A Study of the Use of 6K ACTDP Cryocoolers for the MIRI Instrument on JWST

Abstract

The Mid Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST) is a demanding application for the use of space cryocoolers. During calendar year 2003 an extensive study was carried out examining the application to this mission of hybrid 6K/18K J-T cryocoolers developed by NASA as part of their Advanced Cryocooler Technology Development Program (ACTDP). Among the most challenging requirements of the MIRI application were the requirements to cool down the ∼90 kg 6 K cooling load in less than 30 days and to restrict the location of the compressors with their heat dissipation and vibration generation to a remote spacecraft position some 12 meters away from the cryogenic load. Because the hybrid 6K/18K J-T cryocoolers have unique load-carrying capability as a function of temperature, the cooldown requirement was the primary consideration in cooler sizing. This paper presents the lessons learned and performance achieved in the MIRI cryocooler application. In the final proposed configuration, all of the MIRI/JWST design considerations were successfully met. Although the cryocooler option was eventually deselected in favor of a solid-hydrogen stored cryogen system, the cryocooler study offered an important opportunity for understanding and refining the performance and integration capabilities of this important new class of low-temperature space cryocoolers.