The X-15 could be seen as an ancestor of Virgin's spaceplane's (Credit: Chris Hinkle)
Despite having exceeded the internationally recognised barrier of space of 62 miles (100 kilometres), Walker did not receive a hero’s welcome, ticker tape parade or even astronaut wings. It was just another day as a test pilot and his single-seater X-15 spaceplane pushed the boundaries of what was possible.
“The X-15 is extremely important,” says Michelle Evans, author of X-15 Rocket Plane. “Without the X-15 we wouldn’t have had the Space Shuttle and the idea of dropping a spaceplane off the wing of another plane has been translated into Virgin’s spaceship design.”
The third B-52 Stratofortress built and the oldest surviving, the eight-engine long-range bomber towers above us in the desert sunshine
The X-15 was also used to test spacecraft re-entry, and the Saturn 5 rockets that took men to the Moon used guidance systems developed on the X-15.
Retired in 1968 after 199 flights, three X-15s were built and the two surviving spaceplanes have been preserved in museums. One of the specially adapted B-52s that made these flights possible is on display at Edwards and efforts are now underway to restore the other.
“What we’re doing right now is removing the old paint so we can examine the structure of the aircraft for corrosion,” says James Stemm, director of collections and aircraft restoration at the Pima Air and Space Museum in Tucson, Arizona.
When you’re going out there to double the speed record or triple the altitude records of other aircraft, obviously you’re getting into areas that are a little dangerous – Michelle Evans, author
We stand on the concrete apron outside the restoration hanger as the aircraft is blasted with jets of water and flecks of paint fall away to reveal the bare metal fuselage underneath. The third B-52 Stratofortress built and the oldest surviving, the eight-engine long-range bomber towers above us in the desert sunshine – unaltered since its last flight in 1969.
“The B-52s were designed so they could carry missiles or bombs under the wings,” says Stemm. “Nasa modified the system so it could carry the much larger X-15.”
Adapting the B-52 involved cutting a section out of the starboard wing and slinging a pylon underneath. “It’s incredible,” says Stemm, “that the aircraft had enough surplus lift and wing area that they could make a substantial cut in it without having an effect on the aircraft’s performance.”
As well as a sizeable chunk missing from the wing and the special adapter to hold the spaceplane, this special B-52 (also known as the NB-52A) also boasts unusual markings along the main fuselage. Where some aircraft might have representations of the planes they shot down or the bombs they dropped, this has pictures of X-15s – each signifying one of the 80 missions flown by this particular B-52.
Some of these X-15 images are angled upwards to represent high-altitude test flights. The horizontal ones represent speed attempts. A couple of the X-15s, however, are angled downwards to illustrate flights that failed. Perhaps the one that killed Mike Adams in 1967, after his plane went into a hypersonic spin and broke apart on re-entering the Earth’s atmosphere. Or maybe the one that crushed the spine of Jack McKay in 1962.