Prelaunch Slush Hydrogen Loading Factors Affecting Instrumentation and Control

Abstract

Analysis of theoretical and practical work in the literature indicates that slush hydrogen can be manufactured and transferred through facility piping to a point near a launch vehicle. The rate of flow of the solids, i.e., the product of the volumetric rate of flow, the slush density, and the slush solid fraction at that point, also can probably be determined with reasonable accuracy. However, the percentage solid on board the vehicle at the moment of launch (the process end-point) is difficult to control up to the moment of launch [^1–5]. Various on-stage devices such as nuclear radiation detector arrays arranged in removable blankets, interstage weighing systems, and in-tank capacitance matrices have been proposed for loaded mass determination, together with point liquid level sensors for volume determination [^1,2,6]. These devices do not appear to solve completely the specific slush loading problem which can be simply stated as follows: Load a mass of slush hydrogen into the upper stage of a vehicle on a launch pad, under controlled conditions, so that a prespecified mass of slush hydrogen occupies the upper stage tank immediately prior to liftoff.