1. LAT-PR-01967Section 8.B – Structural Design1 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 9 May 2003 Martin Nordbynordby@slac.stanford.edu With contributions from: Youssef IsmailJohn Ku Mike FossRich Bielawski Michael LoveletteJim Haughton Eric GawehnLarry Wai Gamma-ray Large Area Space Telescope LAT Structural Systems

2. LAT-PR-01967Section 8.B – Structural Design2 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Agenda Mechanical Design Overview –LAT Design –Design and Interface Changes Since Delta PDR –CCB Actions, Trade Studies, and Open Issues Peer Review RFA’s, Responses, and Status Requirements Structural Analysis Model Development Structural Analysis Results –Modal Analysis –Distortion Analysis –Interface Loads Recovery Environmental test plans –Integration and Test flow –Modal Survey Testing –Sine Vibe and Sine Burst Testing –Acoustic Testing –Surveying Summary and Further Work

3. LAT-PR-01967Section 8.B – Structural Design3 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Mechanical Design Overview LAT Overview Anticoincidence Detector (ACD) Mass270.1 kg (Mar 2003 est) Size1806 mm w x 1081.5 mm h InterfacesGrid bolted joint, shear pins Electronics Mass199.3 kg (Mar 2003 est) Size1417 mm sq x 222 mm h InterfacesStand-off to CAL; thermal joint to X-LAT Plate Grid/X-LAT Plate/Radiators Mass329.3 kg (Mar 2003 est) Size1580 mm sq x 236 mm h InterfacesFour-point mount to SC flexures LAT Structural Design Parameters DesignSpec Mass2679.4 kg<3000 kg Center of Gravity149.3 mm<185 mm Width1806 mm<1820 mm Height1081.5 mm1100 mm LAT Mass Budget and Current Estimates (kg) EstimateBudget TKR504.9510.0 CAL1375.81440.0 ACD270.1280.0 Mech329.3345.0 Elec199.3220.0 LAT Total2679.43000 Source: LAT-TD-00564-6 “LAT Mass Status Report Mass Estimates for Mar 2003” Calorimeter (CAL) Mass1375.8 kg (Mar 2003 est) Size364 mm sq x 224 mm h InterfacesGrid bolted friction joint Tracker (TKR) Mass504.9 kg (Mar 2003 est) Size372 mm sq x 640 h InterfacesGrid Ti flexure mount and Cu strap

4. LAT-PR-01967Section 8.B – Structural Design4 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 System Block Diagram TKR Module CFC tray, side walls Grid monolithic alum structure CAL Modules alum bottom plate Elec. Boxes alum electronics box MLI Insulation MLI surrounding underside of LAT ACD Base Elec Ass’y alum frame LAT Radiators on +/- Y sides of LAT Grid Spacecraft LAT mounting structure Spacecraft SC bus structure Solar Arrays S.A. mount MLI Surrounding ACD LAT Block Diagram X-LAT Plate monolithic alum structure Radiator Mnt Bkt Support Radiators at corners of Grid EMI Skirt Shields E-Boxes, supports X-LAT Pl Htr Switch Boxes Operate Radiator heaters Anticoincidence Detector Tracker Mechanical Systems Spacecraft Trigger and Data Flow Electronics Calorimeter Legend

5. LAT-PR-01967Section 8.B – Structural Design5 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Design Details Grid corner detail showing heat pipes and purge grooves; corner chamfer and bottom flange Radiator Mount at Grid corners. Note mid-side Grid Wing Reverse-angle view of VCHP S-bends and DSHP connection TKR mid-side and corner flexures Copper thermal straps

6. LAT-PR-01967Section 8.B – Structural Design6 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Interface Details Grid Wing with SC mount bracket EMI Skirt push-back around SC stay-clear LV fairing static stay-clear PAF, per Boeing PPG Flexure on top of octagonal SC volume

7. LAT-PR-01967Section 8.B – Structural Design7 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Underside Design Details Upside-down view of a Grid Y side, showing DSHP’s, Grid Wing, X-LAT Plate, and EMI Skirt Detail of TEM, TPS, and EPU box stack Empty boxes EPU boxes PDU box GASU box SIU boxes TEM/TPS (16x) LAT Underside View of Electronics Boxes

8. LAT-PR-01967Section 8.B – Structural Design8 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Design Changes Since Delta-PDR Subsystem changes affecting system performance –Re-designed TKR bottom tray: added titanium and CFC reinforcement to CC tray –Modified TKR flexure: accommodated updated bottom tray design and provided for stiffer cantilever mode for TKR –Increased ACD mass: accommodated larger tile overlaps and an increase in structural stiffness/strength LAT internal interface changes –Integrated Grid Wing into bottom flange Incorporated Wing into machined Grid (no longer a bolt-on part) Tapered the Wing into a full bottom flange around Grid perimeter to reduce stress concentrations at SC mount, heat pipe cut-outs, and CAL-Grid tab joints –Changed TKR thermal interface to thermal straps Copper straps provided an improved compliant joint to the Grid –Stiffened TKR flexure connection to Grid by eliminating the shimmed “diving board” This was part of TKR bottom tray re-design Effect was to increase TKR first-mode natural frequency –Moved Electronics Box structural mount to CAL back plate Boxes are now hard-mounted to CAL plate by way of moment-bearing stand-offs Cleaner structural design simplified analysis and test plans for CAL and Electronics groups Forces on the X-LAT Plate are reduced to just the inertial loads of the plate –X-LAT plate thermal connection changed to V-Therm cloth Test program underway –CAL-Grid bolted joint modified to include pins Development program underway to finalize pinned joint design Design incorporated into CDR analysis

9. LAT-PR-01967Section 8.B – Structural Design9 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT External Interface Changes Since Delta-PDR Finalized Radiator dimensions and interface –Modified Radiator aspect ratio at request of Spectrum –Agreed on final width, based on reduction in spacing between Radiators that was requested by Spectrum –Agreed on final height, based on Spectrum’s positioning of the LAT and PAF stay-clear agreements with Boeing –Resulting radiator area has increased to 2.78 m 2, although its efficiency has decreased Finalized Radiator mount location to SC –Moved strut mounting location down at request of Spectrum –This reduced Radiator first-mode natural frequency, but margin to 50 Hz requirements is still large Modified LAT-SC mount region –Finalized bolt pattern and pad size to accommodate Spectrum’s flexure design –Agreed to final LAT and SC stay-clear geometry around flexure Increased LAT envelope around ACD –Increased envelope by 10 mm around the base of the ACD to accommodate the lower ACD tile and connectors –Change was approved by GLAST PO and Spectrum, and is part of the LAT baseline

10. LAT-PR-01967Section 8.B – Structural Design10 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Design Changes Since Delta PDR (cont) LAT Delta PDR Design July 2002 LAT CDR Design May 2003 Radiator panels widened and shortened, reducing thermal efficiency Panels cut-out locations fixed SC-LAT mount region finalized VCHP S-bends

11. LAT-PR-01967Section 8.B – Structural Design11 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Change Control Board Changes Since Delta-PDR ACD mass growth (LAT-XR-01200-01) –Added structural mass to increase design margins –Added mass in scintillating tiles to increase size of tiles and overlap between tiles Mechanical Systems mass growth (LAT-XR-01621-01) –Added mass for Grid box additions: Grid Wing, bottom flange, EMI Skirt stiffening, X-LAT thermal straps –Added mass for slightly increased Radiator area Calorimeter mass de-allocation (LAT-XR-01642-01) –Decreased mass allocation to reflect reduction in size of CsI logs –Log size was reduced to accommodate tolerance stack-up within CFC box structure Power allocation update (LAT-XR-01998-02) –Updated power allocations based on current measured values –New allocations and hot-/cold-case bounds flowed to LAT-TD-00225-05, “A Summary of LAT Dissipated Power for Use in Thermal Design.” –Updated allocations and bounds have been used for CDR thermal analysis

12. LAT-PR-01967Section 8.B – Structural Design12 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Mechanical System Schematic Diagram LAT Schematic Diagram Anticoincidence Detector Tracker Mechanical Systems Spacecraft Trigger and Data Flow Electronics Calorimeter Legend

13. LAT-PR-01967Section 8.B – Structural Design13 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Trade Studies Since Delta PDR Moved Electronics Box structural mount to CAL back plate –Trade issues Hard-mounting the Electronics Boxes to the X-LAT Plates vastly increases the complexity of the structural design, and makes verification testing of the CAL difficult De-coupling the Electronics Boxes produces a stiffer, more testable structural design, at the cost of a lower-conductance thermal design –Trade conclusion Boxes now hard-mounted to CAL plate by way of moment-bearing stand-offs The cleaner structural design simplifies analysis and test plans for CAL and Electronics groups Forces on the X-LAT Plate are reduced to just inertial loads of the plate –Open issues X-LAT Plate to Electronics Box thermal interface is still under development V-Therm is the baseline design, but its implementation is still under development More on this during the Mechanical Subsystem talk Radiator panel top profile –Trade issue Prior to spacecraft selection, a rectangular hole was baselined at the top of the Radiator, to allow for integrating the VCHP’s and accessing the LAT-SC bolted joint This design was structurally adequate, but afforded poor access to the CDR VCHP connection design and limited access to the SC-LAT bolted joint –Trade conclusion Modified the Radiator panel design to include a stepped top profile Radiator area is only marginally impacted The stepped design allows good access along the entire top of the Radiator, under the bottom of the ACD

14. LAT-PR-01967Section 8.B – Structural Design14 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural Interface Open Issues CAL-Grid structural joint –Issue: joint has recently been changed from an all-friction joint to a pinned joint, but analysis and development testing are not yet complete –Closure plan Work with GLAST PO to update interface loads, based on latest CLA results Structural analysis underway  CDR analysis results will be used to finalize joint limit loads Joint testing is underway  Coupon tests will establish joint allowables Process development work underway  Pinned liquid-shim application processes (and the impact on the joint design) are understood; final process qualification is underway Investigate alternate designs if pinned joint design still shows negative margin  alternate concepts being pursued now Re-evaluate LAT modal frequencies with final design X-LAT Plate to Electronics box thermal joint –Issue: thermal strap design was recently abandoned in favor of V-Therm carbon fiber cloth, with much testing yet to be done –Closure plan Materials testing Contamination studies and testing Thermal properties testing Joint design and tolerance study Radiator-SC strut angle –Issue: Spectrum has proposed to change the IRD baseline and angle support struts holding the bottom of the Radiator –Closure plan

15. LAT-PR-01967Section 8.B – Structural Design15 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Summary of Structural RFA’s from Peer Review 17 structural RFA’s 17 responses submitted for review and closure –4 RFA’s closed by originator –6 RFA’s accepted for closure, pending evaluation of response at CDR –6 RFA responses submitted/updated; waiting on response from originator –1 RFA response rejected  issue remains open Open RFA: Consider requesting a set of S/C flexures to use during dynamic testing of LAT –SC flexures have been considered for use during LAT environmental testing, but their use has not been baselined –While the use of the SC flexures is conceptually appealing, the logistics and complications of implementing them into the LAT test planning was deemed not worth the additional cost associated with using them SC flexures not currently designed for LAT test loads, so Spectrum loads requirements would need to be updated and flexures re-designed SC flexure design and analysis details would need to be delivered to the LAT, along with verification test data –The LAT is currently investigating either a fixed-base or flexing mount to STE for structural/dynamics testing Flexure design would be capable of handling LAT test loads  this is the current STE requirements as defined in the LAT Dynamics Test Plan Fixed-base design requires early structural analysis to verify that it does not overload the bolted/pinned joint. –This structural evaluation is planned to be worked after CDR, with the constraint that the final implementation can not affect the flight hardware design

16. LAT-PR-01967Section 8.B – Structural Design16 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Requirements Flow-Down

17. LAT-PR-01967Section 8.B – Structural Design17 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Key LAT Configuration and Structural Requirements

18. LAT-PR-01967Section 8.B – Structural Design18 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Integrated Structural FEA Model LAT structural model moved to NASTRAN –Changed FEA software from ANSYS to NASTRAN to make it more compatible with GLAST project office –Re-built model to improve dynamic analysis capabilities –Model is used to generate system structural response and interface limit loads Subsystem models updated –New TKR model from Hytec—including bottom tray and flexure design modifications –Updated ACD model from GSFC—with new mass baseline –Incorporated reduced CAL model from NRL –New Radiator model from LM— including size and mount point modifications –Re-built electronics—new model based on current E-Box and interface designs –Grid Box model modified—integrated Wing and X-LAT Plate modifications have been included LAT Finite Element Model

19. LAT-PR-01967Section 8.B – Structural Design19 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Subsystem FEA Model Quality Checks Subsystem model evaluation –Review model—units, orientation/coordinate system, size, mesh resolution –Review delivery report—do the report and model agree FEA model check-runs –Free-free modal analysis—check model for mechanisms –Translation check—check model for inadvertent grounding –Gravity check—check that inertial loads are reacted only at boundaries –Temperature check—check that structure is free to expand/contract Analysis comparison runs –Mass, center of mass—compare with subsystem estimate –Modal analysis—check against subsystem detailed model and report

20. LAT-PR-01967Section 8.B – Structural Design20 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT FEA Model Boundary Conditions Accelerations –Used LAT center-of-mass accelerations from LAT Environmental Spec. for structural load cases SC mount boundary condition mimics flexure-type connection –X-Side SC mount Restrained in the Y- and Z-directions Free in all 3 rotational DOF’s and X –Y-Side SC mount Restrained in the X- and Z-directions Free in all 3 rotational DOF’s and Y Radiator mounting –Radiators mounted to Grid through Radiator Mount Bracket –SC boundary condition fixed in Y- direction (out-of-plane) only LAT F.E.A. Properties and Current LAT Estimates Source: LAT-TD-00564-06 “LAT Mass Status Report, Mass Estimates for Mar 2003,” 7 Mar 2003 LAT Static-Equivalent Design Accelerations Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003 LAT F.E.A. Model Metrics

21. LAT-PR-01967Section 8.B – Structural Design21 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT FEA Model Quality Checks FEA model check-runs –Free-free modal analysis—check model for mechanisms –Translation check—check model for inadvertent grounding –Gravity check—check that inertial loads are reacted only at boundaries –Temperature check—check that structure is free to expand/contract Analysis comparison runs –Mass—compare model mass with LAT estimate –Center of mass—compare model center of mass with LAT estimate –Modal analysis—compare subsystem modes in LAT model against fixed-base results

22. LAT-PR-01967Section 8.B – Structural Design22 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Integrated LAT FEA Model Quality Checks: Interfaces TKR to Grid –8 RBE3’s per module; fixed connection (fixed DOFs: 123456) CAL to Grid –36 zero-length RBARs per CAL 8 pins fixed in shear (fixed DOFs: 12) 28 bolts clamping (fixed DOFs: 3) ACD to Grid –8 zero-length RBARs at mid-sides 4 pins fixed in shear at mid-sides (fixed DOFs: 1/23) 4 bolts fixed in clamping (fixed DOFs: 2/1) –4 zero-length RBARs at corners (fixed DOFs: 3) E-Box to CAL –4 zero-length RBARs; pinned connection (fixed DOFs: 123) E-Box to X-LAT –4 MPC’s per bay, constrained in Z (fixed DOFs: 3) Radiator to Grid –4 RBE3s per hold-down; dependent nodes on RAD; two independent nodes on radiator mount bracket for each dependent node. Radiator VCHP to EMI Skirt –6 RBE3s per VCHP; dependent nodes on VCHP; two lateral independent nodes on the EMI skirt for each dependent node. Fixed BCs –SC mount points SPC to ground in tangential DOF (fixed DOFs: 1/23) –Radiator lower mounts SPC to ground in out of plane direction (fixed DOFs: 2)

23. LAT-PR-01967Section 8.B – Structural Design23 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Launch and On-Orbit Load Case Definitions Launch Structural Load Cases On-Orbit Thermal Load Cases

24. LAT-PR-01967Section 8.B – Structural Design24 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Integration and Test Load Case Definitions Integration and Test Structural Load Cases Integration and Test Thermal Load Cases

25. LAT-PR-01967Section 8.B – Structural Design25 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Modal Analysis Results LAT drumhead mode has decreased – 54.6 Hz at 2642 kg estimate –Does not meet requirement of 50 Hz Caused by recent change to pinned CAL joint –As expected, pinned joint is considerably less stiff than bolted friction joint –New pinned joint design also explains 45 degree modes at lower frequency Closure plan on LAT natural frequency –Close on final CAL-Grid design details –Investigate effect of bolted joints on natural frequency Significant LAT Modes LAT Drumhead Mode LAT Modes LAT Modes (CAL bolted joint not participating)

26. LAT-PR-01967Section 8.B – Structural Design26 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Summary of Key Deflections Due to Launch Loads Structural analysis results do NOT include the participation of the bolted CAL-Grid friction joint –Result is that deflections are larger than predicted at Delta-PDR, since LAT is less stiff Grid Deflection –6.8 g thrust load at MECO produces maximum Grid bowing –Grid max deflections Center: 0.88 mm down Corner: 0.53 mm down / 0.28 mm up TKR Gap closing –Dishing of the Grid tends to tip TKR modules together Max gap closing: 0.52 mm Radiator distortion –In-plane max motion: 1.0 mm –Out-of-plane max bowing: 1.0 mm LAT Deflected Shape Plot

27. LAT-PR-01967Section 8.B – Structural Design27 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Interface Deflections Deflections and relative motions extracted directly from integrated FEA model Relative motions at interfaces are part of LAT Environmental Spec interface loads definition

28. LAT-PR-01967Section 8.B – Structural Design28 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Interface Load Recovery The LAT Environmental Specification is the collection point for interface loads for subsystem design and test Current load tables in the LAT Environmental Specification contain results from the Delta-PDR structural model (also being used for the current CLA cycle) –Some interface limit loads were generated by LAT static-equivalent analyses –Some limit loads were gleaned from the preliminary CLA, completed in December, 2001 The goal of CDR analysis is to generate updated loads, based on the CDR design, and compare with Delta-PDR design values –Include results for all load cases to assure that worst-case loads have been captured –Identify interfaces and load cases where CDR analysis shows higher predicts than earlier analysis  develop action plan to resolve these issues –Identify interfaces where loads have come down considerably  investigate reducing limit loads in the Environmental Specification, to increase design margin LAT Mech PDR Structural Analysis Aug, 2001 LAT PDR Structural Analysis Jan, 2002 Prelim CLA Results Out Dec 2001-Mar, 2002 Deliver Mech PDR LAT FEA (Sep, 2001) LAT Delta-PDR Structural Analysis Aug, 2002 Deliver Delta- PDR LAT FEA (Sep, 2002) LAT CDR Structural Analysis May, 2003 LAT Env Spec Mar, 2003 SC Study II Struc Models Deliver CDR LAT FEA (Jun, 2003) Spectrum Proposal Struc Model Mission PDR CLA Results Out May, 2003 LAT Env Spec Jun, 2003 Spectrum PDR Struc Model Mission CDR CLA Results Out Sep, 2003 LAT Env Spec Oct, 2003 LAT Structural Analysis Flow-down Schedule

29. LAT-PR-01967Section 8.B – Structural Design29 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 SC-LAT Interface Load Recovery Loads shown are the maxima for all 4 mount points, for the static- equivalent load cases shown –5.1 g lateral test acceleration defines peak lateral loads –SC-LAT support is designed for this, but LAT test program does not require this high lateral load case –Currently working with GLAST PO to re-define test load cases to more realistic values Environmental Spec loads are the result of the preliminary CLA, but do not include the 5.1 g load case

30. LAT-PR-01967Section 8.B – Structural Design30 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Radiator Interface Load Recovery Loads are derived from the LAT static- equivalent analysis, using LAT center-of- gravity accelerations The preliminary CLA of the LAT/Radiators on a generic spacecraft predicted a maximum strut load of only 365 N, so the CLA does not produce the limit load for this interface Acoustic analysis predictions could alter these limit loads for the interface to the SC mount struts

31. LAT-PR-01967Section 8.B – Structural Design31 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 TKR Interface Load Recovery TKR Flexure joint –Flexures isolate the carbon-fiber TKR structure from thermal strains of the Grid –All flexure normals point to the center of a TKR module –The 8 flexures are not a kinematic mount TKR Flexure force recovery –Nodal forces are retrieved by isolating nodal forces at the TKR Flexure beam elements –Design limit loads are the maxima of the TKR module loads Limit loads identified for peak compressive, tensile, and shear load Peak loads all occur in corner bays

32. LAT-PR-01967Section 8.B – Structural Design32 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 CAL Interface Load Recovery CAL-Grid tab joint –Pins carry all shear load at joint –Bolts carry pull-out and prying loads Load recovery –Tab loads separated into 2 types Shear tabs Bolted tabs –All tabs designed to peak limit loads

33. LAT-PR-01967Section 8.B – Structural Design33 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 ACD Interface Load Recovery ACD Base Electronics Assembly (BEA) to Grid Joint –Bolted connection at 4 corners of BEA carry z-direction (thrust) loads only –Bolted and pinned connections at the center of each of the 4 sides Interface load recovery –Interface loads evaluated by retrieving nodal forces at rigid extension from Grid to BEA –Loads shown are design loads for each bolt/pin Mid-Side Mounts –Shear: RSS of X, Z shears in plane of Grid wall –Tens/Compression: normal to Grid wall Corner Mounts –Shear: assumed to carry no shear –Tens/Compression: parallel to LAT Z-axis

34. LAT-PR-01967Section 8.B – Structural Design34 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Electronics Interface Load Recovery Electronics Box joints –Rigid stand-offs to the CAL carry z-direction (thrust) loads, and lateral loads and moments –Flexible connection to the X- LAT Plates allow transverse motion while providing compressive pre-load CAL interface load recovery –Limit loads extracted from model –Loads shown are at the base (CAL side) of the stand-off X-LAT Plate interface load recovery –Lateral, shearing loads defined to be zero: connection allows lateral motion –Tension/compression loads arise from deflection of the Grid

35. LAT-PR-01967Section 8.B – Structural Design35 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural Analysis Summary and Further Work Summary –Subsystem structural models have been updated to reflect CDR designs –Model quality checks have been completed –LAT structural model being used to generate updates to interface limit loads Further Work –Complete all static-equivalent load cases –Review results of coupled loads analysis from GSFC –Revise LAT Environmental Specification as needed Include updates from static-equivalent, acoustic, CLA analyses Identify all areas where loads have increased, if any, and develop closure plan to identify the risk level and closure plan –Deliver CDR structural model to GLAST PO –Complete thermal-mechanical analysis using temperature predicts from SINDA thermal model

36. LAT-PR-01967Section 8.B – Structural Design36 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Verification Test Outline Integration and Test flow Qualification and verification flow –Strength qualification test flow –Vibro-acoustic test flow Dynamic test plans (see LAT-MD-01196, “Dynamics Test Plan”) –Modal survey –Sine vibration –Sine Burst –Acoustic LAT survey plans (see LAT-MD-00895, “LAT Instrument Survey Plan”) –Optical survey –Cosmic-ray muon survey

37. LAT-PR-01967Section 8.B – Structural Design37 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Integration and Test Flow LAT Integration and Test Flow

38. LAT-PR-01967Section 8.B – Structural Design38 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Strength Qualification Test Flow Grid Box static loading –Without Radiators, TKR’s, and ACD –Includes 16x CAL Plate STE’s –TKR joints tested one bay at a time –SC-LAT tested one joint at a time –Grid Box distorted to strength-qualify CAL joint and Grid Box assembly TKR, CAL, TEM/TPS sine burst –Fixed-base strength qualification of subsystem module and interface design ACD Shell and Base Frame Assembly –Fixed-base strength qualification of internal flexures, subsystem, and interface design LAT sine burst –LAT mounted on vibe test stand –Completes strength qual of Grid and TKR joint ACD Sub-Ass’y Sine Burst A TKR QM Sine Burst, Static Load Q ACD Shell + BFA Sine Burst Q CAL QM Sine Burst Q TEM/TPS QM’s Sine Burst Q E-Box PF QM’s Sine Burst P Grid Box Ass’y Static Load P Radiator Static Load P LAT Ass’y Sine Burst P GLAST Obs Sine Burst P Subsystem Qual Tests Subsystem Acceptance Tests

39. LAT-PR-01967Section 8.B – Structural Design39 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Vibro-Acoustic Test Flow LAT and GLAST vibro-acoustic test plan –LAT modal survey—without Radiators, while at SLAC –LAT sine vibration—without Radiators; includes sine sweep signature –LAT acoustic—without Radiators –GLAST Observatory sine vibration—with Radiators but without solar arrays (TBR); includes sine sweep signature –GLAST Observatory acoustic—with Radiators but without solar arrays (TBR) –GLAST Observatory shock—shock event applied at PAF separation plane ACD Sub-Ass’y Sine Vibe, Random Vibe A ACD Sub-Ass’y Acoustic A TKR Qual Module Sine Vibe, Random Vibe Q TKR Flt Modules Sine Vibe, Random Vibe A ACD Shell + BFA Sine Vibe, Random Vibe Q ACD Shell + BFA Acoustic Q CAL QM’s Sine Vibe, Random Vibe Q CAL FM’s Random Vibe A TEM/TPS QM’s Sine Vibe, Random Vibe Q TEM/TPS FM’s Random Vibe A E-Box PF QM’s Sine Vibe, Random Vibe P Grid Box Ass’y P Radiator Sine Vibe P Radiator Acoustic P LAT Ass’y Modal Survey, Sine Vibe P LAT Ass’y Acoustic P GLAST Obs Sine Vibe P GLAST Obs Acoustic P Subsystem Qual Tests Subsystem Acceptance Tests GLAST Obs Shock P

40. LAT-PR-01967Section 8.B – Structural Design40 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Modal Survey Test goals –Validate the LAT structural finite element analysis (FEA) model by correlating with test results –Measure all primary modes of the LAT/Grid structure. –Measure the first mode, and all modes predicted to have high mass participation, for every subsystem –Measure as many natural frequencies of the LAT up to 150 Hz as practical –Test results will be used to evaluate the predicted expected modal frequencies and mode shapes, and used to modify the structural FEA, if needed. –Finalize test environments and notching plans for sine vibration testing Configuration –Fully integrated, except the Radiators are not mounted –Supported off of its spacecraft (SC) mount brackets, –+Z-axis point vertically up –LAT powered off during testing Specialized test equipment requirements –LAT supported by the Vibe Test Plate which provides a rigid support of each mount point –Vibe Test Plate sits on a massive base-isolated table, to damp high-frequency base noise being transmitted to the structure –Excited using two stingers, located under the LAT

41. LAT-PR-01967Section 8.B – Structural Design41 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Modal Survey (cont) Instrumentation –High-precision accelerometers mounted to the LAT and test stand Outstanding technical issues –Establish excitation levels –Finalize accelerometers for test, based on predicted test levels Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003 ACD Accelerometer Placement CAL Bottom and E-Box Accelerometer Placement TKR, CAL, and Grid Accelerometer Placement

42. LAT-PR-01967Section 8.B – Structural Design42 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Sine Vibration / Sine Burst Tests Test goals –Verify the LAT’s ability to survive the low frequency launch environment –Test for workmanship on hardware such as wiring harnesses, MLI, and cable support and strain-reliefs which will not have been fully verified at the subsystem level –Interface verification test for subsystem structural interfaces to the LAT Grid Configuration –Fully integrated, except the Radiators are not installed –Supported off of its spacecraft (SC) mount brackets, on the Vibration Test Stand –The LAT is tested in all three axes, X, Y, and Z independently, requiring re-configuration between tests –The LAT is powered off during sinusoidal vibration testing, and the E-GSE cable harnesses removed Specialized test equipment requirements –The Vibe Test Stand must support the LAT at the SC interface with flight-like connections –The Stand must allow for reconfiguration to alternate axes, with the LAT attached, to avoid unnecessary handling

43. LAT-PR-01967Section 8.B – Structural Design43 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Sine Vibration / Sine Burst Tests (cont) Instrumentation –Accelerometers mounted to the LAT and test stand, to cover the entire dynamic range predicted for the LAT and subsystems Outstanding technical issues –Accelerometer sensitivity—pre-test dynamic analysis will indicate the level of precision and dynamic range needed for this test –Finalize LAT degrees of freedom at STE connection (simulating a “fixed” connection or a flexure) –Establish test levels based on Observatory CLA, without exceeding interface limit loads Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003 TKR, CAL, and Grid Accelerometer Placement Radiators Accelerometer Placement LAT Sine Vibration Minimum Test Levels

44. LAT-PR-01967Section 8.B – Structural Design44 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Acoustic Test Test goals –Verify the LAT’s ability to survive the acoustic launch environment –Test for workmanship on LAT hardware, especially that hardware which responds to acoustic loading –Validate the acoustic analysis Configuration –LAT is fully integrated, including the Radiators –Mounted to STE using the flight-configuration bolted joint –LAT +Z-axis vertical, and with Radiators integrated to the Grid as well as to the STE at the SC strut mount points –LAT is powered off during acoustic testing, and the E-GSE cable harnesses removed Specialized test equipment requirements –The Vibe Test Stand must support the LAT in the same degrees of freedom as the SC flexures, to avoid over-constraining the Grid and Radiators –The STE fills the volume between the Radiators, so must approximate the acoustic behavior of the SC Instrumentation –Accelerometers mounted to the LAT and test stand –Microphones mounted around the LAT

45. LAT-PR-01967Section 8.B – Structural Design45 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Acoustic Test (cont) Outstanding technical issues –Establish acoustic fill and response requirements of STE to adequately bound response of SC –Define post-test modal signature test to verify that LAT dynamic response matches baseline –Finalize accelerometer and microphone placement –Perform pre-test acoustic analysis LAT Acoustic Test Levels Source: LAT-SS-0077801, “LAT Environmental Specification,” March 2003

46. LAT-PR-01967Section 8.B – Structural Design46 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Surveying Survey program goals –Verify as-integrated interface stay-clears –Verify LAT alignment requirements –Verify science performance requirements Validate analytical thermal-mechanical analysis models Develop correlation functions for thermal-mechanical distortion Predict the expected on-orbit precision of the instrument Survey program description –Optical surveying Subsystem inspection measures position of survey retro-reflector balls with respect to physical features and active elements of subsystem module After integration, laser tracker measures bearing and distances to balls on the LAT and in the integration room Data reduction of measurements produces position location information for all balls relative to room coordinate system, and prediction of measurement precision This will establish location of subsystem surfaces and features in their as-integrated positions, providing a verification check during integration –Muon surveying Uses naturally-occurring cosmic-ray muons Muons generate straight-line tracks through TKR modules Mis-alignments between modules will show up as a step in the reconstructed track With muons generating enough cross-tower tracks, the relative locations of tower can be measured This will be used to precisely establish the locations and attitudes (and changes) of TKR modules

47. LAT-PR-01967Section 8.B – Structural Design47 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Surveying (cont 1) LAT Optical and Muon Surveys During Integration and Test Source: LAT-MD-00895 “LAT Instrument Survey Plan”

48. LAT-PR-01967Section 8.B – Structural Design48 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Surveying (cont 2) Instrumentation –Laser tracker—measurement precision of instrument is less than 10 microns, but actual precision is more a function of room temperature stability, reflector ball location precision –Tracker—measurement precision and instrument calibration will be verified with Calibration Unit beam tests at SLAC Specialized test equipment requirements –Room temperature controlled to within 5 o C (TBR) –LAT and GSE/STE temperature stable to within 2 o C (TBR) –Support stands allow for leveling the LAT to within 0.2 degrees to ensure proper functioning of heat pipes –Chill plates provide a heat sink for the Grid during in-air testing Outstanding technical issues –Investigating the use of inclinometers during thermal-vacuum testing –Thermal-mechanical model of LAT in test configuration has not yet been done—this is needed to establish precision and stability requirements for STE

49. LAT-PR-01967Section 8.B – Structural Design49 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Summary of Structural Test Issues and Further Work Summary –Test plans have been developed for all dynamic tests, and are in the release cycle now –LAT Instrumentation Plan reflects the current test plans as related to test instrumentation Further Work –Run first round of pre-test analysis for all dynamics tests –Finalize test instrumentation configuration –Finalize M-GSE and STE loads and requirements –Revise test plans with updated information resulting from pre-test analyses

50. LAT-PR-01967Section 8.B – Structural Design50 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural Systems Supporting Information Peer Review Detailed RFA Responses and Disposition Subsystem FEA Model Quality Check Detailed Results

51. LAT-PR-01967Section 8.B – Structural Design51 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural RFA’s from Peer Review

52. LAT-PR-01967Section 8.B – Structural Design52 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural RFA’s from Peer Review (cont 1)

53. LAT-PR-01967Section 8.B – Structural Design53 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural RFA’s from Peer Review (cont 2)

54. LAT-PR-01967Section 8.B – Structural Design54 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Structural RFA’s from Peer Review (cont 3)

55. LAT-PR-01967Section 8.B – Structural Design55 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: TKR Model Pedigree –Hytec delivered TKR dynamic model for CLA on 3/6/03 –SLAC modifications included orientation and duplication. FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry and design features are included –Results match detailed model analysis within 2% –Detailed model incorporates significant amount of test verification Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

56. LAT-PR-01967Section 8.B – Structural Design56 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: CAL Model Pedigree –NRL delivered CAL dynamic model on 3/12/03 –SLAC mod’s included modifying Baseplate to be compatible with NASTRAN; changing concentrated mass value to match mass report; changing stiff CBARs to Rigid elements –All SLAC mod’s were conveyed to NRL and they are in the process of checking the SLAC model FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry and design features included –In-plane static results match detailed model; this is most critical loading direction; dynamic results off by up to 16.1%, but at over 200 Hz this is not expected to be an issue Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

57. LAT-PR-01967Section 8.B – Structural Design57 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: ACD Model Pedigree –GSFC delivered ACD dynamic model for CLA on 2/28/03 –SLAC modifications included orientation. FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry and design features are included Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

58. LAT-PR-01967Section 8.B – Structural Design58 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: E-Boxes Model Pedigree –E-Box models built from scratch based on latest geometry and mass properties FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry is included –Load paths are approximated –Stiffening features are not modeled presently; additional detail will be added after CDR Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

59. LAT-PR-01967Section 8.B – Structural Design59 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: Radiators Model Pedigree –LM delivered Radiator dynamic model for CLA on 2/28/03 –SLAC mod’s included conversion to SI units, deletion of mount bracket / patch panel representations, and orientation into LAT CS and duplication FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry and design features are included –Results match LM model within 2%; error is result of numerical round-off Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

60. LAT-PR-01967Section 8.B – Structural Design60 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: X-LAT Plates CLA Model Pedigree –Model built from scratch based on latest geometry and mass properties FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry is included Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

61. LAT-PR-01967Section 8.B – Structural Design61 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: EMI Skirts Model Pedigree –Model built from scratch based on latest geometry and mass proerties FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry are included Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

62. LAT-PR-01967Section 8.B – Structural Design62 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 LAT Subsystem FEA Model Checks: Grid Base Model Pedigree –Model built from scratch based on latest geometry and mass proerties FEA Model Quality Check Summary –Passes all FEA checks –Temperature check TBD, not required for dynamic analysis FEA Model vs Design Check Summary –Latest geometry are included Model Check Results Detailed Summary F.E.A. Model Metrics (each) F.E.A. Model Metrics (each)

63. LAT-PR-01967Section 8.B – Structural Design63 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Gamma-ray Large Area Space Telescope LAT Structural Systems Peer Review RFAs

64. LAT-PR-01967Section 8.B – Structural Design64 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Peer Review RFAs

65. LAT-PR-01967Section 8.B – Structural Design65 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Peer Review RFAs (Continued)

66. LAT-PR-01967Section 8.B – Structural Design66 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Peer Review RFAs (Continued)

67. LAT-PR-01967Section 8.B – Structural Design67 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Peer Review RFAs (Continued)

68. LAT-PR-01967Section 8.B – Structural Design68 GLAST LAT Project CDR/CD-3 Review May 12-16 2003 Peer Review RFAs (Continued)