Theoretical Estimate of Cooling Time of a Liquid Hydrogen Tank during Structural Tests

Russian enterprises continue developing rocket and space vehicles based on cryogenic propellants, i.e. liquid hydrogen, oxygen, and methane. Hence, the issues of fuel tanks’ thermal strength are increasingly important. During structural tests, the operating temperatures of the test object should be simulated, since the temperature condition affects the strength and rigidity of the structure. Consequently, during ground-based experimental tests, hydrogen tanks must be cooled down to 20 K, the boiling point of hydrogen. JSC TsNIIMash is developing a helium system capable of cooling large-sized structures to a temperature of 20 K. Helium can be used in a gaseous state to cool down the structure, since the boiling point of helium, 4 K, is lower than the boiling point of hydrogen. Until now, the tanks were cooled only by filling with liquid nitrogen, therefore the temperature state of the tanks during the tests was simulated only for this case. In order to determine the applicability of the method developed, the cooling time of large-sized containers was estimated by cooling a hydrogen tank, which by its dimensions is typical for an advanced medium-class second stage launcher, to 20 K by gaseous helium.

Investigation of internal flow of Cryogenic injection

As part of an effort to understand the conditions for the ignition of cryogenic propellants in the low pressure environment, we conducted a research of internal flow of cryogenic jet. In this paper, the experimental investigation was exerted focusing on the qualitative morphology study of the cryogenic flow inside the jet injectors. The test facilities were carefully designed and allow for visualization and characterization of the flow. The results show a strong dependence of mass flow rate on the fluid temperature. The two-phase flow was observed even for a long time chilling down of the injector. The Jacob number is proved to be a good indicator for the flow regimes, and the bubbles are present in the flow every time. The injector geometry has an influence on the flow rate, with the tapered injector demonstrating a higher flow rate than the sharp one.

Numerical analysis of the flow dynamics of an N2 cryogenic jet

Injection and mixing of cryogenic propellants are very complex at near-critical and supercritical conditions. The concise description and the reliable measurements on such flows are still questionable. In this work, a Reynolds Averaged Navier-Stokes (RANS) study is performed for a pure N2 fluid injection at transcritical conditions on a laboratory scale test rig. An indepth thermodynamical analysis on the real-gas behavior has allowed N2 density prediction over the experimental range of the injection temperature and for several equations of state (EoS). A focus was thrown on the prediction of the density evolution on the chamber centerline and across the injector. The calculations were performed using both adiabatic and constant temperature conditions for the injector wall. The inner heat transfer in the injector had a significant effect on the jet density distribution and therefore on the overall flow dynamics. Numerical results regarding axial profiles of density and dense core lengths agree fairly well with the experimental data provided by the literature.

Analysis on Thermal Design Concern of Vapor Cooled Shield for Cryogenic Tanks

In the long run, storage of cryogenic propellants on orbit is one of the most crucial technologies for future space exploration. Vapor cooled shield (VCS) has been considered as an effective tool to intercept heat leakage from the environment into the cryogenic tanks. In addition to that, reduce or even eliminate propellant boil-off. This scrutiny ascertains a 3D model to investigate the temperature distribution on VCS, and also conforms to the fact of temperature uniformity assumption in literature. The relationship amid the temperature distribution on VCS, the shield wall thickness, and the vented vapor’s mass flow rate is analyzed for series-type VCS and parallel-type VCS to clarify the existing temperature gradient on VCS and the way it influences the MLI’s insulation performance. The outcomes of the study could act as a beneficial tool for the thermal design of cryogenic VCS.