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Mechanical Design Integration Peer Review, March 2003 5. LAT Environmental Verification Testing

Mechanical Design Integration Peer Review, March 2003 5. LAT Environmental Verification Testing. Martin Nordby nordby@slac.stanford.edu. 23 March 2003. 5. LAT Environmental Verification Testing. Verification Test Plans I&T flow Environmental verification test summary Dynamic test plans

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Mechanical Design Integration Peer Review, March 2003 5. LAT Environmental Verification Testing

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  1. Mechanical Design Integration Peer Review, March 2003 5. LAT Environmental Verification Testing Martin Nordby nordby@slac.stanford.edu 23 March 2003

  2. 5. LAT Environmental Verification Testing • Verification Test Plans • I&T flow • Environmental verification test summary • Dynamic test plans • Outline of tests planned • Modal Survey • Sine Vibe • Acoustic • Thermal test plans • Test descriptions • Test profile and temperatures • LAT survey plans • Surveys planned • Configurations • Summary and Further Work

  3. Integration and Test Flow LAT Integration and Test Flow

  4. Environmental Verification Test Summary • Dynamic Tests • Modal survey • Sine vibration • Acoustic • See LAT-MD-01196, “Dynamics Test Plan” • Thermal Tests • Thermal balance • Thermal vacuum cycle • See LAT-MD-01600, “LAT Thermal Vacuum Test Plan • LAT Surveys • Optical survey • Cosmic-ray muon survey • See LAT-MD-00895, “LAT Instrument Survey Plan”

  5. 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

  6. LAT Modal Survey (cont 1) • Instrumentation • High-precision accelerometers mounted to the LAT and test stand • 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 ACD Accelerometer Placement TKR, CAL, and Grid Accelerometer Placement CAL Bottom and E-Box Accelerometer Placement Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003

  7. LAT Modal Survey Test (cont 2) • Test sequence • Excite LAT at two -X corners in the Z-direction, in phase • Excite LAT at two -X corners in the Z-direction, 180 degrees out of phase—intended to excite LAT “potato chip” mode and other anti-symmetric twisting modes • Excite LAT at two -X corners in the X-direction, in phase—intended to excite LAT, ACD, TKR, and CAL lateral modes • Excite LAT web crossings on either side of the Grid center from the underside—intended to excite LAT drumhead mode • Test levels • TBD • Levels will be set, based on pre-test analysis using as-measured damping coefficients for subsystems • Outstanding technical issues • Establish excitation levels • Finalize accelerometers for test, based on predicted test levels

  8. LAT Sine Vibration Test • 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

  9. LAT Sine Vibration Test (cont 1) • Instrumentation • Accelerometers mounted to the LAT and test stand, to cover the entire dynamic range predicted for the LAT and subsystems • 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 TKR, CAL, and Grid Accelerometer Placement Radiators Accelerometer Placement Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003

  10. LAT Sine Vibration Test (cont 2) • Test sequence • Low-level random vibration signature before and after each vibe • Execute Limited Performance Test after each vibe while still on vibe test stand • X-Direction Sine Vibe • Y-Direction Sine Vibe • Z-Direction Sine Vibe • Test levels • Levels will be established with pre-test analysis to 1.25 times the static-equivalent acceleration values, without exceeding interface limit loads • 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) LAT Sine Vibration Minimum Test Levels Source: LAT-SS-00778-01, “LAT Environmental Specification,” March 2003

  11. 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 • Instrumentation • Accelerometers mounted to the LAT and test stand • Microphones mounted around the LAT • 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

  12. LAT Acoustic Test (cont) • Test sequence • Low-level acoustic to verify that allinstrumentation is operational andtaking useful data • Acceptance level test—ramp up soundpressure level (SPL) to AT levels • PFQ level test—ramp up SPL to QTlevels • Ramp down SPL and turn off • TBD modal signature test • Limited Performance Test—re-connectE-GSE cable harnesses and execute LPT • Test levels • Fairing SPL’s are shown • Final SPL’s for testing will be determinedby pre-test analysis, to factor in fill-fractionin acoustic chamber • 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

  13. LAT Thermal Balance/Thermal-Vacuum Tests • Test goals • Thermal-Balance • Verify that the LAT thermal control system is properly sized to keep maximum temperatures within mission limits, while demonstrating at least 30% control margin • Validate the LAT thermal control system control algorithms • Verify that the VCHP control effectively closes the radiator to when the LAT is off • Validate the LAT thermal model by correlating predicted and measured temperatures • Thermal-Vacuum • Verify the LAT’s ability to survive proto-qualification temperature levels at both the high and low end • 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 • Demonstrate that the LAT meets performance goals at temperature • Provide stable test environment to complete LAT surveys, as detailed in LAT-MD-00895, “LAT Instrument Survey Plan” • Configuration • The LAT instrument will be fully integrated but the SC solar arrays will not be installed • The LAT will be powered on and off during testing per the test procedure • The LAT will be oriented with the Z-axis parallel to the ground to allow all heat pipes to operate and the +X axis facing up • All MLI blanketing will be in its flight configuration for the duration of the 2 tests • The LAT will NOT be reconfigured after the thermal-balance test

  14. LAT Thermal Balance/Thermal-Vacuum Tests (cont) • Instrumentation • Thermocouples and RTD’s will be used to instrument the LAT and test chamber • LAT flight housekeeping instrumentation includes many thermistors and RTD’s. These will also be used for monitoring temperatures within the LAT • Specialized test equipment requirements • Chamber pressure of < 1 x 10-5 Torr • Chamber cold wall temperature of –180 oC to provide a cold sink for accumulation of contaminants • Thermally controlled surfaces in the chamber • 5 plates for ACD surfaces, each individually controlled • 2 plates for the radiators(one for each side), each individually controlled • 1 plate to simulate the bus, controlling the environment to the X-LAT Plate and the back of each radiator • Heat exchangers mounted on the +/– X sides of the LAT Grid, to increase ramp rate during transitions • LAT heat pipes will be leveled to within 0.2 degrees • 20 oC/hr max ramp rate • Facility capable of holding LAT stable to < 2 oC/hr rate of change (TBR)

  15. LAT Thermal-Vacuum Test Profile • Dwell at high and low temps for 12 hours, min • Limited Performance Tests conducted during transitions • Comprehensive Performance Tests • CPT test regime performed at ambient, during cold and hot soaks, and at return to ambient • Limited Performance Tests • LPT test regime performed as indicated • Operating modes will be checked • Units will be monitored for problems or intermittent operation

  16. LAT Thermal Balance/Thermal-Vacuum Test Profile LAT Thermal-Vacuum Test Profile Source: LAT-MD-01600-01, “LAT Thermal-Vacuum Test Plan,” March 2003

  17. Thermal Test Levels • Test strategy • Drive components to PFQ limit for LAT, defined in the MAR as Operating limit +/- 10 oC, min • Minimum test margins • 5 C margin from Operating to AT level • 5 C margin from AT to LAT PFQ level LAT Thermal Verification Test Temperatures Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003

  18. 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

  19. LAT Surveying (cont 1) LAT Optical and Muon Surveys During Integration and Test Source: LAT-MD-00895 “LAT Instrument Survey Plan”

  20. 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 oC (TBR) • LAT and GSE/STE temperature stable to within 2 oC (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

  21. Summary and Further Work • Summary • LAT Dynamics Test Plan has been written and is ready for initial release • LAT Thermal Test Plan has been written and is ready for initial release • LAT Survey Plan has been written, with final pieces coming together for release before CDR • Test instrumentation and levels are understood • Further work • Perform pre-test analysis to finalize instrumentation and STE requirements • Expand test plans with results of pre-test analysis • Complete test implementation plans

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