Mechanical Design Integration Peer Review, March 2003 2. System Engineering

1. Mechanical Design Integration Peer Review, March 2003 2. System Engineering Martin Nordby nordby@slac.stanford.edu 24 March 2003 rev 3

2. 2. System Engineering • Action items from PDR and Delta PDR • Requirements & specifications • Requirements flow-down • Requirements list showing key requirements • Interface control • List of all interfaces and status • Major trades in support of interface finalization • Documentation status, open issues/TBX’s and closure plans • Technical budget allocation updates • Technical budgets (mass, volume, power/thermal) • Allocation flow down to subsystems • Parts and materials • Parts, material, and process list status • Pending issues

3. PDR Action Items • 23 action items were assigned to Mechanical Systems at the January PDR • All have been addressed, and submitted for closure • Actions grouped into 5 classes • Thermal Design: re-evaluate thermal interface requirements and re-design thermal system accordingly • Structural Design: use positive shear restraint, when possible, at all key interfaces • Fabrication and Integration: evaluate integration contingency and costs • Environmental Testing: amplify test plans • Risk: mitigate and manage development and fabrication risks

4. PDR Action Items (cont 1) • Thermal Design: Re-evaluate thermal interface requirements and re-design thermal system accordingly • System-level trades have been accomplished with GLAST Mission input • External interface definition has been improved: LAT IRD updated with significant additions. Optical properties of viewable SC surfaces have been bounded. • Switched radiator coating to 0.25 mm FOSR, with emissivity = 0.85 (6% improvement) • Sensitivity studies of key LAT internal interfaces has been completed and interface designs modified as needed (TKR/Grid, E-Box/X-LAT are two examples) • Re-packaging of Radiators has been completed for Delta PDR and updated with Spectrum involvement • Responsibilities clarified: LAT is now responsible for survival heater control. All survival heater control is passive, including anti-freeze heaters on the VCHP’s. • Added anti-freeze heaters to VCHP’s (power included in survival budget • LAT attitude has been double-checked: for 0 < beta < 52 degrees, beta = 0 is the LAT hot-case orientation

5. PDR Action Items (cont 2) • Structural Design: use positive shear restrain, when possible, at all key interfaces • Positive shear restraint in the form of pins, shoulder bolts, and lap joints are being used at all critical interfaces in the LAT except the CAL-Grid interface, where additional shear restraint is needed. At this location bolt pre-load and friction are being used. • Fabrication and Integration: evaluate integration contingency and costs • An impact assessment has been made of replacing a TKR module. • Environmental Testing: Amplify test plans • LAT Verification Plan has been greatly amplified and released • Strength qualification plans included • Sine test philosophy is included • Added Grid Box thermal-vacuum testing to the Mechanical Systems Test Plan and matrix • Preliminary analysis of cool-down times for thermal-vacuum cycling have been completed. • Subsystem and LAT test temperature have been established, and are collected in LAT-SS-00778, “LAT Environmental Specification.” • Risk: Mitigate and manage development and fabrication risks • The LM heat pipe facility has been returned to the Sunnyvale plant and was certified in December 2003. • Six-month schedule extension has reduced schedule risk associated with cost-driven late fabrication of Radiators • A Delta-PDR for Mechanical Systems was successfully held in July, 2002. • LAT program risk management has been fully re-vamped, and all Mechanical Systems risks are continuously updated and action plans evaluated.

6. Delta PDR Action Items • 19 action items were assigned to Mechanical Systems at the July Delta-PDR • All have been addressed and submitted for closure • Actions are grouped into 5 classes • Thermal Design: Investigate off-design thermal cases and impact of trades on parallel heat transfer paths within the LAT • Structural Design: Evaluate stress concentrations within, and venting of Radiators • Fabrication and Integration: assess inspection and contamination issues as they may affect LAT • Environmental Test: finalize thermal test levels and cycles • Risk: Implement a continuous risk management systems for Mechanical Systems

7. Delta PDR Action Items (cont 1) • Thermal Design: Investigate off-design thermal cases and impact of trades on parallel heat transfer paths within the LAT • Analysis of the impact of heat pipe failures have been completed. The designs are fully redundant, being able to accommodate the loss of any heat pipe • Shimmed and bolted interface conductances and radiative couplings have been updated to reflect the final CDR designs • Transfer orbit thermal analysis has been started, using the draft timeline from Spectrum • Structural Design: Evaluate stress concentrations within, and venting of Radiators • Complete stress analysis of the Radiator VCHP’s has been completed, and will be shown at CDR • Venting of Radiator panels has been addressed with vented honeycomb and close-outs.

8. Delta PDR Action Items (cont 2) • Fabrication and Integration: assess inspection and contamination issues as they may affect LAT. • IR camera inspection of the Radiators has been budgeted. • Ground cooling requirements during LAT integration have been defined (LAT-TD-00997) • LAT CCP has been released, and all subsystems are working to it. A LAT low-temperature bake-out is part of that. • Environmental Test: finalize thermal test levels and cycles. • Test temperatures for all subsystems and the LAT have been finalized (LAT-SS-00778), and include a minimum AT margin of 5 C and QT margin of 10 C over operating • LAT Verification Plan has baselined 8 thermal cycles of the VCHP joints. • LAT thermal test program staffed adequately • Risk: implement a continuous risk management systems for Mechanical Systems • The LAT has completely updated its CRM system, using the GLAST program system at NAS/GSFC. This is managed by the LAT System Engineer, and includes risks and mitigation plans for all subsystems, including Mechanical Systems.

9. Legend GLAST Mission Spec’s LAT Spec’s Subsystem Spec’s LAT Requirements Flow-Down

10. Key LAT Structural and Thermal Requirements

11. Key LAT Structural and Thermal Requirements

12. LAT Block Diagram MLI Surrounding ACD ACD Base Elec Ass’y alum frame TKR Module CFC tray, side walls Grid monolithic alum structure Spacecraft LAT mounting structure Spacecraft SC bus structure CAL Modules alum bottom plate Solar Arrays S.A. mount Elec. Boxes alum electronics box EMI Skirt Shields E-Boxes, supports X-LAT Pl Radiator Mnt Bkt Support Radiators at corners of Grid LAT Radiators on +/- Y sides of LAT Grid X-LAT Plate monolithic alum structure Htr Switch Boxes Operate Radiator heaters MLI Insulation MLI surrounding underside of LAT LAT Block Diagram

13. LAT System Schematic Diagram LAT Schematic Diagram

14. LAT Internal Interfaces

15. Trades Associated With Internal Interface Finalization

16. Internal Interface TBX’s and Open Issues • Tracker-LAT interface • 0 TBX’s in ICD • Interface drawing in draft: working on final tolerancing • Open issue: TKR-Grid copper thermal straps • Being worked by TKR group • Detailed design is complete and in the interface drawing and testing is underway • Closure plan • TKR to complete thermal testing as part of EM test plan closure • Calorimeter-LAT interface • 0 TBX’s in ICD • Interface drawing in final draft • Open issue: CAL-Grid bolted friction joint • Being worked by Mechanical Systems • Friction testing is complete and preliminary joint allowables established • EM testing of joint and 1 x 4 Grid will complete qualification process • Friction joint design has been questioned by GSFC • Currently under discussion with GSFC mechanical branch • ACD-LAT ICD interface • 4 TBX’s in ICD: all have been resolved and will be included in the next revision (in release cycle) • Interface drawing in final draft: finalize fit of mating pieces • Open issues: none

17. Internal Interface TBX’s and Open Issues (cont) • Electronics-LAT interface • # TBX’s • Interface drawing in second draft: awaits X-LAT interface resolution • Open issue: X-LAT Plate to Electronics box thermal joint • Baseline thermal strap design identified to not meet thermal or structural requirements • LAT tiger team convened to resolve interface issues—preliminary thermal design developed, using vel-therm and parallel thermal paths • Closure plan • Incorporate preliminary thermal design into LAT system model to confirm design meets interface temperature requirements (underway) • Finalize X-LAT and E-box structural interface to work around thermal design • Open issue: Heater Switch Box mounting • Switch box design has been finalized, but interface to Radiator Mount Bracket is TBD • Closure plan • Establish interface req’s: loads, heat transfer • Finalize mounting design: bolt sizing, thermal and electrical interface • Open issue: Finalize TCS interface requirements • Details of interface and functionality requirements have not been finalized • Closure plan • Finalize TCS Performance Specification • Use this to spec interface and functionality requirements for Elec-LAT ICD

18. Interface Requirements Documentation Status LAT Internal Interface Control Specifications

19. LAT External Interfaces

20. Trades Associated With External Interface Finalization

21. External Interface TBX’s and Open Issues • Interface requirements documents • Interface design maturation has superseded much of requirements documents • Closure plan • Work with GLAST project to update IRD, MSS to be bring them up to date with latest agreements • SC Flexure to LAT mounting design is not finalized • Actively working design concepts with Spectrum • Hanging Wing bracket design concept is baselined • Working SC shear pin envelope with respect to EMI Skirt stay-clear • Impact on LAT design is well-understood • Closure plan • Work to final concept by mid-April • Incorporate into LAT-DS-00040 drawing and Spectrum ICD by LAT CDR • Lateral center-of-mass requirement flow-down to LAT • LAT center of mass requirement is being developed by Spectrum as part of ACS maturation, in conjunction with LAT input • LAT has evaluated expected worst-case center-of-mass offsets • Closure plan • Spectrum: evaluate impact of this on ACS/de-orbit and propose compromise

22. LAT Metrics: Mass • UPDATE. SHOW ALLOCATION FLOW-DOWN TO SUBSYSTEMS AND CHANGES SINCE dPDR LAT Mass Status Source: LAT-TD-00564-06 “LAT Mass Status Report, Mass Estimates for March 2003,” 7 March 2003

23. LAT Metrics: Mass (cont) LAT Subsystem Mass Status (*) Recommended reserves estimated using guidelines given in ANSI/AIAA G-020-1992 "Estimating and Budgeting Weight and Power Contingencies for Space Craft Systems“ (+) “Mech” includes the Grid, X-LAT Plates, Radiators, and EMI Shield pieces (#) “DAQ Elec” includes all power, communications, and trigger and dataflow systems (PDU, SIU, TEM/TPS/GASU respectively) Source: LAT-TD-00564-06 “LAT Mass Status Report, Mass Estimates for March 2003,” 7 March 2003

24. LAT Metrics: Dimensions • LAT instrument and subsystem stay-clears are governed by Interface Definition Drawings • LAT-SC stay-clears delineated in LAT-DS-00040-8 (reproduced in 433-IRD-0001) • Subsystem stay-clears, interface features, datums, and tolerances established by the IDD’s with each subsystem Key LAT Stay-Clear Dimensions Source: LAT-DS-00040-08 “LAT Instrument Stay Clear,” 12 Feb 2003 Draft LAT-DS-01221-01, “Radiator-LAT Interface Definition Drawing,” 26 Feb 2003 Draft LAT-DS-00309-03, “ACD-LAT Interface Definition Drawing,” 20 Feb 2003 Draft

25. LAT Metrics: Dimensions (cont) LAT Stay-Clear Assembly

26. LAT Metrics: Power LAT Dissipated Power Values Source: LAT-TD-00225-04 “A Summary of LAT Dissipated Power for Use in Thermal Design”, 13 Mar 2003

27. LAT Metrics: Power (cont 1) LAT Dissipated Power Distribution Source: LAT-TD-00225-04 “A Summary of LAT Dissipated Power for Use in Thermal Design”, 13 Mar 2003

28. LAT Materials and Parts • Material requirements • Source: 433-MAR-0001, “Mission Assurance Requirements” • LAT: LAT-SS-00107-01, “Mechanical Parts Plan” • Material Usage Agreement (MUA) needed for non-compliant materials • All materials have been assessed by GSFC materials branch to be compliant to standards and used in conventional methods • Currently the project requires no MUA’s • Relevant procedures and guidelines for material selection • Metallic Materials for Stress Corrosion Cracking Resistance in Sodium Chloride Environment (MSFC-STD-3029) • Fastener Integrity Requirements (541-PG-8072.1.2) • Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials for Outgassing (ASTM-E-595) Total Materials Count on LAT M&P List Source: LAT-DS-00405, “LAT Mechanical Materials and Parts List,” March 2003

29. LAT M&P List: Inorganic, Polymer and Composite Materials • Inorganic materials • Inorganic materials submitted to LAT IPO as of 19 March 2003 • Polymers and Composites • Polymer and composite materials submitted to LAT IPO as of 19 March 2003 Inorganic Materials Count on LAT M&P List Polymer and Composite Materials Count on LAT M&P List Source: LAT-DS-00405, “LAT Mechanical Materials and Parts List,” March 2003

30. LAT M&P List: Lubricants and Processes • Lubricants • Lubricants used only in static applications, largely for bolts • No moving parts within the LAT • Lubricants submitted to LAT IPO as of 19 March 2003 • Processes • M & P list collects process information for all heat treating and surface treatment processes • Processes submitted to LAT IPO as of 19 March 2003 Lubricant Count on LAT M&P List Processes on LAT M&P List Source: LAT-DS-00405, “LAT Mechanical Materials and Parts List,” March 2003

31. Materials List Pending Items • Pending items as of 19 March 2003 • Reasons for status • Specific material not yet chosen • Waiting for “TBD’s” to be filled in • Outgassing testing in progress • Mechanical Parts Review Board will evaluate materials once missing information is collected from test results or work with manufacturer • Final step is to validate materials list • Cross-check against drawing list • Check for missing materials and processes Materials Pending Materials Branch Approval Source: LAT-DS-00405, “LAT Mechanical Materials and Parts List,” March 2003

32. Summary and Further Work • Summary • Internal and External interfaces have been clearly defined • Remaining interface issues are identified and a closure plan is in progress • Mass and Power allocations are understood and being tracked with subsytems • M&P list is up-to-date with subsystems • Further Work • Complete interface documentation • Complete interface closure plans to finalize interfaces • Validate M&P list against subsystem drawing trees