Telescope Mechanical Design

Transcription

1 Telescope Mechanical Design Albert Lin The Aerospace Corporation (310) /27/06 6/27/06 Telescope Mechanical Design 1

2 Overview Design Overview Instrument Requirements Mechanical Requirements Analysis Design Details Next Steps 6/27/06 Telescope Mechanical Design 2

3 Design Overview 3 pairs of thin/thick detectors mounted in rigid structure. TEP mounts allow for thermal expansion and contraction. Instrument is shielded and electrically isolated at interface. Purge runs through channels machined into housing. 6/27/06 Telescope Mechanical Design 3

4 Programmatic Completed Peer Review. Fabricated engineering model. Completed part drawings. Activities since PDR Design Isolated detectors mechanically from TEP mounts. Added G-10 gasket interface to electrically isolate telescope. Purge system added. Performed mechanical properties testing on TEP. 6/27/06 Telescope Mechanical Design 4

5 Peer Review Summary Telescope design requires close machining tolerances for success. Action: Modified design to increase robustness. Detectors are not specified for random vibration and shock seen at the interface mount. Action: Plan to test engineering model detectors mounted in assembly. Thin electrical isolation material specified at PDR may be too thin. Action: Use.063 G-10 sheet for isolation. Purge channel cover screws may not be EMI tight. Action: None at this time. Add more screws if EMI emissions are too high. Detectors will give poor measurements if there is light leakage. Action: Working to specify light tight requirements. Force requirements for TEP preload is not toleranced. Action: Added tolerances to spring requirements. 6/27/06 Telescope Mechanical Design 5

6 Overall Dimensions and Weight Component Structure Circuit Board Telescope Total Weight (kg) Weight (lbs) /27/06 Telescope Mechanical Design 6

7 Overview Design Overview Instrument Requirements Mechanical Requirements Analysis Design Details Next Steps 6/27/06 Telescope Mechanical Design 7

8 Instrument Requirements Level 2 From Instrument Requirements Document (IRD) CRaTER- L2-03 Minimum path length through the total amount of TEP in the telescope shall be at least 60 mm. CRaTER- L2-04 TEP components of 27 mm and 54 mm in length 6/27/06 Telescope Mechanical Design 8

9 Instrument Requirements Level 3 From Instrument Requirements Document (IRD) CRaTER-L3-01 CRaTER-L3-03 CRaTER-L3-04 Adjacent pairs of 140 micron and 1000 micron thick Si detectors Nominal instrument shielding 1524 micron (0.060 ) thick aluminum or equivalent No more than 762 micron (0.030 ) thick aluminum on zenith and nadir fields of view 6/27/06 Telescope Mechanical Design 9

10 Instrument Requirements Level 3 From Instrument Requirements Document (IRD) CRaTER- L3-05 Telescope stack: S1, D1, D2, A1, D3, D4, A2, D5, D6, S2, where: S1, S2 are the zenith and nadir shields, respectively D1, D3, D5 are thin silicon detectors D2, D4, D6 are thick silicon detectors A1, A2 are TEP specimens Nadir CRaTER- L3-07 CRaTER- L3-08 Zenith field of view from D2 to D5 shall be less than 34 Nadir field of view from D4 to D5 shall be less than 70 Zenith 6/27/06 Telescope Mechanical Design 10

11 Overview Design Overview Instrument Requirements Mechanical Requirements Analysis Design Details Next Steps 6/27/06 Telescope Mechanical Design 11

12 Mechanical Requirements From 431-RQMT , Mechanical System Specifications Section Description Levels Verification Net cg limit load 28.9 g* Analysis Sinusoidal Vibration Loads Protoflight; Frequency (Hz) Level Analysis, Test cm D.A g s Acoustics Delta IV Medium: db Test at LRO level Atlas V 401: db Random Vibration See Random Vibration slide Analysis, Test Shock environment See Shock Environment slide Test at LRO level Venting Minimum of.25 in 2 of vent area per cubic foot volume Analysis * Interpolated from Table 3-1 for CRaTER at 6.4 kg. 6/27/06 Telescope Mechanical Design 12

13 Random Vibration Levels Frequency (Hz) Overall Protoflight /Qual (g 2 /Hz) g rms Acceptance (g 2 /Hz) g rms Protoflight/ Qual Random Vibration Spec Acceptance Frequency (Hz) Power Spectral Density (g^2/hz) Random Vibration levels will drive the analysis. 6/27/06 Telescope Mechanical Design 13

14 Updated Shock Environment Frequency 100 Hz 800 Hz 10,000 Hz Level (Q=10) 20 g 930 g 930 g 6/27/06 Telescope Mechanical Design 14

15 Overview Design Overview Instrument Requirements Mechanical Requirements Analysis Design Details Next Steps 6/27/06 Telescope Mechanical Design 15

16 Frequencies and Mass Participations Frequency (Hz) 895 Mass Participation Where Shield 1, Large TEP Assy 1, Housing 1, Circuit Board 1, Small TEP Assy 6/27/06 Telescope Mechanical Design 16

17 Random Vibration Loads 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 = 40 for worst case Protoflight/ Qual Acceptance Random Vibration Spec Frequency (Hz) Frequency (Hz) Protoflight/ Qual (g 2 /Hz) Acceptance (g 2 /Hz) Power Spectral Density (g^2/hz) /27/06 Telescope Mechanical Design 17

18 Random Vibration Loads Factors of Safety used for corresponding material (MEV 5.1) Metals: 1.25 Yield, 1.4 Ultimate Composite: 1.5 Ultimate Margin of Safety = Assume Q=40 Telescope Housing Detector Shield Circuit Board TEP AllowableStress or Load Applied Stress or Load Freq (Hz) 1,563 2, ,680 1,563 3σ load (g) Factor of Safety Stress (psi) 16, ,259 2, MS yield MS ult σ load (g) Worst Normal/Shear (lbs) MS yield MS ult Interface Bolts / /27/06 Telescope Mechanical Design 18

19 Overview Design Overview Instrument Requirements Mechanical Requirements Analysis Design Details Next Steps 6/27/06 Telescope Mechanical Design 19

20 Detector Details 39 mm flat-to-flat Silicon detectors mounted on FR4 mounts 140 micron and 1000 micron thick both bond to the same mount design Micron Semiconductor Limited Lancing Sussex, UK Cable and connector 4 mounting holes 6/27/06 Telescope Mechanical Design 20

21 TEP mounted in conical seats to prevent misalignment. Spring design allows for thermal expansion and contraction Large TEP is clamped into holder with 267 N (60 lbs) preload using 4 springs Estimated maximum load is 207 g s during random vibration Springs nominally secure TEP up to 400 g s Springs that exert > 52 N (11.6 lbs) will secure TEP with a 1.5 factor of safety How the TEP is mounted 6/27/06 Telescope Mechanical Design 21

22 TEP Material Properties Density Tensile Modulus Tensile Yield 20 ºC Compression 20 ºC CTE (20 ºC to 30 ºC) TEP 1,110 kg/m 3 1,958 MPa 14.4 MPa 58.6 MPa 18.9 µ m/m-ºc Delrin 1,411 kg/m 3 3,100 MPa 89.6 MPa 110 MPa 84.6 µ m/m-ºc TEP is resilient to clamping with 75.1 MS. TEP interface will shrink 0.08 mm as it cools from 20ºC to 30ºC. The spring will make up this difference at 30ºC and still exert preload 258 N (58 lbs) preload. 6/27/06 Telescope Mechanical Design 22

23 Purging and Venting Spacers between each pair of detectors for venting No enclosed cavities Purge/vent system shown in red Internal purge line from Ebox connects to telescope purge system 6/27/06 Telescope Mechanical Design 23

24 Overview Design Overview Instrument Requirements Mechanical Requirements Analysis Design Details Next Steps 6/27/06 Telescope Mechanical Design 24

25 Next Steps Finalize MLI attachment near telescope Submit flight drawings for fabrication Make assembly drawings 6/27/06 Telescope Mechanical Design 25

26 Summary Design changes since PDR Modified detector mounting scheme Added vent/purge path Added electrical isolation between telescope from Ebox Peer review successfully completed Further analysis performed Tested TEP material properties Engineering model completed Flight drawings ready to be submitted 6/27/06 Telescope Mechanical Design 26

27 Telescope Mechanical Albert Lin 6/27/06 Telescope Mechanical Design 27

28 Material Properties Density (lb/in 3 ) Young's Modulus (ksi) Tensile Yield (ksi) Tensile Ultimate (ksi) Poisson's Ratio Material Where Used Aluminum 6061-T Structure A286 AMS Fasteners Single Crystal Silicon brittle Detectors Polyimide Glass Circuit Board G-10 Fiberglass Isolator Interface MIL-HDBK-5J Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May 1982, pp Plastics, Edition 8, Ultimate Tensile from Electronic Materials and Properties Boedeker Plastics via 6/27/06 Telescope Mechanical Design 28

29 Bolt Interface Analysis Bolt Inputs Bolt Type # Bolt Material Stainless Steel A286 5 Modulus of Elasticity 29,100,000 psi Yield Strength 85,000 psi Ultimate Strength 130,000 psi Tensile Stress Area in^2 Head Diameter in Bolt Diameter in Bolt Calculations Proof Load Preload l = effective grip length kb = bolt stiffness psi 522 lbs in 720,760 lb/in Member Calculations D in D in Middle Frustrum on Flange Frustra t d D E k (8.14) Material ,700,000 1,322,196 lb/in G ,000,000 4,592,215 lb/in Aluminum ,000,000 11,954,988 lb/in Aluminum ,700,000 2,002,953 lb/in G ,000,000 4,479,377 lb/in Aluminum km = member stiffness 676,212 lb/in Outputs C = joint constant; ratio of load taken up by bolt 0.52 P = load at joint separation (including preload) 1,077 lbs P = Ext Tensile Load at Yield P = Ext Tensile Load at Ultimate 487 lbs 1,077 lbs 6/27/06 Telescope Mechanical Design 29

30 Inputs Normal Load In-Plane Load X In-Plane Load Y In-Plane Load Offset Tensile Yield Tensile Ultimate Shear Yield First fundamental frequency at 1564 Hz 3 sigma load = 194g A286 CRES #6-32 Bolts at Interface Bolt Interface Loading Outputs 545 lb Worst Case Bolt lb Normal Load lb 545 lb Shear Load lb in Margin of Safety Yield lb Margin of Safety Ult lb 464 lb Mechanical Engineering Design, by Shigley RP-1228 NASA Fastener Design 6/27/06 Telescope Mechanical Design 30