The £7.34 Million UK-EPSRC and Rolls Royce funded Transpiration Cooling project is a joint initiative between the University of Oxford, Imperial University, University of Southampton and the University of Birmingham. Bringing together a world-leading team of researchers, it’s aim is to deliver underpinning research to make transpiration cooling a reality.
When spacecraft fly to the surface of other planets or return from a mission back to Earth, they have to cross the atmosphere of planets. They fly through this at several kilometres per second. At these very high speeds, the atmosphere in front of the spacecraft is strongly compressed slowing it down. This in turn leads to a large temperature rise of the atmosphere surrounding the spacecraft. In fact, the temperature becomes so high that it even exceeds the surface temperature of the sun. Consequently, such vehicles need to be equipped with a heat shield to protect the inside from the extreme temperatures they experience.
The transpiration cooling programme aims to investigate one particular strategy to build such a heat shield. The fundamental idea is to use a porous material as the heat shield wall. Such materials contain tiny holes and channels that are interconnected, like a very fine Swiss cheese. It is possible to feed gas from one side to the other through porous materials. The gas, called a coolant, absorbs part of the heat from the material. In a heat shield application, relatively cool gas could be pushed from the inside of a spacecraft through the porous wall to the outside of the heat shield. The coolant would absorb some of the heat from the porous wall and also form a cold layer of gas surrounding the vehicle acting as another layer of protection.