Lifting body

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The lifting body is an aircraft configuration where the body itself produces lift. It is related to flying wing which is a wing without a conventional fuselage. A lifting body is a fuselage that generates lift without the shape of a typical thin and flat wing structure. A flying wing seeks to maximize cruise efficiency at subsonic speeds by eliminating non-lifting surfaces. By contrast, lifting bodies generally minimize the drag and structure of a wing for very high supersonic, hypersonic flight or spacecraft re-entry. Both designs pose challenges for controlled, stable flight.

The Martin Aircraft Company X-24 built as part of a 1963 to 1975 experimental US military program

X-24A, M2-F3 and HL-10 Lifting bodies (NASA)

In 1921 pioneering aviator and aircraft designer Vincent Justus Burnelli patented the simple concept of an airfoil shaped airframe to increase the lift and load capacity of aircraft. [1] Despite a number of business and political setbacks, Burnelli continued to refine and license his designs making a number of refinements to the concept up until his death in 1964. [2] [3]

[edit] Development

Aerospace related lifting body research arose from the idea of spacecraft re-entering the Earth's atmosphere and landing much like a regular aircraft. The traditional capsule-like spacecraft had very little control over where they landed once they re-entered the Earth's atmosphere. A steerable spacecraft with wings could significantly extend the landing envelope. Wings would have to be built that could withstand stresses and temperatures at hypersonic speeds. A proposed answer was to eliminate wings altogether: design the body itself to produce lift. The Space Shuttle contains some of the lifting body principles, although it relies more on the delta wing concept.

NASA's refinements on the lifting body concept in 1962 with Dale Reed of NASA's Dryden Flight Research Center. The first full-size model, the NASA M2-F1, was made of wood. Initial tests were performed by towing the craft along a dry lakebed behind a modified Pontiac Catalina [4]. Later the craft was towed from behind a C-47 and released. Since the M2-F1 was a glider, a small rocket motor was added in order to extend the landing envelope. The M2-F1 was soon nicknamed the "Flying Bathtub".

In 1963, NASA began experimenting with heavier rocket powered craft dropped from a B-52 Bomber. (Of the Dryden lifting bodies, all but the NASA M2-F1 used an XLR-11 rocket engine like the famous Bell X-1.) A follow-on design was the Northrop HL-10, developed at NASA's Langley Research Center. The X-24A and X-24B were based on the M2 concept originated by Alfred Eggers in 1957 at NASA Ames Research Center (called the Ames Aeronautical Laboratory in 1957), Moffett Field, Mountain View, California. The M-2 competed in the design of the Space Shuttle, the most notable lifting body in history.

A major difficulty with these designs was air flow separation; the air stream would become very turbulent causing loss of control and lift. The HL-10 attempted to solve part of this problem by angling the port and starboard vertical stabilizers outward and enlarging the center one. This air flow problem caused the crash of the Northrop M2-F2 lifting body. The rebuilt M2-F2 (now called the Northrop M2-F3) added a central rudder to correct the aerodynamic flaw of its predecessor.

The X-38 was a program under leadership of NASA Johnson Space Center to build a series of incremental flight demonstrators for the proposed Crew Return Vehicle (CRV) for the International Space Station. The X-38 was a lifting body based on the outer mold line of the X-24A.

[edit] Aerospace applications

Lifting bodies pose complex control, structural and internal configuration issues. Lifting bodies would eventually be rejected in favor of a delta wing for the Space Shuttle. Data learned in fast approaches with high sink rates would be used for modeling Shuttle flights. Such a configuration may have been less vulnerable to the wing leading edge failure which doomed the second shuttle loss.

The lifting body concept has been considered for many other aerospace programs, including the Lockheed Martin X-33, BAC's Multi Unit Space Transport And Recovery Device, Europe's EADS Phoenix and the Russian-European cooperation Kliper spaceship. This is mainly because of the three basic shapes usually analyzed for such projects (capsule, lifting body, aircraft) the lifting body offers the best trade-off on terms of maneuverability and thermodynamics.

[edit] Popular Culture

Much of the general public had never heard, or seen, anything about these lifting body designs until watching the 1970s television show The Six Million Dollar Man. The introduction footage showed the M2-F2, piloted by Bruce Peterson, crashing and tumbling violently along the runway. The cause of the crash was attributed to the onset of Dutch roll. Bruce Peterson survived to fly again and, the craft was rebuilt as the M2-F3.

Lifting bodies have appeared in some science fiction works, including the book The Mote in God's Eye. The Discovery Channel TV series conjectured using lifting bodies to deliver a probes to a distant earth-like planet in the computer animated Alien Planet. Gerry Anderson's 1969 Doppelgänger used a VTOL lifting body lander / ascender to visit an earth-like planet, only to crash in both attempts. In the Buzz Aldrin's Race into Space computer game, a modified M2-F2 becomes an alternative lunar capable spacecraft that the player can choose over the Gemini or Apollo capsule.

[edit] Body lift

Some aircraft with wings also employ bodies that generate lift. The Shorts SC.7 Skyvan produces 30% of the total lift from the fuselage, almost as much as the 35% each of the wings produces. Fighters like the F-14 Tomcat also produce substantial lift from the wide fuselage between the wings.

[edit] List of Dryden Flight Research Center lifting body vehicles (1963 to 1975)

• M2-F1
• M2-F2
• M2-F3
• HL-10
• X-24A
• X-24B

[edit] Lifting body pilots and flights

* Wood, Haise and Engle each made a single, car-towed, ground flight of the M2-F1.

[edit] See also

• HL-20 Personnel Launch System
• Facetmobile
• Blended wing body
• Flying wing

[edit] External links

• Lifting Bodies Fact Sheet (NASA)
• NASA Tech Paper 3101: Numerical Analysis and Simulation of an Assured Crew Return Vehicle Flow Field (The math of airflow over a lifting body)
• NASA Photo Collections from Dryden Flight Research Center
  • HL-10
  • M2-F1
  • M2-F2
  • M2-F3
  • X-24A and X24B
  • Short M2-F1 history
  • Some history of lifting body flight
  • Wingless Flight: The Lifting Body Story. NASA History Series SP-4220 1997 PDF