New cryogenic heat switch suitable for operational missions

Cryogenic Heat Switches are common but are, in practice, only used for specific low temperature scientific applications, like the Gas Gap Heat Switch on the Herschel 3He Sorption Cooler. At higher temperatures (between ambient and 30K) where radiation plays a significant role and for operational missions where reliability is crucial, there is no flown example of a Cryogenic Heat Switch.

A TDE activity with Lidax Ingenieria, Spain, has developed a cryogenic heat switch that would function in the range of 30-80K. By developing a reliable Heat Switch capable of operating in this range or even beyond, the activity will provide the space community with a high performance, adaptable device, to be included in the future cryogenic missions working with active cooling, to save power and mass.

Cryogenic heat switches are mainly used to cut off a strong source of heat, such as when a cooler or cryocooler is providing cold to an instrument, like an infrared detector, or if there is a mechanical structure you need for launch but not after. It can cut off this thermal link for operational efficiency. They would be very useful in missions with infrared detectors, Earth observation missions or space observatories e.g. telescopes or space probes with infrared cameras.

The activity has developed a very solid, valid concept, based on CTE technology, which has been demonstrated to be reliable, robust, and to have a good thermal performance in cryogenics, having reached a TRL4.

The concept consists of a passive system based on differential thermal technology, where there is no need for heaters; the Switch turns ON or OFF when the cryocoolers are switched ON/OFF.

The materials were also chosen specifically as a compromise between thermal conductivity and to avoid cold welding, while also considering mechanical strength and space heritage. The operative range covers a wide band within cryogenic temperatures, between 20K to 100K and by changing the shape and size of one element would mean multiple devices could be cooled down with the same device, as capacity is needed.

Overall, the activity demonstrated this model functioned properly and was highly efficient, but both the total mass and the equipment’s complexity was fairly high to make it competitive. Next, the activity plans to reduce the number of parts, streamline the model and get the weight below 1 kg.  

T121-401MT closed in August 2020. All documentation is available on the TEC DMS/ ECLIPSE site.