Transcript Section 3.2 - Changes Since dPDR

GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
GLAST Large Area Telescope:
Mechanical Systems Peer Review
March 27, 2003
Section 3.2- Changes since
Delta PDR
Marc Campell
SLAC
Mechanical Systems Mgr.
[email protected]
Document: LAT-PR-0XXXX
Section 3.2 Changes since dPDR
1
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Topics
Agenda
• Mechanical design changes since ∆PDR
• Impacts on Subsystem design
• Studies since Delta PDR
Document: LAT-PR-0XXXX
Section 3.2 Changes since dPDR
2
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
3
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
4
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
5
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
6
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
7
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
8
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
9
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 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-0XXXX
Section 3.2 Changes since dPDR
10
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
End of
Section 3.2
Document: LAT-PR-0XXXX
Section 3.2 Changes since dPDR
11