board on 4 sidesFrequency, HZ = Average Frequency

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design 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)= q=load intensity=W*Gout/ab My=bending moment at center= DYNAMIC BENDING STRESS Kt= stress concentration factor h=height Sb=6*Kt*My/h^2= lb/in^ FOS Yield FOS Ultimate24kpsi 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)-1MOS For a composite FS=1.5 (Ultimate)

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design E-BOX COVERS, ANALYSIS Top CoverBottom Cover Elastic ModulusE(lb/in sq1.00E+07 Thicknessh(inches)0.063 Poisson ratiou0.33 lengtha (in) widthb (in) weightW (lb) gin/secSq386 pi G125 q D=E*h^3/(12(1-u^2)D= density pmass/area=W/gab E E-05 f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5frequency = Bending moment at center My= q(u/a^2=1/b^2)/(pi^2(1/a^2+1/b^2)^ dynamic bending stress Sb=6*My/h^2Stress= Check S-N curve at StressN=5.E+08 FOS Yield/StressTensile yield, psi Ultimate/StressTensile Ultimate, psi Margin of Safety (allowable stress/applied stress *FOS)-1Tensile yield, psi Tensile Ultimate, psi

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design CURRENT BEST ESTIMATE, MASS PROPERTIES Electronics Assembly gramslbs Analog CCA Digital CCA Interconnect Cable, A/D Internal E-box Cables Mechanical Enclosure Top Cover Bottom Cover Hardware Purge system Electronics Assembly Sub-Total Detector Assembly Circuit Board Telescope Sub-Assy Detector Mechanical Enclosure Detector Assembly Sub- Total MLI and TPS Sub-Total Mounting Hardware Sub-Total40.09 CRaTER CBE Total

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Drawing List Drawing NumberDrawing TitleRev.Layout CompleteDrawing CreatedCheckedReleased CRaTER Assembly0% Electronics Assembly-25% Digital Electronics, PWA0250% Analog Electronics PWA0250% Electronics Enclosure 0195% Cover, Top Electronics Enclosure 0195% Cover, Bottom Electronics Enclosure -95%

C osmic R Ay T elescope for the E ffects of R adiation CRaTER PDR Mechanical Design Material Properties 1.MIL-HDBK-5J 2.Efunda materials list via efunda.com