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Abstract. Recent demonstration of advanced liquid hydrogen storage techniques using Integrated Refrigeration and Storage technology at NASA Kennedy Space Center led to the production of large quantities of densified liquid and slush hydrogen in a 125,000 L tank. Production of densified hydrogen was performed at three different liquid levels and LH2 temperatures were measured by twenty silicon diode temperature sensors. Overall densification performance of the system is explored, and solid mass fractions are calculated. Experimental data reveal hydrogen temperatures dropped well below the triple point during testing, and were continuing to trend downward prior to system shutdown. Sub-triple point temperatures were seen to evolve in a time dependent manner along the length of the horizontal, cylindrical vessel. The phenomenon, observed at two fill levels, is detailed herein. The implications of using IRAS for energy storage, propellant densification, and future cryofuel systems are discussed. IntroductionFluid-based fuels and/or oxidizers are routinely stored on-board vehicles of various types in order to provide chemical potential for an engine. In the vast majority of these applications the fluids are stored in a liquid state due to the significantly larger stored energy capacity compared to the gaseous phase, and can be kept at much lower pressures, avoiding the need for heavy pressure vessels. In either case, the key point is that the fluid acts as an energy carrier, therefore, the denser the fluid the greater the energy stored in a given volume. This is especially important in applications where the transportation of energy in fluid form is the express purpose, such as in ocean-going and roadable tankers. The term "densification" refers to the process of thermodynamically manipulating a fluid with the intent of increasing its density above that of a typical reference value, thereby increasing its energy storage potential. Reference values usually correspond to atmospheric conditions (temperature, pressure, or both), and in the case of cryogenic propellants such as liquid hydrogen (LH2), liquid methane or liquefied natural gas (LNG), and liquid oxygen (LOX), the reference density is that realized at the normal boiling point (NBP); i.e. when the fluid is completely saturated at atmospheric pressure.Historically, the maximum attainable cryofuel density has corresponded to the NBP storage condition. This constraint has been an important driver for the design of any application that utilizes cryogenic propellants, most notably chemical combustion-powered launch vehicles, by effectively dictating the required tank volumes. Therefore, increasing the density of the propellants can have a substantial effect on the overall vehicle design and/or performance. This is especially true for rockets

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Abstract. Field demonstrations of liquid hydrogen technology will be undertaken for the proliferation of advanced methods and applications in the use of cryofuels. Advancements in the use of cryofuels for transportation on Earth, from Earth, or in space are envisioned for automobiles, aircraft, rockets, and spacecraft. These advancements rely on practical ways of storage, transfer, and handling of liquid hydrogen. Focusing on storage, an integrated heat exchanger system has been designed for incorporation with an existing storage tank and a reverse Brayton cycle helium refrigerator of capacity 850 watts at 20 K. The storage tank is a 125,000-liter capacity horizontal cylindrical tank, with vacuum jacket and multilayer insulation, and a small 0.6-meter diameter manway opening. Addressed are the specific design challenges associated with the small opening, complete modularity, pressure systems re-certification for lower temperature and pressure service associated with hydrogen densification, and a large 8:1 length-to-diameter ratio for distribution of the cryogenic refrigeration. The approach, problem solving, and system design and analysis for integrated heat exchanger are detailed and discussed. Implications for future space launch facilities are also identified. The objective of the field demonstration will be to test various zero-loss and densified cryofuel handling concepts for future transportation applications.