This allows the daughter craft to be designed with fewer weight and aerodynamic restrictions allowing for exotic configurations to be used or tested, for example the recent SpaceShipOne, and previously the Bell X-1 and other X-planes.
An early design for SpaceShipOne called for a shuttlecock-like shape that would have made it incapable of landing independently, necessitating mid-air retrieval.
The 2005 recipient was Burt Rutan in recognition for his achievements in the development of SpaceShipOne, winner of the $10 million Ansari X Prize.
Although he was one of four qualified pilots for SpaceShipOne, Siebold did not pilot the craft during the flights later in 2004 to meet the requirements of the Ansari X Prize.
The pilot for these three flights was Marti Sarigul-Klijn and the copilot was Brian Binnie (who later gained fame as pilot of Scaled Composites' SpaceShipOne on its second X-Prize flight).
The SpaceShipTwo project is based in part on technology developed for the first-generation SpaceShipOne, which was part of the Scaled Composites Tier One program, funded by Paul Allen.