Results of an Advanced Development Zero Boil-Off Cryogenic Propellant Storage Test

performance of each component and the ZBO system. The development s in this test are essential to the validation of that tool. This test was the first on a flight re presentative configuration in a thermal ly representat ive environment . The test article was comprised of a spherical 1.4 m diameter insulated propellant tank , with a submerged mixer, a cryogenic heat pipe, flight design cryocooler , and a radiator . All wer e enclosed in a thermal shroud and inserted into and tested in a vacuum chamber that simulate e a LEO thermal environment . Thermal and pressure control tests were performed at sub -critical LN 2 temperatures and approximately 2 atmospheres pressure . The col d side of the ZBO system performed well. In particular , the heat pipe performed better than expected, which suggests that the cryo cooler could be located further from the tanks than anticipated, ie. on a spacecraft bus , while maintaining the desired e ffic iency . Also, the mixer added less heat than expected. The tank heat ing rate through the insulation was higher than expected (9.4 watts) ; also the temperatures on the cryocooler hot side were higher than planned . This precluded the cryocooler from elimina ting the boil -off . The results show t he cryocooler was successful at removing 6.8 watts of heat at approximately 75K and 150 watts of input power, with a h eat rejection temperature of 3 11 K. T he data generated on the ZBO components is essential for the upgrade of the ZBO Cryogenic Analysis Tool to more accurately apply the concept to future missions.