Last month, the United Kingdom announced that it was investing $90 million in what was being billed as the most groundbreaking aeronautical development since the jet engine. The public investment would be used along with private funds to build a prototype of a SABRE engine, a propulsion system that would make the world’s first true “space plane” possible.
This supersonic aircraft, called Skylon, would be able to take off from any runway in the world, accelerate to five times the speed of sound using a hybrid jet-rocket engine, then transition to rocket mode to break through the Earth’s orbit and reach outer space. After dropping off a payload of satellites, astronauts, or tiny screws, the Skylon could return to land on the same runway less than 48 hours later. Used as a traditional aircraft, the Skylon could take 300 passengers from London to Sydney in four hours. This feat would easily surpass the speed and passenger load of the airplane industry’s crowning technological achievement, the Concorde, which retired from service nearly 10 years ago after more than 25 years of transporting travelers across the Atlantic at still unparalleled velocity. News of this British superjet made it seem as though the Concorde’s rightful heir might finally arrive.
The groundbreaking technology behind the SABRE engine was based on a seemingly simple concept: A precooler would allow the jet portion of the hybrid engine to cool itself as it achieved the intense heat and power necessary to send it to Mach 5—2½ times faster than the Concorde on its best day. This crucial precooler technology was tested in 2012 to the satisfaction not only of the company that designed it, but also of the European Space Agency. Because the rocket portion of the engine would be on the aircraft itself, the Skylon would also be completely reusable and require only routine maintenance. “Access to space, access to anywhere in the world within four hours is on the cards,” said Alan Bond, the founder of Reaction Engines, the company behind SABRE.
Reports from scientists and science journalists in Britain were breathless. "This truly is a game-changer and it truly is something that only is available in the UK," said the Guardian’s astronomy writer Stuart Clark. “I think the next few decades we might see some of the science fiction dreams we’ve had actually come true.”
The director of England’s Cranfield Space Research Centre, Steve Hobbs, said the Skylon could have the same impact on the current generation of aerospace engineers as Apollo did in capturing the hearts of Americans or Britain’s own Concorde had in inspiring the Brits. (The Concorde was a joint project between France and Great Britain.) The plan calls to have a prototype of the hybrid jet-rocket engine built by 2017 and the actual plane built by 2019 or 2020, with flights to the International Space Station carrying 15 tons of cargo to follow a few years later.
If the Skylon sounds like an impossible dream that would give Icarus or even the Concorde’s infamously ambitious designers pause, that’s because it probably is. “It looks great from a science fiction standpoint, but it’s really, really tough to do,” says John Hansman, the head of MIT’s International Center for Air Transportation. “Even if you can get the engine to work, it’s extremely challenging to get the entire airplane design to work.”
The costs are astronomical, too. The British government’s financial contribution to the project is just a small fraction of the billions needed to complete it. “Just to do a run-of-the-mill, state-of-the-art subsonic aircraft engine, you’re talking a $1 billion bill,” says Stephen Trimble, an editor at the industry publishing site Flightglobal. “It’s really hard to see that unfolding in the next seven or eight years.”