Modal Propellant Gauging in Low Gravity.

We present results from parabolic flight testing of a low-gravity propellant gauging technology that relies on detection of resonant acoustic mode shifts due to changes in the tank's effective mass as liquid propellant is removed from the tank. The modal propellant gauging (MPG) method is shown to be (1) relatively robust against sloshing, (2) of comparable effective resolution to existing gauging methods for settled propellant, and (3) particularly robust at low fill-fractions where conventional gauging methods are known to be inaccurate. Lab (1-g) measurements of gauging resolution show no more than a 1.