'Critical' Spaceplane Engine Testing Underway
April 29, 2012

‘Critical’ Spaceplane Engine Testing Underway

Testing has begun on an engine that could make it possible for a plane to travel into space, travel at five times the speed of sound, and make it possible to reach any destination on the planet in no more than four hours, Suzannah Hills of the Daily Mail reported on Saturday.

The vehicle in question is the Skylon, an unmanned, reusable spaceplane that is currently in development at UK aerospace company Reaction Engines Ltd (REL). According to Hill, the craft can take off and land from any conventional airport runway, but can actually fly 18 miles above the Earth's surface and out of the planet's atmosphere at Mach 5.

Space Exploration Network (SEN) reporter Ben Gilliland reports that engineers have begun a series of "critical" tests on the Sabre (Synergistic Air-Breathing Rocket Engine) used by the Skylon. The engine can operate like either a jet engine or a rocket engine based on its altitude, he said, and the cooling systems used to keep the engine operational are the focus of the ongoing examinations.

"When the craft takes off it operates in 'air-breathing' mode, allowing the engines to gather oxygen from the air, which is mixed with liquid hydrogen from internal tanks. But as Skylon would travel at five times the speed of sound (Mach 5) the air being sucked into its engines would be heated by friction to 1,000C -- far too hot for the engine to utilize," he said. "This month´s tests will focus on the critical 'pre-cooler' system needed to chill the incoming air to a usable temperature."

"The pre-cooler´s intricate cooling system uses freezing, high-pressure helium to chill the air to -140C before it passes into the engine´s combustion chamber where it is mixed with hydrogen and ignited to produce thrust," Gilliland added. "What makes the system special is that fact that Skylon fills up with oxygen on the go as it flies through the atmosphere, meaning it doesn´t have to launch with a full tank, greatly reducing its weight. Another key part of the design is its ability to chill the air enough to reduce its volume, meaning the craft doesn´t need to carry heavy compressors."

Evan Ackerman of DVice said that the proof-of-concept cooling system has been working "perfectly" in testing thus far -- a good sign for the REL R&D team behind the Sabre engine, because as he notes, it is not just "a functional piece of the final engine" but arguably "it's the hardest piece, meaning everything is downhill from here."

Next up for the Skylon will be a small-scale operational test of the entire engine, Ackerman added. In addition, they will need to produce updated design drawings for the engine and the entire Skylon vehicle, as well as a demonstration of the air intake (engine nacelle) configurations, BBC News Science Correspondent Jonathan Amos said. Amos said that the company has raised 85% of their funding from private investors, but could ultimately need to solicit government funding to raise the $400-plus million needed to continue the next phase of their work.

"We intend to go to the Farnborough International Air Show in July with a clear message," REL Managing Director Alan Bond told the BBC. "The message is that Britain has the next step beyond the jet engine; that we can reduce the world to four hours -- the maximum time it would take to go anywhere. And that it also gives us aircraft that can go into space, replacing all the expendable rockets we use today."

"What we have learned is that a little bit of government money goes a long way," he added. "It gives people confidence that what we're doing is meaningful and real -- that it's not science fiction. So, government money is a very powerful tool to lever private investment."