THERMAL CONTROL

Temperature control aboard spacecraft is, in general, an exercise in cooling. Separate systems are used for external thermal control and for internal control.

External systems utilize in-line heaters and recirculating thermal fluids such as liquid ammonia or chlorofluorocarbons (Freons). Since vacuum conditions exist outside spacecraft, heat flow by conduction and convection is minimal. Radiation is the sole means for heat transfer out of the system. This is accomplished using high surface area radiators. Heat is dissipated via emission of electromagnetic energy in the infrared region of the spectrum.

Internal thermal control systems maintain temperature in the cabin and usually combine other functions including control of: humidity, airborne particulates, and airborne microorganisms. These composite Temperature and Humidity Control (THC) systems utilize condensing heat exchangers (CHX) for the primary cooling effect. Water vapor and heat (latent heat of fusion for water) are removed from the cabin air by the CHX. The water recovered in this way, known as humidity condensate, contains trace levels of water soluble contaminants which are present in the air. Contaminant levels are relatively low, and for this reason, the Russians utilize a separate water reclamation system to purify humidity condensate for the production of drinking water aboard the Mir space station. Control of airborne solids including microorganisms is achieved suing High Efficiency Particulate Air (HEPA) filters.

REFERENCES

Thermal Control:

Amidieu, M., Berthorn, V., and Maciazsek, T., A New Generation of Radiators, SAE Technical Paper Series No. 901364, presented at 20th International Conference on Environmental Systems, Williamsburg, VA, July 9-12, 1990.

Baker, B.C., Voss, F.E., Wolfe, G.W., Thermal/Vacuum Testing of a Two-Phase, Freee Tolerant Radiator Panel, SAE Technical Paper Series No. 951655, presented at 25th International Conference on Environmental Systems, San Diego, CA, July 10-13, 1995.

Beverly, W.D., Dandridge, R.E., and Proden, R.D., A Preliminary Heat Flow Analysis of the U.S. Laboratory and Habitation Modules, SAE Technical Paper Series No. 891460, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 24-26, 1989.

Bond, T.A., Metcalf, J.L., and Asuncion C., Shuttle Orbiter Active Thermal Control Subsystem Design and Flight Experience, SAE Technical Paper Series No. 911366, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Chambliss, J., and Ewert, M., Modular, Thermal Bus-to-Radiator Integral Heat Exchanger Design for Space Station Freedom, SAE Technical Paper Series No. 901435, presented at 20th International Conference on Environmental Systems, Williamsburg, VA, July 9-12, 1990.

Duschatko, R.J., Contact Conductance Evaluation for A Full Scale Space Erectable Radiator Pressurized Interface, SAE Technical Paper Series No. 891463, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 24-26, 1989.

Hajela, G., Gombos, F., Delgado, A., and Goldberg, V., Early External Active Thermal Control for the International Space Station, SAE Technical Paper Series No. 961386, SAE International, Warrendale, PA, 1996.

Head, A.M., High Efficiency Optical Solar Reflectors for Spacecraft, Technical Paper Series No. 891495, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 24-26, 1989.

Helsing, R.A., and Horner, J.E., Space Station Freedom Active Internal Thermal Control System - A Descriptive Overview, SAE Technical Paper Series No. 891458, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 24-26, 1989.

Kantara, J.J., Recommended Space Station Radiator Orientation Profile, SAE Technical Paper Series No. 911343, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

McCabe, M.E., Jr., and Swanson, T.D., Performance Testing of a Two-Phase Interface Heat Exchanger, SAE Technical Paper Series No. 891462, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 24-26, 1989.

Mullaney, K., and Head, A.M., Development of High Efficiency Optical Solar Reflectors for Improved Passive Thermal Control, SAE Technical Paper Series No. 901308, presented at 20th International Conference on Environmental Systems, Williamsburg, VA, July 9-12, 1990.

Raetz, J., and Dominick, J., Space Station External Thermal Control System Design and Operational Overview, SAE Technical Paper Series No. 921106, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Schlapbach, M.E., Sharp, J.B., and Szeto, M.D., A Preliminary Analysis of the Passive Thermal Control System for Space Station Freedom, SAE Technical Paper Series No. 901403, presented at 20th International Conference on Environmental Systems, Williamsburg, VA, July 9-12, 1990.

Thermal and Humidity Control:

Hashimoto, H., Aoki, I., Ishida, H., and Miwa, S., Temperature and Humidity Control System of JEM, SAE Technical Paper Series No. 961368, presented at 26th International Conference on Environmental Systems, Monterey, CA, July 8-11, 1996.

Newbold, D.D., McCray, S.B., Millard, D.L., and Ray, R., Performance of a Membrane- Based Condensate-Recovery Heat Exchanger, SAE Technical Paper Series No. 961356, presented 26th International Conference on Environmental Systems, Monterey, CA, July 8-11, 1996.

Newbold, D.D., Ray, R.J., Pledger, W.A., McCray, S.B., and Brown, M.F., Investigation of Humidity Control Via Membrane Separation for Advanced Extravehicular Mobility Unit (EMU) Application, SAE Technical Paper Series No. 891507, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 24-26, 1989.

Petter, F., and Planert, C., Condensing Heat Exchangers as Main Components in LSS for Manned Spaceflight, SAE Technical Paper Series No. 901284, presented at 20th International Conference on Environmental Systems, Williamsburg, VA, July 9-12, 1990.

Ray, R., Newbold, D.D., McCray, S.B., Friesen, D.T., and Kliss, M., A Novel Membrane Device for the Removal of Water Vapor and Water Droplets from Air, SAE Technical Paper Series No. 921322, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Copyright © 1996, James E. Atwater