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Machine Design

Image Gallery: Celebrating the X-15 altitude record

A little over 50 years ago, NASA’s X-15 rocket-powered aircraft flew to over 354,000 ft., an altitude record that stood for over 40 years. The X-15s flew for the first time in June 1959 and made 199 flights in their 10-year history. NASA had three X-15s built as part of its hypersonic research program. The program let developers and researchers analyze flight controls, airframes, and other subsystems designed for high-speed, high-altitude flight. Scientists also gathered data on the physiological effects on pilots in supersonic aircraft.

North American Aviation (Chicago, Ill.) manufactured the X-15’s airframe, and Reaction Motors Inc. designed and assembled the engines. Two engine models were used. The XLR11 engine powered the first 24 flights with 6,000 lb. of thrust. They were then replaced by the XLR99, which could crank out 57,000 lb. of thrust. The XLR11 was the first liquid-fueled rocket engine with four combustion chambers that could be powered on or off individually.  And the XLR99 could be shut down and restarted in-flight.

Photography courtesy of NASA


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