To any fan of aviation or space history Edwards Air Force Base in California is hallowed ground.
A Harrier jump jet taxis to the runway. Behind it is the vast expanse of flat dry lake floor that made this remote desert location so suitable for landing after dangerous test flights. A few metres away, the fenced-off area where the Bell X-1 was refuelled before the world’s first supersonic flights in the late 1940s. Nearby, a preserved cluster of the weird looking machines that enabled pilots to push the boundaries of the possible. Among them, the stubby wings of the tiny experimental aircraft made famous by the 70s TV series The Six Million Dollar Man.I am here to see a life-sized model of one of the most important aeroplanes ever flown: the North American X-15. These days it is tucked away, out of public view, behind the back of a hangar. But 50 years ago the experimental rocket plane this model represents flew higher and faster than any piloted aircraft before or since. In fact this joint military and Nasa project is better described as the world’s first hypersonic spaceplane. The X-15 resembles not so much a plane as an oversized dart – a needle-nosed torpedo with stubby wings, built around a rocket engine that could propel it to speeds in excess of 4,500mph (7,270km/h). That’s London to New York in 45 minutes.
“In terms of manned aircraft, this was the pinnacle, it made records that have yet to be broken,” says Stephanie Smith, a US Air Force historian at the base, standing beside the battered black fuselage of the dart-shaped plane. “This was the most productive research programme for aviation ever and really gave it that leap forward.”
Over a period of nearly 10 years beginning in 1959, the titanium-clad X-15 flew 199 missions, reaching more than four-and-a-half times the speed of sound. On several occasions, its single giant rocket motor propelled it beyond the atmosphere out into space and the pilots saw the horizon turn from blue to black as they hurtled beyond our planet’s sky. After less than 10 minutes of flight, they would return to Earth to skid to a halt on the Edwards lake floor. Remarkably, only one test pilot was killed in all those flights.
As well as proving that an aircraft could fly from air to space and back again, other achievements from the X-15 programme include the development of the first space suits, the study of thermal protection systems for re-entering the atmosphere and the application of advanced avionics. Some of the flights were equipped with instruments to observe and study the hostile space environment.
“People at Edwards really looked up to those aviators, those astronauts, who flew the X-15,” Smith says. “They idolised them – even the people who worked with them on the project really looked up to those pilots as being out there on the cutting edge, taking the risks.”