Measurement of the liquid volume in a tank under μ-g conditions

A method is described for measuring the liquid content in a storage tank under microgravity conditions. The basic idea employed is that the liquid volume in the closed tank can be obtained by subtracting the volume of the ullage gas in the tank from the tank capacity. The concept employed to obtain the ullage gas involves the use of the ideal gas law. To determine the ullage gas volume, the tank is subjected to periodic displacement of volume. From equations based on the dynamics of the thermal change and leakage in the tank, relations have been obtained that give the ullage gas volume in the tank from the pressure signals. The validity of this method was examined by experimentation under the microgravity conditions