Advanced Cryogenic Integration and Cooling Technology for Space-Based Long Term Cryogen Storage

Abstract

The Air Force Research Laboratory (AFRL), Space Vehicles Directorate has been the lead Department of Defense (DoD) agency for the development of low capacity cryogenic refrigerators and integration technologies for space applications since the late 1980s. High capacity cryocoolers and long term (>20 years) on orbit propellant storage are potentially enabling technology for future High Energy Laser (HEL) space systems, orbital transfer vehicles, and on orbit propellant depots. Cryogenic applications in space based systems requiring long term cryogen storage includes: significant cooling requirements for subcritical cryogens, cryocooler redundancy issues, on orbit cryogen transfer from vehicle to vehicle, large shield cooling, long term gas and liquid cryogen storage, large distributed cooling surfaces, cryogenic system integration issues, and significant spacecraft system penalties due to mass and input power. AFRL has pursued low capacity cryocooler concepts including reverse Brayton cycle, single and multiple stage Stirling cycle, advanced Joule-Thomson cycle, and Pulse Tube (Stirling cycle variant) designs. The cryocooler technology spans a wide range of cooling temperatures (from ∼10 Kelvin to 150 Kelvin) and heat loads (up to 10 Watts at 95 Kelvin). Additionally, AFRL has pursued advanced cryogenic integration technology including cryogenic thermal switches, cryogenic heat transport, thermal storage, and cryogenic integration schemes to reduce system mass and input power penalties.