Long-life vibration-free 4.5K sorption cooler for space applications

Abstract

A breadboard 4.5 K helium sorption cooler for use in vibration-sensitive space missions was developed and successfully tested. This type of cooler has no moving parts and is, therefore, essentially vibration-free. The absence of moving parts also simplifies scaling down of the cooler to small sizes, and it contributes to achieving a very long lifetime. In addition, the cooler operates with limited dc's so that hardly any electromagnetic interference is generated. This cooler is a favorite option for future missions such as ESA's Darwin mission, a space interferometer in which the sensitive optics and detectors can hardly accept any vibration. The system design consists of a hydrogen stage cooling from 80 to 14.5 K and a helium stage establishing 5 mW at 4.5 K. Both stages use microporous activated carbon as the adsorption material. The two cooler stages need about 3.5 W of total input power and are heat sunk at two passive radiators at temperatures of about 50 and 80 K-radiators which are constructed at the cold side of the spacecraft. We developed, built, and tested a demonstrator of the helium cooler. This demonstrator has four sorption compressor cells in two compressor stages. Test experiments on this cooler showed that it performs within all specifications imposed by ESA. The cooler delivered 4.5 mW at 4.5 K with a long-term temperature stability of 1 mK and an input power of 1.96 W. So far, the cooler has operated continuously for a period of 2.5 months and has not shown any sign of performance degradation.

Development of a 15 K Hydrogen-Based Sorption Cooler

“…The cooling power of 25 mW is considered to be adequate to precool the helium stage of the Darwin cooler [1] and to deal with the parasitic heat load [2]. …”

“…In addition, the cooler operates with limited DC currents so that hardly any electromagnetic interference is generated. In the previous ESA-TRP project, the helium stage was realized and successfully tested [1].…”

Development of a sorption-based Joule-Thomson cooler for the METIS instrument of E-ELT

“…Funded by ESA Technological Research Programme (TRP), a 4.5 K helium sorption cooler for the ESA Darwin mission was developed, manufactured and tested [39,40] at the University of Twente. It was able to produce 4.5 mW cooling power at 4.5 K with an input power of 1.96 W at a heat-sink temperature of 50 K. The temperature stability in 1 hour is 1 mK with controlling.…”

“…The baseline design of the sorption compressor cell remains the concept used in a 4.5 K helium cooler [40] and 14.5 K hydrogen cooler in previous studies [41]. As schematically illustrated in Figure 3.2, the cell consists of a cylindrical, thin-wall container that is filled with activated saran carbon pills.…”

“…Initially, most developments of sorption coolers were done for space applications [31,34,40] because of their unique advantages that have been already mentioned in Chapter 1. In space applications, the coefficient of performance (COP) of the sorption JT cooler is of great importance because it directly relates to the size of the radiator on the spacecraft.…”