Reaction Engines Ltd believes its novel Sabre engine, which would operate like a jet engine in the atmosphere and a rocket in space, could displace rockets for space access and transform air travel by bringing any destination on earth to no more than four hours away.
That ambition was given a boost on Wednesday by ESA, which has acted as an independent auditor on the Sabre test programme.
"ESA are satisfied that the tests demonstrate the technology required for the Sabre engine development," the agency's head of propulsion engineering Mark Ford told a news conference.
"One of the major obstacles to a re-usable vehicle has been removed," he said. "The gateway is now open to move beyond the jet age."
The space plane, dubbed Skylon, only exists on paper. What the company has right now is a remarkable heat exchanger that is able to cool air sucked into the engine at high speed from 1,000 degrees Celsius to minus 150 degrees in one hundredth of a second.