Transcript Slide 1

Telescope Mechanical Design
Albert Lin
The Aerospace Corporation
(310) 336-1023
[email protected]
6/27/06
Cosmic RAy Telescope for the Effects of Radiation
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Telescope Mechanical Design
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Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Analysis
Design Details
Next Steps
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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.
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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.
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Peer Review Summary
1. Telescope design requires close machining tolerances for success.
Action: Modified design to increase robustness.
2. Detectors are not specified for random vibration and shock seen at the
interface mount.
Action: Plan to test engineering model detectors mounted in assembly.
3. Thin electrical isolation material specified at PDR may be too thin.
Action: Use .063” G-10 sheet for isolation.
4. Purge channel cover screws may not be EMI tight.
Action: None at this time. Add more screws if EMI emissions are too high.
5. Detectors will give poor measurements if there is light leakage.
Action: Working to specify light tight requirements.
6. Force requirements for TEP preload is not toleranced.
Action: Added tolerances to spring requirements.
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Overall Dimensions and Weight
Weight
(kg)
Weight
(lbs)
Structure
0.699
1.54
Circuit Board
0.145
0.32
Telescope
0.430
0.95
Total
1.274
2.81
Component
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Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Analysis
Design Details
Next Steps
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Telescope Mechanical Design
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Instrument Requirements – Level 2
From Instrument Requirements Document (IRD) 32-01205
CRaTERL2-03
Minimum path length
through the total amount
of TEP in the telescope
shall be at least 60 mm.
CRaTERL2-04
TEP components of 27 mm
and 54 mm in length
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Instrument Requirements – Level 3
From Instrument Requirements Document (IRD) 32-01205
Adjacent pairs of 140 micron
CRaTER-L3-01 and 1000 micron thick Si
detectors
Nominal instrument
shielding 1524 micron
CRaTER-L3-03
(0.060”) thick aluminum or
equivalent
No more than 762 micron
(0.030”) thick aluminum on
CRaTER-L3-04
zenith and nadir fields of
view
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Instrument Requirements – Level 3
From Instrument Requirements Document (IRD) 32-01205 Nadir
CRaTERL3-05
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
CRaTERL3-07
Zenith field of view from D2 to
D5 shall be less than 34°
CRaTERL3-08
Nadir field of view from D4 to D5
shall be less than 70°
Zenith
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Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Analysis
Design Details
Next Steps
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Telescope Mechanical Design
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Mechanical Requirements
• From 431-RQMT-000012, Mechanical System Specifications
Section
Description
Levels
Verification
3.1.1.2
Net cg limit load
28.9 g*
Analysis
3.1.4.2
Sinusoidal
Vibration Loads
Protoflight;
Frequency (Hz)
5 - 17.7
17.7 – 50
3.1.5
Acoustics
Delta IV Medium: 140.0 dB
Atlas V 401: 137.0 dB
3.1.6.1
Random Vibration
See Random Vibration slide
3.1.7
Shock environment
See Shock Environment slide
Test at LRO level
3.1.8
Venting
Minimum of .25 in2 of vent area
per cubic foot volume
Analysis
Analysis, Test
Level
1.27cm D.A.
8 g’s
Test at LRO level
Analysis, Test
* Interpolated from Table 3-1 for CRaTER at 6.4 kg.
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Random Vibration Levels
Protoflight
Acceptance
Frequency
/Qual
(Hz)
(g2/Hz)
(g2/Hz)
Random Vibration Spec
Protoflight/ Qual
Acceptance
Frequency (Hz)
1
10
100
1000
10000
20
0.026
0.013
50
0.160
0.080
800
0.160
0.080
2000
0.026
0.013
14.1 grms
10.0 grms
Overall
0.1
Power Spectral Density (g^2/Hz)
1
0.01
Random Vibration levels will drive the analysis.
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Updated Shock Environment
Frequency
Level (Q=10)
100 Hz
20 g
800 Hz
930 g
10,000 Hz
930 g
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Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Analysis
Design Details
Next Steps
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Frequencies and Mass Participations
Frequency
(Hz)
Mass
Participation
Where
895
0.003
Shield
1,369
0.46
Large TEP Assy
1,564
0.70
Housing
1,680
0.41
Circuit Board
1,688
0.04
Small TEP Assy
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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
Protoflight/ Qual
Acceptance
Frequency (Hz)
1
10
100
1000
10000
Frequency
(Hz)
Protoflight/
Acceptance
Qual
(g2/Hz)
2
(g /Hz)
20
0.026
0.013
50
0.16
0.08
800
0.16
0.08
2000
0.026
0.013
0.1
Power Spectral Density (g^2/Hz)
1
0.01
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Random Vibration Loads
• Factors of Safety used for corresponding material (MEV 5.1)
– Metals:
– Composite:
Margin of Safety 
Assume Q=40
1.25 Yield, 1.4 Ultimate
1.5 Ultimate
Allowable
Stress or Load
Applied Stress or Load  Factor of Safety
1
Freq (Hz)
3σ load (g)
Stress (psi)
MSyield
MSult
Telescope Housing
1,563
207
16,415
0.7
0.8
Detector
2,130
172
411
-
29.3
895
255
11,259
1.5
1.7
Circuit Board
1,680
187
2,144
-
14.5
TEP
1,563
207
75.4
-
75.1
Shield
Interface Bolts
3σ load (g)
Worst Normal/Shear
(lbs)
MSyield
MSult
194
53 / 45
48
174
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Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Analysis
Design Details
Next Steps
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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
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How the TEP is mounted
• 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
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TEP Material Properties
TEP
Delrin
Density
1,110 kg/m3
1,411 kg/m3
Tensile Modulus
1,958 MPa
3,100 MPa
Tensile Yield Strength
@ 20 ºC
14.4 MPa
89.6 MPa
Compression Strength
@ 20 ºC
58.6 MPa
110 MPa
CTE (20 ºC to –30 ºC)
18.9 μm/m-ºC
84.6 μm/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.
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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
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Overview
Design Overview
Instrument Requirements
Mechanical Requirements
Analysis
Design Details
Next Steps
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Next Steps
• Finalize MLI attachment near telescope
• Submit flight drawings for fabrication
• Make assembly drawings
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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
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Telescope – Mechanical
Albert Lin
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Material Properties
Density
1
1
2
Material
Aluminum 6061-T6
A286 AMS 5731
Single Crystal Silicon
Polyimide Glass
G-10 Fiberglass
3
4
3
(lb/in )
0.098
0.287
0.084
0.065
0.065
Young's
Modulus
Tensile
(ksi)
Yield (ksi)
9900
35
29100
85
27557
brittle
2800
2000
28
Tensile
Ultimate
(ksi)
42
130
17.4
50
45
Poisson's
Ratio
0.33
0.31
0.19
-
Where Used
Structure
Fasteners
Detectors
Circuit Board
Isolator Interface
1. MIL-HDBK-5J
2. Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May
1982, pp 420-457
3. Plastics, Edition 8, Ultimate Tensile from Electronic Materials and Properties
4. Boedeker Plastics via www.matweb.com
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Bolt Interface Analysis
B o lt In p u ts
B o lt T yp e
# 6 -3 2
B o lt M a te ria l
M o d u lu s o f E la s tic ity
Y ie ld S tre n g th
U ltim a te S tre n g th
T e n s ile S tre s s A re a
H e a d D ia m e te r
B o lt D ia m e te r
S ta in le ss S te e l A 2 8 6
8
2 9 ,1 0 0 ,0 0 0
8 5 ,0 0 0
1 3 0 ,0 0 0
0 .0 0 9 0 9
0 .2 1 8
0 .1 3 8
5
psi
psi
psi
in ^2
in
in
B o lt C a lc u la tio n s
P ro o f L o a d
P re lo a d
l = e ffe c tive g rip le n g th
k b = b o lt s tiffn e s s
76500 psi
5 2 2 lb s
0 .3 6 7 in
7 2 0 ,7 6 0 lb /in
M e m b e r C a lc u la tio n s
D1
D2
M id d le F ru s tru m o n
0 .4 1 9 in
0 .2 0 7 in
F ru s tra
1
2
3
4
5
k m = m e m b e r s tiffn e s s
F la n g e
t
0 .0 6
0 .1 2 4
0 .0 5 1
0 .0 6 3
0 .0 6 9
d
0 .1 4
0 .1 4
0 .1 4
0 .1 4
0 .1 4
D
0 .2 0 7
0 .2 4 2
0 .2 8 3
0 .2 4 7
0 .2 0 7
E
2 ,7 0 0 ,0 0 0
1 0 ,0 0 0 ,0 0 0
1 0 ,0 0 0 ,0 0 0
2 ,7 0 0 ,0 0 0
1 0 ,0 0 0 ,0 0 0
k (8 .1 4 )
1 ,3 2 2 ,1 9 6
4 ,5 9 2 ,2 1 5
1 1 ,9 5 4 ,9 8 8
2 ,0 0 2 ,9 5 3
4 ,4 7 9 ,3 7 7
lb /in
lb /in
lb /in
lb /in
lb /in
M a te ria l
G -1 0
A lu m in u m
A lu m in u m
G -1 0
A lu m in u m
6 7 6 ,2 1 2 lb /in
O u tp u ts
C = jo in t c o n s ta n t; ra tio o f
lo a d ta k e n u p b y b o lt
P = lo a d a t jo in t s e p a ra tio n
(in c lu d in g p re lo a d )
P = E x t T e n s ile L o a d a t Y ie ld
P = E x t T e n s ile L o a d a t
U ltim a te
0 .5 2
1 ,0 7 7 lb s
4 8 7 lb s
1 ,0 7 7 lb s
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Bolt Interface Loading
Inputs
Normal Load
In-Plane Load X
In-Plane Load Y
In-Plane Load Offset
Tensile Yield
Tensile Ultimate
Shear Yield
Outputs
545
545
545
1.682
487
1077
464
lb
lb
lb
in
lb
lb
lb
Worst Case Bolt
Normal Load
Shear Load
Margin of Safety Yield
Margin of Safety Ult
24
53.02 lb
45.42 lb
48
174
First fundamental frequency at 1564 Hz
3 sigma load = 194g
A286 CRES #6-32 Bolts at Interface
Mechanical Engineering Design, by Shigley
RP-1228 NASA Fastener Design
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