A Cryogenic Lightweight Mass Gauging System for Expendable and Reusable Launch Vehicles

Abstract

Recent investigations involving the use of densified propellants in the RLV, EELV, and ELV programs have identified the need for and prompted the development of a versatile lightweight mass gauging system. Precise measurement of the temperature and liquid level of densified propellants are necessary to adequately monitor the thermodynamic states and liquid stratification induced through vehicle maneuvers, propellant usage, and tank wall heating in both prelaunch and in-flight environments. The limited capabilities of existing systems have motivated Sierra Lobo to develop the Cryo-TrackerTM Mass Gauging System (CTMGS). The CTMGS consists of a patented ultra-light flexible sensing probe, a sophisticated electronics package, and mass gauging software. The system measures both liquid level and temperature, and then calculates propellant mass and propellant mass uncertainty. The mass gauging software is also used to optimize the design of the sensing probe for a given propellant tank. Sierra Lobo has successfully tested an engineering prototype of the Cryo-Tracker Mass Gauging System for NASA under the 2d Generation Reusable Launch Vehicle Program. Test results demonstrate the capability of the CTMGS to determine stratified cryogenic propellant mass to better than 0.5% accuracy using a single probe.