GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review May 12-16, 2003
GLAST Large Area Telescope:
Mechanical Systems
WBS: 4.1.8
Section 13
Marc Campell
SLAC
Mechanical Systems Manager
marcc@slac.stanford.edu
Document: LAT-PR-01967
Section 13 Mechanical Systems
1
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Overview
Section 13.1
Section 13 Mechanical Systems
2
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Mechanical Systems Organization
Mechanical Systems Mgr
Marc Campell
Program Manager
Linda Roberson
Grid Box Engineer
Bill Olson
X-LAT Plate Engr
Giang Lam
Performance &
Safety Assurance
Darren Marsh
Engr Model Testing
M. Campell
Giang Lam
Thermal Systems PM
M. Campell
Systems Engr.
Leonard Lee
Development
Development
Development
Radiator/HP Devel.
Specifications
Analysis
Analysis
Analysis
Radiator/HP Fab.
Test Plans
Fabrication
Fabrication
Fabrication
Rad./HP Verification
Verification Testing
Verification Testing
EM Testing
S. Morrison PM
J. Stieber
D. Plaza
C. Wilder
J. Hodgson
M. Molini
Document: LAT-PR-01967
C. Wilder
G. Lam
J. Hodgson
M. Molini
LM team
L. Lee
J. Hodgson
J. Ku
Section 13 Mechanical Systems
3
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Mechanical Subsystems Overview
Grid Assembly
Grid Box Base Assy
Grid Box Assy
Mid-Plate
+Z
X-LAT Plate
EMI Shields
Radiator Mount Brkt
HPPP
DSHP
Document: LAT-PR-01967
Section 13 Mechanical Systems
4
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Major Subassemblies
• Grid Assembly
– 4x4 Grid + Radiator Mount Brackets
• Grid Box Base Assembly (GBBA)
– Grid Assy + Top Flange & Downspout HP + HP Patch Panel
– Configuration delivered to I & T for LAT integration
• Grid Box Assembly
– GBBA + EMI Skirt + X-LAT & Mid-plates
– Mechanical Systems Top Assembly test configuration
– Static Load and Thermal Cycle tests
• Radiators
– Fabricated and tested by LM
• X-LAT and Mid-plates
– Fabricated and tested by LM
Document: LAT-PR-01967
Section 13 Mechanical Systems
5
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator & X-LAT Placement
+Z
Document: LAT-PR-01967
+Z
Section 13 Mechanical Systems
6
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Design & Fabrication Responsibilities
Manufacturing/Integration Activity
Grid Assembly
Fabricate, inspect Grid structure
Fabricate, test Top Flange heat pipes
Fabricate, test Downspout heat pipes
Assemble, test Grid assembly
Fabricate, inspect EMI Skirt parts
X-LAT Thermal Plate
Fabricate, inspect X-LAT Plate parts
Fabricate, test X-LAT heat pipes
Assemble, test X-LAT Thermal Plates
Assemble, test mid-plate
Radiators
Quantity
Flt/Spare
Responsible
Organization
Work
Performed
1/0
5/1
12 / 1
1/0
1/0
SLAC
LM-ATC
LM-ATC
SLAC
SLAC
Sub
LM-HPPC
LM-HPPC
SLAC
SLAC
9/1
2/1
1/0
LM-ATC
LM-ATC
LM-ATC
LM-ATC
LM
LM-HPPC
LM-ATC
LM-ATC
LM-ATC
Sub
Fabricate, inspect Radiator parts
Fabricate, test Radiator VC heat pipes
12 / 1
LM-ATC
LM-HPPC
Assemble, inspect Radiators
2/0
LM-ATC
LM-HPPC
LM-ATC
LM-ATC
SLAC
LM-ATC
Sub
LM-ATC
Test Radiators
Thermal Control System
Fabricate TCS hardware
Thermal-balance test TCS system
1/1
1/0
Mechanical Systems
Legend
LM-ATC
LMHPPC
SLAC
Sub
Lockheed-Martin Advanced Technology Center, Palo Alto CA
Lockheed-Martin Heat Pipe Product Center, Sunnyvale CA
Stanford Linear Accelerator Center, Menlo Park CA
Subcontractor to be determined
Document: LAT-PR-01967
Section 13 Mechanical Systems
7
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Design Problem Areas
• CAL-GRID Interface
• Electronics-Box to X-LAT Interface
Document: LAT-PR-01967
Section 13 Mechanical Systems
8
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Cal Plate to Grid Interface Status
• The design shown at PDR for the Calorimeter to Grid interface
was a bolted joint with 54 - #8 bolts & 16 - #6 bolts
• Two pins provide alignment – one slip fit and one slot
• Further analysis has shown that this design is inadequate
– Inadequate margin between the required friction coefficient
to prevent slipping and the achievable coefficient
• Alternate designs are being pursued by analysis and test
– Create a pinned joint using structural epoxy around a bolt
– A combination of pins and bolts
– An alternate path for shear loads leaving the original
arrangement of bolts for clamping in Z
– Unique Cal plates around the periphery
• The Instrument Office and the Project Office are reviewing the
shear load requirements
• This interface remains an open issue
Document: LAT-PR-01967
Section 13 Mechanical Systems
9
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
CAL-Grid I/F Closure Plan
• Re-evaluated approach for deriving the shear load requirement
– Factor of ~2 reduction predicted 5/6
• New shear loads from CLA
– First look 5/16
– Verified 5/30
• EM test of CAL Shear plate concept
– First look 5/21 (load capability)
– Full up test 6/7
• Detail design complete 6/27
– Coordinated with CAL, I & T and ELEC (cable trays)
• 1 x 4 EM testing complete 7/31
Document: LAT-PR-01967
Section 13 Mechanical Systems
10
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT to Electronics-Box Thermal Joint Design
Problem Status
• At PDR & dPDR the baseline design was a bolted and thermally
bonded joint between bottom of each E-Box and the X-LAT
plate. There were flexures between the top of the E-box stack
and the CAL plates.
X-LAT Plate
– Concern that E-boxes were not serviceable
• Large bonded area to de-mate.
• Re-verification issues after re-integrating.
GRID
• At Peer Review, trade study presented for design that
– Carried the thermal load of E-Boxes into X-LAT heat pipes
– Accommodate tolerance buildup from E-Box and Grid Box
components
– Repeatable interface (make & break)
– Minimize schedule & verification impacts resulting from XLAT plate removal for Electronics box access
Document: LAT-PR-01967
Section 13 Mechanical Systems
11
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT to Electronics-Box Thermal Joint
Design Problem Resolution
• Design changed to rigidly mount E-Box stack to CAL plate and
create a thermally compliant thermal joint between the E-box &
X-LAT plate
• Trade study results indicate that graphite “felt” material
optimally meets requirements and has the following
characteristics:
– Highly conductive graphite fibers
– Mechanically compliant
– Meets out-gassing requirements
– Allows TEM/TPS to be mated to CAL through out
its Acceptance testing
• However, this approach has limited Flight heritage and must be
qualified for our application
– GSFC Wide Field Planetary Camera 3 has qualified an
application
Document: LAT-PR-01967
Section 13 Mechanical Systems
12
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Vel-Therm Design Closure Plan
• Design trades 5/30
– Contact pressure distribution (# bolts, preload)
– Particle containment
– E-box – X-LAT mechanical connection details
• Vel-therm EM tests
– Coupon tests (load-deflection & conductance-psi) 5/30
– Full scale tests 7/15
– Life tests – thermal and/or mechanical cycling 12/12
• Flight designs 8/29
– Finalize interface
– Revise/release affected hardware
– Assembly plans & procedures
– Coordinate with I & T
Document: LAT-PR-01967
Section 13 Mechanical Systems
13
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Peer Review Significant Findings
•
Is the design maturity, qualification and verification planning near CDR level?
– With the exception of the electronics to X-LAT interface, Yes, but still
missing an appropriate level of verification with the engineering models
and final dynamics analysis.
•
Has the Subsystem identified open design issues and established appropriate
resolution plans to ensure closure?
– Yes, the issues have been identified but issues may still develop during
engineering model testing and final analysis.
•
Is the Subsystem near readiness for manufacturing?
– Many element of the subsystem are ready for manufacture (e.g. radiator),
however other items need to wait until analysis and successful engineering
model completion.
•
Has the Subsystem identified open manufacturing issues and established
appropriate resolution plans?
– Yes. Specific concerns are captured in the RFAs.
•
Are there other issues that should be addressed?
– Mechanical assembly of the LAT will be a complex process that will require
development of detailed processes and procedures.
– The mechanical team has just recently staffed up. Re-plan of work that has
been delayed needs to be completed and may delay design finalization.
Document: LAT-PR-01967
Section 13 Mechanical Systems
14
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Major RFA’s and Overall Status
• 19 of 46 Mechanical/Thermal RFA’s owned by Mechanical
Systems (M. Campell & S. Morrison)
– 0 closed
– 19 submitted
Document: LAT-PR-01967
Section 13 Mechanical Systems
15
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Major RFA’s and Overall Status
Top 5 RFA Summary
• #12 a) Address the intermetallic layer issue at the friction joint of the
bimetallic joint for VCHP’s; b) request information on manufacturing
processes; c) are CCHP end caps friction welded?
– Leakage through intermetallic layers is an issue in pressure
vessel design. It can be aggravated by the friction-welding
process since these layers can be aligned to result in leak paths.
LM has instituted strict controls on material purity to preclude the
formation of intermetallic layers which can lead to leakage.
– Temperatures are controlled during subsequent fusion welding
processes to remain below approximately 200 oF. Fusion welding
is automated, allowing minimum heat input to the parts. Inert gas
flow provides sufficient cooling to limit temperatures during and
after the welding process. This ensures that material integrity is
not compromised due to overheating. LM has had no failures in
these joints in over 15 years of flight experience using our
material and process controls.
• #29 Establish a realistic schedule for drawing release include spans
for design engineering, check, stress, configuration management, etc
– Schedule has been revised to include these items
Document: LAT-PR-01967
Section 13 Mechanical Systems
16
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Major RFA’s (Cont)
Top 5 RFA Summary (Cont)
• #34 Verify that proposed Vel-therm X-LAT to electronics thermal
joint design thermal performance does not degrade over time
(aging issue), after multiple installation/de-installations, and
during the course of the mechanical vibration
– A qualification program will be developed for this interface to
address these issues. Looking for guidance from GSFC WFC3 program.
• #42a) What is the detailed schedule for the Vel-Therm EM Test
program.
Test
Load vs Deflection
Thermal conductivity vs
Deflection
Random vibe (or lateral
excursion)
Thermal vac performance
Document: LAT-PR-01967
Sample
Small .125" thk samples
Small .125" thk samples in high vacuum
(Ames)
Full sized footprint with min & max
allowable gaps from above
Full sized footprint with simulated E-box
thermal loads
Section 13 Mechanical Systems
ECD
5/2/03
5/30/03
5/30/03
7/15/03
17
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Major RFA’s (Cont)
Top 5 RFA Summary (Cont)
• #42 b) What is the back-up design if the EM program is not
successful using Vel Met? New baseline is unconventional.
– 3 Back-ups are under consideration; #1 will be developed
– “Thick” RTV bond line between E-box and X-LAT plate with a
0.0005 inch thick Teflon film between one of the interfaces to
allow disassembly.
– A thermal strap that is laminated with the Grafoil (high
conductance graphite).
– Delete existing X-LAT plate and rigidly attach the X-LAT heat
pipes to the E-boxes. The heat pipes would become the
flexible member. A cap would fit over the entire assembly to
act as EMI enclosure. Variation on this is a X-LAT plate that
ties the E-boxes together, but is not tied to the EMI skirt. This
keep the boxes moving in-phase.
Document: LAT-PR-01967
Section 13 Mechanical Systems
18
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Mechanical Systems’ Status Summary
•
•
•
•
•
•
Final Design Established With Known Closure Plans For Design Trades
– X- LAT Plate To Electronics Interface - ECD: 7/15/03
• Qual tests ECD: 11/15/03
– CAL-Grid Interface – ECD: 7/15/03
– EM Model Tests Complete - ECD: 9/03
– Grid Box Assy Drawings – ECD: 8/03
• 0/26 Drawings Released, 23/26 Drawings Draft
– Radiator & X-LAT Drawings – ECD: 6/15/03
• 0/39 LM Drawings Released, 39/39 LM Drawings Draft
Internal & External Interfaces Established
– 87 TBX’s with closure planned – ECD: 6/1/03
Performance Analyses Will Show Compliance Including Sufficient Design Margin
– Analyses ECD: 5/30/03
– Exception: CAL-Grid interface currently has negative margins
Qualification & Verification Plans
– X-LAT test plan ECD: 5/30/03
– GBA Static Load test case definition ECD: 8/03
– TCS Thermal Balance test definition ECD: 8/03
Subsystem Risk Areas Identified And Mitigation Plans Established
Cost & Schedule Manageable
– +$364K Cost and -$544K Schedule Variance with recovery plans in work
– 60 Days Schedule Float to Flight Delivery Need Dates
Document: LAT-PR-01967
Section 13 Mechanical Systems
19
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Key Requirements
Section 13.2
Section 13 Mechanical Systems
20
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Key Mechanical Systems
Requirements (1of 2)
Sect Requirement
8
Configuration
8.1.
Mass
The total mass of Mechanical Systems <345 kg
8.3.
8.6.
329.3
15.7
Y
I
LAT-TD-00125-1
>1.89m
1.895
Y
I
IRD 3.2.2.3
Stay-Clear Volume and Dimensions
Radiator positioned according to IRD Appendix A
8.5.
Design Margin Comply Method Req.Source
When on, Radiator VCHP heater power < 35 W
13W
22W
Y
D
When off, orbit-average survival heater power
<220 W @ 27 V min
158W
62W
Y
D
When off, peak survival heater power < 560 W
533
27W
Y
D
55.5 Hz
11%
Y
T
IRD 3.2.2.8.1.2
Y
T, A
IRD 3.2.2.8.1.2
Stiffness
Fixed-base first-mode > 50 Hz
Provisions for Integration and Test
During Obs T-Vac, TCS capable of full functionality
Ok
“lying on its side”
Document: LAT-PR-01967
TD-00125-1(Derived)
IRD 3.2.4.1.7.6
(Derived)
IRD 3.2.4.1.7.6
(Derived)
Section 13 Mechanical Systems
21
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Key Mechanical Systems
Requirements (2 of 2)
Sect Requirement
10
Design Margin Comply Method Req.Source
Structural Load Environment
10.1. Structural Loads
Capable of exposure to launch loads
11
Ok
Y*
Capable of withstanding static loads in thrust and lateral Ok
simultaneously
Thermal Environment and Heat Loads
T, A
IRD 3.2.2.8.2
Y
A
Y
T, A
LAT-TD-00225-5
Y
T, A
IRD 3.2.3.4.5
Provide thermal control with LAT pointed 2pi/24/7/365 73.4W/Rad 0W/Rad
during any normal LAT mode
Y
T, A
MSS 3.3.2.3
(Derived)
Capable of maintaining thermal control during exposure
to IR, Albedo, Solar fluxes
Y
T, A
IRD 3.2.3.5
(Derived)
11.1. Process and Interface Heat Loads
Maximum process power indefinite dissipation
615W LAT+
35W Rad
0.6 C
hot case
Capable of normal operation when loaded by 75 W/Rad
From SC solar arrays
IRD 3.2.2.8.2
11.3. Environment Heat Loading and Orbital Parameters
* Will comply for CAL-Grid interface
Document: LAT-PR-01967
Section 13 Mechanical Systems
22
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review May 12-16, 2003
Design
Grid Box Assembly
Section 13.3
Document: LAT-PR-01967
Section 13 Mechanical
Systems
Design
23
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Drawing Tree
Mechanical Systems Drawing Tree
1
Grid Box Assy
M
Connector Panel
TCS External Box
M
TCS Connector
Support Bracket
EMI Shield
Details
(4 drawings)
2
X-LAT Plate Assy
SCD
Mid-Plate Assy
SCD
External Box
Base
LH & RH Down
Spout Heat Pipe
SCD
External Box
Cover
LH & RH Heat
Pipe Patch Panel
Grid Box Base
Assy
M
Grid Assy
Top Flange Heat
Pipe
SCD
4 x 4 Grid
LH & RH
Radiator Mount
Bracket
Purge Groove
Cap
NOTES:
1. Grid Box Assy is for Mechanical Systems Testing only.
2. Grid Box Base Assy is delivered to I&T for LAT integration
along with all of the uninstalled Grid Box Assy parts.
Thermistors
Flight Heaters
SCD
Grid Schematic
Document: LAT-PR-01967
Section 13 Mechanical Systems
24
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Assembly Design
+Z
CAL-Grid Interface
Mid-Plate
X-LAT Plate Assy
+Z
Radiator Mount Bracket
Heat Pipe Patch Panel
EMI Shields
S/C Mount Interface
Document: LAT-PR-01967
Section 13 Mechanical Systems
25
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Structure
+Z
S/C mount
Helicoils for CAL bolts
+Z
Top Flange Heat Pipes
Purge grooves
Integral Wing
Document: LAT-PR-01967
Section 13 Mechanical Systems
26
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid
Design Drivers
• Provides structural backbone for all LAT Subsystems
• Provides electrical ground for all LAT Subsystems
• Provides thermal path to Radiators for all LAT Subsystems except
Electronics boxes (carried by X-LAT plates)
– Embedded Heat Pipes in top flange of Grid to move heat out
– Downspout Heat pipes tie Grid to Radiators
• Thermostatically controlled heaters on Grid corners are part of LAT
thermal control system
Construction
• Machined from 10.25” thick 6061 AL plate
• Heat treated to T6 after rough machining
• Grid surface is alodine, class 3. Electrically conductive and good
surface for adhesive bonding thermal components, harness supports,
Tracker cables, MLI supports, EMI tape etc
• Integral purge grooves allow for N2 purging of the CAL’s during
ground operations
Document: LAT-PR-01967
Section 13 Mechanical Systems
27
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Spacecraft Interface Stiffener (Wing)
Design Drivers
• Primary function is to spread the point load inputs from the
Spacecraft & locally stiffen the Grid against the lateral loads.
– Distortions in this area drive the CAL-Grid interface design
• Defines Spacecraft interface to LAT
Construction
• Integral part of Grid (was separate part)
• S/C Interface is a raised pad with 2 – 12.7 mm dia inserts &
1 – 14.3 mm dia pin hole at each location
– Installed with Spectrum Astro provided fixture
+Z
Document: LAT-PR-01967
Section 13 Mechanical Systems
28
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Mount Bracket
Design Drivers
• Supports & locates Radiators & their Heat Pipes
• Supports & locates X-Lat Plates & their Heat Pipes
• Provides access to ACD mounting bolts
• Supports & locates alignment optics
• Provisions for mounting Heater Control
Box or Heater Control Connector Bracket
for Thermal Control System
• Corner lugs for MGSE attachment (sized
to carry entire Observatory mass with 2
lugs if required)
Construction
• 6061-T6 Al machining, alodine
• Bolts/pinned to 3 orthogonal surfaces of
Grid corner
Document: LAT-PR-01967
Section 13 Mechanical Systems
29
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
EMI Shield
Design Drivers
• Encloses LAT Electronics boxes (EMI tight)
• Consists of 4 Radiator Mount Brackets, 4 Heat Pipe Patch
Panels, 4 X-side Shields and 4 center Shields
• Mechanically supports 3 way heat pipe joint – Downspout, XLAT and Radiator HP’s
• Supports X-LAT plates
• Provides mounting for Connecter Patch Plates from
Electronics
+Z
Construction
• 6061-T6 AL machining,
alodine
• Pieces bolted to Grid &
each other
Document: LAT-PR-01967
Section 13 Mechanical Systems
30
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Calorimeter to Grid Interface
• Interleaved CAL baseplate tabs are bolted and pinned to –Z
surface of Grid
• CAL baseplates close-out the Grid structure which increases
natural frequency of LAT
• Bolted interface applies clamping force for Z axis loads and
provides good thermal contact
• Features to carry shear loads are under investigation
• 2 pins per CAL locate it on the Grid bay and are used as datum
for hole pattern in Grid and other features such as Tracker
cable cut-outs in Grid walls
Document: LAT-PR-01967
Section 13 Mechanical Systems
31
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Plate to E-Box Thermal Joint
• Thermal joint design drivers
– Carry thermal load of stack of E-Boxes into X-LAT Heat
Pipes
– Accommodate tolerance stack up E-Box and Grid Box parts
– Be repeatable & reliable
– Minimize schedule & verification impacts due to removal of
X-LAT plates for access to Electronics
• Graphite felt material selected
– Highly conductive graphite fibers
– Mechanically compliant
– Meets out-gassing requirement
– Vel-Therm & Vel-met are brand
names
Document: LAT-PR-01967
Section 13 Mechanical Systems
32
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Electronics Stack Cross-Section
• 4 cm wide graphite felt strip placed around perimeter of
each box optimizes conduction vs contact pressure
required
Midplate to X-LAT
Thermal Joint, 2 PLCS,
60 #6 Fasteners
each side
Vel-Therm
X-LAT Plate
Midplate
Bolting X-LAT Plate
to EMI Shields,
60 #8 Fasteners per
Plate
X-LAT Plate
EMI
Shields
EMI
Shields
GRID
Note: View along Y-axis
Document: LAT-PR-01967
Section 13 Mechanical Systems
33
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Stress Analysis
Topics
• Cal-Grid interface load recovery
• Grid Stress analysis
• Radiator Mount Bracket analysis
Document: LAT-PR-01967
Section 13 Mechanical Systems
34
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
CAL Interface Load Recovery
• CAL-Grid joint
– 1152 connections (72 per CAL module)
– CAL plate stiffens LAT by closing out bottom side of Grid
• Load recovery
– Interface loads are backed out from the FEA model by
resolving nodal forces at the interface into shear (X & Y)
loads at the pin locations and Z loads at bolt locations
– EM pinned joint tests validated manufacturability but
Capacity req’d at
insufficient load capacity
highest loaded tab
Demonstrated
Best We
with 1.25 factor
Load Capacity
Can Do*
Grid Wall
750 lb
Cal Plate Tab
750
925 lb
1300
1460-2010 lb
1460-2010
* Includes 0.160 close fit pin in grid wall and CAL plate tab and
material properties of 2618A for CAL plate
Document: LAT-PR-01967
Section 13 Mechanical Systems
35
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Stress Analysis
• Grid stress analysis indicates positive margins of safety for all
regions
– Nominal maximum Von Mises stress is order of magnitude
below yield for material
– Large corner radii in the actual design, not included in the
model, limit stress risers
– Top flange in model has a weighted-average cross section
which is no more than twice the minimum cross sectional area
• Highest stresses occur in transition regions around SC mount
• Grid material properties
– Material: 6061-T6 aluminum (6061-T651, stress-relieved, then
heat-treated during fabrication)
– Sy = 240 MPa (35 ksi)
– Su = 290 MPa (42 ksi)
• Factors of safety (per NASA-STD-5001)
– Metallic structures
• Yield: FSy = 1.25
• Ultimate: FSu = 1.4
Document: LAT-PR-01967
Section 13 Mechanical Systems
36
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Mount Bracket Analysis
Design Loads and critical load cases
•
Loads defined in Environmental Spec
– FS=1.25 (PFQ) used for launch loads
– FS=1.40 used for lift case
• Assume Observatory lift load is carried in 2 of 4 fittings
•
Critical Load Cases Study results
CASE
X [N]
Y [N]
Z [N]
+X/-Z
994
0
-1670
-X/-Z
-994
0
-1670
+Y/-Z
0
333
-1670
-Y/-Z
0
-333
-1670
LIFT
0
0
32400
–
–
–
–
Lift case induces the highest stresses
Margins of safety are good for all design cases
Calculated stiffness is high, which is conservative for loads
determination
The radiator attachment bracket meets or exceeds all design
requirements
Document: LAT-PR-01967
Section 13 Mechanical Systems
37
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Summary
• Summary
– Integrated LAT structural analysis results of the staticequivalent load cases indicate that LAT deflections and
stresses are within required limits
– Grid stress analysis shows that the Grid design is not
highly-stressed, but driven more by the natural frequency
requirement
Document: LAT-PR-01967
Section 13 Mechanical Systems
38
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review May 12-16, 2003
Verification Program
Grid Box Assembly
Section 13.4
Document: LAT-PR-01967
Section 13 Mechanical Systems
39
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Assembly Verification
Topics
• EM Tests
• Qualification & Flight Test Overview
• Mechanical Systems Verification Test Flow
• Mechanical Systems Verification Matrix
Document: LAT-PR-01967
Section 13 Mechanical Systems
40
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
EM Test Plans Overview
• EM test plans developed for:
– CAL-Grid Joint Testing (complete)
• Friction characterization
• Bolt-Helicoil pair characterization
• Bolted Pull tab coupons
• Pinned Pull tab coupons
– 1x4 Grid
– Grid heat pipe bonding process qualification
– Thermal Joint candidates (complete)
• “Wet” adhesive or gasket
• Low contact pressure
• No contact pressure
– X-LAT heat pipe characterization (complete)
Document: LAT-PR-01967
Section 13 Mechanical Systems
41
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
1 x 4 Grid Planned Tests
• Purpose: Validate finite element model used for LAT
predictions to date
– Model created from full up model
– Full scale CAL-Grid interactions
• Test Set up: 1 x 4 Grid design is flight like
– Partial bays with partial CAL plates provide
interleaving CAL tabs
– Load hydraulically applied 6 places
– Reacted out at corners
– Deflections measured along length
– Record load vs deflection
1 x 4 Grid
Document: LAT-PR-01967
Section 13 Mechanical Systems
42
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Planned Process Tests
1 x 4 Grid unit fabrication
• Objectives
– Demonstrate Grid manufacturability
– Demonstrate purge gas system
– Provide unit to I&T group for I&T EM testing
• Risks mitigated or retired
– Fabrication errors, process problems (cost & schedule impact)
Document: LAT-PR-01967
Section 13 Mechanical Systems
43
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
3-Way Heatpipe Thermal Joint Conductance Test
3-Way heatpipe thermal joint conductance test
• Objectives
– Determine thermal joint that can meet conductance and
ease of assembly requirement
– Develop design-specific empirical conductance values for
actual bolted joint configuration
• Results
– Conductance values agree with published data
– Nusil CV2946 is difficult to work with
– Single 3 way joint assembled
• Risks mitigated
– Validates thermal model based on empirical thermal
conduction values
Document: LAT-PR-01967
Section 13 Mechanical Systems
44
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Thermal Joint Further Work
• Demonstrate Radiator installation process
– 6 wet RTV joints in vertical orientation & restricted access
– Complete within pot life limits (bonded & torqued)
– Verify bond line integrity (uniform thickness & % voids)
• Demonstrate Radiator removal process
– Separate 6 joints with restricted access
– No damage or distortions of heat pipes
– Verify material can be cleaned up & surface prepared again
for another bond
Document: LAT-PR-01967
Section 13 Mechanical Systems
45
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT to E-box Thermal Joint Candidates Tested
• “Wet” adhesive or gasket joints
– Thermally conductive silicone adhesive, Nusil CV2946
– SilPad, VO Gap Pad
• Low contact pressure joints
– Off-the-shelf EMI gasket products, i.e. BeCu spring fingers,
electrically conductive elastomers
– Graphite velvet pad (Vel-Therm from ESLI or Vel-Met)
• No contact pressure joints
– High conductivity materials mechanically fastened at both
ends
– Formed Copper sheets (30 mils)
– Pyrolytic Graphite Sheet (4 mils thick stock)
• Conductance vs. various gaps and/or pressures examined
Document: LAT-PR-01967
Section 13 Mechanical Systems
46
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Thermal Joints EM Evaluation Summary
•
•
Vel-Therm material is best candidate among those evaluated to meet
all design drivers
– Thermal data indicate material can meet required conductance
– Material is bonded to one surface prior to installing X-LAT plate,
minimal fasteners required
– Allow sliding contact for lateral flexibility
– .125” thick material can fill gap of .05 to .10”
Vel-Therm Cycle
Quantify contact pressure versus brush compression
20.00
18.00
16.00
14.00
Force (Lbs)
12.00
10.00
Compr
8.00
6.00
4.00
2.00
0.00
0.00
Document: LAT-PR-01967
0.01
0.02
0.03
0.04
Displacement(Inches)
0.05
0.06
Section 13 Mechanical Systems
0.07
47
0.08
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Planned Work
• Additional Vel-Therm coupon tests
– Conductance in high vacuum vs. contact pressure
• Additional thermal joint configuration tests
– Mock up box stackup configuration with heaters on
sidewalls to simulate electronics heat source
– Flight like installation procedure for Vel-Therm to identify
process problems and errors
– Perform Random Vibe and Thermal Vacuum tests to retire
risks associated with contamination, thermal conductance
at min & max fiber compression levels
Document: LAT-PR-01967
Section 13 Mechanical Systems
48
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT EM Heat Pipe Characterization Tests
• Objectives
– Verify thermal performance of EM X-LAT heat pipe in
simulated on-orbit thermal cases
• Key Result
– Alternate Heat Pipe condensers at each end were cycled on
and off without Heat Pipe dry out.
– Heat pipe was not sensitive to small tilt angles at the
thermal loads applied
• Risks mitigated
– Demonstrate adequate design margins
– Assure that heat pipe performs as predicted
Document: LAT-PR-01967
Section 13 Mechanical Systems
49
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Mechanical Systems
Verification Test Flow
Grid Structure
-Proof Load
-Mass Properties &
C.G.
-Dimension Check
Radiator Mount
Bracket
X-LAT Plates
-Static Load Test
-Mass Properties & C.G.
-Dimension Check
-Thermal Vacuum Test
Grid Box
Base Assembly
Disassemble
Grid Box
Base Assembly
Grid Box
Assembly
-Static Load
-Thermal Cycle
-Mass Properties
& C.G.
-Dimension
Check
-Alignment
-Functional
-Static Load
Grid Assembly
LAT Integration
X-LAT Plates
Mid-Plate
X-LAT Plates
-Static Load Test
-Mass Properties & C.G.
-Dimension Check
Radiator
-Sine Sweep
-Acoustic
-Mass Properties & C.G.
-Dimension Check
-Interface Verification
-EMI/EMC
-Functional
Document: LAT-PR-01967
Assemble Radiator
pair test configuration
Radiators
LAT Level
Verification Tests
-Thermal Balance
-Mass Properties & C.G.
-Dimension Check
Section 13 Mechanical Systems
50
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Mechanical Subsystem Verification Matrix
1
1
P
P
TQ
P
P
4
TQ
TA
TA
P
TQ
TQ
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
I
I
TA
TA
Non-Condensible Gas(NCG)
Comments
Validates HP bonding process
EM testing of CAL-Grid joint
Validates Grid fab processes
Qual's HP thermal joint design
Proofs tapped holes
TA TA HP's qual'd by similarity
TA TA HP's qual'd by similarity
TQ
T
Heat Transport
Thermal Cycle
1
Thermal Balance
2
1
Thermal Vacuum
Thermal Control System
Controller Unit
Radiator Pair w/ TCS
Functional
C PF Q
S PF Q
ESD (Grounding)
1
EMI/EMC
12
2
Interface Verif
Radiator Assemblies
Radiator VC Heat Pipes
Radiator Ass'y (individual)
M
I
I
Alignment
C PF A
A PF Q
T
T
T
Fit / Dim Chk
1
6
1
2
1
Electrical Environmental
Mass, C.G.
X-LAT Thermal Plate/Mid-Plate
X-LAT Heat Pipe EM
X-LAT Heat Pipes
X-LAT Thermal Plate Qual Unit
X-LAT Thermal Plate
Mid-Plate
Pressure
Q
A
Q
A
Q
Mech shock
E
F
PF
F
PF
Acoustic
A
C
A
A
A
Random Vibe
1
3
1
3
1
5
12
1
1
Sine Sweep
Grid Assembly
Grid Top Flange Heat Pipe Bond.
CAL-Grid Joint Shear Test
Grid Mock-up -1 x 4
Heat Pipe Thermal Interface Test
Grid Structure
Top Flange Heat Pipe
Down Spout Heat Pipe
Grid Box Base Assembly
Grid Box Assembly
Static Load
Q
Q
Q
Q
Q
A
A
Q
Q
Proof Test
E
E
E
E
PF
F
F
PF
PF
Component
Flight Spares
Qualification Level
A
A
C
A
C
C
C
A
A
Quantity
Unit Type
Mechanical
Assembly Level
Hardware
TQ
Thermal cycle w/ STE heaters
TQ
TQ TQ
I
TA
TQ
TA
TA TA HP's qual'd by similarity
Qual's X-LAT thermally, struc
TA TA Gas test to be used in lieu of NCG
I
TQ
TQ TQ
TQ
TQ TQ
TQ TQ TQ
Part of SIU qual
LEGEND
Assembly Level
S – Subsystem
A- Assembly
C – Component
Unit Type
PF – Proto Flight
F – Flight
S – Spare
Document: LAT-PR-01967
Q – Qual
E – Engineering Model
V – Verification Model
Verification Method
T – Test
TQ – Test, Qualification Level
A –Analysis
TA – Test, Acceptance Level
M – Measurement
P – Proof
I – Inspection
Section 13 Mechanical Systems
51
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
4 x 4 Grid Structure Verification
Mass Properties
& C.G. Verified
Document: LAT-PR-01967
Dimension
Check Verified
Proof Test
of Inserts
Section 13 Mechanical Systems
52
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Assembly Verification
Grid Box
Assembly
Dimension
Check
Grid Box
Assembly
Functional
Test
Document: LAT-PR-01967
Grid Box
Assembly
Mass
Properties/C.
G.
Grid Box
Assembly
Thermal Cycle
Grid Box
Assembly
Alignment
Check
Grid Box
Assembly
Functional
Test
Grid Box
Assembly
Functional
Test
Grid Box
Assembly
Static Load
Test
Section 13 Mechanical Systems
53
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Static Load Test
•
•
Test Objectives
– Primary Objective: Verify static strength and stability of the Grid
Box Assembly under worst case Delta II-H vehicle loads of 1.25
times limit loads
• Achieve maximum stresses in grid box assembly
• Load subsystem interfaces to qualification design loads
– Secondary Objective: Verify the design analysis process by
comparing measured strains and deflections to predictions from
the finite element analysis model
Test Success Criteria
– Successful test completion is when all load cases have been
performed and it is verified that no yielding, buckling, de-bonding,
or fractures have been observed.
• A visual inspection is to be performed after each load case to
check the critical joints and bonded interfaces
• A review of all pertinent data during test including deflections
and strains to verify linearity
Document: LAT-PR-01967
Section 13 Mechanical Systems
54
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Static Load Test Configuration
•
•
The test configuration consists of all primary structure grid box
components as described below
The test article will be grounded at the SC Mount Brackets with
correct degrees of freedom
Grid - Flight
Radiator Mount
Brackets - 4X Flight
EMI Skirts - Flight
Calorimeter
Plates -16X Flight-like
Down spout
HPs - 12X - Flight
Spacecraft Mount
Brackets - 4X - Flight
XLAT Plate - Flight
Document: LAT-PR-01967
Section 13 Mechanical Systems
55
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review May 12-16, 2003
Fabrication Process
Grid Box Assembly
Section 13.5
Document: LAT-PR-01967
Section 13 Mechanical Systems
56
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Assembly Overview
Grid Assy
Grid
Grid Box Base
Assy
Grid Box Assy
Ready for Test
Radiator Mount
Bracket
EMI Skirt Details
Heat Pipe Patch
Panels
X-LAT Plates
Heat Pipes
Purge Groove
Cover
CAL Plates
(Temporary)
Legend
Accepted Hardware
Test activity
Assembly activity
Document: LAT-PR-01967
Grid Box Assembly
Configuration
Section 13 Mechanical Systems
57
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Machining Assembly
• “Grid Box Machining” is a temporary assembly for machining:
– EMI shields coplanar for X-LAT plate mounting
– Each pair of Radiator Mounting Brackets coplanar
– Control relative positions of Radiator & X-LAT locating pins
to Grid datum’s so 3 sets of heat pipes will mate properly
•
•
•
•
•
•
Install the EMI Skirt components on Grid
Machine bottom edges of the EMI Skirt
components co-planer
Machine X-LAT locating pin holes and
fastener holes in the EMI Skirt
components
Machine mounting features & locating
pins holes in Radiator Mounting Brackets
Install locating pins and Helicoils
Mark parts for specific location on Grid
X-LAT Pins
Radiator Pins
Document: LAT-PR-01967
Section 13 Mechanical Systems
58
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review May 12-16, 2003
Design, Analysis & Fabrication
Radiator and X-LAT Assemblies
Section 13.6
Brenda Costanzo
Lockheed Martin
Systems Engineer
brenda.costanzo@lmco.com
Program Manager: Susan Morrison
E-Mail: susan.morrison@lmco.com
Document: LAT-PR-01967
Section 13 Mechanical Systems
59
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Responsibility Overview
• Lockheed Martin hardware responsibilities:
– Design, fabrication, and test of the Top Flange Heat Pipes
– Design, fabrication, and test of the Downspout Heat Pipes
– Design, fabrication, and test of the Radiator Assembly
– Design, fabrication, and test of the X-LAT Assembly
• Additional Lockheed Martin responsibilities:
– Thermal analysis for the LAT instrument (covered
separately)
– LAT thermal systems engineering consultation
Document: LAT-PR-01967
Section 13 Mechanical Systems
60
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Requirements Basis
• Radiator requirements based on:
– Radiator Level IV Design Specification,
• LAT-SS-00394-1-D6, draft
• Dated 5 Mar 2003
– LAT Mechanical Systems Interface Definition Drawing, RadiatorLAT Interface
• LAT-DS-01221, draft
• Dated 25 Feb 2003
• X-LAT requirements based on:
– X-LAT Plate Performance Specification
• LAT-TD-01240-D3, draft
• Dated 19 March 2003
– X-LAT Plate Assy Source Control Drawing
• LAT-DS-01247, draft
• Dated 7 March 2003
– Mid-Plate Assy Source Control Drawing
• LAT-DS-01257, draft
• Dated 7 March 2003
Document: LAT-PR-01967
Section 13 Mechanical Systems
61
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Hardware Overview (HPs)
• Top Flange Heat Pipes (TFHP)
– Five constant conductance pipes
– Mounted in the +Z surface of the grid
– Isothermalize grid
– Move energy to DSHP’s
• Down Spout Heat Pipes (DSHP)
– Twelve (6 +Y, 6 –Y) constant conductance pipes
– Mounted to the +Y and –Y sides of the grid
– Move energy from the TFHP’s to the radiator heat pipes
Document: LAT-PR-01967
Section 13 Mechanical Systems
62
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Heat Pipe Sizing
• All worst case pipe requirements derived from detailed thermal
model hot case with the following assumptions and results
Heat Pipe
Pipe
Failure
Condition
Maximum
Power, W
Transport
Required
@ 10 C
Transport
Margin
Top Flange
1 of 5
252 W
9.2 W-m
>1.3
Downspout
1 of 12
252 W
7.6 W-m
>1.3
1 of 6
359.9 W
59.5 W-m
>1.3
X-LAT
VCHP
Document: LAT-PR-01967
1 of 12
612 W with
Max Env 113.9 W-m
Load
>1.3
Section 13 Mechanical Systems
63
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Heat Pipe Structural Analysis
•
•
•
Top Flange and Downspout Heat Pipes external loads insignificant
relative to internal loads due to mounting configuration
X-LAT Heat Pipe analysis will be performed once LAT loads are received
VC Heat Pipe preliminary analysis covering reservoir and transition
complete with the following assumptions and results:
– MEOP of 377 PSI (140ºF)**(requirements changed to 490 PSI)
– MPP of 882 PSI (210 ºF)
– Acceleration loads of 35 G’s replace external flight loads
Location
Loading Condition
Yield
Ultimate
FOS
M.S.
FOS
M.S.
Reservoir – Inertia Weld
MEOP
1.5
3.5
4.0
1.0
Reservoir – Inertia Weld
MPP
1.1
1.6
1.25
1.7
Transition Tube – Orbital Weld
MEOP
1.5
6.7
4.0
6.2
Transition Tube – Orbital Weld
MPP
1.1
3.8
1.25
9.5
Transition Tube – Inertia Weld
MEOP
1.5
7.0
4.0
6.5
Transition Tube – Inertia Weld
MPP
1.1
3.7
1.25
9.3
Transition Tube – Inertia Weld
MEOP + Acceleration
1.6
3.6
2.0
8.2
Document: LAT-PR-01967
Section 13 Mechanical Systems
64
•
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Hardware Overview (Radiators)
Two radiator panels
– Honeycomb core with Aluminum
facesheets
– Six Variable Conductance Heat
Pipes (VCHPs) embedded in each
panel
– FOSR radiating surface
– MLI on non-radiating surfaces
– Maintains LAT temperatures
– Structural interfaces at the LAT grid
and S/C
– Thermal interface between Radiator
VCHPs, X-LAT CCHPs, and
Heat Pipe
downspout CCHPs
Interface
(6 pl/Rad)
+Z
+Y
+X
Radiator
Panels
Document: LAT-PR-01967
Section 13 Mechanical Systems
65
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Panel, Exploded
Outer Facesheet
VCHPs
Doublers
Honeycomb
Core
1.56 m
Inner
Facesheet
Z
X
Y
Reservoir Support Bar
1.82 m
Document: LAT-PR-01967
Section 13 Mechanical Systems
66
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Structural Performance Summary
•
•
•
Preliminary analysis indicates the revised Acoustic spectrum produce
smaller loads than the assumed dynamic load factor of 30g
Positive stress margins obtained for sandwich panel, bolts, inserts and
heat pipes
Frequency requirement, >50 Hz, satisfied. Design frequency 61.6 Hz
No Shear
Deformation
Mode
No.
1
2
3
4
5
Frequency
(HZ)
62.4
70.5
93.6
118.9
125.6
Including
Shear
Deformation
Frequency
(HZ)
61.6
66.8
92.0
112.8
118.1
Mode Shape
1st YZ Bending Mode
1st XZ Bending Mode
1st Twisting Mode
2nd YZ Bending Mode
2nd Twisting Mode
Normal Mode 1, f1 = 61.6 Hz,
Radiator First Five Natural Frequencies
Document: LAT-PR-01967
1st YZ Bending Mode
Section 13 Mechanical Systems
67
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Stress Analysis Detailed Results
Face Sheet Margins
•
•
Facesheet stress analysis indicates positive margins of safety for all highstress regions
Facesheet material properties
–
–
–
Material: 6061-T6 aluminum (Top: 0.060” thk, Btm: 0.030” thk)
Ftu = 296 MPa (43 ksi)
Fty = 255 MPa (37 ksi)
Panel Location
Elem
Location
Near Brackt (HDC)
711
At Brackt (Dblrs)
709
FWD Cut-out region
315
At Tie-Down
4660
Aft Sq. hole
4915
S/A hole region
4638
Edge, Resvr_Cut_out
5946
Sxx
( Pa)
(ksi)
34.49
5.00
22.69
3.29
26.62
3.86
19.99
2.90
14.53
2.11
19.57
2.84
14.36
2.08
Syy
( Pa)
(ksi)
17.69
2.57
17.54
2.54
2.13
0.31
24.52
3.56
28.45
4.13
-0.32
-0.05
1.18
0.17
Sxy
( Pa)
(ksi)
7.07
1.03
6.10
0.89
3.78
0.55
0.33
0.05
0.08
0.01
0.29
0.04
2.55
0.37
Failure
MSu
MSy
Seff
( Pa) (FS=1.25) (FS=1.4) Mode
(ksi)
Tension
5.1
4.9
32.29
4.68
Tension
8.1
7.8
23.16
3.36
Tension
7.0
6.7
26.45
3.84
Tension
7.6
7.3
22.60
3.28
Tension
6.4
6.2
24.64
3.57
Tension
9.7
9.3
19.73
2.86
Tension
13.6
13.1
14.49
2.10
Facesheet Stresses and Margins of Safety
Document: LAT-PR-01967
MSy = Fty/(1.25 si) –1
MSu = Ftu/(1.4 si) –1
Section 13 Mechanical Systems
68
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Stress Analysis Detailed Results
Core Shear Margins
•
Core shear stress analysis indicates positive margins of safety for all highstress regions
–
Basic Core Material: 5000 series aluminum
•
•
–
Fsu12 = 35 kPa (5 psi)
Fsu13 = 1379 kPa (200 psi) Ribbon Dir; Fsu23 = 758 kPa (110 psi)
Hi_Den Core Material: 5000 series aluminum, density is ~2*basic core density
•
•
Fsu12 = 69 kPa (10 psi)
Fsu13 = 3.62 MPa (525 psi) Ribbon Dir; Fsu23 = 2.10 MPa (305 psi)
Panel Location
FWD Supprt
HD + Doublrs
FWD End Cut-outs
LD
FWD Sq. hole Edge
LD
AFT Sq. hole Edge
LD
AFT Circ. hole Edge
LD
at Tie-Down
HD + Doublr
Res_Cut_Edge
LD
Elem
Location
709
315
1825
4753
4634
4660
6145
Sxz
(k Pa)
(psi)
1094.0
158.7
340.2
49.3
246.2
35.7
409.1
59.3
126.5
18.3
804.0
116.6
171.5
24.9
Syz
(k Pa)
(psi)
1293.5
187.6
260.4
37.8
148.2
21.5
68.4
9.9
17.1
2.5
794.9
115.3
91.2
13.2
MSu
(1.4)
Failure Mode
0.02
Core Shear (Qx, Qy)
0.32
Core Shear (Qx, Qy)
0.88
Core Shear (Qx, Qy)
0.19
Core Shear (Qx, Qy)
2.84
Core Shear (Qx, Qy)
0.46
Core Shear (Qx, Qy)
1.73
Core Shear (Qx, Qy)
LD = Basic core material
HD = High density core
material
Bi-axial quadratic failure criterion:
MSu = 1/SQRT((Fs.tyz/(Ks*Fsu13))2
+ (Fs.txz/(Ks*Fsu23))2) -1
Where: Ks=0.9
Core Stresses and Margins of Safety
Document: LAT-PR-01967
Section 13 Mechanical Systems
69
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Stress Analysis Detailed Results
Heat Pipe Margins
•
•
Heat pipe stress analysis indicates positive margins of safety for all
stressed regions
Heat pipe material properties
– Material: 6063-T6 aluminum
– Ftu = 241 MPa (35 ksi); Fty = 214 MPa (31 ksi)
Panel Location
H-Pipe at bolted suppt
Single flanged
H Pipes S-Shape
Bent, Round
H Pipes (no flange),
junction of panel
H Pipes in Panel
Single Flange
Extension @ Resrvr
304 CRES Tube
Extension Aluminum
Round
Elem
Loc
6805
6810
6820
6967
6877
6875
Axial
(N)
(lb)
-32.4
-7.3
54.2
12.2
-44.4
-10.0
-418.4
-94.1
18.1
4.1
-43.9
-9.9
Mz
(N-m)
(in-lb)
-1.9
-17.1
-3.6
-31.6
2.1
18.9
-2.9
-25.4
0.5
4.8
-0.1
-1.2
My
(N-m)
(in-lb)
-0.2
-1.4
-0.2
-1.7
0.0
-0.2
0.4
3.7
-0.1
-0.7
0.0
0.1
Tq
(N-m)
(in-lb)
0.0
0.0
-0.2
-1.5
0.4
3.8
0.2
2.2
0.5
4.5
-0.1
-0.5
Sx(pi)
s
t
MSy
(N)
( Pa) ( Pa) (1.25)
(ksi)
(ksi)
(ksi)
2.4
6.0
0.1
13.6
0.4
0.9
0.0
2.4
29.4
1.1
3.9
0.4
4.3
0.2
2.4
17.1
2.2
6.5
0.4
2.5
0.3
2.4
11.7
0.5
9.0
0.4
1.7
0.1
9.3
9.3
4.4
4.0
1.4
1.3
0.6
3.5
2.6
0.3
14.1
0.5
0.4
0.0
Heat Pipe Stresses and Margins of Safety
(includes 170 psi int. pressure)
Document: LAT-PR-01967
MSu
(1.4)
13.8
4.0
6.6
9.1
10.2
14.2
MSy = Fty/(1.25 si) –1
MSu = Ftu/(1.4 si) –1
Section 13 Mechanical Systems
70
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Stress Analysis Detailed Results
Bolt/Insert Margins
•
•
Bolt and insert analysis indicates positive margins of safety
Bolt material properties
–
–
–
•
Material: CRSS A-286 stainless steel
Ftu = 1.103 GPa (160 ksi); Fty = 0.827 GPa (120 ksi)
Fsu = 0.655 GPa (95 ksi)
Insert ultimate strengths (Estimated from existing tests. GLAST specific tests
to be performed)
–
5/16”-24 UNF insert
•
•
–
Pull-out = 6.47 kN (1454 lb)
Shear = 7.16 kN (1610 lb)
10-32 UNF insert
•
•
Pull-out = 3.56 kN (800 lb)
Shear = 4.79 kN (1077 lb)
Bolt Loads
Location
Brackets
4 bolts
Tie-Down
4 bolts
Bolt
Size
Dia PreLoad
(mm)
(kN)
(in)
(lb)
7.94
15.1
5/16"-24 0.3125
3400.0
4.83
5.1
No. 10-32 0.190
1151.3
Axial Shear
(kN)
(kN)
(lb)
(lb)
3.9
0.9
873.9 213.6
0.8
0.4
184.7
80.0
Bolt Margins*
MSu
MSy
(1.4)
(1.25)
(1.4)
(1.4)
1.28
0.91
0.03
3.68
0.53
0.29
1.69
8.36
* Note: Factor of safety on Ultimate = 1.4, Yield = 1.25, Fittng factor = 1.15
Bolt and Insert Stresses and Margins of Safety
Document: LAT-PR-01967
Insert Margins*
Tension Shear
MSy = Fty/(1.25 si) –1
MSu = Ftu/(1.4 si) –1
Section 13 Mechanical Systems
71
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Thermal Performance Summary
•
•
* Value pending
Document: LAT-PR-01967
Hot RIT Temperatures
12
+Y Radiator
-Y Radiator
10
Temperature, °C
•
LAT input powers
– Qmax = 602 W (615 W analyzed)
– Qmin = 475 W (495 W analyzed)
Requirement: Tmax RIT <15 °C
Qavg Reservoir < 48 W
– Predictions
• Tmax RIT = 10 °C
• T maxRIT = 14 °C, 1 HP failed
• Qavg Reservoir = 0 W
Requirement: Tmin RIT >-10 °C
Qavg Reservoir < 48 W
– Predictions
• Tmin RIT = -5 °C
• Qavg Reservoir = 13 W
Requirement: Tmin RIT >-20 °C, Survival
Qavg Reservoir < 58 W *
– Predictions
• Tmin RIT = -20 °C
• Qavg Reservoir = 42 W
8
6
4
2
0
0
50
100
150
200
250
300
350
400
450
500
450
500
Time over 5 orbits, minutes
RIT Cold Temperatures over 5 Orbits
0
0
50
100
150
200
250
300
350
-0.5
-1
Cold RIT Temperatures
Temperature, C
•
-1.5
-2
-2.5
-3
-3.5
-4
-4.5
Time over 5 orbits, min
Section 13 Mechanical Systems
72
400
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Requirement Compliance (1 of 2)
• Key requirements not formally defined or compliance is in question
Parameter
Requirement
Design
Margin
Comply
Ver.
Method
86 kg
80.9 kg
5.1 kg
(5.9%)
Y (Low
Margin)
I
>720 mm from
datum*
±2 mm beyond
static envelope*
730 mm from
datum
± 1.5 mm
(Launch Loads)
10 mm
Y
I
0.5 mm
(FS=1)
Y
A, T
Mass
Center of Gravity, Zdirection
Dynamic Envelope
Radiator Panel Dimension
Per ICD
(Static Envelope)
EMI Testing
Verification by test
2A18037 &
2A18038
Verification at
higher level
Locally
TBD,
exceeded working ICD
N/A
TBD
I
TBD
* Specification Change Pending
Document: LAT-PR-01967
Section 13 Mechanical Systems
73
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Requirement Compliance (2 of 2)
•
Key requirements not formally defined or compliance is in question
Parameter
Reservoir Peak Power,
Normal Mode
Reservoir Avg Power,
Normal Mode
Reservoir Power,
Survival Mode
(Reservoirs are
powered continuously)
Anti-Freeze Peak
Power, Survival Mode
Anti-Freeze Average
Power, Survival Mode
Margin, Anti-Freeze
Sizing, Survival Mode,
Cold
Requirement
Design
Margin
Comply
Ver.
Method
58 W *
48 W (29 V)
10 W
Y
A, T
35 W *
0 W/13 W
Y
A, T
58 W *
42 W (27 V)
48 W (29 V)
22 W
(>169%)
16 W
10 W
Y
A, T
320 W *
227 W (35V)
93 W
Y
A, T
125 W *
89 W
36 W
Y
A, T
>30% margin on
power
40%
10%
Y*
A, T
* Specification Change Pending
Document: LAT-PR-01967
Section 13 Mechanical Systems
74
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Compliance Mitigation Plans (1 of 2)
•
Mass
– Primary mitigation step is for SLAC to increase the radiator mass
allotment if necessary
– If mass allotment is exceeded, can reduce thickness of
honeycomb core
• Impact to structural design margin
•
CG in Z-direction
– Expected mitigation is to change requirement to CG located no
less than 720 mm from datum
– If requirement change is not incorporated, can add weights to –Z
edge of radiator panel
• Impact to structural design margin
• Impact to mass
•
Dynamic envelope
– Expected mitigation is to change requirement of dynamic
envelope to +2 mm beyond static envelope.
– If change is not incorporated, can reduce thickness of honeycomb
core
• Impact to structural design margin
Document: LAT-PR-01967
Section 13 Mechanical Systems
75
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Compliance Mitigation Plans (2 of 2)
•
Static envelope
– Currently working with SLAC to increase localized static envelope
– If envelope can not be increased, can do all or some of the
following:
• Reduce thickness of honeycomb core
– Impact to structural design margin
• Remove MLI from back side of VCHP reservoirs
– Impact to heater power
– Impact to VCHP performance
• Remove option of repinching VCHPs (1 pinch per fill tube)
– Increase cost risk
•
Power allocations
– Expected mitigation is to impose requirements that bound current
design case (see compliance tables).
– If power can not be allocated, can do all or some of the following
• Decrease radiator size
– Impact to hot case LAT temperatures
Document: LAT-PR-01967
Section 13 Mechanical Systems
76
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Fabrication (1 of 2)
Obtain
Facesheet
Material
Shear
Obtain Remaining
Flight Materials
Bond Pipes
To OB
Facesheet
N/C Machine
Log Flight
Materials
Inspect
Thermal Bond
Visual
Process
Samples
To Lab
CMM Inspect
Geometry
Inspect
Doublers
Document: LAT-PR-01967
Bond OB
Doublers
AC Cure
Inspect
Purchasing
Clean, Etch
& Prime
Inspection/Test
Manufacturing
Inspect
Verify Flight
Materials
Fit Check
Core
Inspect
Holes w/
Pins
Verify Cure
Profile
Assemble
Panel and
Bond
Verify Cure
Profile
Prep and
Install Inserts
& Spools
Bond Top
Edge Closure
Inspect
Inserts &
Spools
Machine
Transfer
Datums
Bond IB
Doublers
RT Cure
A
Section 13 Mechanical Systems
77
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Fabrication (2 of 2)
A
Bond
Reservoir
Supports
Install
Reservoir
Bushings
Fit Check
Reservoir
Bushings
Inspect
Reservoir
Supports
Inspect
Bushings
Apply Blanket
Velcro
Machine
Bushings
Apply Edge
Closure Tape
Apply
Thermal
Blanket
Inspect
Bushings
Structural
Testing
Final Cosmetic
Damage
Map
Thermal
Testing
Notes
1) All panel moves require: inspection documentation of panel for damage; packaging for
transport; and flight approved move procedures.
2) No outside storage.
3) Qualified flight transportation personnel and equipment.
Document: LAT-PR-01967
Section 13 Mechanical Systems
78
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Hardware Overview (X-LAT Assy)
•
X-LAT Assembly
– Two X-LAT plate assemblies
• 3.2 mm (1/8”) solid
Aluminum plate
• Three Constant
Conductance Heat Pipes
(CCHPs) per plate
– One mid-plate
• 4.8 mm (3/16”) solid
Aluminum plate
– Moves heat from electronics
to radiators
– Load shares between
radiator panels
Heat Pipe
Interface
(6 pl/Side)
Document: LAT-PR-01967
+Z
X-LAT
Assembly
Section 13 Mechanical Systems
79
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Design
•
•
•
CCHPs are bonded and riveted to X-LAT plates
X-LAT plates are interchangeable
Material is 0.125” 6061 Aluminum
X-LAT Plate Assy (2x)
CCHP
(3 pl)
Mid- Plate (1x)
Push-Pull Bolt
Interface Hole
(12 pl, TBR)
Push-Pull Bolt
Interface Hole
(24 pl, TBR)
X-LAT Plate
Interface to Mid-Plate
Interface To X-LAT
Plate (both sides)
Radiator Bracket
Alignment Pin
Hole
Document: LAT-PR-01967
Section 13 Mechanical Systems
80
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Structural Performance Summary
•
•
•
•
Model was simply supported at the edges,
and constrained in the Z direction only at
each of the spacer locations
Frequency Requirement, > 50 Hz
– Analysis: First mode = 97.7 hz
Loads
– Highest load on plate is random
vibration
– Calculate 3s random vibration load
factor in g using Miles’ equation =>
3*sqrt((p/2)*PSD*Q*f)), where:
• PSD at first resonant frequency is
0.08 g**2/Hz (source – LAT-TD01240)
• Q = 50 (1% damping)
• F = 97.7 Hz
Load cases run
– 74.4 g acceleration normal to plate
– 74.4 g g lateral in plane of plate
Load Case
Stress
(KSI)
Yield
Safety
Margin
Ultimate
Safety
Margin
1: 74.4 g
Normal Load
11.2
+1.92
+1.68
2: 74.4 g InPlane Load
.32
+101.
+93.
Stress for 74.4 g normal load
Document: LAT-PR-01967
Section 13 Mechanical Systems
81
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Thermal Performance Summary
17.3 °C
EPU
17.3
°C
EPU
PDU
20.3 °C
20.4 °C
Comb
22.6 °C
20.3 °C
24.2 °C
GASU
22.3 °C
21.3 °C
Comb
•
17.3 °C
Comb
•
Qmax = 359.9 W
Qmin = 286.2 W
Requirement: Tmax <35 °C
– Predictions
• Tmax = 24.2 °C
Requirement: Tmin >-10 °C
Qavg Reservoir < 48 W
– Predictions
• Tmin RIT = -5 °C
Note: Not identified are the
16 TEM/TPS stacks
Comb
•
•
•
19.4 °C
EPU
SIU
SIU
20.1 °C
Y
X
Document: LAT-PR-01967
Section 13 Mechanical Systems
82
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Requirement Compliance
• The following table addresses key requirements that are not
yet defined
Parameter
Requirement
Design
Margin
Comply
Ver.
Method
Operational Temperature
Limits
-20 C to +35 C
(TBR)
-5 C to +24.2 C
15/10.8 C
Y, TBR
A, T
Electronics Power Input
Per Spec, (TBR)
Per 2A15712 and
2A15716
N/A
N/A
N/A
TBD
TBD
TBD
Per 2A15712 and
2A15716
TBD
TBD
TBD
TBD
pending
payload
analysis
A, T
A,T
Dynamic Envelope
LAT Input Loads
Document: LAT-PR-01967
Section 13 Mechanical Systems
83
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Compliance Mitigation Plans
• Must define/finalize requirements and determine whether there’s a
non-compliance. If there is, the following plan will be activated:
– Temperature Limits and Electronics Power Values
• Increase conduction from the X-LAT to the warm electronic(s)
• If there is still a problem, increase the thickness of the X-LAT
panel(s)
– Impact on structural and mass margins
– Envelope
• Increase dynamic envelope to accommodate dynamic motion
• If dynamic envelope can not be changed, increase panel
thicknesses
– Impact on thermal, structural, and mass margins
– Loads
• Adjust panel thicknesses
– Impact on thermal, structural, and mass margins
Document: LAT-PR-01967
Section 13 Mechanical Systems
84
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
CDR/CD-3 Review May 12-16, 2003
Verification
Radiator and X-LAT Assemblies
Section 13.7
Brenda Costanzo
Lockheed Martin
Systems Engineer
brenda.costanzo@lmco.com
Program Manager: Susan Morrison
E-Mail: susan.morrison@lmco.com
Document: LAT-PR-01967
Section 13 Mechanical Systems
85
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator and X-LAT Verification
• Test plan is document GLS0002-03
• All testing will have procedures written prior to commencement
• Inspection occurs throughout the testing at points specified in the
procedure
• Flash reports will be written within 3 working days of test completion
• Full reports will be written within 30 days of test completion or by
pre-ship review, whichever is earlier
Radiator
In-Process
Tests
Radiator
Acceptance
Tests
VCHPs
Only
Heat Pipe
In-Process
Tests
Heat Pipe
Acceptance
Tests
X-LAT
CCHPs Only
X-LAT
In-Process
Tests
Document: LAT-PR-01967
Integrated
Radiator & XLAT Assy
Thermal Test
X-LAT Assy
Acceptance
Tests
Delivery InPlace to SLAC
TCS Thermal
Test (TBR)
Deliver to
SLAC
Section 13 Mechanical Systems
86
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Structural and EMI Verification
• Each radiator panel tested individually
Radiator Vibration Testing
PreVibration IR
Signature
Low Level
Sine
Survey
Low Level
Sine
Survey
Acoustic
Vibration
Sine
Vibration
Limit
Load Test
PostVibration IR
Signature
Radiator EMI Testing (TBR)
Mass
Properties
Radiated
Emissions
Conducted
Emissions
Radiated
Susceptibility
Conducted
Susceptibility
X-LAT/Radiator Assy
Thermal Testing
• Tested at the X-LAT Assembly level
X-LAT Vibration Testing
Low Level
Sine Survey
Random Vibration
(TBR)
Document: LAT-PR-01967
Static
Load Test
Sine Vibration
(TBR)
Acoustic Vibration
(TBR)
Low Level
Sine Survey
Mass
Properties
Section 13 Mechanical Systems
Deliver to
SLAC
87
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator & X-LAT Assy Thermal Testing
(1 of 2)
•
•
Hardware configuration
– X-LAT Assy
– Radiator Assy
– Heater plate to introduce
heat into the system
– Lab electronics to control
VCHPs
Hardware orientation
– +X side up
– Level within 0.10”
NO SCALE
Flight
Radiators (2)
X-LAT Assy
+X
MLI
Blanket
Cold
Wall
+Y
Document: LAT-PR-01967
Gravity is
into page
Section 13 Mechanical Systems
88
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator & X-LAT Assy Thermal Testing
(2 of 2)
Pump Down
Chamber
Pre-Cycling
Functional Test
Thermal Cycle 1
Bakeout / Hot
Survival
Hot Temperature
Turn-On
Cold
Survival
Cold Temperature
Turn-On
Thermal Cycle 3
Thermal
Cycle 2
Hot Balance
Point
Cold Balance
Point
Thermal Cycle 4
Hot Balance
Point
Cold Portion of
Thermal Cycle
Post-Cycling
Functional Test
Delivery InPlace to SLAC
Document: LAT-PR-01967
IR
Signature
TCS Thermal
Testing (TBR)
Section 13 Mechanical Systems
89
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
TCS Thermal Testing
• Hardware Configuration
– Radiator Assy
– X-LAT Assy
– Downspout heat pipes (TBR)
– LAT mass simulator
• Test Objective
– Verify VCHP reservoir heater operational algorithm
• Test Flow
Pump Down
Chamber
Pre-Cycling
Functional Test
Hot Balance
Point
Cold Balance
Point
Document: LAT-PR-01967
Bakeout /
Hot Survival
Cold Temperature
Turn-Off
Hot Balance
Point
Hot Temperature
Turn-On
Cold
Survival
Post-Cycling
Functional Test
Cold Temperature
Turn-On
Repressurize
Chamber
Section 13 Mechanical Systems
90
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Further Work
• Design
– Review finalized control documents to assess impacts to
requirements compliance, cost, and schedule
– Resolve any non-compliances
• Fabrication
– Begin writing shop orders
– Complete fixture design and manufacture
• Test
– Complete development tests
• Heat Pipe bend
• Insert pull tests (radiator)
• Push-pull bolt lateral slip testing (X-LAT)
– Negotiate contract terms to allow joint thermal testing of
radiator and X-LAT assemblies
– Determine need for TCS thermal testing
Document: LAT-PR-01967
Section 13 Mechanical Systems
91
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Cost and Schedule
Section 13.8
Section 13 Mechanical Systems
92
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
CCB Actions Affecting 4.1.8
Change Request #
Description
Status
LAT-XR-01149-01
Lockheed Martin
Contract Rebaseline
Approved, $56K
LAT-XR-01159-01
Procurements Move
from FY04 to FY03
Approved, $0K
LAT-XR-01585-01
Transfer to 4.1.1.5
Instrument Design
Engineering
Approved, -$1.4M
LAT-XR-01621-01
Mass Allocation
Increase
Approved, 22 kg
LAT-XR-01752-02
SLAC/HEPL Labor
Escalation Rates
Approved -$39K
Document: LAT-PR-01967
Section 13 Mechanical Systems
93
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
4.1.8 Work Flow Summary
Document: LAT-PR-01967
Section 13 Mechanical Systems
94
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Key Deliverable Milestones
Activity
Description
FY 04
FY 05
JAN FE B MAR AP R MAY JUN JUL AUG SE P OCT NOV DE C JAN FE B MAR AP R MAY JUN JUL AUG SE
OCT
P
4.1.8 Mechanical
Flight Grid RFI-Mech to I&T
X-LAT T hermal Plate RFI from Mech to I&T
Radiators ready for I&T (from Mech to I&T )
Run Date
04/21/03 15:05
Data Date
04/01/03
© Primavera Systems, Inc.
Document: LAT-PR-01967
G LA ST L A T PR OJ EC T
A V: F loa t to
Le ve l 3 M ile sto nes
Forecast
Baseline
Product Available Date
Forecast
Baseline
Integration Need Date
LT-T7: Level 3 to AV :(tb)
FL-D7 Integration Mil estones CDR
AV : Up Triangle, L3: Down Triangl e
Section 13 Mechanical Systems
Sheet 5
95
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Critical Path
Completion of CAL-Grid I/F EM tests
Complete Grid Assy Design
Award Subcontract for Grid Assy
Complete X-LAT Design
X-LAT Tooling RFU
Deliver X-LAT
Grid Box Assembly Integration
Grid Box Assembly Test
Grid Box Base Assy to I&T
Document: LAT-PR-01967
5/15/2003
4/12/2003
5/30/2003
5/12/2003
8/15/2003
12/12/2003
2/9/2004
3/9/2004
3/23/2004
Section 13 Mechanical Systems
96
Budget vs Actuals vs Performance
DOE + NASA Project Expenditures
4.1.8 Mechanical Systems
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Budget, Cost, Performance
$M, Then-Year Dollars
15
10
5
Actual Commitments
ACWP
BCWP
BCWS+ Planned Commitments
BCWS
0
. .
FY00
. .
. .
. .
FY01
Document: LAT-PR-01967
. .
. .
. .
. .
FY02
. .
. .
. .
. .
. .
FY03
. .
. .
. .
. .
. .
. .
FY04
Section 13 Mechanical Systems
. .
. .
FY05
97
. .
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Cost/Schedule Status
•
Status as of March 31, 2003:
Item
In k$
Budget at Complete
10,373
Budgeted Cost for Work Scheduled (a)
4,643 (a)
Budgeted Cost for Work Performed (b)
4,099 (b)
Actual Cost for Work Performed
3,735
Cost Variance
364
8.9% of (b)
Schedule Variance
-544
-11.7% of (a)
Document: LAT-PR-01967
Section 13 Mechanical Systems
98
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Procurements
• Long-Lead Procurements
– Aluminum Billets (placed)
– Heat pipe extrusions (LM - placed)
– Solid State thermostats (LM)
• Major Upcoming Procurements Near-Term (< 4 months)
– Lockheed Martin Phase 2
– Grid Assembly
– Flight Hardware for Thermal Control System
• Major Upcoming Procurements Long-Term (>4 months)
• Minor Upcoming Procurements
– GSE
– Grid Assembly Fixtures, Test Equipment
– Thermal-vac Test Fixtures
Document: LAT-PR-01967
Section 13 Mechanical Systems
99
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Risk and Summary
Section 13.9
Section 13 Mechanical Systems
100
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Risk Summary
ID #
Risk Rank
Risk Description
Risk Mitigation
Ability to ramp up & maintain personnel
required to execute Mechanical Systems
plan
Mech
0008
High
Document: LAT-PR-01967
Update manpower plan.
Locate or request additional funds.
Hire additional help.
Negotiate transition of technicians
from MECH to I&T that is acceptable
to both with IPO buy in.
Section 13 Mechanical Systems
101
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Risk Summary
ID #
Risk Description
Risk Rank
Risk Mitigation
•X-LAT plate to Electronics box thermal
joint does not perform as designed
•1) Clarity interface responsibilities
and requirements -complete
•2) Detail interface options -complete
•3) Complete interface analysis –
prelim. Complete (Wang)
Mech
0001
•4) Prototype interface techniques
(Lam )
High
•5) Complete detail box thermal
analysis (Haller)
•6) Select Design approach
(Campell)
•7) Complete integrated analysis
(Wang)
•8) Complete EM Test (Lam)
• Repeatable
•Same as Mech 0001
X-LAT Thermal Joint
performance
Mech
0006
Moderate
•X-LAT plates are removed to service
electronics boxes
•X-LAT plates could be removed after LAT
or Observatory thermal testing
Document: LAT-PR-01967
Section 13 Mechanical Systems
102
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Risk Summary
ID #
Risk Rank
Risk Description
Risk Mitigation
•Delays in Lockheed Martin document
finalization may impact cost & schedule.
Mech
0009
Mech
0010
•All future changes controlled by
formal revision through Contracts
Moderate
Moderate
•Release Radiator & X-LAT level IV
specifications & IDD's by 5/12/03
Incorrect hardware may be built due to
changes and proposed changes being given
to various LM personnel
Document: LAT-PR-01967
Release controlling documents.
Changes to these documents to be
sent through Contracts (May 03 and
beyond)
Section 13 Mechanical Systems
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Risk Summary
ID #
Risk Rank
Risk Description
Risk Mitigation
•Repeatable Radiator Thermal Joint
Performance
Mech
0007
Moderate
•1) Same as Mech 0002
•“Wet” joint is disassembled & reassemble after LAT thermal balance test
•6 joints per radiator must be made within
pot life of thermal adhesive
Mech
0002
Low
Document: LAT-PR-01967
• Radiator VCHP to Downspout and X-LAT
heat pipes thermal joint fails during
thermal vac test
•1) Prototype verification test (ECDJuly 03)
•2) Develop process control
requirements (ECD-Aug 03)
Section 13 Mechanical Systems
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Risk Summary
ID #
Mech
0005
Risk Rank
Risk Description
Risk Mitigation
•Availability of Grid and ACD-BEA for match
drilling at mutually acceptable timeframes
•Establish multiple windows of
opportunity to do the operation and or
additional tooling
Low
• 1) Develop schedule window workarounds (ECD – June 03)
•2) Evaluate creating drill template to
remove schedule dependency (ECDJune 03)
Document: LAT-PR-01967
Section 13 Mechanical Systems
105
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Appendix A
Requirements
Section 13 Mechanical Systems
106
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CDR/CD-3 Review May 12-16, 2003
Topics
Agenda
• Requirements Flow down And Document Status
• Key Mechanical Systems Requirements (Level 3)
• Heat Pipe Performance Requirements
• Radiator Design Requirements
• Main X-LAT Design Requirements
• Driving X-LAT Thermal Requirements
Document: LAT-PR-01967
Section 13 Mechanical Systems
107
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CDR/CD-3 Review May 12-16, 2003
Requirements Flow-Down and Documentation Status
LAT Perf Spec
LAT-SP-00010-1
31 Aug 2000
LAT Stay-Clear
Drawing
LAT-DS-00040-5
LAT Envir. Spec
LAT-SS-00778-1
10 Feb 2003
Subsystem ICD’s
Mech Systems
Subsystem Spec
LAT-SS-00115-2
Subsystem IDD’s
LAT Thermal
Design Param’s
LAT-TD-00224-3
LAT Dissipated
Power Summary
LAT-TD-00225-3
LAT Instrument
Layout Dwg
LAT-DS-00038-3
Document
LAT-SS-00115-2: Mechanical Systems Subsystem
Specification—Level III Specification
LAT-SS-00240-3: X-LAT Level IV Specification
LAT-SS-00394-1: Radiator Level IV Specification
X-LAT Design
Spec
LAT-SS-00124-3
X-LAT Plate SCD
LAT-DS-01247-1
Radiator Design
Spec
LAT-SS-00394-1
Mid-Plate SCD
LAT-DS-01257-1
Grid Box Design
Spec
LAT-SS-00775-1
Thermal Control
Sys. Perf. Spec
LAT-SS-00715-1
Radiator IDD
LAT-DS-01221-1
LH/RH Down
Spout Heat Pipe
SCD
LAT-DS-01392-1
LAT-DS-01393-1
Status
Rev 2 released, Rev 3 in work
Final draft out for review
Final draft out for review
LAT-SS-00715-1: Thermal Control System Performance Specification
First draft out for review
LAT-SS-00775-1: Grid Box Level IV Specification
LAT-DS-01221-1: Radiator IDD
LAT-DS-01247-1: X-LAT Plate Source Control Drawing
LAT-DS-01257-1: Mid-Plate Source Control Drawing
Final draft out for review
Rev 1 complete;out for review
Rev 1 complete;out for review
Rev 1 complete;out for review
Document: LAT-PR-01967
Top Flange Heat
Pipe SCD
LAT-DS-01393-1
Section 13 Mechanical Systems
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Heat Pipe Performance Requirements
Heat Pipe/
Parameter
Top Flange/
Transport
Downspout/
Transport
X-LAT/
Transport
VCHP/
Transport
Req
Margin Comply
Ver.
Method
9.2 W-m, 10 C
>1.3
Y
A, T
7.6 W-m, 10 C
>1.3
Y
A, T
59.5 W-m, 10 C
>1.3
Y
A, T
113.9 W-m, 10 C
>1.3
Y
A, T
Based on: Results of Overall LAT Thermal Math Model
Verification Methods
A: Analysis
T: Test
Margin is determined by: EP/Req
Must be > 1.3
Document: LAT-PR-01967
Section 13 Mechanical Systems
109
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CDR/CD-3 Review May 12-16, 2003
Driving Design Requirements
(Radiator: Mechanical)
Parameter
Requirement
Design
Margin
Comply
Ver.
Method
86 kg
xx kg
x (x%)
Y
I
Center of Gravity, Z-direction
In work
797 mm from
+Z edge
TBD
Y, TBD Still
working
I
Center of Gravity, X- and Ydirection
+/- 10 mm from
location shown in
ICD (Only X shown)
Per ICD
Y: 25 mm from
datum A
X: 2.6 mm
Y: TBD
X: 7.4 mm
Y: TBD,
X: Y
I, A
Mass
Radiator Panel Dimension
Radiator to LAT Mechanical
Interfaces
Radiator to S/C Mechanical
Interface
Radiator to LAT Electrical
Radiator to S/C Electrical
Test Orientation
Operational Life
Document: LAT-PR-01967
Per ICD
Per ICD
TBD
TBD
Must function in 1-g
when +X side is up
5 year
2A18037 &
2A18038 Radiator
Assy Dwg
Locally N, TBD Still
exceeded working ICD
comply
Complies
N/A
Y, TBD Still
working ICD
Y, TBD Still
working ICD
TBD
TBD
Y
5 year, min
0+ yr
Y
comply
Section 13 Mechanical Systems
110
I
I
I
I
I
T
A
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Driving Design Requirements
(Radiator: Structural)
Requirement
Design
Margin
Comply
Stiffness
> 50 Hz
> 60 Hz
+10 Hz
Y
Ver.
Method
A, T
Dynamic
Envelope
Shown in ICD
± 1.8 mm (Launch
Loads)
0.2 mm
Y
A, T
Static Loads
See Table 8
(TBR)
Core Shear MSu =
Gx = 5.1 g, Gy = 30 0.02; Brckt Inserts
g, and Gz = 8.5 g MSu = 0.03; Heat
Pipes MSy = 0.39
Y
A
insert tests
Acoustic Loads
See Table 9
Included above
Y
A, T
Shock Loads
See Table 10
TBD
TBD
TBD
A, Test at
Obs. Level
Sinusoidal
Vibration
See Table 11
Enveloped by above
(TBR)
Enveloped by
Static Loads
Y
A, T
Parameter
Document: LAT-PR-01967
Loads included in
above margins
Section 13 Mechanical Systems
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CDR/CD-3 Review May 12-16, 2003
Driving Design Requirements
(Radiator: Thermal)
Operational Temperature Limits
-10 C to +15 C
(RIT)
Temperature Stability (RIT)
+/- 7C
Survival Temperature Limits
-20 C to +30 C
Reservoir Average Power, Normal
35 W
Mode
Reservoir Peak Power, Normal Mode
58 W
Anti-Freeze Average Power, Normal
0W
Mode
Anti-Freeze Peak Power, Normal
0W
Mode
Reservoir Average Power, Survival
58 W
Mode
Reservoir Peak Power, Survival
58 W
Mode
Anti-Freeze
Average Power, Survival
125 W
Mode
Anti-Freeze
Peak Power, Survival
320 W
Mode Power draw from LAT
Survival
155 W
Margin, Heater Sizing, Normal Mode
Duty Cycle
Margin, Heater Sizing, Survival Mode, >30%<70%
margin on
Cold
power to fully
close VCHP's
VCHP Failure, Hot Operation
Document: LAT-PR-01967
+15°C
-5°C to +10°C +5/+5°C
+/- 4°C
+/- 3°C
-20 °C to TBD 0°C/TBD
13 W
63 %
48 W
17 %
0W
0W
0W
0W
42 W (27V)
28 %
48 W (29V)
17 %
89 W
36 W
227 W (35V)
93 W
61 W
94 W
31 %
39 %
40%
10%
+14°C
+1 °C
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
A, T
Y
A, T
Section 13 Mechanical Systems
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Driving Design Requirements
(Radiator: Mechanical)
Parameter
Requirement
Design
Margin
Comply
Ver.
Method
86 kg
xx kg
x (x%)
Y
I
Center of Gravity, Z-direction
In work
797 mm from
+Z edge
TBD
Y, TBD Still
working
I
Center of Gravity, X- and Ydirection
+/- 10 mm from
location shown in
ICD (Only X shown)
Per ICD
Y: 25 mm from
datum A
X: 2.6 mm
Y: TBD
X: 7.4 mm
Y: TBD,
X: Y
I, A
Mass
Radiator Panel Dimension
Radiator to LAT Mechanical
Interfaces
Radiator to S/C Mechanical
Interface
Radiator to LAT Electrical
Radiator to S/C Electrical
Test Orientation
Operational Life
Document: LAT-PR-01967
Per ICD
Per ICD
TBD
TBD
Must function in 1-g
when +X side is up
5 year
2A18037 &
2A18038 Radiator
Assy Dwg
Locally N, TBD Still
exceeded working ICD
comply
Complies
N/A
Y, TBD Still
working ICD
Y, TBD Still
working ICD
TBD
TBD
Y
5 year, min
0+ yr
Y
comply
Section 13 Mechanical Systems
113
I
I
I
I
I
T
A
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Driving Design Requirements
(X-LAT)
Parameter
Requirement
Design
Margin
N/A
Per SCD
Panel Dimensions
Per 2A15712 and
N/A
Per SCD
X-LAT to LAT Mechanical
2A15716
Interfaces
4.6 kg (12%)
33.8 kg
<38.4 kg
Mass
47.7 Hz
97.7 Hz
> 50 Hz
Stiffness
TBD
TBD
TBD
Dynamic Envelope
>1.68
See Table IV (TBR)
Static Loads
Per 2A15712 and
>1.68
See Table V
Acoustic Loads
2A15716
>1.68
See Table VI
Sinusoidal Vibration
>11C
-5 C/+24.2 C
-20C to +35 C
Operational Temperature
(TBR) at 286.2 W
min or 359.9 W max
Comply
Ver.
Method
Y
Y
I
I
Y, TBD
Y
TBD
TBD
pending
Y
TBD
pending
Y
I,A
T,A
A, T
A
A,T
A,T
A,T
Test Orientation
Must function in 1-g
when +X side is up
Complies
N/A
Y
T
Operational Life
5 year
5 year, min
0+ yr
Y
A
Document: LAT-PR-01967
Section 13 Mechanical Systems
114
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Appendix B
Fabrication Process
Grid Box Assembly
Section 13 Mechanical Systems
115
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CDR/CD-3 Review May 12-16, 2003
Topics
Agenda
• Fabrication plans
• Assembly plans
• MGSE
• Performance and Safety Assurance plans
• Further Work
Document: LAT-PR-01967
Section 13 Mechanical Systems
116
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CDR/CD-3 Review May 12-16, 2003
Mechanical Parts & Materials Plan
•
Material requirements flow down from the Mission Assurance
Requirements 433-MAR-0001 and the Mechanical Parts Plan LAT-SS00107-01.
•
LAT Material selection of low outgassing and flight heritage
• Outgassing specs: TML < 1%
•
CVCM < 0.1%
Important Procedures and Guidelines for Material selection
• Fastener Integrity Requirements (541-PG-8072.1.2)
• Metallic Materials for Stress Corrosion Cracking Resistance in
Sodium Chloride Environment (MSFC-STD-3029)
• Standard Test Method for Total Mass Loss and Collected Volatile
Condensable Materials for Outgassing (ASTM-E-595)
Document: LAT-PR-01967
Section 13 Mechanical Systems
117
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LM M & P Plan & EEE Parts
• LM M & P Plan submitted to SLAC (GLS00018-2, dated 1 Feb
2003)
• LM EEE Parts
– Heaters: Minco Kapton Foil Heaters per GSFC S-311-P-079
– Thermistors: YSI Thermistors per GSFC S-311-P-18
– RTDs: Rosemount PRT per GSFC S-311
– Solid State Thermostats: Micropac 52372”O”
• Submitted to SLAC for approval Nov 2002
Document: LAT-PR-01967
Section 13 Mechanical Systems
118
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Grid Box Assembly Overview
Grid Assy
Grid
Grid Box Base
Assy
Grid Box Assy
Ready for Test
Radiator Mount
Bracket
Spacecraft
Interface (Wing)
EMI Skirt Details
Heat Pipe Patch
Panels
X-LAT Plates
Heat Pipes
Purge Groove
Cover
Legend
Accepted Hardware
CAL Plates
(Temporary)
Grid Box Assembly
Configuration
Test activity
Assembly activity
Document: LAT-PR-01967
Section 13 Mechanical Systems
119
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Assembly
The Grid Assembly consists of;
• 4 x 4 Grid
• Radiator Mounting Brackets - 2 as shown and 2 opposite.
Radiator Mounting Bracket
Document: LAT-PR-01967
Grid Assembly
Section 13 Mechanical Systems
120
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Base Assembly
The Grid Box Base Assembly is the next level assembly, and is the
configuration delivered to I&T. It consists of:
• Grid Assembly
• Heat Pipe Patch Panels, 2 as shown and 2 opposite
• Heat Pipes
– 5 Top Flange Heat Pipes (TFHP)
– 12 Downspout Heat Pipes (DSHP)
• 2 Purge groove covers
• Flight heaters, thermostats &
thermistors on
Grid
Once this assembly is put
together, it is not intended
to be taken apart.
Grid Box Base Assembly
Heat Pipe Patch Panel
Document: LAT-PR-01967
Section 13 Mechanical Systems
121
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Assembly
•
•
•
•
•
The Grid Box Assembly is the
Mechanical Systems’ top assembly
test configuration. It consists of:
Grid Box Base Assembly
Remaining EMI skirt parts
– 4 Center EMI Shields
– X-EMI Shields, 2 as shown and
2 opposite
Grid Box Assembly
2 X-LAT plates with heat pipes
X-LAT Mid-plate
16 Temporary Calorimeter plates.
Center EMI Shield
Document: LAT-PR-01967
X-EMI Shield
Section 13 Mechanical Systems
122
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Grid Fabrication
Grid
Procure
aluminum
NDT plate
(x-ray, UT, other)
Rough
machine Grid
Stress-relieve
heat treat
Finish machine
Grid
Remove, mach
test samples
Test samples
Clean Grid
Inspect Grid
Inserts
Procure inserts,
mount h’ware
Repair as
required
Alodine
Install inserts
Proof inserts
Ready for Grid
Box Machining
SLAC Buy-off
Final Inspection
Legend
Fabrication activity
Inspection/test
Assembly activity
Document: LAT-PR-01967
Section 13 Mechanical Systems
123
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Grid Box Machining
EMI Skirt
Grid
Procure
aluminum
Grid
Machine
Radiator Brkts
Machine Patch
Panels
Clean EMI Skirt
Components
Inserts
Procure inserts,
mount h’ware
Machine Center
EMI Shields
Machine X-EMI
Shields
Install inserts in
EMI Skirt Parts
Inspect
Repair as
required
Install Radiator
Brkts, Patch
Panels, Center
EMI Shields, &
X-EMI Shields
on Grid
Repair as
required
Inspect
Clean Assy
Drill Pin and Bolt
Holes in EMI
Skirt Parts &
Radiator Brkts
Machine Radiator
mounting surface
features in Radiator
Brkts
Machine EMI
Skirt Co-planer
Legend
Install inserts in
EMI Skirt Parts
Deliver To SLAC
Fabrication activity
Inspection/test
Assembly activity
Document: LAT-PR-01967
Section 13 Mechanical Systems
124
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Radiator Fabrication (1 of 2)
Obtain
Facesheet
Material
Shear
Obtain Remaining
Flight Materials
Bond Pipes
To OB
Facesheet
N/C Machine
Log Flight
Materials
Inspect
Thermal Bond
Visual
Process
Samples
To Lab
CMM Inspect
Geometry
Inspect
Doublers
Document: LAT-PR-01967
Bond OB
Doublers
AC Cure
Inspect
Purchasing
Clean, Etch
& Prime
Inspection/Test
Manufacturing
Inspect
Verify Flight
Materials
Fit Check
Core
Inspect
Holes w/
Pins
Verify Cure
Profile
Assemble
Panel and
Bond
Verify Cure
Profile
Prep and
Install Inserts
& Spools
Bond Top
Edge Closure
Inspect
Inserts &
Spools
Machine
Transfer
Datums
Bond IB
Doublers
RT Cure
A
Section 13 Mechanical Systems
125
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CDR/CD-3 Review May 12-16, 2003
Radiator Fabrication (2 of 2)
A
Bond
Reservoir
Supports
Install
Reservoir
Bushings
Fit Check
Reservoir
Bushings
Inspect
Reservoir
Supports
Inspect
Bushings
Apply Blanket
Velcro
Machine
Bushings
Apply Edge
Closure Tape
Apply
Thermal
Blanket
Inspect
Bushings
Structural
Testing
Final Cosmetic
Damage
Map
Thermal
Testing
Notes
1) All panel moves require: inspection documentation of panel for damage; packaging for
transport; and flight approved move procedures.
2) No outside storage.
3) Qualified flight transportation personnel and equipment.
Document: LAT-PR-01967
Section 13 Mechanical Systems
126
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Mechanical Systems MGSE
Item
Grid Box Assembly Stand
Grid Box Assembly Lifting Sling
GBA Static Load Test Fixtures
Dummy CAL baseplates for SLT
DSHP Covers
TFHP Covers
LM Provided MGSE
Radiator Lifting Sling
X-LAT & Mid-Plate Lifting Sling
LAT Mass Simulator (if req'd)
Document: LAT-PR-01967
Qty
1
1
16
12
5
Function
Assemble Grid Box Assy
Handling Grid through GBA
Protect DSHP during assy ops
Protect TFHP during assy ops
Status
Concept
Concept
Concept
In work
Concept
Concept
1 Lifting & handling
1 Lifting & handling
1 for Radiator thermal balance test
Concept
Concept
Concept
Section 13 Mechanical Systems
127
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Performance Assurance System
• Mechanical Systems will comply with the following:
– LAT Performance Assurance Implementation Plan (PAIP),
LAT-MD-00039
– LAT Quality Manual, LAT-MD-00091
– Configuration Management Plan, LAT-MD-00068
– Instrument Performance Verification Plan, LAT-MD-00408
– Calibration Program, LAT-MD-00470
– System Safety Program Plan (SSPP), LAT-MD-00078
• Additionally, above requirements have been flowed down to
Suppliers and Subcontractors.
Document: LAT-PR-01967
Section 13 Mechanical Systems
128
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Appendix C
Peer Review RFAs
Section 13 Mechanical Systems
129
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RFA Response
ID #
1
10
Status
Open
Open
Document: LAT-PR-01967
RFA Description
RFA Response/Closure Plan
•Verify that Grid Finite Element
Model reflects the flange
cutaways for the downspout
heat pipes. Assess stress
concentrations at these
reduced flange section areas.
•The Grid has been re-designed to
incorporate the spacecraft interface
wing as an integral feature of the
grid. The lower flange has been
extended to become the wing. This
removes the discontinuities that
were in the old design. Analysis for
this new design has just begun.
ECD: 5/12/03
Complete design and structural
analysis of S/C to LAT
interface. Present margins of
safety for LAT side of interface
hardware
Analysis is in work. ECD: 5/12/03
Section 13 Mechanical Systems
130
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RFA Response
ID #
12
Status
Open
Document: LAT-PR-01967
RFA Description
RFA Response/Closure Plan
1) Address the intermetallic
layer issue at the friction joint
of the bimetallic joint for
VCHPs. 2) What does LMC do
from a manufacturing process
point of view to preclude this
layer from forming during the
integration welding process,
including temperature control
during processing? 3) Do LMC
CCHPs use a friction weld to
cap off CCHPs?
Leakage through intermetallic
layers is an issue in pressure
vessel design. It can be aggravated
by the friction-welding process
since these layers can be aligned to
result in leak paths. LM has
instituted strict controls on material
purity to preclude the formation of
intermetallic layers which can lead
to leakage. Temperature control is
not directly applicable to the
friction welding process, however
other process controls on weld
energy are used in conjunction with
weld process certification to
carefully regulate weld quality. LM
has had no failures in these joints
in over 15 years of flight experience
using our material and process
controls.
Section 13 Mechanical Systems
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RFA Response
ID #
27
Status
Open
RFA Description
Please identify and capture
development of process
specifications for adhesive
applications, painting (if any)
etc
Title
General cleaning
Epoxy bonding
Heatpipe Thermal bonding (RTV)
Polyimide Heater bonding
Thermostat bonding
Grounding (part inst'l & verif)
Protection of Dissimiliar Metals
Alodine touch-up
Solder per
Wire Harness fab/bonding
Strain gage installtion/removel
Thermocouple installation/removal
Document: LAT-PR-01967
RFA Response/Closure Plan
LAT processes are being developed
by Jerry Clinton. MECH specific
processes will be developed and
written prior to flight hardware
assembly. Here is a list of
processes MECH will use in the
assembly of the Grid Box
Assembly.
Used on
Need date ECD
parts & assy work
Nov-03
Sep-03
GBBA
Dec-03
Sep-03
TFHP, DSHP,GBBA,
Dec-03
Sep-03
GBBA
Dec-03
Sep-03
GBBA
Dec-03
Sep-03
Grid Assy
Nov-03
Sep-03
?
Nov-03
Sep-03
Grid Assy
Dec-03
Sep-03
GBBA
from ELEC from ELEC
GBBA
from ELEC from ELEC
GBA Static Load test
Jan-04
Oct-03
GBA Thermal Cycle test
Jan-04
Oct-03
Section 13 Mechanical Systems
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RFA Response
ID #
28
29
32
Status
RFA Description
RFA Response/Closure Plan
•Protective covers will be used for
as long as practical. They have
been added to the MECH MGSE
list.
Open
•Review heat pipe installation
to see whether any protection
covers can be used during
ground handling and
mechanical operations to
prevent any accidental
damage. Both the grid and
radiator design appears to be
vulnerable to damage.
Open
Establish a realistic schedule
for drawing release with
“buyin” from all parties
required for process
completion, i.e. design
engineering, check, stress,
configuration management,
etc
The drawing release plan is being
revised to add time for feedback
from the interested parties. ECD:
5/12/03
Verify ESD requirements are
correctly flowed down to LMC
from LAT
Working with ELEC to define
applicable ESD requirements to
flow down to LM. ECD: 5/12/03
Open
Document: LAT-PR-01967
Section 13 Mechanical Systems
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RFA Response
ID #
33
Status
RFA Description
RFA Response/Closure Plan
Open
•The plan is to put the antifreeze heaters on the
front/FOSR side of the radiator
and have the FOSR cover the
heater. Look at the impact of
putting the heater on the
backside. At the temperatures
the anti-freeze heaters will
operate, the panel gradients
should be small (small qdot =
small delta T).
•A study will be performed to
evaluate the anti-freeze heater
design. Specifically, the study will
address the plausibility of placing
the anti-freeze heaters on the nonradiating side of the radiators. It is
anticipated that this study will be
complete by CDR. 5/12/03
Document: LAT-PR-01967
Section 13 Mechanical Systems
134
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
34
Status
Open
Document: LAT-PR-01967
RFA Description
RFA Response/Closure Plan
Verify that proposed Vel-therm
X-LAT to electronics thermal
joint design thermal
performance does not degrade
over time (aging issue), after
multiple installation/deinstallations, and during the
course of the mechanical
vibration these program.
A qualification program will be
developed for this interface to
address these issues. However,
the Wide Field Planetary Camera-3
(WFC3) is a GSFC program that
used this material. The instrument
is waiting to fly. Therefore, it must
have qualified and acceptance
tested. If GSFC could provide the
details of what testing was done
and the test results, it would
streamline our testing. Perhaps
there is Qual by Similarity
possibilities here that would
reduce costs as well.
Section 13 Mechanical Systems
135
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
36
37
38
39
Status
Open
Open
Open
Open
Document: LAT-PR-01967
RFA Description
RFA Response/Closure Plan
•Define allowable load transfer
into LAT (or radiator strut
stiffness) at connection of
radiator to S/C.
An effective stiffness of the
spacecraft support strut of at least
200,000 lb/in (strut plus Spacecraft)
was used in the Radiator analysis.
This should be flowed down to
Spectrum Astro in the S/C working
group or as a requirement from
GSFC to Spectrum.
Limit load tests should qualify
the design (1.25 x flight limit
loads)
The Level IV spec will be revised.
ECD: 5/12/03
Update yield F.S. to 1.25
(currently @1.1). Verify that
this requirement has been
flowed down to all other
subcontractors.
The Level IV spec will be revised.
ECD: 5/12/03
Provide more detailed
summary of stress margins of
safety for the LAT instrument.
Stress analyses are in work. ECD:
5/12/03
Section 13 Mechanical Systems
136
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
40
41
Status
Open
Open
Document: LAT-PR-01967
RFA Description
RFA Response/Closure Plan
•Review high conductance
graphic interface material
available from a company
named “UCAR” (formerly part
of Union Carbide). They have
high conductance graphite
material gaskets greater than
10 mil in thickness. They
have space experience.
•Received 0.020” & 0.025” thick
samples from Vendor. While the
material (Grafoil) has excellent
compressive properties, it has very
low tensile strength (~1,000 psi).
Therefore, when bending the
material, it breaks. We are
investigating laminated versions of
the product to see if they are
feasible for this application.
Verify that the flight data
certification packages that
accompany hardware
delivered by Lockheed to
SLAC are consistent with
NASA Quality Assurance
Requirements.
NASA has not imposed any
requirements for data package
requirements on LAT (per Darren
Marsh). However, Lockheed’s data
package will be consistent with the
LAT’s internal requirements
(Mechanical to I & T) and their own
standards for their Government
Customers.
Section 13 Mechanical Systems
137
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
42
Status
Open
RFA Description
•1) What is the detailed
schedule for completion of the
EM Test program for the X-LAT
Thermal/Mech Design, will it be
complete by CDR?
•1)EM test program schedule
(below)
•2) What is the back-up design
if the EM program is not
successful using Vel Met? New
baseline is unconventional
Test
Load vs Deflection
Thermal conductivity vs
Deflection
Random vibe (or lateral
excursion)
Thermal vac performance
Document: LAT-PR-01967
RFA Response/Closure Plan
Sample
Small .125" thk samples
Small .125" thk samples in high vacuum
(Ames)
Full sized footprint with min & max
allowable gaps from above
Full sized footprint with simulated E-box
thermal loads
ECD
5/2/03
5/30/03
5/30/03
6/15/03
Section 13 Mechanical Systems
138
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
42
Cont.
Status
Open
RFA Description
RFA Response/Closure Plan
•1) What is the detailed
schedule for completion of
the EM Test program for the
X-LAT Thermal/Mech Design,
will it be complete by CDR?
2) Back-up designs (in descending order)
“Thick” RTV bond line between E-box and
X-LAT plate with a 0.0005 inch thick Teflon
film between one of the interfaces to allow
disassembly. The existing push-pull bolts
would still be required for Z axis restraint
(parts are not bonded together).
A thermal strap that is laminated with the
Grafoil (high conductance graphite, see
RFA # 40).
Delete existing X-LAT plate and rigidly
attach the X-LAT heat pipes to the Eboxes. The heat pipes would become the
flexible member. A cap would fit over the
entire assembly to act as EMI enclosure.
Variation on this is a X-LAT plate that ties
the E-boxes together, but is not tied to the
EMI skirt. This keep the boxes moving in
phase.
•2) What is the back-up
design if the EM program is
not successful using Vel
Met? New baseline is
unconventional
Document: LAT-PR-01967
Section 13 Mechanical Systems
139
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
43
Status
Open
Document: LAT-PR-01967
RFA Description
RFA Response/Closure Plan
Consider including GRID &
DSHPs in the “Complete TCS”
TB test. Schedule chart 1.2-4
shows cycling of grid assy by
¾ with “complete TCS test” in
6/04. Chart on page 3.1-10
conveys this config for the TB
test
Definition of the test & hardware
requirements is in work.
Examining schedule options
including combining the thermal
vacuum acceptance testing of the
radiators & X-LAT plates with this
TCS TB test. The Grid delivery to
I&T need date currently precludes
its availability for this test, but will
be part of configuration trade
study (configuration vs. cost,
schedule & risks mitigated). ECD:
7/13/03
Section 13 Mechanical Systems
140
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
45
Status
RFA Description
RFA Response/Closure Plan
•GSFC (Brad
Parker/Materials Board)
provide recommendation to
SLAC/LM team regarding the
use of bimetal element used
in heatpipes
Same as #12.
Leakage through intermetallic layers is an
issue in pressure vessel design. It can be
aggravated by the friction-welding
process since these layers can be aligned
to result in leak paths. LM has instituted
strict controls on material purity to
preclude the formation of intermetallic
layers which can lead to leakage.
Temperature control is not directly
applicable to the friction welding process,
however other process controls on weld
energy are used in conjunction with weld
process certification to carefully regulate
weld quality. LM has had no failures in
these joints in over 15 years of flight
experience using our material and
process controls.
Open
Document: LAT-PR-01967
Section 13 Mechanical Systems
141
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
RFA Response
ID #
46
Status
RFA Description
RFA Response/Closure Plan
Will add a “Qualification” (one time-one
part) test to the Lockheed Martin Radiator
specification and/or SOW. ECD 5/12/03
Open
Consider defining a “control
performance” test for each
VCHP that verifies ability to
entirely block off the
condensor, as well as ability
to run full open under spec
boundary conditions
Document: LAT-PR-01967
Section 13 Mechanical Systems
142
GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
Document: LAT-PR-01967
CDR/CD-3 Review May 12-16, 2003
Back-up charts
Section 13
Section 13 Mechanical
Systems
Risk & Summary
143
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
CAL-Grid I/F Closure Plan
• New shear loads from CLA
– First look 5/16
– Verified 5/30
• EM test of CAL Shear plate concept
– First look 5/21 (load capability)
– Full up test 6/7
• Detail design complete 6/27
– Coordinated with CAL, I & T and ELEC (cable trays)
• 1 x 4 EM testing complete 7/31
Document: LAT-PR-01967
Section 13 Mechanical Systems
144
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Cal Plate to Grid Interface Status
• Loads analysis of interface used to determine required friction
coefficients to prevent slipping at cal tab locations. Required
friction compared to that determined to be achievable in test.
– The upper limit of friction achievable with special surface
treatments is needed to prevent slipping with the baseline
design.
– Devices to increase clamping force at perimeter of grid still
require friction coefficients at a small number of locations
which exceed the friction achievable with normal surface
finishes.
– Friction alone has not been shown to provide high confidence
that local (not bulk) slipping will not occur. Analysis to
determine load redistribution and potential for subsequent
slipping after initial slipping is not readily accomplished.
Document: LAT-PR-01967
Section 13 Mechanical Systems
145
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Cal Plate to Grid Interface Status (cont)
• Converting select fasteners in clearance holes to pins via epoxy
fill of the clearance gap studied as a means to provide confidence
against local slipping.
– Epoxy installation technique and strength demonstrated on
test coupons.
– Upon application of shear load, male threads of fastener
mating with female threads in grid rib cause excessive dead
band. Mated threads do not effectively carry shear loads.
• Other techniques for strengthening the interface under study
– Replace select fasteners with traditional shear pins in tight
holes. Requires template for drilling grid and cal plates. Most
dead band found in threads will be eliminated but strength of
grid walls and / or cal tabs may be inadequate.
– Carry shear loads directly from cal plates to grid wings by
adding shear plates that attach to cal plates at existing GSE
fastener location. Existing fasteners from cal plates to grid
provide axial restraint forces.
Document: LAT-PR-01967
Section 13 Mechanical Systems
146
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
CAL Shear Plate Concept
5/16 bolts pressed or tight slip fit into CAL plates and Grid perimeter.
Cal plate location is at current location of tapped GSE hole.
Grid perimeter
Document: LAT-PR-01967
Section 13 Mechanical Systems
147
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
CAL Shear Plate Concept
PRO’s
•Allows shear loads to be carried
to be carried through M8 ( 5/16
inch) fasteners
• Cal plate tabs and grid walls are
not in the primary shear load path
• No dependence on friction
• Minor changes to cal plates and
wings.
• Epoxy shear holes will be in
shear plates so that no holes need
to be drilled in M8 fasteners.
Document: LAT-PR-01967
CON’s
• Mold release and a design feature are
required on bolts with epoxy fill in order
to accomplish shear plate removal. Some
additional confidence testing in epoxy is
required.
• Clearance envelope above the pressed
in bolts in the cal plate needs to be
checked.
• Removal of a cal plate requires
removal of shear plates on adjacent cal
plates
Section 13 Mechanical Systems
148
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Vel-Therm Design Closure Plan
• Design trades 5/30
– Contact pressure distribution (# bolts, preload)
– Particle containment
– E-box – X-LAT mechanical connection details
• Vel-therm EM tests
– Coupon tests 5/30
– Full scale tests 7/18
– Life tests – thermal and/or mechanical cycling 12/12
• Flight designs 8/29
– Finalize interface
– Revise/release affected hardware
– Assembly plans & procedures
– Coordinate with I & T
Document: LAT-PR-01967
Section 13 Mechanical Systems
149
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Back-up Thermal Design Plans
•
Develop concepts
1. “Thick” RTV bond line between E-box and X-LAT plate with a 0.0005
inch thick Teflon film between one of the interfaces to allow
disassembly. The existing push-pull bolts would still be required for Z
axis restraint (parts are not bonded together). Complete
2. A thermal strap that is laminated with the Grafoil (high conductance
graphite, see RFA # 40). ECD 5/30
3. Delete existing X-LAT plate and rigidly attach the X-LAT heat pipes to
the E-boxes. The heat pipes would become the flexible member. A cap
would fit over the entire assembly to act as EMI enclosure. Variation
on this is a X-LAT plate that ties the E-boxes together, but is not tied
to the EMI skirt. This keep the boxes moving in phase. ECD ? Need
Analysis
•
Coupon test #1 6/13
Document: LAT-PR-01967
Section 13 Mechanical Systems
150
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
X-LAT Plate Thermal Loads
+Y
EPU
39W
15W
15W
15W
15W
15W
21W
21W
GASU
SIU
21W
PDU
21W
42W
37W
EPU
39W
Heat Source
within box
15W
Note: View from X-LAT Plate to E-boxes
Power shown include 15 W from TEM/TPS boxes
Document: LAT-PR-01967
15W
-X
Power numbers
Source:
LAT-TD-00225-4
(draft)
EPU
39W
X-LAT Heatpipe
6 Required
Section 13 Mechanical Systems
151
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Particulate Containment Options
• Perimeter (foam) gasket
• Tape over the Vel-therm
• Vel-therm sandwich between 2 Aluminum plates with Kapton
tape close outs
• Shower cap bonded to X-LAT & slip over E-box
Document: LAT-PR-01967
Section 13 Mechanical Systems
152
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Conductance vs Pressure
Space Grade Gelvet Conductance, Gold Plated Aluminum and BeO
Interfaces
6.0
5.5
Conductance (W/C-in^2)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
0.020" Gelvet Conductance 0 C
Exponential best fit to 0C data
Extrapolation of exponential fit
1.5
1.0
0.5
0.0
0
200
400
600
800
1000
1200
1400
1600
1800
Pressure (psi)
Document: LAT-PR-01967
Section 13 Mechanical Systems
153
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
vs Compression
Vel-ThermPressure
Pressure
vs. Deflection
90
80
8,500 < h (W/m2-K) < 11,500
70
Pressure (psi)
60
60 mils thk
50
20 mils thk
125 mils thk
40
30
550 < h (W/m2-K) < 700
20
TBD < h (W/m2-K) < TBD
To be tested
10
0
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Compression (inch)
Document: LAT-PR-01967
Section 13 Mechanical Systems
154
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Drawing Release Plan
draft
check
stress
release
4x4 Grid
23-May
13-Jun
13-Jun
20-Jun
EMI Skirt Details
23-May
13-Jun
13-Jun
20-Jun
Radiator Mount Bracket
23-May
13-Jun
13-Jun
20-Jun
Grid Box Machining Assy
23-May
13-Jun
13-Jun
20-Jun
Grid Box Base Assy &
details
Grid Box Assy
MGSE
Document: LAT-PR-01967
13-Jun
27-Jun
27-Jun
7-Jul
7-Jul
14-Jul
14-Jul
21-Jul
1-Aug
15-Aug
15-Aug
22-Aug
Section 13 Mechanical Systems
155
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Summary of Margins of Safety
FS=
2.0
Nom Stress
Peak Stress
Margin
+X/-Z
[Mpa]
8
17
13.2
Max Von Mises Stresses
-X/-Z
+Y/-Z
-Y/-Z
[Mpa]
[Mpa]
[Mpa]
9
4
3
18
9
7
12.4
27.2
35.6
LIFT
[Mpa]
94
189
0.3
Allowable
[Mpa]
241
15
27
25
12
11
16
13
Attachment Point Margins of Safety
Attach
against
against
against
Point
Tension
Bearing
Tearout
11
32.4
16.8
6.8
12
NA
7.9
2.9
13
NA
15.0
6.0
14
NA
3.4
1.4
15
NA
28.0
14.6
16
119.0
68.4
27.1
22
NA
9.5
3.6
23
NA
11.8
4.6
24
NA
11.6
4.5
25
19.2
5.1
2.0
26
9.1
3.3
0.5
27
9.1
3.3
0.5
22
23
24
Tension
Failure
Document: LAT-PR-01967
26
14
Bearing
Failure
Tear Out
Failure
Section 13 Mechanical Systems
156
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Topics
Agenda
• Mechanical design changes since ∆PDR
• Impacts on Subsystem design
• Studies since Delta PDR
Document: LAT-PR-01967
Section 13 Mechanical Systems
157
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Design Changes Since Delta PDR
• X-LAT to E-Box thermal joint
– WAS: Rigid bonded joint with flexures at CAL-TEM
interface
– IS: Rigid interface at CAL-TEM with compliant joint at XLAT plate and a thermal velvet material (Vel-therm) used
to fill gap between bottom box & X-LAT
• X-LAT plate
• WAS: honeycomb panel; IS: .125” plate
• CAL-Grid bolts:
• Use #8’s everywhere except at TRK cables pass-thru’s to
increase clamping force on CAL plate
Document: LAT-PR-01967
Section 13 Mechanical Systems
158
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Design Changes Since Delta PDR
• Refined S/C interface stiffener (wing) to reduce grid distortions
• S/C attach method
– WAS: onto –Z surface of Grid
– IS: tang that protrudes down from wing
• S/C stayclear & center EMI shield design modified to
accommodate above
Document: LAT-PR-01967
Section 13 Mechanical Systems
159
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Design Changes Since Delta PDR
• E-box harnesses
– WAS: bulkhead connectors in EMI skirt
– IS: 8 Connector patch panels into EMI skirts that E-box
harness mount directly to
• Added 2 TCS external box & 2 brackets – mounting
accommodated on Radiator Mount Brackets
• Added vents to EMI Electronics enclosure
Document: LAT-PR-01967
Section 13 Mechanical Systems
160
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Design Changes Since Delta PDR
• Radiator Heat Pipes
– WAS: U shaped bend to Grid
– IS: S shaped bend to Grid
• Radiator panel has top stepped for integration access
• Radiator – SC interfaces have been finalized
– SA Boom cutout size & location, strut locations
• Radiator reservoir size
– WAS 300 cc; IS: 75 cc
• Radiator VCHP extrusion
– WAS 1.75” wide; IS: 2.0” wide
• LM will design, fabricate and test X-LAT plates
Document: LAT-PR-01967
Section 13 Mechanical Systems
161
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Impact of Changes on Subsystem Designs
•
•
•
•
•
LAT
– No impact
TKR
– No impact
CAL
– Baseplate design has been modified for #8 fasteners
ACD
– No impact
Electronics
– Improved reliability by reducing bulkhead connection
– External TCS boxes have been accommodated
Conclusion: Changes consistent with PDR to CDR design
maturity. Design changes have been incorporated within the
Mechanical Subsystem
Document: LAT-PR-01967
Section 13 Mechanical Systems
162
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Studies since Delta PDR
• X-LAT to Electronics Thermal Joint Design
• Optimize joint design to accommodate
– Maximum thermal conductance
– Repeatable and verifiable thermal joint
– Ease of integration & removal to service E-boxes
– Compliance in X-Y plane required either at E-box to CAL or
E-box to X-LAT
– Tolerance stack up of E-boxes, EMI skirts & CAL plates
• RTV, thermal gaskets, spring fingers, thermal straps and VelTherm traded
• Compliant joint at E-box to X-LAT interface with Vel-Therm
material in between selected.
Document: LAT-PR-01967
Section 13 Mechanical Systems
163
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Studies since Delta PDR
• CAL-Grid interface shear load capability
– No bulk movement of CAL with 70 Fasteners & μ=.01
– Isolated concern as small local motions of Grid wall
underneath grid tabs
– Optimize wing design to reduce loads (FEM)
– Examined friction of various surface treatments
– Examined Tungsten Carbide flame spray as a way to
guarantee high coefficient of friction at interface
– Maximized clamping force available from fasteners
– Examined backing bars on top of CAL tabs to create
“double shear” joint
– Examined perimeter clamping bars that increase preload on
all CAL tabs around the perimeter of the Grid
– Developed maps from FEM showing required coefficient of
friction at each bolt location for a given clamping force
Document: LAT-PR-01967
Section 13 Mechanical Systems
164
GLAST LAT Project
CDR/CD-3 Review May 12-16, 2003
Studies since Delta PDR
• CAL-Grid interface shear load capability (cont)
• Summary:
• A friction joint will prevent bulk slippage of the CAL and
maintain the LAT natural frequency.
• 89% of fasteners require μ < 0.2. Plan to run an analysis to show
that load redistribution for the remaining 11% does not
adversely affect the LAT natural frequency.
• GSFC has recommended that a bolted-pinned joint be adopted.
– Design implementation study and impact study would be the
next step.
Document: LAT-PR-01967
Section 13 Mechanical Systems
165