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6/27/06 Telescope Mechanical Design 1
Cosmic RAy Telescope for the Effects of Radiation
Telescope Mechanical Design
Albert LinThe Aerospace Corporation
(310) 336-1023albert.y.lin@aero.org
6/27/06
6/27/06 Telescope Mechanical Design 2
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsAnalysisDesign DetailsNext Steps
6/27/06 Telescope Mechanical Design 3
Cosmic RAy Telescope for the Effects of Radiation
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 4
Cosmic RAy Telescope for the Effects of Radiation
Activities since PDR
Programmatic• Completed Peer Review.• Fabricated engineering model.• Completed part drawings.
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 5
Cosmic RAy Telescope for the Effects of Radiation
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 theinterface 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 6
Cosmic RAy Telescope for the Effects of Radiation
Overall Dimensions and Weight
0.950.430Telescope
2.811.274Total
0.320.145Circuit Board
1.540.699Structure
Weight(lbs)
Weight(kg)Component
6/27/06 Telescope Mechanical Design 7
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsAnalysisDesign DetailsNext Steps
6/27/06 Telescope Mechanical Design 8
Cosmic RAy Telescope for the Effects of Radiation
Instrument Requirements – Level 2
From Instrument Requirements Document (IRD) 32-01205
Minimum path lengththrough the total amount ofTEP in the telescope shall beat least 60 mm.
CRaTER-L2-03
TEP components of 27 mmand 54 mm in length
CRaTER-L2-04
6/27/06 Telescope Mechanical Design 9
Cosmic RAy Telescope for the Effects of Radiation
Instrument Requirements – Level 3From Instrument Requirements Document (IRD) 32-01205
No more than 762 micron(0.030”) thick aluminum onzenith and nadir fields ofview
CRaTER-L3-04
Nominal instrumentshielding 1524 micron(0.060”) thick aluminum orequivalent
CRaTER-L3-03
Adjacent pairs of 140 micronand 1000 micron thick Sidetectors
CRaTER-L3-01
6/27/06 Telescope Mechanical Design 10
Cosmic RAy Telescope for the Effects of Radiation
Instrument Requirements – Level 3From Instrument Requirements Document (IRD) 32-01205
Nadir field of view from D4 to D5shall be less than 70°
CRaTER-L3-08
Zenith field of view from D2 toD5 shall be less than 34°
CRaTER-L3-07
Telescope stack: S1, D1, D2, A1,D3, D4, A2, D5, D6, S2, where:S1, S2 are the zenith and nadirshields, respectivelyD1, D3, D5 are thin silicondetectorsD2, D4, D6 are thick silicondetectorsA1, A2 are TEP specimens
CRaTER-L3-05
Nadir
Zenith
6/27/06 Telescope Mechanical Design 11
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsAnalysisDesign DetailsNext Steps
6/27/06 Telescope Mechanical Design 12
Cosmic RAy Telescope for the Effects of Radiation
Mechanical Requirements
• From 431-RQMT-000012, Mechanical System Specifications
Analysis
Test at LRO level
Analysis, Test
Test at LRO level
Analysis, Test
Analysis
Verification
Minimum of .25 in2 of vent areaper cubic foot volume
Venting3.1.8
See Shock Environment slideShock environment3.1.7
See Random Vibration slideRandom Vibration3.1.6.1
Delta IV Medium: 140.0 dBAtlas V 401: 137.0 dB
Acoustics3.1.5
Protoflight;Frequency (Hz) Level5 - 17.7 1.27cm D.A.17.7 – 50 8 g’s
SinusoidalVibration Loads
3.1.4.2
28.9 g*Net cg limit load3.1.1.2
LevelsDescriptionSection
* Interpolated from Table 3-1 for CRaTER at 6.4 kg.
6/27/06 Telescope Mechanical Design 13
Cosmic RAy Telescope for the Effects of Radiation
Random Vibration Levels
10.0 grms
0.013
0.080
0.080
0.013
Acceptance(g2/Hz)
Protoflight/Qual
(g2/Hz)Frequency
(Hz)0.02620
0.16050
0.160800
14.1 grmsOverall0.0262000
Random Vibration levels will drive the analysis.
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
6/27/06 Telescope Mechanical Design 14
Cosmic RAy Telescope for the Effects of Radiation
Updated Shock Environment
Level (Q=10)Frequency
930 g10,000 Hz
930 g800 Hz
20 g100 Hz
6/27/06 Telescope Mechanical Design 15
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsAnalysisDesign DetailsNext Steps
6/27/06 Telescope Mechanical Design 16
Cosmic RAy Telescope for the Effects of Radiation
Frequencies and Mass Participations
Circuit Board0.411,680
Small TEP Assy0.041,688
Housing0.701,564
Large TEP Assy0.461,369
Shield0.003895
WhereMass
ParticipationFrequency
(Hz)
6/27/06 Telescope Mechanical Design 17
Cosmic RAy Telescope for the Effects of Radiation
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 150-255 g• Assume Q = 40 for worst case
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
0.0130.02620000.080.168000.080.16500.0130.02620
Acceptance(g2/Hz)
Protoflight/Qual
(g2/Hz)
Frequency(Hz)
6/27/06 Telescope Mechanical Design 18
Cosmic RAy Telescope for the Effects of Radiation
Random Vibration Loads
• Factors of Safety used for corresponding material (MEV 5.1)– Metals: 1.25 Yield, 1.4 Ultimate– Composite: 1.5 Ultimate
1Safety ofFactor Loador Stress Applied
Loador Stress Allowable Safety ofMargin −•
=
14.5-2,1441871,680Circuit Board
75.1-75.42071,563TEP
1.71.511,259255895Shield
29.3-4111722,130Detector
0.80.716,4152071,563Telescope HousingMSultMSyieldStress (psi)
3σ load(g)Freq (Hz)Assume Q=40
174MSultMSyield
Worst Normal/Shear(lbs)3σ load (g)
4853 / 45194Interface Bolts
6/27/06 Telescope Mechanical Design 19
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsAnalysisDesign DetailsNext Steps
6/27/06 Telescope Mechanical Design 20
Cosmic RAy Telescope for the Effects of Radiation
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 andconnector
4 mountingholes
6/27/06 Telescope Mechanical Design 21
Cosmic RAy Telescope for the Effects of Radiation
How the TEP is mounted
• TEP mounted in conical seats toprevent misalignment.
• Spring design allows for thermalexpansion and contraction
• Large TEP is clamped into holderwith 267 N (60 lbs) preload using4 springs
• Estimated maximum load is 207g’s during random vibration
• Springs nominally secure TEP upto 400 g’s
• Springs that exert > 52 N (11.6lbs) will secure TEP with a 1.5factor of safety
6/27/06 Telescope Mechanical Design 22
Cosmic RAy Telescope for the Effects of Radiation
TEP Material Properties
CTE (20 ºC to –30 ºC)
Compression Strength@ 20 ºC
Tensile YieldStrength @ 20 ºC
Tensile Modulus
Density
84.6 µ m/m-ºC18.9 µ m/m-ºC
110 MPa58.6 MPa
89.6 MPa14.4 MPa
3,100 MPa1,958 MPa
1,411 kg/m31,110 kg/m3
DelrinTEP
• 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 preload258 N (58 lbs) preload.
6/27/06 Telescope Mechanical Design 23
Cosmic RAy Telescope for the Effects of Radiation
Purging and Venting
• Spacers between each pair of detectors forventing
• 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 24
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design OverviewInstrument RequirementsMechanical RequirementsAnalysisDesign DetailsNext Steps
6/27/06 Telescope Mechanical Design 25
Cosmic RAy Telescope for the Effects of Radiation
Next Steps
• Finalize MLI attachment near telescope• Submit flight drawings for fabrication• Make assembly drawings
6/27/06 Telescope Mechanical Design 26
Cosmic RAy Telescope for the Effects of Radiation
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 27
Cosmic RAy Telescope for the Effects of Radiation
Telescope – Mechanical
Albert Lin
6/27/06 Telescope Mechanical Design 28
Cosmic RAy Telescope for the Effects of Radiation
Material Properties
• MIL-HDBK-5J• Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May
1982, pp 420-457• Plastics, Edition 8, Ultimate Tensile from Electronic Materials and Properties• Boedeker Plastics via www.matweb.com
MaterialDensity (lb/in3)
Young's Modulus
(ksi)Tensile
Yield (ksi)
Tensile Ultimate
(ksi)Poisson's
Ratio Where UsedAluminum 6061-T6 0.098 9900 35 42 0.33 StructureA286 AMS 5731 0.287 29100 85 130 0.31 FastenersSingle Crystal Silicon 0.084 27557 brittle 17.4 0.19 DetectorsPolyimide Glass 0.065 2800 - 50 - Circuit BoardG-10 Fiberglass 0.065 2000 28 45 - Isolator Interface
112
34
6/27/06 Telescope Mechanical Design 29
Cosmic RAy Telescope for the Effects of Radiation
Bolt Interface AnalysisBolt InputsBolt Type 8
Bolt Material 5Modulus of Elasticity 29,100,000 psiYield Strength 85,000 psiUltimate Strength 130,000 psiTensile Stress Area 0.00909 in^2Head Diameter 0.218 inBolt Diameter 0.138 in
#6-32
Stainless Steel A286
Bolt CalculationsProof Load 76500 psiPreload 522 lbsl = effective grip length 0.367 inkb = bolt stiffness 720,760 lb/in
Member CalculationsD1 0.419 inD2 0.207 inMiddle Frustrum on Flange
Frustra t d D E Material1 0.06 0.14 0.207 2,700,000 1,322,196 lb/in G-102 0.124 0.14 0.242 10,000,000 4,592,215 lb/in Aluminum3 0.051 0.14 0.283 10,000,000 11,954,988 lb/in Aluminum4 0.063 0.14 0.247 2,700,000 2,002,953 lb/in G-105 0.069 0.14 0.207 10,000,000 4,479,377 lb/in Aluminum
km = member stiffness 676,212 lb/inOutputsC = 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 487 lbs
P = Ext Tensile Load at Ultimate 1,077 lbs
k (8.14)
6/27/06 Telescope Mechanical Design 30
Cosmic RAy Telescope for the Effects of Radiation
Bolt Interface Loading
Mechanical Engineering Design, by Shigley
RP-1228 NASA Fastener Design
First fundamental frequency at 1564 Hz3 sigma load = 194gA286 CRES #6-32 Bolts at Interface
Inputs Outputs545 lb 24545 lb 53.02 lb545 lb 45.42 lb
1.682 in 48 487 lb 174
1077 lb464 lb
Tensile Yield
Shear YieldTensile Ultimate
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 Yield
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