Saturn S-IV Cryogenic Weigh System Part I: Propellant Utilization

In order to achieve maximum vehicle efficiency, it is essential that the vehicle propellants be loaded to desired values and that these propellants approach simultaneous depletion at the end of powered flight. To accomplish precise loading and assure minimum residuals, a highly accurate and repeatable, vehicle located, propellant management (PM) or propellant utilization (PU) system must be used. As the ability to load propellants to predetermined values depends directly on the ability of the system to accurately sense the propellant masses, it is essential that the system be calibrated with respect to propellant mass under conditions resembling those to be experienced during final loading and powered flight. The use of a cryogenic weigh system will reduce the unknown factors in capacitance sensor element shaping, tank geometry, and propellant properties to a degree which will permit the determination of propellant masses to within 0.25%. This paper describes the basic purpose for acryogenic weigh system in connection with the calibration of the Saturn Propellant Utilization System used on the S-IV stage.