A Compact Thermal Heat Switch for Cryogenic Space Applications Operating near 100 K

TL;DR

This paper presents a simple, reliable, and power-free thermal heat switch based on thermoplasts for cryogenic space applications near 100 K, reducing thermal losses and enhancing system efficiency.

Contribution

It introduces a novel thermoplast-based heat switch design that operates without power and is suitable for cryogenic space systems, with long-term performance analysis.

Findings

Successful prototype of the thermoplast heat switch.

Effective reduction of thermal heat loss in cryogenic systems.

Long-term stability of the thermoplast material at cryogenic temperatures.

Abstract

A thermal heat switch has been developed intended for cryogenic space applications operating around 100 K. The switch was designed to separate two pulse tube cold heads that cool a common focal plane array. Two cold heads are used for redundancy reasons, while the switch is used to reduce the thermal heat loss of the stand-by cold head, thus limiting the required input power, weight and dimensions of the cooler assembly. After initial evaluation of possible switching technologies, a construction based on the thermal expansion coefficient (CTE) of different materials was chosen. A simple design is proposed based on thermoplasts which have one of the highest CTE known permitting a relative large gap width in the open state. Furthermore, the switch requires no power neither during normal operation nor for switching. This enhances reliability and allows for a simple mechanical design. After a single switch was successfully built, a second doubleswitch configuration was designed and tested. The long term performance of the chosen thermoplast (ultra-high molecular weight polyethylene) under cryogenic load is also analysed.