- Lifting body
The lifting body is an
aircraftconfiguration where the body itself produces lift. It is related to flying wingwhich 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.
In 1921 pioneering aviator and aircraft designer
Vincent Justus Burnellipatented the simple concept of an airfoil shaped airframe to increase the lift and load capacity of aircraft. [ [http://www.aircrash.org/burnelli/chrono1.htm Burnelli's Lifting Bodies A Photographic Chronology ] ] 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. [ [http://www.mysteriesofcanada.com/Canada/Canada_Car/burnelli_designs.htm Burnelli's Later Designs and the Current Planes That Copied Them] ] [ [http://bennun.biz/features/burnelli.html Burnelli Aircraft (The Sunday Telegraph Magazine, 2002)] ]
Aerospace-related lifting body research arose from the idea of
spacecraftre-entering the Earth's atmosphere and landing much like a regular aircraft. Following atmospheric re-entry, the traditional capsule-like 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 hypersonicflight. A proposed solution eliminated wings altogether: Design the fuselage body itself to produce lift. The Space Shuttleimplements some of the proven lifting body principles, though its design relies more on the delta wingconcept.
NASA's refinements of the lifting body concept began in 1962 with
Dale Reedof NASA's Dryden 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 California dry lakebed at present-day Edwards Air Force Base, behind a modified Pontiac Catalina[ [http://www.classicalpontiac.com/articles/nasa.html Classical Pontiac and NASA] ] . Later the craft was towed behind a C-47 and released. Since the M2-F1 was a glider, a small rocket motorwas 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 carried aloft by and dropped from under the port wing of a B-52 aircraft. Of the Dryden lifting bodies, all but the unpowered
NASA M2-F1used an XLR-11rocket engine as was used on the famous Bell X-1.) A follow-on design designated the Northrop HL-10was developed at NASA Langley Research Center. The X-24A and X-24B lifting body designs were based on the M2 concept originated in 1957 by Alfred Eggers of NASA Ames Aeronautical Laboratory. The M-2 competed in the design of the Space Shuttle.
A major instability problem with these designs was discovered during the course of flight testing and was determined to be induced by "air flow separation" whereby 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. Air flow separation caused the crash of the Northrop M2-F2lifting body. The successor Northrop M2-F3added a third (central) vertical stabilizer to the aerodynamically flawed M2-F2 design in an attempt to correct the flow separation instabilities.
X-38program, developed under leadership of NASA Johnson Space Center, built an incremental series of flight demonstrators pursuant to 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-24.
Lifting bodies pose complex control, structural, and internal configuration issues. Lifting bodies were eventually rejected in favor of a delta wing design for the Space Shuttle. Data acquired in flight test using high-speed landing approaches at very steep descent angles and high sink rates was used for modeling Shuttle flight and landing profiles.
In planning for atmospheric re-entry, the landing site is selected in advance. For reusable reentry vehicles, typically a primary site is preferred that is closest to the launch site in order to reduce costs and improve launch turnaround time. However, weather near the landing site is a major factor in flight safety. In some seasons, weather at landing sites can change quickly relative to the time necessary to initiate and execute re-entry and safe landing. Due to weather, it is possible the vehicle may have to execute a landing at an alternate site. Furthermore, most airports do not have runways of sufficient length to support the approach landing speed and roll distance required by spacecraft. Few airports exist in the world that can support or be modified to support this type of requirement. Therefore, alternate landing sites are very widely spaced across the U.S. and around the world.
The Shuttle's delta wing design was driven by these issues. These requirements were further exacerbated by military requirements (the USAF would use the future shuttle for defense satellite payloads and other missions) that extended the Shuttle's flight landing envelope.
Although a lifting body configuration may have been less vulnerable to the wing leading edge failure that caused the second shuttle loss.Fact|date=August 2007, such a configuration could not meet the flight envelope requirements of both NASA and the military.
Nonetheless, the lifting body concept has been implemented in a number of other
aerospaceprograms such as the Lockheed Martin X-33, BAC's Multi Unit Space Transport And Recovery Device, Europe's EADS Phoenixand the joint Russian-European Kliperspacecraft. Of the three basic design shapes usually analyzed for such programs (capsule, lifting body, aircraft) the lifting body may offer the best trade-off in terms of maneuverability and thermodynamics while meeting it's customers' mission requirements.
Much of the general public had never heard of nor seen anything about these lifting body designs until watching the 1970s
television show" The Six Million Dollar Man". The show's introduction footage showed the M2-F2, piloted by Bruce Peterson, crashing and tumbling violently along the Edwards dry lakebed runway. The cause of the crash was attributed to the onset of " Dutch roll" stemming from control instability as induced by flow separation. Bruce Peterson survived to fly again and the craft was rebuilt as the M2-F3.
Lifting bodies have appeared in some
science fictionworks, including the book " The Mote in God's Eye", the movie Marooned, and as John Crichton's spacecraft Farscape-1 in the TV series " Farscape". The Discovery ChannelTV series conjectured using lifting bodies to deliver a probe to a distant earth-like planet in the computer animated " Alien Planet." Gerry Anderson's 1969 Doppelgänger used a VTOLlifting body lander / ascender to visit an earth-like planet, only to crash in both attempts. In the Buzz Aldrin's Race into Spacecomputer game, a modified X-24A becomes an alternative lunar capable spacecraft that the player can choose over the Gemini or Apollo capsule.
Some aircraft with wings also employ bodies that generate lift. The
Short SC.7 Skyvanproduces 30% of the total lift from the fuselage, almost as much as the 35% each of the wings produces. Fighters like the F-15 Eaglealso produce substantial lift from the wide fuselage between the wings.
Apparently, because the F-15 Eagle's wide fuselage is so efficient at lift, an F-15 was able to land successfully with only one wing. (Videos available on YouTube).
On the summer of 1983, an Israeli F-15 staged a mock dogfight with Skyhawks for training purposes, near Nahal Tzin in the Negev desert. During the exercise, one of the Skyhawks miscalculated and collided forcefully with the F-15's wing root. The F-15's pilot was aware that the wing had been seriously damaged, but decided to try and land in a nearby airbase, not knowing the extent of his wing damage. It was only after he had landed, when he climbed out of the cockpit and looked backward, that the pilot realized what had happened: the wing had been completely torn off the plane, and he had landed the plane with only one wing attached. A few months later, the damaged F-15 had been given a new wing, and returned to operational duty in the squadron. The engineers at McDonnell Douglas had a hard time believing the story of the one-winged landing: as far as their planning models were concerned, this was an impossibility.
List of Dryden Flight Research Center lifting body vehicles (1963 to 1975)
Lifting body pilots and flights
:* Wood, Haise and Engle each made a single, car-towed, ground flight of the M2-F1.
HL-20 Personnel Launch System
Blended wing body
* [http://www.dfrc.nasa.gov/Newsroom/FactSheets/FS-011-DFRC.html Lifting Bodies Fact Sheet (NASA)]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19920000943_1992000943.pdf 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
** [http://www.dfrc.nasa.gov/gallery/photo/HL-10/ HL-10]
** [http://www.dfrc.nasa.gov/gallery/photo/M2-F1/ M2-F1]
** [http://www.dfrc.nasa.gov/gallery/photo/M2-F2/ M2-F2]
** [http://www.dfrc.nasa.gov/gallery/photo/M2-F3/ M2-F3]
** [http://www.dfrc.nasa.gov/gallery/photo/X-24/ X-24A and X24B]
** [http://members.lycos.co.uk/derekhorne/m2f1.html Short M2-F1 history]
** [http://www.centennialofflight.gov/essay/Evolution_of_Technology/lifting_bodies/Tech29.htm Some history of lifting body flight]
** [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980169231_1998082126.pdf Wingless Flight: The Lifting Body Story. NASA History Series SP-4220 1997 PDF]
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