X-ray Missions Delta: AXSIO Redux

1. X-ray Missions Delta:AXSIO Redux Thermal Kimberly Brown 30 April – 1 May, 2012

2. Thermal Control Subsystem Summary for S/C Bus • Passive S/C radiators for spacecraft components • Thermal coating applied to exterior of closeout panels on anti-sun side • Heat pipes embedded in radiator panels • Cho-therm interface material used for box to panel interface (electrically and thermally conductive) except for battery (Nusil interface) • Heat pipes transfer heat from boxes (not mounted to radiators) to radiator panels • Active heater control via mechanical thermostats (operational and survival) • Primary and redundant heat circuits • Two thermostats in series per circuit • Kapton film heaters attached to components, including propellant tanks • Line heaters on propellant lines and fill-and-drain valves • Internal surface coatings has high emittance (Aeroglaze Z307 black paint) • Except for radiators, exterior of S/C bus and metering structure is insulated with MLI blankets (15 layers make-up) • S/C bus is thermally isolated from FMA (24 mounting points) • Back side of portion of solar array that serves as sunshield is insulated with MLI • Flight thermistors for telemetry of temperatures

3. Thermal Control Subsystem Summary for Instruments • FMA is cold biased and has active heater control via heater controllers • Primary and redundant heat circuits • Same heater circuits for operational and survival (10ºC lower set point for survival) • FMA is thermally isolated from S/C bus • Passive radiators for XMS and XGS components • Radiators shaded from sun • Heat pipes isothermalize radiator panels, except for XGS CCD radiator • Heat pipes transfer heat from components to radiator panels, except for XGS CCDs • Active heater control via mechanical thermostats (survival mode) • Primary and redundant heat circuits • Two thermostats in series per circuit • Kapton film heaters attached to components • Heat pipes and backside of radiators are insulated with MLI blankets (15 layers make-up) • Flight thermistors for telemetry of temperatures

4. S/C Bus Thermal Control Subsystem Functional Block Diagram Thrusters RW RW RW RW RWE RWE RWE RWE Battery (Li-Ion) Radiators Reject Waste Heat to Space FMA PSE Comm System Avionics Gyro Propellant Tanks, Lines and Fill-and-Drain Valves Radiators MLI Thermostatically controlled heaters

5. Orbit Thermal and Charged Particle Environment • L2 provides excellent thermal environment for passive (radiative) cooling • Earthshine and moonshine negligible • Thermal disturbances • Sun angle changes due to ±10º roll and ±45º pitch • Seasonal variation of solar flux • Charged particles environment requires electrically conductive thermal coatings • Radiators (anti-sun side) have NS43G yellow paint which has a high emittance (0.9) • Flown on WIND, POLAR, MAP, etc. • MLI outer covers have silver conductive composite coating (ITO/SiOx/Al2O3/Ag) which has a low absorptance (0.08 at BOL) and high emittance (0.6) • Flown on WIND, IMAGE, etc.

6. Instrument Radiator Sizing XMS Cryocooler Radiator Ammonia Heat Pipe (Redundancy Not Shown) Cryocooler (Compressor & Control Electronics) Electronics Boxes E-Box Radiator

7. Instrument Radiator Sizing *Option A: 2 pair of 30-deg gratings sectors, 2 x 8-CCD cameras Option B: 1 pair of 45-deg grating sectors, 1 x 10-CCD camera CCD Power Dissipation: 0.1 W each (1.6 W Total) DEA & DPA Power Dissipation: 50 W (-40°C to 50°C operating; -55°C to 60°C survival) Radiator Cools CCDs to -90°C Passively Ammonia Heat Pipe Transport Heat from DEA & DPA to Remote Radiator CCDs are cold biased and trim heaters maintain temperature stable Ethane heat pipes isothermalize CCDs Instrument shown will be scaled down from 32 to 16 CCDs

8. XGS CCD Parasitic Heat Load CCD Radiator Heat Rejection: 1.6 W + 0.4 W = 2 W (2.6 W after adding 30% contingency)

9. Instrument Power Dissipation Summary One radiator for cryocooler (compressor and control electronics) and one radiator for XMS electronics boxes and XGS DEA and DPA

10. Radiator and Heat Pipe Orientation • Cryocooler compressor motor mount and control electronics located slightly below radiator • Allows cryocooler CCHP operate in reflux mode to overcome gravity problem in ground testing • CCHPs transfer heat from electronics boxes to radiator • CCHP attached to exterior of components (IceSat GLAS heritage) • Multiple CCHPs provides sufficient heat transport capacity and redundancy • 2.8575 cm diameter ammonia pipe; 1372 W-m limit • 1.27 cm diameter: 152 W-m limit • Radiators slightly above CCHP evaporators to allow CCHP operate in reflux mode in ground testing

11. Instrument Survival Heater Circuits • Survival heaters and thermostats attached to exterior of electronics boxes and cryocooler motor mount • Set point of primary heater circuit thermostats is 3ºC larger than redundant heater circuit • Powered by S/C bus directly

12. FMA Thermal Requirement • Mirror segment temperature gradient requirement depends on gradient topology • Rule of thumb is 20°C±0.5°C • Recent IXO STOP analysis has a ± 0.1°C goal

13. FMA Thermal Design • FMA is cold biased • Active heater control maintain mirror segment temperature stable and meets thermal gradient requirement • Heater locations • Conductive portion of thermal pre-collimator • Exterior of module walls • Fore section of metering structure • Non-conductive portion of thermal pre-collimator minimizes heater power • Sunshield prevents direct solar impingement on FMA • FMA thermally isolated from S/C bus

14. FMA Heater Locations Non-Conductive Portion of Pre-collimator Fore Portion of Metering Structure Exterior Conductive Portion of Pre-collimator

15. S/C Bus Power Dissipation • *Pressure Transducer • **Used for radiator sizing

16. S/C Bus Thermal Control Sunshield MLI MLI on Exterior of Metering Structure MLI on Exterior of S/C Bus with Exception of Radiators MLI on Backside of Sunshield Portion of Solar Array

17. S/C Bus Thermal Control MLI on interior to radiatively isolate from FMA CCHP isothermalizes mounting interfaces for FMA (redundancy not shown) CCHP embedded in honeycomb radiator panel

18. S/C Bus Propulsion Subsystem Thermal Control Propellant tanks, lines and valves are thermally isolated from S/C bus structure 0.559 m Diam. Heaters, thermostats and MLI to maintain temperature of propellant tanks, lines and valves above 10ºC. Heater circuits have redundancy. Aluminum tape spreads heat along propellant lines Cat-bed heaters commanded to heat reactors on prior to firing

19. Thermal Model Solar Array XGS CCD Radiator S/C Bus XMS Cryocooler Radiator S/C Bus Radiators Metering Structure Instrument Radiators

20. Thermal Model Mirror Module Conductive Portion of Pre-collimator (Heater Controlled) Pre-collimator Stray Light Baffle

21. Summary of Radiator Sizes

22. Summary of Instrument Survival Heater Power

23. Summary of S/C Bus Survival Heater Power

24. Mass Estimates/TRL

25. Mass Estimates/TRL

26. Mass Estimates/TRL

27. Conclusions and Recommendations • S/C bus, XMS and XGS thermal design meets temperature requirements and have sufficient margin • Instrument radiators must be above CCHP evaporators to make CCHP testable (in reflux mode) during ground testing • STOP analysis is needed to evaluate if FMA thermal design meets thermal-structural distortion requirement • Evaluate thermal effect of solar array as sunshield on FMA mirror temperature gradient • If necessary, consider optical solar reflector/ITO (no solar cells) on “sunshield” portion of solar array

28. Delta Charts for AXSIO Redux • Change in the MEL are the following: Removed mass for • XMS Cryocooler Radiator, Paint, MLI on backside of Radiator • XMS Spreader heat pipes for XMS CryocoolerRaditor • XMS Electronics Radiator, Paint, MLI on backside of Radiator • XMS Electronics MLI Tent • Buttons, Velcro and Tape for MLI (included in MLI weights)

29. AXSIO Redux MEL • AXSIO Redux New MEL includes: • Metering Structure MLI, thermistors • S/C MLI, paints, heaters, thermostats, thermistors • Heat Pipes embedded in S/C closeout panels • Heat Pipes for transporting heat from electronic boxes to radiators • Heat Pipes for isothermalizing FMA mounting interfaces • XGS Electronics MLI tent, heaters, thermistors, thermostats, Radiator, Radiator Paint, MLI on backside of Radiator. • XGS CCD Radiator, Radiator Paint, MLI on backside of Radiator. Sized a Radiator for XGS based on 50 Watts 0.182 m2 to add in MEL Removed 12 heaters for tanks and lines from MEL (estimate) of how many per tank

30. S/C Bus Thermal Control Subsystem Functional Block Diagram Thrusters RW RW RW RW RWE RWE RWE RWE Battery (Li-Ion) Radiators Reject Waste Heat to Space FMA PSE Comm System Avionics Gyro Propellant Tanks, Lines and Fill-and-Drain Valves Radiators MLI Thermostatically controlled heaters