The water cooling of a conceptual hypersonic transport system's wing leading edges is being investigated for the European Union's €7.3 million ($10.93 million) Future High-Altitude High-Speed Transport (Fast) 20XX programme, expected to start early in 2010.
The transport system is German aerospace centre DLR's liquid oxygen/liquid hydrogen-propelled Spaceliner concept. It has two stages, an unmanned booster first stage and an orbiter with 50 passengers.
Designed for civil transport, the Spaceliner has been a vision vehicle around which DLR has conducted technology studies.
An orbiter sub-scale wing leading edge section made of carbonfibre-reinforced carbon (known as carbon-carbon and developed for use in the nose cones of intercontinental ballistic missiles, as well as Space Shuttle leading edges) will be water cooled. In theory the temperature of the orbiter's wing leading edges could reach up to 2,500 Kelvin (2,227°C).
"With water you can use small amounts because it takes so much energy for a phase state change [from liquid to gas]. The leading edge will cool to the temperature of the boiling water and natural capillary action will constantly draw the fluid through the material to the surface at the rate we need," says DLR space launcher systems analysis group research engineer Arnold Van Foreest.
While carbon carbon is not naturally porous to enable the capillary action, Van Foreest says there are manufacturing processes that can produce the porosity needed.
He adds that preliminary avionics and propellant management design would also be carried out under Fast 20XX and Italy's aerospace research agency CIRA is to conduct orbiter boundary layer transition research.
The beginning of Fast 20XX has been delayed since May due to a protracted process of partner company validation by the European Commission.