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January 3-4, 2008 PowerPoint Presentation
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January 3-4, 2008 - PowerPoint PPT Presentation

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January 3-4, 2008
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  1. CRaTER Pre-Ship Review(I-PSR)Thermal AnalysisChristine Cottingham LM/GSFC 545Hume Peabody GSFC 545 January 3-4, 2008

  2. Overview • Pre-test Analysis • Balance Test Setup / Flight Environment versus Test Setup • Balance Test Temperatures • Balance Testing versus Temperature Cycling Testing • Thermal Model Correlation • Forward Plan / Work To Be Done • Conclusions

  3. Pre Test Analysis • Hume Peabody of NASA GSFC made Thermal Desktop Model in Test Configuration • Made pre-test predictions • Verified mounting plate heater was adequate CRaTER model CRaTER / TV chamber model CRaTER model with top removed

  4. Balance Test Setup • CRaTER was mounted to a ½” thick aluminum plate in the shape of the flight mounting surface • The radiator side of the mounting plate was black anodize and it looked at the bottom of the chamber shroud • 12 Thermocouples were installed on the external surfaces of the instrument and mounting surface • Flight like blankets were installed on the instrument (3mil Kapton facing out) • Apertures had 1 layer GBK • Flight blankets will have GBK outer layer (Kapton has same emissivity as GBK) • Chamber temperature was run at ambient temperatures for hot case and LN2 temperatures for cold and survival cases • In cold and survival the heaters on the mounting plate held the plate at -30°C and -40°C respectively • Telescope hot case environmental radiation sinks were 21°C verses flight effective radiation sinks of -1°C for –Z and 23°C for +Z

  5. Balance Test Setup

  6. Balance Test Temperatures (°C)

  7. Balance Test Temperatures (°C) vs Thermal Cycle Temperatures • Issue: Does the TV cycle bound the ICD temperature limits by at least 10°C? • Yes for Hot Case: • The hot balance interface temperature ran ~4°C warmer than flight temperature limits due to test setup • Pretty Close for Cold Case: • The cold TV cycle telescope temperature was 7°C colder than flight temperatures and all other temperatures were 10°C or better • Orbiter flight predicts have about 10°C margin to limits for CRaTER interface • A waiver will be written against this one temperature and should have no trouble being approved because of the low risk involved

  8. Balance Test Temperatures

  9. Balance Test Temperatures

  10. Thermal Model Correlation

  11. Thermal Model Correlation • Original thermal model vs test temperature was up to 4°C different • After correlation most points are within 2°C and two hot case points to within 3°C • Two things were changed to the thermal model to correlate it to test data • MLI effective emissivity was changed from 0.03 to 0.01 • Conductance from the feet to the mounting surface was reduced by 50% • Need to verify PRT temperature in cold balance case • Doesn’t match near by flight telemetry • Flight telemetry was a little noisy

  12. Forward Plan / Work to be Done • Include in the model where and how power changes in the instrument as the voltage changes • 27.0 VDC = > 6.4 watts • 31.0 VDC = > 6.6 watts • 35.0 VDC = > 6.9 watts • Model in the important components on the boards • To ensure limits are met • To make the flight telemetry predictable • Develop reduced thermal model • Publish Thermal Acceptance Package (joint MIT/GSFC task)

  13. Conclusions • Thermal RFAs have been submitted for closure • A waiver will be written for the TV cycle telescope temperature margin to limits • Thermal model has been correlated (both GSFC and MIT) • Work to be done is understood • The thermal performance of CRaTER is understood and is acceptable