1168. Toroidal Tank Evaluation

Paper

Abstract

A study was made to determine the impact of using two toroidal tank s in place o f four spherical tanks in an advanced spin-stabilized spacecraft. The specific application investigated was an advanced Pioneer-type Jupiter orbiter using N2O4 and ‘H propellants.
Fluid behavior in spinning toroids was evaluated and the need for a propellant acquisition system was established. A passive surface tension system was selected to provide gas-free liquid flow from a single outlet for both normal propellant feed and emergency draining. The common tank acquisition device system can be used with either propellant.
A two-toroid system is attractive because of packaging, mass, center of mass, spin control, and propellant outflow considerations. The tanks can be stacked at the aft end of the spacecraft, centered about the spin axis. Liquid motion in the tanks tends to be balanced, e.g., symmetrical propellant settling during thrusting. A more balanced space craft requiring lesser control should result. Also, a two-tank system is inherently more reliable and eliminates the outflow balancing needed with parallel feed in a four-tank system.
Fabrication of toroidal tanks from either titanium or aluminum alloys is feasible with available manufacturing methods. Materials evaluated were 2219 and 6061 aluminum and 6Al-4V titanium. The titanium toroids are only slightly heavier than four spheres. The two toroids using surface tension acquisition devices would actually be lighter than four spheres using bladder-type expulsion.
Support of toroidal tanks in the spacecraft appears relatively simple and structurally efficient. In fact, integration of two toroidal tanks in place of four spherical tanks provides overall spacecraft weight, packaging, structural mounting, thermal control, and stability advantages.