Martin Marietta X-24

Martin Marietta X-24. The X-24 was an American experimental aircraft developed from a joint United States Air Force and NASA program to explore the flight characteristics and viability of lifting body designs for unpowered re-entry and landing. It was the final aircraft in a series of lifting body research vehicles that included the earlier Northrop M2-F2 and the Northrop HL-10, providing critical data on low-speed handling and landing approaches. The program successfully demonstrated that a wingless vehicle could be flown from high altitude and landed precisely on a conventional runway, contributing directly to the development of the Space Shuttle program.

Development and Design

The X-24 program originated from research initiated by the United States Air Force's Aerospace Research Pilot School at Edwards Air Force Base and NASA's Flight Research Center, now the Armstrong Flight Research Center. The vehicle's design evolved from the earlier Martin SV-5J concept, a manned version of a proposed military space plane studied under the Air Force Flight Dynamics Laboratory's START (Spacecraft Technology and Advanced Reentry Tests) program. The airframe was constructed by Martin Marietta, with its distinctive "flying flatiron" shape optimized for aerodynamic stability during atmospheric re-entry. Unlike the Northrop M2-F2 and Northrop HL-10, which had rounded shapes, the X-24 featured a more elongated, pointed design, which engineers believed would offer better performance at higher speeds. The cockpit was equipped with a standard center stick and rudder pedals, and the vehicle was designed to be air-launched from a modified Boeing B-52 Stratofortress mothership, a technique perfected during the earlier North American X-15 program.

Flight Testing Program

The flight test program commenced with unpowered glide flights. The X-24 made its first captive-carry flight on 4 April 1969, followed by its first free glide flight on 17 April 1969, piloted by NASA research pilot John Manke. These initial flights validated the craft's basic handling qualities and approach and landing capabilities. Powered flight testing began on 19 March 1970, with pilot John Manke at the controls, using a Thiokol XLR-11 rocket engine, the same type used in the Bell X-1. The X-24A configuration completed 28 flights in total, reaching a maximum speed of Mach 1.6 and a peak altitude of 71,407 feet. In 1972, the vehicle was returned to Martin Marietta and rebuilt into the X-24B, a radically different shape with a long, pointed nose and delta-like planform, designed to test a more advanced re-entry configuration. The X-24B, piloted by individuals like John Manke and Bill Dana, flew 36 missions, achieving a top speed of Mach 1.76 and demonstrating precise unpowered landings on the dry lake bed at Edwards Air Force Base.

Technical Specifications

The X-24A had a length of 24.5 feet, a width of 11.5 feet, and a height of 9.7 feet. Its initial shape was characterized by a rounded nose and a flat bottom. The rebuilt X-24B had a length of 37.5 feet, with a sharply pointed nose and a double-delta planform with a wingspan of 19.0 feet. Both versions were constructed primarily from aluminum alloy. The propulsion system for powered flights was a four-chamber Thiokol XLR-11-RM-13 rocket engine, providing up to 8,480 pounds of thrust. The vehicle had no landing gear; it landed on its retractable skid. Avionics were relatively basic, including flight control systems and instrumentation for recording aerodynamic and performance data, which was analyzed by engineers at NASA and the United States Air Force.

Legacy and Influence

The X-24 program provided an invaluable database on the controllability and piloting techniques for wingless re-entry vehicles. Its successful demonstration of precise unpowered landings from high altitude was a direct precursor to the landing phase of the Space Shuttle program. Data on heating and stability informed the design of the Space Shuttle Orbiter's fuselage. The X-24B, in particular, represented a shape more applicable to future spaceplane concepts. The program's pilots, including John Manke, Bill Dana, and Einar Enevoldson, earned accolades for their work. The sole X-24B aircraft is now on public display at the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Ohio, serving as a testament to this pioneering era of aerospace research.

Category:United States experimental aircraft 1960–1969 Category:Lifting body aircraft Category:Martin Marietta aircraft Category:NASA aircraft