CRaTER PDR
Mechanical Design
Mechanical Design,
CRaTER Assembly and Electronics Assembly
Preliminary Design Review
Matthew Smith
Mechanical Engineer
(617)-252-1736
matt@space.mit.edu
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Overview
Instrument and Assembly Description
Mechanical Environments and Requirements
Mechanical Design Details
Near Term Tasks
Back-up slides
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Instrument and Assembly Description
•
Crater integrates two main sub-assemblies:
The Telescope Assembly and
The Electronics Assembly.
–
–
–
–
The Telescope Assembly is being designed
and built by The Aerospace Corporation
The Analog Board is being designed by
Aerospace. The Flight Analog Boards will be
built by MIT
The Digital Board and Electronics Enclosure
Assembly are being designed and built by
MIT.
MIT will integrate the sub-assemblies and
perform all functional, environmental and
acceptance testing.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Instrument and Assembly Description
Cosmic RAy Telescope for the Effects of Radiation
Mechanical Environments
•
CRaTER PDR
Mechanical Design
From 431-RQMT-000012, Environments Section 2.
Section
Description
Levels
2.1.2
Net cg limit load
12 g
2.4.2
Sinusoidal Vibration Loads
Frequency:
Protoflight/Qual:
Acceptance:
2.5
Acoustics
•Enclosed box without exposed thin
surfaces
OASPL Protoflight/Qual: 141.1 dB
OASPL Acceptance:
138.1 dB
2.6.1
Random Vibration
See Random Vibration slide
2.7
Shock environment
40 g at 100 Hz
2665g at 1165 to 3000 Hz.
No self induced shock.
2.8
Venting
Per 431-SPEC-000091 LRO Thermal
Subsystem spec.
Cosmic RAy Telescope for the Effects of Radiation
5-100 Hz
8g
6.4g
Mechanical Requirements and Verification
•
CRaTER PDR
Mechanical Design
From 431-RQMT-000012, Verification Requirements Section 3.
Section
Description
Levels
3.1.2.1
3.1.2.2
Stowed fundamental Hz
Deployed fundamental Frequency
Freq >35
>3 Hz
3.2.1
Factors of Safety
See FOS table
3.2.2
Test factors
See Test Factors table
3.2.3.2
MEVR-10 Perform frequency verification test for
Instruments with frequencies above 50 Hz..
MEVR-11 Report frequencies up to 200Hz
Low level sine sweep
We will be above 50Hz.
3.3
Finite Element Model requirements
We will be above 75Hz and will not be
required to submit an FEM of CRaTER.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
General Thermal Subsystem Requirements
from 431-Spec-000091
Section
Description
4.1
Exterior facing MLI blankets
shall have 3 mil Kapton with
VDA in outer Coating.
4.2
MLI Blanket Grounding:
All blankets shall be grounded per
431-ICD-00018
4.3
MLI Blanket Documentation:
The location and shape
documented in as-built ICDs.
4.4
Attachment to MLI Blankets:
All exterior MLI blankets shall be
mechanically constrained at least
at one point.
Cosmic RAy Telescope for the Effects of Radiation
DESIGN DETAILS
Electronics Assembly
•
CRaTER PDR
Mechanical Design
Natural Frequency Estimates
– Based from Steinberg Vibration Analysis for Electronic Equipment(Simply supported on 4 sides.)
•
•
•
•
Top Cover~ 199 Hz
Bottom Cover ~ 159 Hz
Analog Board~ 138 Hz
Digital Board~ 149 Hz
– From SOLID WORKS model of E-Box
• frequency is 702Hz at the middle plate that holds the two Circuit Card Assemblies.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
DESIGN DETAILS
Mechanical Environments, 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 75-150 g
Random Vibration Spec
Assume Q=10
Frequency (Hz)
1
10
100
1000
10000
Protoflight/ Qual
1
Freq Protoflight/
(Hz)
Qual
Acceptance
20
50
800
2000
0.026
0.16
0.16
0.026
Overall 14.1 Grms
0.1
0.013
0.08
0.08
0.013
10.0 grms
0.01
Cosmic RAy Telescope for the Effects of Radiation
Acceptance
Power Spectral Density (g^2/Hz)
•
•
DESIGN DETAILS
Stress Margins, Electronics Assembly Pieces
•
•
•
CRaTER PDR
Mechanical Design
Load levels are superceded by random vibration spec
Factors of Safety used for corresponding material from 431-SPEC-000012.
– 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
Material Desc.
MS Yield
MS Ultimate
Comments
Top Cover
Aluminum 6061
+14.2
+19.5
Note 1
Bottom Cover
Aluminum 6061
+13.4
+18.4
Note 1
Digital Board
FR4
brittle
+1.5
Note 1
Analog Board
FR4
Brittle
+0.2
Note 1
E-box
Structure
Aluminum 7075
> +2.8
>+3.1
Note 2
Note 1. From Steinberg, Vibration Analysis for Electronic Equipment
Note 2. From SOLID WORKS, COSMOS excluding top and bottom covers in the model.
All components have positive Margin of Safety
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Mechanical Design Details
•
The first fundamental frequency is estimated to be 149 Hz.
– Not required to produce an FEM since our predicted first frequency is >75 Hz.
•
•
•
All positive margins of safety.
Meet all factors of safety.
No Fracture Critical Items.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Internal Requirements for the Electronics Assembly
•
Derived Internal Mechanical Requirements for Electronics Enclosure
–
–
–
Have adequate contact area (.5 in^2 min) to the spacecraft to support Thermal requirements.
Provide safe structure, within Factors of Safety specified, to support Telescope Assembly.
Provide for mounting 2 Circuit Card Assemblies.
•
–
–
–
–
–
The Analog Board to provide direct linear path for electronics from the telescope interface to the
Digital Board interface to reduce noise.
Provide means to route cable from telescope to the Analog side of the Electronics Enclosure.
Electrically isolate the electronics Enclosure from the Telescope, yet provide sufficient thermal
conductance path.
Provide adequate surface area for mounting electrical components.
Interface to the Spacecraft to be on one side of the Electronics Enclosure.
•
–
–
The Analog Board and Digital Board must be separated by an aluminum plate.
The interface connectors to be on the Digital side of the Electronics Enclosure (separate from the Analog side)
Provide GN2 purge interface inlet and outlet ports.
Follow the octave rule for natural frequency of the PWAs to the Electronics Enclosure.
The Electronics Assembly meets all internal requirements except for …
–
–
Details need to be worked out for the GN2 design.
Electrical isolation of the E-box and Telescope needs more thought.
Cosmic RAy Telescope for the Effects of Radiation
DESIGN DETAILS
Electrical/Mechanical Interface
CRaTER PDR
Mechanical Design
Interface Connectors
J1 9 Pin D-Sub Male
311409-1P-B-12
J2 9 Pin D-sub Female 311409-1S-B-12
J3 1553,
BJ3150
J4 1553,
BJ3150
Mounting Hardware - Six #10-32 SHCS
Surface roughness of 63 micro inches or
better for interface surfaces.
Mounting surfaces have Electrically
Conductive finish (MIL-C-5541 Cl 3)
PART OF MID DRAWING NUMBER 32-02003.02
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
NEAR TERM TASKS
– Update MICD to reflect latest configuration.
– Further develop analysis on natural frequencies and stresses using SOLID WORKS and
COSMOS on the complete CRaTER Assembly.
– Finalize interface between Telescope Assembly and Electronics Box Assembly.
• Specify the electrical isolation material between the telescope and the E-Box.
– Identify the GN2 purge system (mechanical interface to the spacecraft, internal flow,
pressure measurements…)
– Complete the drawings for part and assembly fabrication.
– Define attachment points and outline for thermal blankets.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Backup Slides
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
Factors of Safety
Table 3-1 from 431-SPEC-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
CRaTER PDR
Mechanical Design
BOARD ANALYSIS
Analog Board Analysis
1
2
3
4
4.21E+05
4.21E+05
5
6
an 8.429 x 5.95 board separated into two parts
Polyimide modulus of elasticity
E (lb/in sq
4.21E+05
Thickness
h (inches)
0.06
0.09
0.1
0.11
0.12
0.15
u
0.12
0.12
0.12
0.12
0.12
0.12
length
a (in)
4.215
4.215
4.215
4.215
4.215
4.215
width
b (in)
5.95
5.95
5.95
5.95
5.95
5.95
weight
W (lb)
0.6
0.65
0.69
0.71
0.73
0.79
in/secSq
386
386
386
386
386
386
3.14
3.14
3.14
3.14
3.14
3.14
D=
7.69
25.95
35.60
47.38
61.51
120.14
mass/area=W/gab
6.19797E-05
7.13E-05
7.33E-05
7.54E-05
8.16E-05
Frequency=(Hz)
47
83
94
107
120
161
Frequency=(Hz)
91
160
182
207
232
312
Average Frequency
69
138
157
poisson ratio
g
pi
D=E*h^3/(12(1-u^2))
density p
4.21E+05
6.7145E-05
4.21E+05
4.21E+05
for a a simply supported board on 4 sides
f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5
From Steinberg, vibration analysis for electronic equipment page 149
for a fixed beam on 4 sides
121
Cosmic RAy Telescope for the Effects of Radiation
176
237
CRaTER PDR
Mechanical Design
BOARD ANALYSIS
Analog Board Analysis Cont’d
STRESS
Gin=peak load(g's)=
125
125
125
125
125
125
Q=transmisibility=
10
10
10
10
10
10
Gout=Gin*Q=
W=board weight(lb)=
1250
1250
1250
1250
1250
1250
0.6
0.65
0.69
0.71
0.73
0.79
q=load intensity=W*Gout/ab
13.393
14.509
15.402
15.848
16.295
17.634
My=bending moment at center=
6.641
7.195
7.637
7.859
8.080
8.744
3
3
3
3
0.1
0.11
0.12
0.15
13747
11691
10100
6995
DYNAMIC BENDING STRESS
Kt= stress concentration factor
3
h=height
Sb=6*Kt*My/h^2= lb/in^2
3
0.06
0.09
Stress due to bending
33206
15988
24000 psi
0.7
1.5
1.7
2.1
2.4
3.4
number of cycles before
failure
10^4
>10^8
>10^8
>10^8
>10^8
>10^8
-0.5
0.0
0.2
0.4
0.6
1.3
FACTORS OF SAFETY
FOS Yield
FOS Ultimate
NUMBER OF CYLES BEFORE FAILURE
check S-N curve for board type Ch 12 to determine if
board will fail
MARGIN OF SAFETY
MOS=(Allowable stress/applied stress*FS)-1
For a composit Fs=1.5 Ultimate
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
BOARD ANALYSIS
Digital Board Analysis
1
2
3
4
5
6
E, psi
4.21E+05
4.21E+05
4.21E+05
4.21E+05
4.21E+05
4.21E+05
h(inches)
0.06
0.09
0.1
0.11
0.12
0.15
u
0.12
0.12
0.12
0.12
0.12
0.12
length
a (in)
4.281
4.281
4.281
4.281
4.281
4.281
width
b (in)
7.488
7.488
7.488
7.488
7.488
7.488
weight
W (lb)
0.55
0.57
0.58
0.59
0.6
0.61
in/secSq
386
386
386
386
386
386
3.142857
143
3.14285714
3.142857
3.142857
3.142857
3.142857
D=
7.69
25.95
35.60
47.38
61.51
120.14
mass/area=W/gab
4.44492E05
4.6066E-05
4.69E-05
4.77E-05
4.85E-05
4.93E-05
47.32
85.39
99.14
113.41
128.14
177.60
Frequency, HZ =
94.79
171.06
198.61
227.19
256.69
355.79
Average Frequency
71
128
149
170
192
267
a 8.562 x 7.488 board two sections
modulus of eleasticity Polyimide fiberglass
Thickness
poisson ratio
g
pi
D=E*h^3/(12(1-u^2))
density p
for a a simply supported board on 4 sides
f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5
Frequency, HZ =
This is from an example by Steinberg, vibration analysis for electronic equipment page 149
for a fixed board on 4 sides
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
BOARD ANALYSIS
Digital Board Analysis Cont’d
STRESS
Gin=peak load(g's)=
125
125
125
125
125
125
Q=transmisibility=
10
10
10
10
10
10
Gout=Gin*Q=
1250
1250
1250
1250
1250
1250
W=board weight(lb)=
0.55
0.57
0.58
0.59
0.6
0.61
q=load intensity=W*Gout/ab
12.277
12.723
12.946
13.170
13.393
13.616
My=bending moment at center=
5.782
5.992
6.097
6.202
6.307
6.412
3
3
3
3
3
3
0.06
0.09
0.1
0.11
0.12
0.15
28908
13315
10974
9226
7884
5130
0.8
1.8
2.2
2.6
3.0
4.7
>10^8
>10^8
>10^8
>10^8
>10^8
>10^8
0.6
1.2
1.5
1.7
2.0
3.1
DYNAMIC BENDING STRESS
Kt= stress concentration factor
h=height
Sb=6*Kt*My/h^2= lb/in^2
FOS Yield
FOS Ultimate
24kpsi
check S-N curve for board type Ch 12 to determine if
board will fail
MARGIN OF SAFETY
MOS=(Allowable stress/applied stress*FS)-1
MOS
For a composite FS=1.5 (Ultimate)
Cosmic RAy Telescope for the Effects of Radiation
E-BOX COVERS, ANALYSIS
CRaTER PDR
Mechanical Design
Top Cover
Bottom Cover
Elastic Modulus
E(lb/in sq
1.00E+07
1.00E+07
Thickness
h(inches)
0.063
0.063
u
0.33
0.33
length
a (in)
9.343
9.119
width
b (in)
6.623
8.443
weight
W (lb)
0.41
0.46
in/secSq
386
386
3.142857143
3.142857143
G
125
125
q
0.828233449
0.746833585
Poisson ratio
g
pi
D=E*h^3/(12(1-u^2)
density p
f=pi/2((D/p)^.5)(1/a^2+1/b^2))^.5
D=
mass/area=W/gab
frequency =
233.837392
233.837392
1.71655E-05
1.54784E-05
199
159
1.9009
2.0061
2874
3033
5.E+08
5.E+08
Bending moment at center
My= q(u/a^2=1/b^2)/(pi^2(1/a^2+1/b^2)^2
dynamic bending stress
Sb=6*My/h^2
Stress=
Check S-N curve at Stress
N=
FOS
Yield/Stress
Ultimate/Stress
Tensile yield, psi
35000
12.18
11.54
Tensile Ultimate, psi
42000
14.6
13.8
Tensile yield, psi
35000
14.2
13.4
Tensile Ultimate, psi
42000
19.5
18.4
Margin of Safety
(allowable stress/applied stress *FOS)-1
Cosmic RAy Telescope for the Effects of Radiation
CURRENT BEST ESTIMATE, MASS PROPERTIES
grams
lbs
Analog CCA
480
1.05
Electronics Assembly
Digital CCA
540
1.19
Interconnect Cable, A/D
52
0.11
Internal E-box Cables
122
0.27
Mechanical Enclosure
1800
3.96
Top Cover
250
0.55
Bottom Cover
225
0.49
Hardware
166
0.36
Purge system
178
0.39
3813
8.38
Electronics Assembly Sub-Total
Detector Assembly
Circuit Board
138
0.30
Telescope Sub-Assy
1398
.87
Detector Mechanical Enclosure
525
1.15
Detector Assembly Sub- Total
1061
2.32
MLI and TPS Sub-Total
250
.55
Mounting Hardware Sub-Total
40
.09
5164
11.34
CRaTER CBE Total
Cosmic RAy Telescope for the Effects of Radiation
CRaTER PDR
Mechanical Design
CRaTER PDR
Mechanical Design
Drawing List
Drawing Number
Drawing Title
Rev.
32-1000
CRaTER Assembly
32-10200
Electronics Assembly
32-10201
Layout Complete
Drawing Created
0%
-
25%
Digital Electronics, PWA
02
50%
32-10202
Analog Electronics PWA
02
50%
32-10203
Electronics Enclosure
01
95%
32-10204
Cover, Top Electronics
Enclosure
01
95%
32-10205
Cover, Bottom Electronics
Enclosure
-
95%
Cosmic RAy Telescope for the Effects of Radiation
Checked
Released
CRaTER PDR
Mechanical Design
Material Properties
Density
2
2
1
2
Material
Aluminum 6061-T6
Aluminum 7075
A286 AMS 5731
Polyimide 30% glass
3
(lb/in )
0.098
0.098
0.287
0.065
Young's
Tensile
Tensile
Modulus
Ultimate
Yield (ksi)
(ksi)
(ksi)
9,900
6.9
16.6
9,900
13.7
32
29,100
85
130
420
24
45
Poisson's
Ratio
0.33
0.33
0.31
-
1. MIL-HDBK-5J
2. Efunda materials list via efunda.com
Cosmic RAy Telescope for the Effects of Radiation
Where Used
Covers
Structure
Fasteners
Circuit Board