The bid was based on REL’s single-stage-to-orbit Skylon rocket and its air-breathing Sabre motor, a radical new engine capable of switching to rocket mode in the upper reaches of Earth’s atmosphere.

Mark Hempsell, REL’s future projects director, says that Skylon “looks like something out of Star Wars.” But the technology is gaining traction with modest financial backing from the British government, and had drawn ESA’s interest even before the NELS tender was issued.

Although REL lost out on the NELS award, Dordain says the company may be onto something that might ultimately provide a new departure for future launch vehicles. He said the bid was intriguing enough to warrant a meeting between REL and ESA’s head of launchers, Antonio Fabrizi, before month’s end.

Hempsell says he thought his company’s bid was on target, but conceded it would require an investment of roughly $10 billion over a decade. This compares to preliminary French and German estimates of a next generation of Europe’s current Ariane 5 heavy-lift launcher of $5-8 billion.

In the meantime, REL is pushing ahead with public funding and continued technical support from ESA, which Hempsell says validated the credibility of recent tests of the Sabre engine’s air pre-cooler technology, which continuously cools the incoming airstream from more than 1,000C to below 150C, six times faster than the blink of an eye.

A final series of demos is set to begin in August.

“ESA has crawled all over Skylon,” says Hempsell. “On what we’re doing, you don’t always like somebody looking over your shoulder. But they’re doing a lot to help us.”