1. GLAST Large Area Telescope:
Gamma-ray Large Area Space Telescope
GLAST Large Area Telescope:
Marc Campell
SLAC
Subsystem Manager
(650)
Mechanical Systems

2. Overview – MECH SYS Responsibilities
Grid Box Base Assembly (GBBA)
Grid + Radiator Mount Brackets + Top Flange Heat Pipes + Thermal Control hardware
Configuration delivered to I & T for LAT integration
Grid Box Assembly (Qual unit only)
Grid #2 is Qualification unit
GBBA + EMI Skirt + Dummy CAL Baseplates
Combined Grid Static Load and LAT strength test
Radiators
Fabricated and tested by LM
X-LAT Plates

3. Mechanical Subsystems Overview
4 x 4 Grid >> Grid Box Base Assy >> Grid Box Assy
Test Configuration
(CAL Baseplates not shown)
1.6 m
.24 m
Shear Plates
TFHP
EMI Shields
Radiator Mount Brkt
TCS Hardware

4. Radiator Panel - Exploded View
Variable Conductance Heat Pipe
FOSR
Honeycomb
Core
Outer Facesheet
Doublers
1.56 m Z X Y
Inner
Facesheet
Reservoir
1.82 m
Reservoir Support Bar

5. Radiator & X-LAT Placement
Top Flange Heat Pipe
3 Way Heat Pipe Joint +Z +Z
Down Spout Heat Pipe
X-LAT Heat Pipe

6. Recent Accomplishments
Grid Box
Grid #1 rough machining complete
Grid #1 finish machining 50% complete (shown below)
Grid #2 rough machining & heat treat complete

7. Recent Accomplishments (cont)
Lockheed Martin
Downspout Heat Pipes complete (shown below)
Top Flange Heat pipes complete
Radiator detail parts fabrication 20% complete

8. Mechanical Systems Critical Path
Flight Hardware for TCS
6/30/04 / 0
Grid Box Base Assembly #1 Operations
7/22/04 / 0
GBA Assembly fixtures/ MGSE 6/30/04 / 0
Flight
Grid RFI #1
7/22/04 / 0
Fabricate Flight Grid (4X4) #1
6/15/04 / 0
Inspect Flight Grid, EMI skirt, details #1 06/16/04 / 0
Fabricate EMI skirt, Grid details) #1
6/15/04 / 0
GBA #1 Fit Check Operations
6/30/04 / 0
Inspect Flight Grid, EMI skirt, details #2 9/3/04 / 0
Fabricate Flight Grid (4X4) #2
8/27/04 / 0
Grid Box Assembly #2 Operations
10/18/04 / 0
Static Load Test Complete
12/16/04 / 0
Completion Dates/Variance to Baseline

9. Rationale for Second Grid
LAT Sine Burst (Strength) Test deleted Fall 2003
Concerns about over-testing LAT
Objectives could be met by adding test cases to Grid Static Load Test
Results approximately 1 year earlier
Reduced LAT schedule
Grid Static Load plan changed during Re-baseline
Original plan was to rough machine second grid and hold as flight spare
Re-baseline plan completes machining of second Grid and components required to complete Grid Box Assembly
Perform test on second grid as a Qualification test
Pulled delivery of Flight unit (Grid #1) forward approximately 2 months and maintain delivery to I & T milestone

10. Radiator Critical Path
VC Heat Pipe Fab
5/19/04 / 0
Radiator Assy Complete
11/28/04 / 0
Radiator Details Fab
5/19/04 / 0
Protoqual Testing
Sine Vibration Survey
12/15/04 / 0
Acoustic Test
1/28/05 / 0
Sine Vibration Survey
2/14/05 / 0
Thermal Vacuum / Balance Test
4/7/05 / 0
Deliver to SLAC
4/21/05 / 0
Completion Dates/Variance to Baseline

11. X-LAT Plate Critical Path
X-LAT Heat Pipe Fab
9/15/04 / 0
X-LAT Plate Assy Complete
10/29/04 / 0
P/Qual Thermal Vacuum Test
11/30/04 / 0
Deliver to SLAC
12/09/04 / 0
Completion Dates/Variance to Baseline

12. Open Issues
Radiator VCHP Helium leak rate may impact ACD Photomultiplier Tubes (PMT’s )
LM can substitute another inert gas, but it impacts ground (not on-orbit) performance.
LM given the “OK to Fab” the VCHP’s up to the charging operation (3rd week of April).
Dispersion analysis is underway to evaluate impacts to PMT’s. ECD: 4/16/04
Coordination of TCS validation, LM Radiator Thermal Vacuum & Balance test plans
TCS risk assessment and Qual test plan requested by GSFC. ECD: 4/30/04
TCS – location of Grid heaters, thermostats, RTD’s and associated wiring needs to be finalized (top assembly drawing)
ECD: 5/3/04
Radiator integration sequence
Grid has been modified to allow integration via pure translation of the Radiators.
Demonstration and detailed procedure are in work. ECD: May 04

13. Risk List Problem Impact Mitigation Status
Failure of Radiator VCHP to Down-spout & X-LAT HP thermal joint during LAT TH/Vac testing
Day for day LAT schedule slip during anomaly resolution
Installation process control and prototype verification of 3 way joint
Verification tests planned for May ‘04
Failure of Grid thermal control components during LAT TH/Vac testing
Perform ambient continuity & isolation test of heaters. Thermo-stats tested at part level.
Availability of Grid & ACD’S BFA for match drilling
Schedule slip for either subsystem
Multiple windows have been established
Currently planned for 5/3 – 5/19/04

14. Key Schedule Issues
Problem: Late changes to Grid interface requirements
Impact: Grid #1 delivery from Tapemation (vendor)
Is: 6/15/04; Re-Baseline: 3/30/04
Mitigation steps taken or planned to get back on schedule:
Freeze Grid design (interfaces) and build it
Reduced Grid plating time 4 weeks by changing thermal requirement from 3 to 2 plating types (Alodine and Nickel plating – black anodize deleted)
Working with Tapemation to incorporate producibility improvements to design

15. Key Schedule Issues (cont)
Problem: Late Grid delivery to SLAC drives delivery to I&T
Impact: Grid to I & T delivery date
Is: 7/22/04; Re-Baseline: 6/15/04
Mitigation steps taken or planned to get back on schedule:
Static Load testing on second Grid established during re-baseline activity
Minimized Mechanical Systems assembly operations
Deleted Grid Box Assembly operations (fit check only)
Deleted Thermal Cycle testing of Grid Box assembly
Postponed some operations until after delivery to I&T

16. Key Schedule Issues (cont)
Problem: Late start on fabrication of X-LAT Plate Assembly
Impact: Delays X-LAT Plate delivery date to SLAC
Is: 12/9/04; Re-Baseline: 8/12/04
Mitigation steps taken or planned to get back on schedule:
Lockheed performing preliminary design to draft versions
Interfaces to DAQ boxes and Grid were defined
Lockheed will be given permission to build the X-LAT Heat Pipes prior to the Manufacturing Readiness Review

17. Approved Cost Changes Since Rebaseline
(k$)
4.1.8 Baseline, November 03 $13,384
Changes:
Align Schedule w/ Grid Deliv $ (22)
Grid Assy & TCS Replan $
Stanford Benefits Rate Increase $
Total Change $
4.1.8 Baseline, February 04 $13,478

18. Variances Cost variances: LM = +$158K. Will be used in upcoming months
SLAC = -$57K. For contractor engineering support.
Schedule variances:
LM = zero
SLAC = -$189K. Receive flight hardware for thermal control system (-$184K)

19. Looking Ahead 6 Months Grid #1 delivered to I&T
Supporting I&T integration operations
Grid #2 delivered to SLAC
Static Load Test preparations underway
X-LAT Plate fabrication complete and ready for test
Radiator fabrication 75% complete

20. Summary Major interface issues have been resolved in last 6 months
CAL – Grid, X-LAT – DAQ and Tracker - Grid
Designs are released (except X-LAT plate)
Fabrication of both Grids is underway
Fabrication of Radiators is underway
LM effort has ramped up significantly
No major issues with hardware fabrication
Focus now on resolving test issues
MECH is off of the LAT critical path