Nonuniform Propellant Distribution in Multiple Tank Rocket Feed Systems

Abstract

Nomenclature a = axial acceleration / = propellant feed line length P = pressure R, r = distance from spacecraft centerline to propellant tank centerline and propellant tank radius, respectively / = time K/ ? vi' = weight of propellant in tank and propellant flow rate, respectively 7 = propellant density A --• indicates difference between parameters 6 =--= direction of resultant force vector or thrust misalignment angle p, = propellant viscosity co = spacecraft angular velocity Dimensionless ratios A* = raj 2 /a y* = 72/71 h* = AP/7Â /* -(/2 -/l)//l ft* = 1^2/^1 R* = R/r A/^* = Afl/r = AH//(f77T 3 7 2 ) = kW = /2//1 component one component two (opposite one) maximum residual total amount Theme M ANUFACTURING tolerances on propulsion systemcomponents and variations in operational environment result in differing amounts of propellant in each tank of a manifolded multiple tank system. This propellant difference causes a mass unbalance which cannot be completely compensated for prior to launch and has been neglected on the majority of spacecraft; however, precision pointing accuracy on communication satellites requires that they be very accurately balanced. 1 " 3 This paper surveys the various causes of propellant unbalance between tanks and presents corresponding estimates.

Thermal Gauging and Rebalancing of Propellant in Multiple Tank Satellites

“…The ground-based algorithm uses temperature and heater status telemetry to generate and send appropriate heater commands to the satellites to create the desired temperature differences. It is interesting that estimates made in 1972 predict that a nonuniform thermal environment could be the primary cause of an imbalance between multiple tanks [2].…”