Skylon, in development by the British company Reaction Engines, would be the Holy-Grail-meets-cold-fusion of space travel, a single-stage-to-orbit spaceplane powered by the Sabre engine, which is both a jet and a rocket. While still belong to a hazy future, has put us a fraction closer to cheap hypersonic travel.

The Sabre engine is fiendishly complicated, so much so that it borders on the impossible. It would have to work as a jet engine all the way to the upper reaches of the atmosphere where it would switch to rocket mode and send the slender Skylon into space.

There are issues, and the addresses only one of many: How to cool the 1,000-degree intake gases the engine would encounter at high speed to -220 °F in 10 milliseconds? This is slightly more complicated than .

Enthusiasts now have three (err... two, because one of them is pretty much the exact same as the…

Or, as the BBC’s science editor David Shukman :

I like the team and their ambition and their Britishness. And I admire their grit in the face of so many obstacles. [Skylon designer] Alan Bond may yet be proved correct. But right now we really can’t tell if his dream will soar beyond Oxfordshire.

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