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NASA and the USAF developed the X-15 Rocket Plane

Posted in Aerospace, Aviation, Space, Technology on Thursday, 28 March 2013

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This edited article about aviation originally appeared in Look and Learn issue number 214 published on 19 February 1966.

X-15 rocket plane, picture, image, illlustration

X-15 Rocket Plane by Wilf Hardy

The sun glinting on its metal fuselage, the giant B-52 bomber scored eight vapour trails across the purple sky. Hanging beneath its port wing was a sharp-nosed rocket plane, the X-15, looking like something out of a science fiction story, with its huge wedge-shaped fins and short stub wings.

It was July 17, 1962, and sitting in the cockpit of the rocket plane, wearing a silver pressure suit that was in fact a full space suit, was Major Robert White, a test pilot for the United States Air Force. In a few minutes he would be released from the B-52 and propelled by rocket beyond the earth’s atmosphere.

All the X-15’s complex machinery was working satisfactorily, the big XLR-99 rocket engine was primed and ready to go and the jet fighter chase planes that would help guide the rocket back to base after the flight were in position. The X-15 suddenly dropped away from the bomber’s wing and as the rocket engine exploded into life, a thirty-foot flame, laced with white diamond-shaped shock waves, shot from the tail.

For eighty-four seconds White endured the thunderous roar from the rocket that propelled him to 314,750 ft. above the earth. There he hung in space, at the top of a long curving arc, before skilfully piloting the X-15 back home to Edwards Air Force Base, Southern California.

For this achievement Major White qualified for his U.S. Astronaut “wings,” a badge awarded to men who have travelled fifty miles above the earth.

The North American X-15 which carried him to this stupendous height is one of the most valuable research tools that the western world possesses. After each of its flights it brings back large amounts of information, for fitted inside the aircraft’s fuselage and wings are delicate instruments that measure all the stresses and strains of ultra high-speed flight and re-entry into the earth’s atmosphere. The X-15 that Major White flew (there are now three of them flying) carried 1,300 lb. of research instruments that measured the temperature at 600 different points and the pressure at 140 points on the aircraft’s fuselage.

The aircraft has been modified and improved again and again during the past five years of flying and it is still hard at work with the National Aeronautics and Space Administration (NASA). Much of the success of America’s space programme can be credited to the X-15 which pioneered space research in many technical fields.

The X-15 contract, a joint United States Air Force and NASA project, was awarded to North American Aviation in 1955. It called for an aircraft capable of travelling at 4,500 m.p.h. at 250,000 ft., a specification that demanded all the skill and ingenuity of the design engineers.

One of the men responsible for its success was Scott Crossfield, a top NASA test pilot who had flown every rocket and jet plane that had come to the organization. When he heard about the X-15 project he resigned his position and went to North American to offer his services. They looked at his flying and technical qualifications and took him on. Crossfield’s knowledge and enthusiasm, and the skill of the engineers took the X-15 from a drawing-board dream to a flying reality, but the project was not without its dramas.

The X-15’s big XLR-99 rocket engine was behind schedule, so the first two aircraft were each fitted with two lower powered LR-11 engines (see colour illustration) of the type which had powered the Bell X-1 aircraft. These made successful flights and when the XLR-99 finally arrived it was fitted straight into X-15 Number Three. On June 8, 1960, Crossfield ran the engine in a static ground test and it blew up, hurling him and the nose-cone section right across the test stand, but the snags were soon ironed out and then the engines ran perfectly. In one demonstration flight, Crossfield throttled the XLR-99 engine right down and kept the air brakes wide open – even so the X-15 travelled at nearly 2,000 miles per hour in a shallow climb to 50,000 ft.!

Nowadays the X-15’s fly regularly at over 4,000 m.p.h. and at altitudes of over 300,000 ft. on research flights. The pilots “fly” the mission in a flight simulator before they go on the actual journey. Coming back from space the pilots perform “re-entry” just like any spacecraft while sensitive instruments feel out the aircraft’s attitude and give the pilot corrections so he can avoid overheating the nickel-alloy steel skin, capable of withstanding temperatures of up to 1,200 deg. F. Even then the nose and the leading edges on the wings glow cherry red with the heat generated by friction as the rocket plane skims back into the atmosphere. In the near-vacuum above the earth’s atmosphere the pilot manoeuvres his aircraft with gas-jets similar to those on a Gemini spacecraft and then reverts to his normal controls as he reaches the air layers – the X-15 is truly a space plane!

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