Liquid oxygen and hydrogen are used as oxidizer and fuel respectively in cryogenic propulsion system. These liquids are stored in foam insulated tanks of cryogenic propulsion system and are pressurized using warm pressurant gas supplied for tank pressure maintenance during cryogenic engine operation. Heat leak to cryogenic propellant tank causes buoyancy driven liquid stratification resulting in formation of warm liquid stratum at liquid free surface. This warm stratum is further heated by the admission of warm pressurant gas for tank pressurization during engine operation. Since stratified layer temperature has direct bearing on the cavitation free operation of turbo pumps integrated in cryogenic engine, it is necessary to model the thermal stratification for predicting stratified layer temperature and mass of stratified liquid in tank at the end of engine operation. These inputs are required for estimating the minimum pressure to be maintained by tank pressurization system. This paper describes configuration of cryogenic stage for ground qualification test, stage hot test sequence, a thermal model and its results for a foam insulated LH2 tank subjected to heat leak and pressurization with hydrogen gas at 200 K during liquid outflow at 38 lps for engine operation. The above model considers buoyancy flow in free convection boundary layer caused by heat flux from tank wall and energy transfer from warm pressurant gas etc. to predict temperature of liquid stratum and mass of stratified liquid in tank at the end of engine operation in stage qualification tests carried out in ISRO facility.

A gas used to drive a fluid through a fluid system.: #* The helium pressurant supplies the energy for the propellant transport from the tanks to the combustion chamber.<ref name="def1">https://web.archive.org/web/20170215221854/http://www.dtic.mil/dtic/tr/fulltext/u2/a013774.pdf Schneider, D.A., Air Force Weapons Laboratory Report AFWL-TR-74-270, June 1975.</ref> #* During tank pressurization under some circumstances, rapid mixing of relatively warm pressurant gas with cryogenic propellant can lead to rapid densification of the gas and loss of pressure in the tank.<ref name="def2"> http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070003730_2007003015.pdf Ahuja, V, et. al, Runtime and Pressurization Analyses of Propellant Tanks, Abstract, July 2007. </ref>

Cryogenic systems, used in industries such as medicine, electronics, and space exploration, have grown in importance over the years. Recently, the push for greener energy and efficient storage solutions has brought them into focus in aerospace and aviation. For space applications, reusable launch systems require advanced modeling to predict and manage complex phenomena, such as thermal dynamics and propellant behavior under varying conditions. Meanwhile, the aviation sector is exploring hydrogen as a clean fuel, which requires addressing boil-off losses and storage efficiency. This study compares three simplified numerical methods for modeling cryogenic storage systems - BoilFAST, CryoTank, and Simcenter Amesim - selected for their rapid and reliable predictions with low computational cost. The models are compared against the same test cases to assess how their different modeling approaches result in varying levels of accuracy and computational efficiency for specific configurations and scenarios. By evaluating these models under conditions such as pressurization, sloshing, and filling, and accounting for variations in tank shape and fluid type, the study highlights their differing strengths. BoilFAST excels in steady-state evaluations and routine monitoring, CryoTank balances computational efficiency with accuracy for dynamic scenarios like pressure control and sloshing, and Simcenter Amesim provides detailed insights into complex processes such as pre-cooling and filling. T

<div class="htmlview paragraph">The application of cryogenic fluid storage systems to manned spacecraft is considered attractive primarily because of the substantial weight and volume saving afforded compared with high-pressure gaseous storage at ambient temperature. The major use of the stored fluids has been as a metabolic support (oxygen) and as reactant supply (hydrogen and oxygen) to the fuel cell for power generation. In addition cryogenic helium is used for descent propellant tankage pressurization aboard the lunar module.</div> <div class="htmlview paragraph">The subsystems developed for the NASA Gemini program, the firts full-scale operational application of this type of equipment, are discussed as a baseline for comparison with more advanced designs for subsequent programs. State-of-the-art design improvements are presented in some detail.</div> <div class="htmlview paragraph">Current programs (i.e., Apollo, Lunar Module, Biosatellite (primate), Manned Orbiting Laboratory, and the Air-lock Module) utilize cryogenic storage and supply subsystems for the usages mentioned earlier. A comparison of the physical and thermodynamic characteristics of these subsystems indicates a well-controlled evolution of the basic Gemini design concept. Further advantageous evolution of this concept of storing the cryogen as a single-phase supercritical fluid is anticipated for programs, such as the Apollo applications mission. However, it does not appear likely that further significant

This paper provides a comparative structural comparison of cryogenic Liquid Hydrogen (LH₂) tanks for aerospace use, where the aim is to maximize weight, strength, and deformation against harsh cryogenic conditions. The study examines six potential materials—Aluminium 6061, Aluminium 7075, Structural Steel, Stainless Steel 304, Titanium alloy Ti-5Al-2.5Sn, and Magnesium alloy AZ31—via finite element simulations in ANSYS Static Structural at 77 K, subjected to an internal pressure of 5 MPa and an 80% fill. Results indicate that although Stainless Steel 304 and Structural Steel have minimum deformation, the excessive weight and high induced stresses limit their applications in aerospace. Aluminium alloys yield moderate strength and deformation at lower weight, making Al6061 a practical lightweight candidate. Magnesium AZ31 has minimum weight and comparable mechanical performance, although it poses a flammability risk as a design issue. Titanium alloy Ti-5Al-2.5Sn performs better than all other materials, with lowest stress and deformation and optimum strength-to-weight ratio and is, therefore, the best choice for aerospace-quality LH₂ containment. The results emphasize the necessity for expanded research on dynamic loading, thermal flux behavior, and multi-material hybrid configurations to optimize the safety and efficiency of next-generation cryogenic propulsion systems.

hydrogen involves pressurized tanks at 250–350 bar (25–35 MPa; 3,600–5,100 psi). With materials available in the 2020s, the mass of tanks strong enough to Aviation fuels are either derived from petroleum or are blends of petroleum and synthetic fuels, and are used to power aircraft. These fuels have more stringent requirements than those used for ground-based applications, such as heating or road transportation. They also contain additives designed to enhance or preserve specific properties that are important for performance and handling. Most aviat Any fueling…

tank stood gleaming in the sunlight. Mrazek asked, “What’s inside it?” To which Bossart responded, “Nitrogen.” Nitrogen was used for pressurization until