Paraffin and asphalt based-solid fuels for the SpaceShipTwo (SS2) rocket motor have been tested by Virgin Galactic's prime contractor Scaled Composites.

Speaking to Flight International at the roll-out of SS2 carrier aircraft WhiteKnightTwo on 28 July at Mojave air and spaceport, Scaled founder and chief technology officer Burt Rutan commented on the solid fuel, but did not discuss the oxidiser.

White Knight Two
 © Alan Radecki

SpaceShipOne (SS1) used a hybrid rocket motor that combusts a solid fuel in a gaseous oxidiser and SS2 will use the same propulsion system. Because SS2 is a much larger vehicle than SS1 there has been speculation that the solid fuel could change. The oxidiser is expected to remain nitrous oxide despite the accident in July 2007 that killed three Scaled employees.

"I can tell you that we have tested several types of solids. In the tests that we have done so far, we have tested paraffin-based and asphalt-based materials," Rutan says.

He adds that he has not tested hydrides - hydrogen compounds - for solid fuels, but expects to be able to give more details about the propulsion work after the next report on the fatal accident is published. NASA's Glenn Research Center published research on paraffin hybrid motors in 2007, while asphalt-based solid fuels were first developed in the 1940s in the USA.

Source: Flight International