1. GLAST Large Area Telescope:
Gamma-ray Large Area Space Telescope
GLAST Large Area Telescope:
Mechanical Systems Peer Review
March 27, 2003
Section XLAT Thermal Design
Boris Yendler
Lockheed Martin
Thermal Engineer

2. Topics Requirements Thermal Design Overview Thermal Model Results
Summary & Future Work

3. Driving X-LAT Thermal Requirements
Verification Methods A: Analysis, T: Test
Based on: X-LAT Plate Performance Specification, LAT-TD D2, Draft, Dated 6 Mar 2003
X-LAT Plate Assy Source Control Drawing, LAT-DS-01247, Draft, Dated 7 Mar 2003
Mid-Plate Assy Source Control Drawing, LAT-DS-01257, Draft, Dated 7 Mar 2003
Agreement Reached at Electronic Box Thermal Design Red Team Mtg, 14 Mar 2003
Based on: X-LAT Plate Performance Specification, LAT-TD D2, Draft, Dated 6 Mar 2003
X-LAT Plate Assy Source Control Drawing, LAT-DS-01247, Draft, Dated 7 Mar 2003
Mid-Plate Assy Source Control Drawing, LAT-DS-01257, Draft, Dated 7 Mar 2003
Agreement Reached at Electronic Box Thermal Design Red Team Mtg, 14 Mar 2003

4. Thermal Design Overview
All TEM/TPS Positions w/o an Electronic Module have EMPTY Boxes mounted to them.
Thermal Design Goals
Remove Heat from Stacks
Reduce temperature gradient on X-LAT
Provide temperature at the box baseplates 40 C
EPU
PDU
EPU
GASU
EPU
SIU 1
SIU 2 +X +Y +Z
Four central TEM/TPS Positions have Comb Bracket mounted to them.

5. Comb Bracket

6. X-LAT plate Thermal Model
Foot Print of Stacks Z Y
Comb Bracket X
heat pipe
EPU
PDU
EPU
heat pipe
Empty
Empty
GASU
middle plate
Empty
Empty
heat pipe
EPU
SIU
SIU
Empty
heat pipe
heat pipe
Hot Case

7. XLAT Thermal Model (cont)
X-LAT plate consists of 3 plates AL 6061 T6
Plates are jointed by #6-32 bolts 1 in apart
Side plates – mm (1/8 in.) Middle plate mm (3/16 in)
CCHP flange is connected to X-LAT plate via RTV and rivets
All stacks are thermally connected to X-LAT plate through 4 cm wide strips of Veltherm, fiber based material (150 W/m2-K)
10 stacks consist of 3 boxes: TEM, TPS assembly and EPU, SIU, or EMPTY box

8. Electronics Box Thermal Model
1 stack - 2 TEM/TPS assemblies connected to PDU
1 stack - 4 central TEM/TPS assemblies connected to GASU and to Comb Brackets
Flange determines contact area between boxes in a stack.
A box in a stack consists of four walls, top and bottom. Heat is generated on wall and /or top/bottom
Each side of the box is represented by one node
X-LAT plate is represented by 1763 nodes

9. Thermal Results (X-LAT plate)Y
17.3
17.3
17.3
EPU
PDU
EPU X
20.4
20.3
20.3
24.2
GASU
22.6
22.3
21.3
19.4
EPU
SIU
SIU
20.1

10. Thermal Results (box level)
TEM
TEM
35.6 C
33.8 C
TPS
TPS
33.7 C
33.5 C
EPU
SIU
23.4 C
26.5 C
TEM
28.3 C
TPS
27.4 C
Empty
23.9 C
Heat pipe temperature is assumed 17 C

11. Electronics Box Thermal Results (cont)
TEM
35.2 C
TPS
32.0 C
PDU
24.4 C
TEM
35.4 C
TPS
32.8 C
GASU
GASU
26.8 C
30.0 C
Comb
Heat pipe temperature is assumed 17 C

12. Summary & Future Work Summary
X-LAT Assembly Temperature Gradient is 5 C
Maximum Electronics Box Baseplate Temperature is 35.6 C
Future Work
Update X-LAT Model
Refine Nodalization
Optimize Localized Plate Thickness
Incorporate SLAC Electronics Box Model
Heat Pipe Failure Analysis