The rocket motor for SpaceShipTwo has been fired successfully – and the spacecraft itself is on course for a glide flight from the mothership by the end of the year.
That's the news from Virgin Galactic this week, following the completion of the first series of hot firings of what is the biggest motor of its type in the world.
Tests will continue on the motor in the months ahead, and next year it will be attached to SpaceShipTwo. In the meantime the spacecraft is on course for a trial flight later this year. It will be carried aloft by the mothership and released for a glide flight back to earth.
SpaceShipTwo is powered by a hybrid engine burning solid HTPB fuel with liquefied nitrous oxide gas as an oxidiser.
HTPB (hydroxy-terminated polybutadiene) is a common ingredient in motor tyres. Nitrous oxide gas is the familiar medical and dental anaesthetic known as 'laughing gas'.
The use of a liquid oxidiser provides control over the motor. It can be throttled back or turned off by regulating the flow of oxidiser, and the spacecraft can then glide in to land on a conventional runway. Conventional solid-fuel rockets burn until all their fuel is gone.
Video footage of the motor's firing can be seen on the Virgin Galactic site. The company say that a series of exhaustive tests will now be gone through, leading up to flight testing by the end of the year. This will mean that the spacecraft will be air-launched from the WhiteKnightTwo carrier.
The mothership herself, named after Sir Richard Branson's mother Eve, will make her first long test flight on 19 June. That's the day of the ground breaking ceremony of Spaceport America at New Mexico, and she will fly overhead as part of a non-stop round trip from Mojave.
Then on 28 July she will appear at the aviation show at Oshkosh to make two demonstration flights.
Details of the progress of the project were given by Virgin Galactic president Will Whitehorn at the International Space Development conference in Orlando, Florida. In his presentation he outlined the wider areas of opportunitiy within which space tourism will provide a key income stream.
He spoke of satellite launches and of space and upper atmosphere research, and he also described research to develop a bio-butanol fuel produced by algae, for use in WhiteKnightTwo's Pratt & Whitney Canada 308A engines.