[5][6] In 2018, researchers at the University of Oxford were experimentally testing transpiration cooling as a Thermal Protection System for Hypersonic Vehicles such as rockets or spaceplanes.
[5] Transpiration cooling is being considered for use in space vehicles reentering the Earth's atmosphere at hypersonic velocities where a transpirationally cooled outer skin could serve as a part of the thermal protection system of the reentering spacecraft.
[8][9][1][10] SpaceX publicly mentioned such a system in 2019 for use on their Starship reusable second stage and orbital spacecraft to mitigate the harsh conditions of reentry.
The design concept envisioned a double stainless-steel skin, with active coolant flowing between the two layers, with some areas additionally containing multiple small pores that would allow for transpiration cooling.
[8][11][1] After design and testing in terrestrial labs, SpaceX subsequently stated that although an alternative heat mitigation approach—using low-cost ceramic tiles on the windward side of Starship—was being developed,[12][13] transpiration cooling could be used in some areas.