M2 and Transfer Optics Thermal Control

1. M2 and Transfer Optics Thermal Control 25 August 2003 ATST CoDR Dr. Nathan Dalrymple Air Force Research Laboratory Space Vehicles Directorate

2. M2 & Transfer Optics Thermal Control • Function: Mitigate mirror seeing • Function:Reduce thermally-induced figure errors seeing

3. Requirements • Minimize mirror seeing • Racine experiment: q = 0.38 (TM - Te) 1.2 • Iye experiment: q greatly reduced by flushing • IR HB aerodynamic analysis: q = q(DT, V, l) • Bottom line: requirements on surface-air DT and wind flushing • Minimize thermally-induced figure error Ref: Racine, Rene, “Mirror, dome, and natural seeing at CFHT,” PASP, v. 103, p. 1020, 1991. Iye, M.; Noguchi, T.; Torii, Y.; Mikama, Y.; Ando, H. "Evaluation of Seeing on a 62-cm Mirror". PASP 103, 712, 1991

4. Error Budgets Must share this allocation with M1. Most of the budget will be given to M1.

5. Diffraction-Limited Error Budget (10 nm rms, est.) Blue contours: rms wavefront error (nm) l = 500 nm Acceptable operating range Note: No AO correction assumedGreen range is larger with AO correction. Sign must be reversed for M2, which is inverted.

6. Seeing-Limited Error Budget (0.02 arcsec, est.) Blue contours: 50% encircled energy (arcsec) l = 1600 nm Acceptable operating range

7. Coronal Error Budget (0.02 arcsec, est.) Blue contours: 50% encircled energy (arcsec) l = 1000 nm Acceptable operating range

8. Thermal Loads Compare with 0.25 W on the DST tip-tilt mirror

9. Thermal Loads (cont.) M3 irradiance (34x larger than M2) M2 irradiance (nearly the same as M1)

10. Thermal Loads (cont.) M5 irradiance (9x larger than M2) M4 irradiance (6x larger than M2)

11. Thermal Loads (cont.) M6 irradiance (8x larger than M2)

12. M2 Thermal Control System Concept SiC Air jets inserted in backside cells

13. M2 Cooling System Flow Loop Insert diagram here

14. 3D NASTRAN Model

15. 3D NASTRAN Results for M2 No coolant under mount point Enhanced Cooling Temperature Profile (˚C above Ambient) Temperature Range of Approximately 0.14˚C Peak-to-Valley.

16. 3D NASTRAN Results for M2: Time History

17. M2 Thermal Control System Specs • Next steps: • Fan and system curves • Heat exchanger specs • Chiller specs • Time response of fluid volume

18. High-k Edge cooling of conductive substrate M3, M4, and M6 Thermal Control System Concept

19. M3, M4, and M6 Cooling System Flow Loop Insert diagram here

20. M3, M4, and M6 Thermal Control System Performance M4 M6 M3 All have surface to coolant T’s of less than 4 ˚C. Relatively easy to obtain good temperature control.

21. M5 (DM) Thermal Control System Concept Force flow of air or dielectric liquid (Freon) past actuator array on the rear of the faceplate. Must work with the DM manufacturer to integrate cooling scheme. Q = 22.1 W q = 903 W/m2 Need: h = 90 W/m2-KT = 10 K

22. M5 Cooling System Flow Loop Insert diagram here

23. Summary • With highly conductive substrates, we do not expect major difficulties controlling surface temperatures of M3, M4, or M6. • M2 performs well thermally with air jet array cooling. • Cooling flow option: use the same primary coolant for M1, M2, M3, M4, M5, and M6 (and maybe HS). Use shunts and throttling valves for each load.