Liquid volume measurement for cryogen under microgravity condition

A Helmholtz resonance technique was employed as an effective technique for measuring volumes of cryogenic propellants in orbit. A closed-type resonator was developed and experiments that measured the volume of liquid nitrogen in micro-gravity conditions during parabolic flights were conducted. A loudspeaker installed in the resonator was driven by a swept sound from 249.5 to 649.5 Hz, and the response of the electrical impedance was analyzed by the maximum entropy method to determine the resonant frequency every 743 ms. The resonant frequencies obtained under the micro-gravity conditions agree with the data obtained under normal gravity conditions.