Jonathan Amos reports on the UK Space Agency (UKSA) long-simmered design/proposal called Skylon:
Skylon has been in development in the UK in various guises for nearly 30 years.
It is an evolution of an idea first pursued by British Aerospace and Rolls Royce in the 1980s.
That concept, known as Hotol, did have technical weaknesses that eventually led the aerospace companies to end their involvement.
But the engineers behind the project continued to refine their thinking and they are now working independently on a much-updated vehicle in a company called Reaction Engines Limited (REL).
Realising the Sabre propulsion system is essential to the success of the project.
The engine would burn hydrogen and oxygen to provide thrust — but in the lower atmosphere this oxygen would be taken directly from the air.
This means the 84m-long spaceplane can fly lighter from the outset with a higher thrust-to-weight ratio, enabling it to make a single leap to orbit, rather than using and dumping propellant stages on the ascent — as is the case with current expendable rockets.
Update: Lewis Page has more on the Skylon project.
