Lifting Body Technology Demonstrator Aircraft
The X-24B was developed from the existing X-24A series of experimental aircraft designed to test lifting body theories.
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The Martin Marietta X-24B was part of a focused NASA project intended to collect data on "lifting body" aircraft. A lifting body utilized characteristics (mainly a balanced lift-versus-drag quality) of a "flying wing" in which no true tail unit was featured and the body and wing elements were blended elegantly together to form a single shape. The concept appeared as far back as World War 1 (1914-1918) and made considerable research progress in the 1960s and 1970s. The X-24B, and its related counterpart the X-24A, were both products of this period with the former flying for the first time on August 1st, 1973. It was used until November 26th, 1975 under the banners of both NASA and the United States Air Force (USAF).
The aircraft was, in fact, a heavily modified version of the preceding X-24A (mainly due to the higher-performance expected of this second round of tests), both vehicles developed by Martin Marietta, now Lockheed Martin.
The lifting body aircraft could reach very-high-altitudes and glide back to earth relying on its specialized form for natural lift, eventually landing on a wheeled tricycle undercarriage as if a conventional airplane. The aircraft could conduct precision landings on its three legs under no mechanical power, and such studies were critical in the development of re-entry space vehicles such as the soon-to-be Space Shuttle series which took the place of manned rockets in the latter stages of the Cold War (1947-1991) period.
In the X-24B, the aircraft was given a most unique form (akin to that of a 1950s space fighter): its nose assembly was dart-like, well-pointed and long, with the single-seat cockpit positioned near midships. The wing mainplanes were embedded members of the fuselage giving the aircraft an overall slim delta-like planform. The tail unit was also integrated into the design and consisted of three vertical planes - a central plane and a pair of outward-cranked planes to aid with control. Under the nose was a twin-wheeled retractable leg while a pair of single-wheeled legs made up the main members. Clearly notable in the X-24B is the placement of all physical obstructions over the imaginary fuselage horizontal line with all of the dorsal area being completed flat - this was done to add surface area in an attempt to gain operational range as well as improve inherent lift and general control of the vehicle when gliding under no power.
Internally, the X-24B carried a single Reaction Motors XLR-11 series rocket booster engine developing 9,800lb of thrust with a pair of Bell LLRV 500lb thrust rockets optionally used for landing. With this arrangement, the relatively compact aircraft could fly at speeds of 1,165 miles-per-hour (roughly Mach 1.75) and reach altitudes of just over 74,000 feet.
The pilot was positioned directly at center of the aircraft under a lightly-framed bubble-style canopy with restricted viewing to the rear due to the raised fuselage spine. As the X-24X was a data-collecting research vehicle and not a warplane, this was an acceptable design quality of many such aircraft types of the period.
To expedite the test portion of the X-24B, the vehicle was simply airlifted under the wing of a modified NASA-controlled Boeing B-52 "Stratofortress" strategic long-range bomber and released when at altitude (typically around 45,000 feet). This allowed the vehicle to not have to expend its own power/energy climbing from runaway to altitude and also worked well to shorten the test portion of each flight. One released in-air, the X-24B could engage its own rocket motor to achieve even greater altitudes (as high as 70,000 feet in some cases) and descend under no power as if the Space Shuttle itself. The futuristic-looking test vehicle was flown in such fashion across thirty-six total flights in which twenty-four of these were powered (with glide landings) and the rest operating in an unpowered glider-like fashion from beginning to end.
With its data-collection work finally completed, the X-24B's flying days ended in 1975. From then on, the Space Shuttle was operated in the same way when conducting its re-entry/landing phase - heavily influenced by the contributions of vehicles like the demonstrator-minded X-24B.