Telescope Mechanical Design

1. Telescope Mechanical Design Albert Lin The Aerospace Corporation Mechanical Engineer (310) 336-1023 albert.y.lin@aero.org 9/28/05

2. Overview Design Overview Instrument Requirements Mechanical Requirements Design Details Next Steps

3. Design Overview • Detectors are housed in stiff structure and decoupled from the interface circuit board • TEP mounts allow for thermal expansion/contraction • Instrument is shielded and electrically isolated at interface

4. Overall Dimensions • Weight = 2.32 lbs

5. Overview Design Overview Instrument Requirements Mechanical Requirements Design Details Next Steps

6. Instrument Requirements From Instrument Requirements Document (IRD) 32-01205 All requirements incorporated into model

7. Telescope Geometry All Requirements Met • A-150 TEP of 27 mm and 54 mm in length • Pairs of thin (~140 micron) and thick (~1000 micron) Si detectors used • 0.060” nominal aluminum shielding • 0.030” thick aluminum on top and bottom apertures • Telescope stack consistent with requirement • 35 degree FOV Zenith • 75 degree FOV Nadir

8. Overview Design Overview Instrument Requirements Mechanical Requirements Design Details Next Steps

9. Mechanical Requirements • From 431-RQMT-000012, Mechanical System Specifications

10. 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 100-150 g • Assume Q = 15

11. Stress Margins • Load levels are superceded by random vibration spec • Factors of Safety used for corresponding material (MEV 5.1) • Metals: 1.25 Yield, 1.4 Ultimate • Composite: 1.5 Ultimate • Margin of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 All components have positive Margin of Safety

12. First Fundamental Frequency • First Fundamental Frequency at 2340 Hz

13. Overview Design Overview Instrument Requirements Mechanical Requirements Design Details Next Steps

14. How to Mount TEP • Limited Material Properties information on A-150 TEP • Need to mount TEP to • Minimize deformation of TEP during assembly • Allow for thermal contraction • Exert 20 lbs preload to withstand random vibration Springs exert 20 lbs at hot and cold cases Detectors TEP Sample Solution • Oversized mounting hole to allow for changes in radial dimension • Spring clamp to hold in TEP with preload at all temperatures

15. Mounting Details, Purging and Venting • Detectors mounted using #2-56 fasteners • Pigtail connector feeds through hole and plugs into the Analog board in the E-box • Spacers between each pair of detectors for venting • No enclosed cavities • Internal purge line from Ebox connects to telescope purge system (not shown) • Detailed design of purge system pending Connection

16. Overview Design Overview Telescope Requirements Mechanical Requirements Design Details Next Steps

17. Next Steps • Finalize interface between telescope assembly and electronics box • Detail purge design • Complete drawings for fabrication

19. Backup Slides

20. CRaTER-L2-04 • 4.4.1 Requirement Break the TEP into two components, of 27 mm and 54 mm in length.

21. 6.1 CRaTER-L3-01Thin and thick detector pairs • 6.1.1 Requirement The telescope stack will contain adjacent pairs of thin (approximately 140 micron) and thick (approximately 1000 micron) Si detectors. The thick detectors will be used to characterize energy deposition between approximately 200 keV and 100 MeV. The thin detectors will be used to characterize energy deposits between 2 MeV and 1 GeV. 6.2 CRaTER-L3-02 Nominal instrument shielding • 6.2.1 Requirement The shielding due to mechanical housing the CRaTER telescope outside of the zenith and nadir fields of view shall be no less than 0.06” of aluminum.

22. 6.3 CRaTER-L3-03 Nadir and zenith field of view shielding • 6.3.1 Requirement The zenith and nadir sides of the telescope shall have no less than 0.03” of aluminum shielding. 6.4 CRaTER-L3-04 Telescope stack • 6.4.1 Requirement The telescope will consist of a stack of components labeled from the nadir side as zenith shield (S1), the first pair of thin (D1) and thick (D2) detectors, the first TEP absorber (A1), the second pair of thin (D3) and thick (D4) detectors, the second TEP absorber (A2), the third pair of thin (D5) and thick (D6) detectors, and the final nadir shield (S2).

23. 6.6 CRaTER-L3-06 Zenith field of view • 6.6.1 Requirement The zenith field of view, defined as D1D6 coincident events incident from deep space, will be 35 degrees full width. 6.7 CRaTER-L3-07 Nadir field of view • 6.7.1 Requirement The nadir field of view, defined as D3D6 coincident events incident from the lunar surface, will be 75 degrees full width.

24. Bolt Interface Loading First fundamental frequency at 2340 Hz, which is off of the random vibe data set Assume worst-case loading at 2000 Hz 3 sigma load = 105g A286 CRES Bolts at Interface Worst Case Bolt Mechanical Engineering Design, byShigley RP-1228 NASA Fastener Design

25. Interface Circuit Board Board Resonance • First Mode: 632 Hz • Total nodes: 25225 • Total elements: 12901 COSMOSWorks 2005

26. Detector Board Stress • Using Miles Equation, assume Q = 15, FS = 1.5 • 3σ g loading = 146 g • Material = Polyimide-Glass • Max Stress = 3,663 psi • MS ultimate = 24,000 psi / (1.5 * 3* 3,663 psi) - 1 = 0.45

27. Detector Analysis • Assuming Q = 15 • Detector Material = Silicon • Fundamental Frequency = 2130 Hz; 2000 Hz yields 3 sigma load of 105g • Ultimate Margin of Safety = (17,400 psi / (1.4 * 252 psi) – 1 = 48.3

28. Sensitivity Analysis • Preceding calculations used a nominal Q of 15 • This table shows how the 3 sigma g-loads vary with Fundamental Frequency and Q Most structures have Q between 10 and 20

29. Factors of Safety Used

30. Material Properties • MIL-HDBK-5J • Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May 1982, pp 420-457 • www.efunda.com 1 1 1 2 3