Propellant interaction with the payload control system of dual-spin spacecraft

Significant interaction between the payload control system and the liquid propellant on dual-spin spacecraft is shown to exist for a new class of vehicles with large liquid mass fractions. Experience during the transfer orbit operations of the first two LEASAT synchronous orbit communications satellites has demonstrated that lateral sloshing modes within the propellant can become unstable when coupled to the payload control system. Scaled-model single-axis transfer function testing is shown to define critical propellant modal parameters accurately. Analytical modeling techniques using this propellant modal test data are presented that can be used to predict both the strength and basic stability of the interaction. Design guidelines are presented for use in selecting system parameters to ensure stability. On-orbit verification of the interaction hypotheses, validating the test data and analytical modeling, is demonstrated with results of experiments conducted on the third LEASAT spacecraft. (Author)