ICE (Integrated Cooler Experiment) for COOLSAT

Abstract

This paper discusses the concept and development of a small Stirling-cycle mechanical refrigerator integrated with a phase-change substance (methanol) for cooling a space borne atmospheric gravity wave imager. A system employing this concept, called ICE (Integrated Cooler Experiment), is proposed to fly on COOLSAT (Cryogenic fluid management, Oxygen nightglow, Orbital attitude control, Low-cost cooler Science And Technology). COOLSAT is a proposed satellite by Utah State University for the USRA STEDI (STudent Explorer Demonstration Initiative) pilot mission.

Imager operational heat loads will be absorbed by the latent heat of fusion of the methanol melting across its triple-point. The refrigerator would be turned off during sensor operation to eliminate vibrations and turned on only as necessary to refreeze the methanol during the instruments quiescent period. Costly refrigerator vibration suppression systems are unnecessary. Because the refrigerator need not be sized to meet the peak heating load, it can be down-sized to have lower mass and input power requirements. Two refrigerators will be used on the flight system: one operational and one backup. The integrated cooler has particular application for cooling intermittently operating sensors on small satellites with stringent power, mass, and cost constraints.

Also discussed is a laboratory experiment to demonstrate the temperature stability of the triple-point methanol and to investigate the sufficiency of copper foam conducting heat between the methanol and heat sources and sinks. Results of this preliminary test indicate that a constant temperature during freezing and melting is possible if the heat loads into the system are low enough to maintain the phase-change substance near equilibrium. The development of a full engineering model and its associated testing is also presented.

The design of mechanical supports, multilayer insulation, sensor shutter, etc., to allow the refrigerator to produce a net positive cooling during refreeze periods, is also included.