Enhanced Radiation Cooling

Abstract

Current-day space vehicle are equipped with a passive Thermal Protection System (TPS), but these systems operate at the edge of their capabilities. The research into the next generation reusable space vehicle demands the use of active TPS, these systems are not limited to the capabilities of the used material but depend on the active cooling mechanism. A system of cooled metallic TPS is developed at the TU Delft resulting in an increase in the maximum allowable thermal load for a given TPS temperature, this system is the enhanced radiation cooling TPS. The research question is: "Can an active thermal protection system improve the flying characteristics and the flight performance of a re-entry vehicle?". The first step in answering this question is to verify the process behind the active TPS. This thesis aims to design an experiment to verify this process.

To answer the research question two tools were developed: a flight simulator and a thermodynamic analyser. The flight simulator provides insight in the behaviour of the rocket and shows the consequences of implementing the enhanced radiation cooling TPS on the rocket. The thermodynamic analyser is used to estimate the wall temperature of the system and shows the effect of the sensitivity analysis of the design of the cooling subsystem. The enhanced radiation cooling system is designed to be mounted on the T-Minus Dart and an experiment to verify the impact of the active TPS is derived using the nominal mission of the rocket. Sensitivity analysis resulted in thin outer shell and a insulation sphere filled with the coolant. The outer shell needs to be as thin as possible in order to maximize the cooling effect. For an outer shell of 0.5 millimetres, the maximum allowable thermal load can be doubled in comparison with an non-cooled flight. If an identical thermal loading is assumed for two return vehicles, the active cooled vehicle can be designed with a nose radius of around 30 % smaller that the non-cooled vehicle. This will result in a vehicle with a higher lift-over-drag ratio, extending the return trajectory which increases the safety of the re-entry flight.

The validity of performing an enhanced radiation cooling experiment is shown by the use of the tools developed in this thesis. The incoming heat flux can be doubled while maintaining the same wall temperatures if the cooling system is applied. This opens the possibility of redesigning re-entry vehicles to achieve a high lift-to-drag ratio.