FEASIBILITY DEMONSTRATION OF CRYOGENIC FLUID GAUGING FOR SPACE-VEHICLE APPLICATIONS

This article describes a gauging concept for determining the mass of l iquid contained in a tank in a low-gravity environment. The concept, w hich is referred to herein as the ''compressibility gauge,'' is based on the thermodynamic principle that the pressure of gas or vapor chang es when its volume changes. In operation, the tank volume is changed s lightly by an oscillating bellows (pulser) and the corresponding chang e in tank pressure is measured. The primary objective of the present i nvestigation of this concept was to explore the effects specific to ga uging cryogenic fluids, such as heat, mass, and momentum transport at the liquid-vapor-tank interfaces, on the accuracy of the gauge. Freon- 11 was used as a convenient laboratory fluid to simulate liquid hydrog en and other cryogens. The test results and analyses indicate that cry ogenic effects can have a significant effect on gauging accuracy. None theless, it is concluded that the gauge has the potential of high accu racy in low gravity, to use simple hardware, and to be lightweight for space vehicle applications.