Method and Apparatus for Determination of Propellant Mass in Micro-Gravity

Docket: UAH-P-12004


Propellant mass gauging in micro-gravity has posed a challenge for decades. Various methods have been applied, including ultrasonics, capacitance probes, point level sensors, and thermal detectors, as well as nuclear devices. All have problems in terms of how to provide accurate measurements irrespective of the fluid orientation in the tank. 

Researchers at UAH have developed a low-cost method for determining propellant mass based on average measurements of tank capacitance over time. In principle, the dielectric constant of a liquid is known for a given temperature and/or density for a given pressure. 

This method provides measurements that are reasonably accurate (~ 1% error) regardless of the orientation of the liquid within the tank. The tank simply requires a few wires that form a capacitor with the tank walls grounded. There are no high voltages or EMI, and measurements are easily taken using COTS hardware. This method is low cost, robust, and easily integrated into propellant tanks or other storage tanks. 


  • Liquid Storage Containers
  • Spacecraft
  • Aircraft, ships, tankers


  • Accurate
  • Low cost
  • Robust
  • Can be used with large propellant tanks or liquid acquisition devices


  • State of Development: Prototype
  • Licensing Status: Available for licensing
  • Patent Status: Patented