A lifting body is a fixed-wing aircraft or spacecraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing. Whereas a flying wing seeks to maximize cruise efficiency at subsonic speeds by eliminating non-lifting surfaces, lifting bodies generally minimize the drag and structure of a wing for subsonic, supersonic and hypersonic flight, or spacecraft re-entry. All of these flight regimes pose challenges for proper flight safety. Lifting bodies were a major area of research in the 1960s and 1970s as a means to build a small and lightweight crewed spacecraft. The United States built a number of lifting body rocket planes to test the concept, as well as several rocket-launched re-entry vehicles that were tested over the Pacific. Interest waned as the United States Air Force lost interest in the crewed mission, and major development ended during the Space Shuttle design process when it became clear that the highly shaped fuselages made it difficult to fit fuel tankage. Advanced spaceplane concepts in the 1990s and 2000s used lifting-body designs. Examples include the HL-20 Personnel Launch System (1990) and the Prometheus spaceplane (2010). The Dream Chaser lifting-body spaceplane, an extension of HL-20 technology, was proposed as one of three vehicles to carry American crew members to and from the International Space Station, but eventually was selected as a resupply vehicle instead. In 2015 the European Space Agency Intermediate eXperimental Vehicle performed the first-ever successful reentry of a lifting body spacecraft.
History The lifting body had been imagined by 1917, in which year an aircraft with something like a delta wing plan form with a thick included fuselage was described in a patent by Roy Scroggs. The lifting body is inefficient at low airspeeds, however, and it did not enter mainstream airplane design. Aerospace-related lifting body research arose from the idea of spacecraft re-entering the Earth's atmosphere and landing much like a regular airplane. Following atmospheric re-entry, the capsule spacecraft from the Mercury, Gemini, and Apollo series had very little control over where they landed. A steerable spacecraft with wings could significantly extend its landing envelope. However, the vehicle's wings would have to be designed to withstand the dynamic and thermal stresses of both re-entry and hypersonic flight. One proposal eliminated wings altogether, designing the fuselage body to produce lift by itself.
The National Air and Space Administration's (NASA's) refinements of the lifting body concept began in 1962 with R. Dale Reed of the NASA Flight Research Center (now the Armstrong Flight Research Center). The first full-size model to come out of Reed's program was the NASA M2-F1, an unpowered craft made of wood. Initial tests were performed by towing the M2-F1 along a dry lakebed at Edwards Air Force Base, California, behind a modified Pontiac Catalina convertible. Later the craft was towed behind an R4D (the United States Navy version of the C-47 Skytrain) and released. Since the M2-F1 was a glider, a small rocket motor was added to extend the landing envelope. The M2-F1 was soon nicknamed the "Flying Bathtub". In 1963, NASA began programs with heavier rocket-powered lifting-body vehicles to be air launched from under the starboard wing of a NB-52B, a derivative of the B-52 jet bomber. The first flights started in 1966. Of the Dryden lifting bodies, all but the unpowered NASA M2-F1 used an XLR11 rocket engine as was used on the Bell X-1. A follow-on design designated the Northrop HL-10 was developed at NASA Langley Research Center. Air flow separation caused the crash of the Northrop M2-F2 lifting body. The HL-10 attempted to solve part of this problem by angling the port and starboard vertical stabilizers outward and enlarging the center one. Starting in 1965 the Soviet lifting body Mikoyan-Gurevich MiG-105 or EPOS (Russian acronym for Experimental Passenger Orbital Aircraft) was developed and several test flights made. Work ended in 1978 when the efforts shifted to the Buran program, while work on another small-scale spacecraft partly continued in the Bor program. The IXV is a European Space Agency lifting body experimental re-entry vehicle intended to validate European reusable launchers which could be evaluated in the frame of the FLPP program. The IXV made its first flight in February 2015, launched by a Vega rocket. Orbital Sciences proposed a commercial lifting-body spaceplane in 2010. The Prometheus is more fully described below.
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