GLAST Large Area Telescope: Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Marc Campell SLAC Subsystem Manager marcc@slac.stanford.edu (650) 926-4658 Mechanical Systems

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 $ 53 Stanford Benefits Rate Increase $ 63 Total Change $ 94 4.1.8 Baseline, February 04 $13,478

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)

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

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