Radio Frequency Mass Gauge on Parabolic

Propellant quantity gauging is a critical function for space vehicles, yet the only way to gauge the amount of propellants in a low-gravity environment is to “settle” the liquid in the tanks by accelerating the vehicle and measuring the liquid level. Although this settled-gauging technique works well in many instances, e.g. during launch or main engine burns, it has drawbacks and penalties. At a low settling thrust the liquid slosh times are long, leading to inaccurate level sensor data. The penalty for this propellant gauging inaccuracy is additional propellant load, to cover the uncertainty margin. Without a settling thrust, the propellant quantity is even more uncertain. These difficulties could be overcome with a low-gravity propellant gauging technology, such as the Radio Frequency Mass Gauge (RFMG). The RFMG is a technology being developed at NASA to gauge cryogenic propellants in low-gravity, or under low settling thrust conditions where sloshing is also an issue. The technique has been proven to work very well in ground tests using liquid hydrogen and liquid oxygen, but lacked low-g testing prior to the parabolic flights. Related to T0024.
Work continues as a technology demonstrator onboard the ISS.

BIBLIOGRAPHY G. A. Zimmerli, M. Asipauskas, J. D. Wagner, and J. C. Follo, “Propellant Quantity Gauging Using the Radio Frequency Mass Gauge”, AIAA 2011-1320, 49th AIAA Aerospace Sciences Meeting, January 2011, Orlando, FL