MICROGRAVITY RESTART OF LIQUID ROCKET ENGINE WITH LOW PROPELLANT RESIDUALS

The active deorbiting and passivation of launch vehicles has become key for the implementation of modern space debris mitigation guidelines. Appropriate engine restart conditions must be provided as part of this process. Ullage motors have been traditionally employed to induce active settling and ensure a gas-free propellant supply to the engines. Although robust and reliable, ullage rockets are also heavy, which motivates the study of alternative approaches to the problem. This paper explores for the first time several high-risk-high-return propellant settling strategies that may result in significant benefits for future space systems. In particular, three distinct Magnetic Positive Positioning concepts, a hydrogen-peroxide-based Propellant Gasification System, and a hybrid device that combines both approaches are introduced. The preliminary feasibility analysis indicates that the successful development of these technologies may lead to mass savings of hundreds of kilograms and economic gains of several hundred thousand dollars per launch. However, the robustness of some of these methods may be compromised by complex fluid-structure interactions that require a careful numerical and/or experimental analysis.