1 / 8

X-Ray Gratings Mission

X-Ray Gratings Mission. Flight Mirror Assembly Thermal Mike Choi 19 – 23 March 2012. Thermal Difference from IXO or AXSIO. All flight mirror assembly (FMA) modules in this study have gratings IXO had a CAT X-Ray Grating Spectrometer (XGS) study at IDL in May 2009

yule
Download Presentation

X-Ray Gratings Mission

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. X-Ray Gratings Mission Flight Mirror Assembly Thermal Mike Choi 19 – 23 March 2012

  2. Thermal Difference from IXO or AXSIO • All flight mirror assembly (FMA) modules in this study have gratings • IXO had a CAT X-Ray Grating Spectrometer (XGS) study at IDL in May 2009 • Only 4 of 24 FMA outer mirror modules had gratings • Most mirrors have direct view of metering structure • Grating typically has low emittance and significant thermal impact • Mirrors have direct view of gratings instead of metering structure • Gratings form a thermal radiation barrier between mirrors and metering structure

  3. Thermal Model Mirror Module Non-Conductive Pre-Collimator: 13.6 cm Tall Mirrors Grating

  4. Worst Hot Case Temperature Predictions: EOL and 0˚ Pitch ˚C ˚C Mirror Segments No Heaters On Metering Structure. Heaters On Conductive Portion of Pre-Collimator and Module Walls. Heater Power : 450 W peak (315 W average) for 16 Mirror Modules and Gratings.

  5. Worst Cold Case Temperature Predictions: BOL and -45˚ Pitch ˚C ˚C Mirror Segments No Heaters On Metering Structure. Heaters On Conductive Portion of Pre-Collimator and Module Walls. Heater Power : 470 W peak (329 W average) for 16 Mirror Modules and Gratings.

  6. Heater Power Summary *Average is peak multiplied by 70% per GOLD Rules. **Heater resistance is sized based on Vmin2/R=470 Pitch or roll has small impact on heater power because: ·FMA is thermally isolated from spacecraft bus. ·Grating surfaces facing metering structure have low emittance.

  7. FMA Heater Power Prediction • Worst cold case heater power prediction is 470 W for 16 mirror modules and gratings • Mirrors have no heat gain from metering structure which has no active heater control • Heater power may be reduced by increasing non-conductive pre-collimator height • For example, increasing height from 13.6 cm to 18.6 cm reduces heater power from 470 W peak (329 W average) to 421 W peak (295 W average) • Difference from IXO: IXO FMA had heaters on metering structure and pre-collimator/module walls • Mirror modules had no gratings • Mirrors gained heat from both heated metering structure and pre-collimator/module walls • Heater power for metering structure reduces heater power for pre-collimator/module walls

  8. Heater Control for Metering Structure: Conclusion and Recommendation • It is assumed that gratings have low emittance surfaces facing metering structure • They reduce heat radiation between mirrors and metering structure • Presently emittance is assumed to be 0.1 • Unlike IXO or AXSIO, if emittance of gratings is low (about 0.1 or less), active heater control on metering structure close to FMA is not required • Heater power prediction for 16 mirror modules with gratings is 470 W peak (329 W average) • Heater power may be reduced by increasing non-conductive pre-collimator height (e.g., increasing height from 13.6 cm to 18.6 cm reduces heater power from 329 W to 295 W average) • Heaters on metering structure would be required if emittance is not low • Measure emittance of gratings and repeat thermal analysis if it is significantly larger than 0.1 • Refine heater controller set points in thermal model to meet 20˚C±0.5˚C or better

More Related