Telescope Mechanical Design
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Transcript of Telescope Mechanical Design
Cosmic RAy Telescope for the Effects of Radiation
Telescope Mechanical Design
Albert LinThe Aerospace Corporation
Mechanical Engineer(310) 336-1023
[email protected]/28/05
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsDesign DetailsNext Steps
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
Overall Dimensions• Weight = 2.32 lbs
Component Weight (lbs)Structure 1.150Circuit Board 0.300Telescope 0.870Total 2.320
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsDesign DetailsNext Steps
Cosmic RAy Telescope for the Effects of Radiation
Instrument RequirementsFrom Instrument Requirements Document (IRD) 32-01205
Item Requirement
CRaTER-L2-04 TEP components of 27 mm and 54 mm in length
CRaTER-L3-01 Adjacent pairs of 140 micron and 1000 micron thick Si detectors
CRaTER-L3-02 Aluminum shielding 0.06” thick
CRaTER-L3-03 0.030” thick aluminum on both ends of the telescope
CRaTER-L3-04 Telescope stack: S1, D1, D2, A1, D3, D4, A2, D5, D6, S2
CRaTER-L3-06 Zenith field of view from D1D6 at 35 degrees
CRaTER-L3-07 Nadir field of view from D3D6 at 75 degrees
All requirements incorporated into model
Cosmic RAy Telescope for the Effects of Radiation
Telescope GeometryAll 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
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsDesign DetailsNext Steps
Cosmic RAy Telescope for the Effects of Radiation
Mechanical Requirements• From 431-RQMT-000012, Mechanical System Specifications
Requirement Description Levels
2.1.2Net CG limit loads•Superceded by Random Vibration
12 g
2.4.2Sinusoidal Vibration Loads•Superceded by Random Vibration
Frequency: 5-100 HzProtoflight/Qual: 8gAcceptance: 6.4g
2.5Acoustics•Enclosed box without exposed thin surfaces
OASPL Protoflight/Qual: 141.1 dBOASPL Acceptance: 138.1 dB
2.6.1 Random Vibration See next slide
2.7.2 Shock Environment40 g at 100 Hz2665 g at 1165-3000 HzNo self induced shock
3.1.2.1
3.3
Minimum Fundamental Frequency Minimum > 35 HzRecommended > 50 HzWill not provide FEM model > 75 Hz
Cosmic RAy Telescope for the Effects of Radiation
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
Random Vibration Spec
0.01
0.1
11 10 100 1000 10000
Frequency (Hz)
Pow
er S
pect
ral D
ensi
ty (g
^2/H
z)
Protoflight/ Qual
Acceptance
Freq (Hz)
Protoflight/ Qual Acceptance
20 0.026 0.01350 0.16 0.08
800 0.16 0.082000 0.026 0.013
Cosmic RAy Telescope for the Effects of Radiation
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
Description MS yield MS ultimate
Bolt Interface Loading +7,291 +14,709
Interface Circuit Board brittle +0.45
Silicon Detector brittle +48.3
All components have positive Margin of Safety
Cosmic RAy Telescope for the Effects of Radiation
First Fundamental Frequency• First Fundamental Frequency at 2340 Hz
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsDesign DetailsNext Steps
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewTelescope RequirementsMechanical RequirementsDesign DetailsNext Steps
Cosmic RAy Telescope for the Effects of Radiation
Next Steps• Finalize interface between telescope assembly and electronics box• Detail purge design• Complete drawings for fabrication
Cosmic RAy Telescope for the Effects of Radiation
Cosmic RAy Telescope for the Effects of Radiation
Backup Slides
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-04• 4.4.1 Requirement
Break the TEP into two components, of 27 mm and 54 mm in length.
Cosmic RAy Telescope for the Effects of Radiation
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.
Cosmic RAy Telescope for the Effects of Radiation
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).
Cosmic RAy Telescope for the Effects of Radiation
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.
Cosmic RAy Telescope for the Effects of Radiation
Bolt Interface Loading
-3.000
0.000
3.000
6.000
9.000
-3.000 0.000 3.000 6.000 9.000
Mechanical Engineering Design, by Shigley
RP-1228 NASA Fastener Design
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
0 lb 18231 lb 4.71 lb
0 lb 9.63 lb1.2 in 7,291
593 lb 14,709 907 lb356 lb
Margin of Safety Ult
Normal Load Worst Case BoltIn-Plane Load X Normal LoadIn-Plane Load Y Shear LoadIn-Plane Load Offset Margin of Safety YieldTensile Yield
Shear YieldTensile Ultimate
Cosmic RAy Telescope for the Effects of Radiation
Interface Circuit Board Board Resonance• First Mode: 632 Hz• Total nodes: 25225• Total elements: 12901
COSMOSWorks 2005
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
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
(g's)1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
5 85 81 78 75 72 70 68 66 64 62 6110 121 115 110 106 102 99 96 93 90 88 8615 148 141 135 130 125 121 117 114 111 108 10520 170 163 156 150 144 140 135 131 128 124 12125 191 182 174 168 162 156 151 147 143 139 136
Fundamental Frequency (Hz)
Q F
acto
r
Most structures have Q between 10 and 20
Cosmic RAy Telescope for the Effects of Radiation
Factors of Safety Used
Table 3.1 from 431-RQMT-000012Type of Hardware Yield UltimateTested Flight Structure - Metallic 1.25 1.4Tested Flgiht Structure - Beryllium 1.4 1.6Tested Flight Structure - Composite N/A 1.5Pressure Loaded Structure 1.25 1.5Pressure Lines and Fittings 1.25 4.0Untestest Flight Structure - Metallic Only 2.0 2.6
Design Factor of Safety
Cosmic RAy Telescope for the Effects of Radiation
Material Properties
1. MIL-HDBK-5J2. Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May 1982, pp 420-4573. www.efunda.com
MaterialDensity (lb/in3)
Young's Modulus
(ksi)Tensile
Yield (ksi)
Tensile Ultimate
(ksi)Poisson's
Ratio Where UsedAluminum 6061-T6 0.098 9,900 35 42 0.33 StructureBeryllium Copper TH02 0.298 18,500 160 185 0.27 TEP SpringA286 AMS 5731 0.287 29,100 85 130 0.31 FastenersSingle Crystal Silicon 0.084 27,557 brittle 17.4 0.19 DetectorsPolyimide-Glass 0.065 2,000 brittle 24 - Circuit Board
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