The objective of the 20 Watt 20 Kelvin Cryocooler for Thermal Control of Space-Based Liquid Hydrogen (20W 20K Cryocooler) Project is to develop cryocooler hardware to demonstrate high capacity active thermal control at 20 degrees Kelvin, a temperature just below the normal boiling point of hydrogen. Cryocoolers (essentially refrigerators that function at cryogenic temperatures) operate to remove heat and to maintain a set temperature.
To expand human presence into the solar system and to the surface of Mars, high specific impulse cryogenic liquid hydrogen and oxygen propellants must be stored in space for weeks or months at a time. However, heat radiated from the Sun and the Earth causes liquid hydrogen (as well as liquid oxygen) to pressurize and boil-off (change state from liquid to gas). Without a way to intercept and reject this heat, propellant storage tanks must relieve the pressure buildup and vent themselves, yielding less propellant available for propulsion purposes. Use of 20 Kelvin cryocoolers will achieve Zero Boil-Off (ZBO) that will enable long loiter periods in low Earth orbit and reduce the mass of cryogenic upper stages, but the cryocoolers necessary for propellant storage applications are at a relatively low state-of-the-art.
The Project will design, fabricate, acceptance test, and deliver a flight-representative 20 Watt 20 Kelvin cryocooler, intended for infusion within a NASA future-defined Liquid Hydrogen Zero Boil Off test, in support of the overall vision of thermal control of space-based liquid hydrogen.
The 20W 20K Cryocooler Project is funded by NASA Space Technology Mission Directorate’s Game Changing Development Program. The Project is led by Glenn Research Center.