Asymmetric Propellant Positioning in Symmetric Tanks and Propellant Management Devices

Abstract

Dangers of assuming symmetric liquid and gas positioning in symmetric tanks with symmetric propellant management device vanes are identified. Examples from spaceflight history plus modeling of proposed designs illustrate the issue in numerous geometries. Spaceflight hardware and research geometries present the same behavior: that the minimum-energy state for static positioning of liquid and gas in a partially filled vessel with axial symmetry or with, for example, fourfold symmetry of propellant management device vanes need not be symmetric. Because it is simple to assume a symmetric solution, the reality of the nonsymmetric solution may surface as a potentially crippling anomaly in spaceflight or in 0 research operations. Altered mass properties and thermal response of tanks to heaters are two important changes that nonsymmetric liquid positioning can produce. The surprises are avoidable by ground-based analysis and modeling that consider the possibility of such solutions.