Transcript Slide 1

Telescope Mechanical Design
Albert Lin
The Aerospace Corporation
Mechanical Engineer
(310) 336-1023
[email protected]
9/28/05
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Design Details
Next Steps
Cosmic RAy Telescope for the Effects of Radiation
Design Overview
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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
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Weight = 2.32 lbs
Component
Weight (lbs)
Structure
Circuit Board
Telescope
1.150
0.300
0.870
Total
2.320
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Design Details
Next Steps
Cosmic RAy Telescope for the Effects of Radiation
Instrument Requirements
From 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 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
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Design Details
Next Steps
Cosmic RAy Telescope for the Effects of Radiation
Mechanical Requirements
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From 431-RQMT-000012, Mechanical System Specifications
Requirement
2.1.2
2.4.2
2.5
2.6.1
2.7.2
3.1.2.1
3.3
Description
Levels
Net CG limit loads
•Superceded by Random Vibration
12 g
Sinusoidal Vibration Loads
•Superceded by Random Vibration
Frequency:
Protoflight/Qual:
Acceptance:
Acoustics
•Enclosed box without exposed thin surfaces
OASPL Protoflight/Qual: 141.1 dB
OASPL Acceptance:
138.1 dB
Random Vibration
See next slide
Shock Environment
40 g at 100 Hz
2665 g at 1165-3000 Hz
No self induced shock
Minimum Fundamental Frequency
5-100 Hz
8g
6.4g
Minimum > 35 Hz
Recommended > 50 Hz
Will not provide FEM model > 75 Hz
Cosmic RAy Telescope for the Effects of Radiation
Random Vibration
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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
Frequency (Hz)
1
10
100
1000
10000
Protoflight/ Qual
1
Freq Protoflight/
(Hz) Qual
20
50
800
2000
0.026
0.16
0.16
0.026
Acceptance
0.013
0.08
0.08
0.013
0.1
0.01
Cosmic RAy Telescope for the Effects of Radiation
Acceptance
Power Spectral Density (g^2/Hz)
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Stress Margins
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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
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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
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First Fundamental Frequency at 2340 Hz
Cosmic RAy Telescope for the Effects of Radiation
Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Design Details
Next Steps
Cosmic RAy Telescope for the Effects of Radiation
How to Mount TEP
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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
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Oversized mounting hole to allow for changes in radial dimension
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Spring clamp to hold in TEP with preload at all temperatures
Cosmic RAy Telescope for the Effects of Radiation
Mounting Details, Purging and Venting
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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 Overview
Telescope Requirements
Mechanical Requirements
Design Details
Next Steps
Cosmic RAy Telescope for the Effects of Radiation
Next Steps
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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
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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
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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
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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
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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
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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
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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
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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
Normal Load
In-Plane Load X
In-Plane Load Y
In-Plane Load Offset
Tensile Yield
Tensile Ultimate
Shear Yield
0
231
0
1.2
593
907
356
lb
lb
lb
in
lb
lb
lb
Worst Case Bolt
Normal Load
Shear Load
Margin of Safety Yield
Margin of Safety Ult
First fundamental frequency at 2340 Hz,
which is off of the random vibe data set
18
4.71 lb
9.63 lb
7,291
14,709
9.000
6.000
Assume worst-case loading at 2000 Hz
3.000
3 sigma load = 105g
A286 CRES Bolts at Interface
0.000
-3.000
0.000
Mechanical Engineering Design, by Shigley
RP-1228 NASA Fastener Design
Worst
Case
Bolt
-3.000
Cosmic RAy Telescope for the Effects of Radiation
3.000
6.000
9.000
Interface Circuit Board Board Resonance
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First Mode:
632 Hz
Total nodes:
25225
Total elements: 12901
COSMOSWorks 2005
Cosmic RAy Telescope for the Effects of Radiation
Detector Board Stress
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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
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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)
Q Factor
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5
10
15
20
25
1000
85
121
148
170
191
1100
81
115
141
163
182
1200
78
110
135
156
174
Fundamental Frequency (Hz)
1300
1400
1500
1600
75
72
70
68
106
102
99
96
130
125
121
117
150
144
140
135
168
162
156
151
1700
66
93
114
131
147
Most structures have Q between 10 and 20
Cosmic RAy Telescope for the Effects of Radiation
1800
64
90
111
128
143
1900
62
88
108
124
139
2000
61
86
105
121
136
Factors of Safety Used
Table 3.1 from 431-RQMT-000012
Design Factor of Safety
Type of Hardware
Yield
Ultimate
Tested Flight Structure - Metallic
1.25
1.4
Tested Flgiht Structure - Beryllium
1.4
1.6
Tested Flight Structure - Composite
N/A
1.5
Pressure Loaded Structure
1.25
1.5
Pressure Lines and Fittings
1.25
4.0
Untestest Flight Structure - Metallic Only
2.0
2.6
Cosmic RAy Telescope for the Effects of Radiation
Material Properties
Density
1
1
1
2
3
Material
Aluminum 6061-T6
Beryllium Copper TH02
A286 AMS 5731
Single Crystal Silicon
Polyimide-Glass
3
(lb/in )
0.098
0.298
0.287
0.084
0.065
Young's
Modulus
Tensile
(ksi)
Yield (ksi)
9,900
35
18,500
160
29,100
85
27,557
brittle
2,000
brittle
Tensile
Ultimate
(ksi)
42
185
130
17.4
24
Poisson's
Ratio
0.33
0.27
0.31
0.19
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Where Used
Structure
TEP Spring
Fasteners
Detectors
Circuit Board
1. MIL-HDBK-5J
2. Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May 1982, pp 420-457
3. www.efunda.com
Cosmic RAy Telescope for the Effects of Radiation