CRaTER CDR
Mechanical Design
Mechanical Design,
CRaTER Assembly and Electronics Assembly
Critical Design Review
Matthew Smith
(617)-252-1736
matt@space.mit.edu
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CRaTER CDR
Mechanical Design
Overview
Assembly Description
Mechanical Environments and Requirements
Mechanical Design Details
Near Term Tasks
Back-up slides
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CRaTER CDR
Mechanical Design
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 two sub-assemblies
and perform all functional, environmental
and acceptance testing.
L13.5”x W9” x H 6”
Weight 6.4Kgs max.
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CRaTER CDR
Mechanical Design
Assembly Description
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7/15/2016
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CRaTER CDR
Mechanical Design
Overview
Assembly Description
Mechanical Environments and Requirements
– Imposed
– Internal
Mechanical Design Details
Near Term Tasks
Back-up slides
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Mechanical Environments - Imposed
•
CRaTER CDR
Mechanical Design
From 431-RQMT-000012, Rev A, Environments Section 3.1.
Section
Description
Levels
3.1.1.2
Net cg limit load
28.9 g*
3.1.4.2
Sinusoidal Vibration Loads
Protoflight;
Frequency (Hz)
5 - 17.7
17.7 – 50
Level
1.27cm D.A.
8 g’s
3.1.5
Acoustics
Delta IV Medium: Protoflight OASPL 140.0 dB
Atlas V 401: Protoflight OASPL: 137.0 dB
3.1.6.1
Random Vibration
See Random Vibration slide
3.1.7
Shock environment
See Shock Environment slide
3.1.8
Venting
Minimum of .25 in^2 of vent area per cubic foot
volume
* Interpolated from Table 3-1 for CRaTER at 6.4Kgs.
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CRaTER CDR
Mechanical Design
Mechanical Environments, Imposed
Random Vibration
Random Vibration Levels
Random Vibration Spec
Protoflight/
Qual
Acceptance
20
0.026
50
0.16
800
0.16
2000
0.026
Overall 14.1 Grms
Frequency (Hz)
1
10
100
1000
0.013
0.08
0.08
0.013
10.0 Grms
10000
Protoflight/ Qual
1
0.1
Acceptance
Power Spectral Density (g^2/Hz)
Freq
(Hz)
0.01
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CRaTER CDR
Mechanical Design
Mechanical Environments, Imposed
Shock Environment
Table 3-12 LRO/PAF Shock Response Spectrum
Delta IV (1194 PAF)
Frequency (Hz)
100
100-1,000
1,000-10,000
Level (Q=10)
150 g
+9.2 dB/Octave
5,000 g
Atlas (Type B1194 PAF)
Frequency (Hz)
100
100-1,400
1,00-10,000
Level (Q=10)
100 g
+7.6 dB/Octave
2,800 g
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CRaTER CDR
Mechanical Design
Mechanical Environments,
Imposed
Shock Environment
Table 3-13 Deployable Separation Mechanism Shock Response Spectrum
Separation Nut (SN9423-2)
Frequency (Hz)
100
100-3,000
3,000-10,000
Level (Q=10)
50 g
+7.8 dB/Octave
4,000 g
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CRaTER CDR
Mechanical Design
Mechanical Requirements and Verification
•
From 431-RQMT-000012, Rev A, Frequency Requirements Section 3.2.
Section
Description
Levels
3.2.2.1
Fundamental frequency, Hz
> 35 Hz
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Mechanical Requirements and Verification
•
CRaTER CDR
Mechanical Design
From 431-RQMT-000012, Rev A, Verification Requirements Section 3.3.
Section
Description
Levels/Comments
3.3.1
Factors of Safety
See FOS table
3.3.2
Test factors
See Test Factors table
3.3.3.2
Perform frequency verification test for Instruments
with frequencies above 50 Hz..
Verify and report frequencies up to 200Hz
Low level sine sweep
3.4
Finite Element Model requirements: Instruments
with predicted first frequencies below 75 Hz shall
provide Finite Element Models.
CRaTERs first fundamental frequency is
well above 75Hz.
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CRaTER CDR
Mechanical Design
Mechanical Requirements- Imposed
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
These are applied to the protoflight level testing
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Mechanical Requirements - Imposed
CRaTER CDR
Mechanical Design
Test Factors Table 3-16
Test
Structural Loads
Level
Duration
Centrifuge
Sine Burst
Protoflight
Comments
1.25 x Limit Load
30 seconds
5 Cycles Full Level
Acoustic
Level
Duration
Will be tested at LRO Level
Limit Level +3 dB
1 minute
Random Vibration
Level
Duration
Limit Level +3 dB
1 minute per axis
Sine Vibration
Level
Sweep Rate
1.25 x Limit Level
4 Octave/Minute per Axis
Shock
Actual Device
Simulated
2 Actuations
1.4 x Limit Level
1 Actuation/Axis
Will be tested at LRO Level
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CRaTER CDR
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.
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CRaTER CDR
Mechanical Design
Overview
Assembly Description
Mechanical Environments and Requirements
– Imposed
– Internal
Mechanical Design Details
Near Term Tasks
Back-up slides
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CRaTER CDR
Mechanical Design
Internal Requirements for the Electronics Assembly
•
Derived Internal Mechanical Requirements for Electronics Assembly
–
–
–
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.
•
–
–
–
Provide means to route cable from telescope to the Analog side of the Electronics
Assembly to minimize noise.
Electrically isolate the Electronics Enclosure from the Telescope, yet provide sufficient
thermal conductance path.
Electrical connector 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 that routes to the telescope assembly and an outlet port
at the digital board side of the internal volume.
Follow the octave rule for natural frequency of the PWAs to the Electronics Enclosure.
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CRaTER CDR
Mechanical Design
Overview
Assembly Description
Mechanical Environments and Requirements
Mechanical Design Details
Near Term Tasks
Back-up slides
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DESIGN DETAILS –Natural Frequencies
•
CRaTER CDR
Mechanical Design
Natural Frequency Estimates
– From SOLID WORKS cosmos package, 2005
• CRaTER Assembly
–
–
First frequency at 326 Hz (bottom cover)
Dominant Frequency at 1516 Hz (main assembly)
• Analog Board- 195 Hz
• Digital Board- 161 Hz
• Bare E-box
–
–
First mode frequency is 1002 Hz at the side with connectors.
Third mode Frequency is 1239 Hz at the middle plate that holds the two Circuit Card Assemblies.
• Top Cover- 284 Hz
• Bottom Cover - 351 Hz
• Telescope Assembly
–
–
First frequency- 1910 Hz
Dominant Frequency-
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CRaTER CDR
Mechanical Design
Random Vibration Loads
•
Load levels are dominated by random vibration spec.
•
For resonances in the Random Vibration Spec, Miles’ Equation shows 3 sigma loading
on the order of 85-154 g
•
Assume Q=20
Description
CRaTER
Assembly
Analog
Board
Digital
Board
E-Box
Enclosure
Top Cover
Bottom
Cover
Part No.
Frequency
(Hz)
ASD
(g^2/Hz)
Associated
g load (g)
3 sigma
load (g)
32-10000
1516
0.055
51.3
153.9
30-10201
195
0.160
31.3
93.9
32-10202
161
0.160
28.4
85.3
32-10203
1239
0.084
49.4
148.3
32-10204
284
0.084
27.3
81.9
32-10205
351
0.160
42.0
126.0
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DESIGN DETAILS
Stress Margins, Electronics Assembly Pieces
•
•
•
CRaTER CDR
Mechanical Design
Load levels are driven 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
CRaTER Assy
Aluminum, 7075
and 6061
+ 1.7
+ 1.8
Top Cover
Aluminum 7075
+12.8
+12.9
Bottom Cover
Aluminum 7075
+1.5
+1.5
Digital Board
Polyimide glass
brittle
+0.9
Analog Board
Polyimide glass
Brittle
+0.1
E-box
Structure
Aluminum 7075
+17.7
+17.9
Note 1. From SOLID WORKS, COSMOS excluding top and bottom covers in the model.
All components have positive Margin of Safety
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CRaTER CDR
Mechanical Design
DESIGN DETAILS
Stress Margins, Hardware
•
•
•
Load levels are driven by random vibration spec
Factors of Safety used for corresponding material from 431-SPEC-000012.
– Metals:
1.25 Yield, 1.4 Ultimate
Margin of Safety = (Allowable Stress or Load)/(Applied Stress or Load x FS) – 1
Description
Location/ # of bolts
Material Desc.
MS Yield
MS Ultimate
Comments
#4-40 SHCS
Analog Board/30
CRES, A 286
+14.2
> +19.5
4 Bolts
# 4-40 SHCS
Digital Board/35
CRES, A 286
+13.4
> +18.4
8 Bolts
#4-40 SHCS
Top Cover/37
CRES, A 286
brittle
> +1.5
4 Bolts
#2-56 SHCS
Bottom Cover/32
CRES, A 286
Brittle
> +0.2
4 Bolts
#10-32 SHCS
Mounting Feet/6
CRES, A 286
+2.8
+3.1
6 Bolts
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CRaTER CDR
Mechanical Design
Mechanical Design Details
Summary
•
The first fundamental frequency is estimated to be 327 Hz.
– Not required to submit an FEM since our predicted first frequency is >75 Hz.
– Meets stowage and deployed frequency requirements
•
•
Design meets all factors of safety.
All positive margins of safety. No Fracture Critical Items.
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CURRENT BEST ESTIMATE, MASS PROPERTIES
grams
lbs
Analog CCA
340
0.75
Electronics Assembly
Digital CCA
362
0.80
DC/DC converters and EMI filter
100
0.22
Interconnect Cable, A/D
91
0.20
Internal E-box wire, heater, Thermostats,
connectors
227
.50
Mechanical Enclosure
1848
4.08
Top Cover
195
0.43
Connector access cover
32
0.07
Bottom Cover
240
0.53
InternalHardware
163
0.36
Purge system
113
0.25
Electronics Assembly Sub-Total
3710
8.19
Detector Assembly Sub- Total
1309
2.89
MLI and TPS Sub-Total
249
.55
Mounting Hardware Sub-Total
41
.09
5309
11.72
CRaTER CBE Total
CRaTER CDR
Mechanical Design
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CRaTER CDR
Mechanical Design
Engineering Unit Drawing List
Drawing Number
Drawing Title
Rev.
Layout Complete
32-20000
CRaTER Assembly
90%
32-20200
Electronics Assembly
90%
32-20201
Digital Electronics, PWA
32-20201.0101
Digital Electronics, PWB
32-20201.01
Digital Electronics, Outline Dwg.
32-20202
Analog Electronics PWA
32-20202.0101
Analog Electronics, PWB Dwg
32-20202.01
Analog Electronics, Outline Dwg.
32-20203
Electronics Enclosure
32-20204
Cover, Top
32-20205
Cover, Bottom
32-20206
Cover, Access
32-20208
Cable, Interconnect D/A
Drawing Created
Checked
Released
B
100%
√
√
√
A
100%
√
√
√
√
√
√
A
100%
√
√
01
100%
√
√
√
01
100%
√
√
√
01
100%
√
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CRaTER CDR
Mechanical Design
Material Properties
Density
1
1
1
2
Material
Aluminum 6061-T6
Aluminum 7075-T651
A286 AMS 5731
Polyimide 30% glass
3
(lb/in )
0.098
0.101
0.287
0.065
Young's
Tensile
Tensile
Modulus
Ultimate
Yield (ksi)
(ksi)
(ksi)
9,900
35
42
10,300
58
68
29,100
85
130
450
24
Poisson's
Ratio
0.33
0.33
0.31
-
Where Used
Access Cover
Covers, Structure
Fasteners
Circuit Board
1. MIL-HDBK-5J
2. Efunda materials list via efunda.com
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CRaTER CDR
Mechanical Design
Mechanical Requirements and Verification Summary
Requirement Section
Description
Method
3.1.1.2
Net cg limit load
3.1.4.2
Sinusoidal Vibration Loads
A,T
3.1.6.1
Random Vibration
A,T
3.1.7
Shock environment
A,T
3.1.8
Venting
A, I
Stowed fundamental Frequency
A,T
3.2.2.1
A
3.3.1
Factors of Safety
A
3.3.2
Test Factors
A
Frequency verification and reporting
T
3.3.3.2
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CRaTER CDR
Mechanical Design
Mechanical Requirements and Verification Summary
•
We also meet all of our internal requirements:
–
–
–
–
–
–
–
–
–
–
Have adequate contact area (.5 in^2 min) to the spacecraft to support Thermal requirements. (min is .51 in^2)
Provide safe structure, within Factors of Safety specified, to support Telescope Assembly.
Provide for mounting 2 Circuit Card Assemblies.
• The Analog Board and Digital Board must be separated by an aluminum plate.
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 with minimizing noise.
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 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.
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CRaTER CDR
Mechanical Design
Overview
Assembly Description
Mechanical Environments and Requirements
– Imposed
– Internal
Mechanical Design Details
Near Term Tasks
Back-up slides
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CRaTER CDR
Mechanical Design
NEAR TERM TASKS FROM PDR
– Update MICD to reflect latest configuration.
• Released the MICD.
– Further develop analysis on natural frequencies and stresses using SOLID WORKS and
COSMOS on the complete CRaTER Assembly.
• Completed all natural frequency and stress analysis.
– 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…)
• Completed the design of purge system.
– Complete the drawings for part and assembly fabrication.
• Completed the fabrication drawings for the engineering unit. Assembly drawings are in process.
• Flight drawings to be completed shortly after engineering unit is completed and tested.
– Define attachment points and outline for thermal blankets.
• To be completed after Engineering unit is finished.
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CRaTER CDR
Mechanical Design
NEAR TERM TASKS-Post CDR
–
–
–
–
Finish assembly of the Engineering Unit.
Complete the drawings of FLIGHT parts and assembly for fabrication.
Define attachment points and outline for thermal blankets.
Vibration testing of Engineering Unit. Generate procedures for Vibe tests.
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CRaTER CDR
Mechanical Design
Backup Slides
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Stress Margins Results
•
Load levels are dominated by random vibration spec.
•
Factors of Safety, FS, used for corresponding material (MEV 5.1)
*
-
Metals: 1.25 Yield, 1.4 Ultimate
-
Composite: 1.5 Ultimate
CRaTER CDR
Mechanical Design
Margin of Safety (MOS)= (Allowable Stress or Load)/(Applied Stress or Load x FS)-1
Description
CRaTER
Assembly
Analog
Board
Digital
Board
E-Box
Enclosure
Top Cover
Bottom
Cover
First
Frequency
(Hz)
Q
Associated
g load (g)
3 sigma
load (g)
1516
30
62.8
188.5
195
20
31.3
93.9
15212
4.8
-
0.1
198
20
31.5
94.6
8646
2.8
-
0.9
1239
50
90.3
270.8
284
50
43.2
129.5
351
50
66.4
199.2
Max Stress
Min FOS Y Min FOS U
(psi)
#VALUE!
MOS
MOS
Yield
ULT
#VALUE! #VALUE!
#VALUE!
#VALUE!
#VALUE! #VALUE!
5738
10.11
11.9
7.1
7.5
43497
1.33
1.6
0.1
0.1
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CRaTER Assembly Resonance
CRaTER CDR
Mechanical Design
• First Mode 326 Hz
• Dominant Mode 1516 Hz
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CRaTER Assembly Stresses
CRaTER CDR
Mechanical Design
• Using Miles Equation,
Assume Q=20,
• 3 sigma g loading= 154 g
• Max Stress is 21,400 psi
• MOS Y= 1.7
• MOS U= 1.8
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Analog Board Resonance
CRaTER CDR
Mechanical Design
• First Mode 195 Hz
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Analog Board Stresses
CRaTER CDR
Mechanical Design
• Using Miles Equation
• Assume Q=20,
• 3 sigma g loading= 93.9g
• Max Stress is 15,212 psi
• MOS Ult= 0.1
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Digital Board Resonance
CRaTER CDR
Mechanical Design
• First frequency is 198 Hz.
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Digital Board Stresses
CRaTER CDR
Mechanical Design
• Using Miles Equation
• Assume Q=20,
• 3 sigma g loading= 85.3 g
• Max Stress is 8,646 psi
• MOS Ult= 0.9
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Top Cover Resonance
CRaTER CDR
Mechanical Design
• First Mode 288 Hz
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CRaTER CDR
Mechanical Design
Top Cover Stresses
• Using Miles Equation,
Assume Q=20,
• 3 sigma g loading= 98 g
• Material is aluminum
• Max Stress is 4248 psi
• MOS Y= 6.9
• MOS U= 6.1
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Bottom Cover Frequency
CRaTER CDR
Mechanical Design
• First frequency is 351 Hz.
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Bottom Cover Stresses
CRaTER CDR
Mechanical Design
• Using Miles Equation,
• Assume Q=20,
• 3 sigma g loading= 126 g
• Max Stress is 23.8 kpsi
• FOS= 3.1
• MOS Y= 1.5
• MOS U= 1.5
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