NASA cryocooler technology developments and goals to achieve zero boil-off and to liquefy cryogenic propellants for space exploration

Abstract

NASA's interest in human exploration of Mars has driven it to invest in 20K cryocooler technology to achieve zero boil-off of liquid hydrogen and 90K cryocooler technology to achieve zero boil-off liquid oxygen or liquid methane as well as to liquefy oxygen or methane that is produced on the surface of Mars. These investments have demonstrated efficiency progress, mass reductions, and integration insights. A history of the application of cryocooler technology to zero boil-off propellant storage is presented. A trade space on distributed cooling is shown, along with the progress of reverse turbo-Brayton cycle cryocoolers, where the specific power and specific mass have dropped, decreasing the mass and power of these cryocoolers. Additionally, the cryocooler technology advancements of recuperators and compressors are described. Finally, NASA's development ideas with respect to zero boil-off technology are discussed.

Modelling of Liquid Hydrogen Boil-Off

“…Currently, the space industry is an important user of LH 2 , with long duration storage of cryogenic hydrogen being essential in orbital transfer vehicles, the upper stages of rockets, and deep space exploration probes [29][30][31][32][33][34]. Boil-off is particularly important during atmospheric departure, where frictional drag forces result in substantial heat ingress into the containment vessel, thereby increasing vapor temperature and pressure [31].…”

Flexible Cotton Fiber-Based Composite Films with Excellent Bending Stability and Conductivity at Cryogenic Temperature

“…These materials possess outstanding mechanical and electrical stability so that they can withstand bending or stretching without affecting their electronic performance . In recent years, with the development of aerospace, low-temperature physics, biomedicine, , and other fields involving low-temperature environments, flexible conductors that could be applied at low temperatures are required. For example, in medical treatment, some tissues, cells, and organs need to be stored at about −50 °C.…”

A Reverse Turbo-Brayton Cycle Cryocooler for Zbo Storage of Liquid Hydrogen in Space

“…The heat produced by the refrigerator is discharged to space from the radiator in the form of thermal radiation. This combination of passive adiabatic and active refrigeration can effectively control the temperature of propellant and completely prevent liquid storage gasification to achieve ZBO storage of propellant [2].…”

“…At high cooling loads, the turbo-Brayton cycle has a clear advantage over other cycles in system performance, size, and mass. In addition, the continuous-flow nature of the Brayton cycle is ideal for cryogen storage missions where the cycle gas can be directly interfaced with a broad area cooling (BAC)system attached to the storage tank [3].…”