This paper was presented at the Twenty-first Annual National Conference of the Society of Aeronautical Weight Engineers at Seattle, Washington, May 14-17, 1962. This paper presents a new technique for capacity calibration of space-vehicle cryogenic-propellant tanks. This new method, which uses cryogenic propellants instead of water as the calibration fluid, is being developed for the Saturn S-IV Stage Vehicle. This technique results in greater accuracy than that of the traditional water calibration system, which loses accuracy because of the need for extrapolating to cryogenic temperatures.
The cryogenic calibration technique provides an end-to-end calibration of the propellant utilization and loading sensor against the accurately measured propellant mass. The calibration begins with the vehicle in the static test and calibration stand. First, the vehicle is protected from the indeterminate tares of ice formation and wind gusts by an environmentally controlled boot immediately surrounding the vehicle, and by a canvas wind shield attached to the test stand. The actual calibration is performed by filling and draining each propellant separately. At previously-determined intervals during the drain, the mass of propellant is measured by a test stand weighing system. Simultaneously, the propellant mass sensor (capacitance probe) signal output and propellant density and volume parameters are recorded. The weigh system output is corrected for load cell and measuring circuit non-linearity, recorder drift, air buoyancy, and such tare weights as umbilical connections, weigh ring weight, and dry vehicle weight. These data result in a propellant mass sensor calibration curve at the calibration conditions.