Directory of U.S. Military Rockets and Missiles|
Appendix 4: Undesignated Vehicles
|Copyright © 2006-2009 Andreas Parsch|
During the early to mid 1990s, McDonnell Douglas (and later Boeing, which acquired McDD) studied airliner designs of blended wing/body (BWB) configuration, which is essentially a flying wing with a wide lifting-body shaped center fuselage. In cooperation with NASA and other research organizations, a small propeller-driven BWB model airplane of 5.2 m (17 ft) wingspan was built, and test-flown in 1997.
|Photo: Boeing||Image: NASA|
|5.2 m (17 ft) span BWB model airplane||BWB airliner design|
As a continuation of the project, Boeing and NASA developed a design for a BWB transport aircraft powered by three large turbofan engines. Such an aircraft could be a very efficient airliner and cargo transport with high capacity and long range. In early 2000, Boeing began the construction of the BWB-LSV (Blended Wing Body - Low Speed Vehicle), an unmanned 14% scale vehicle of the BWB transport, to evaluate the design in actual flight tests. In late 2001, the official designation X-48A was allocated to the BWB-LSV.
The X-48A was made primarily of composites, had a wing span of 10.7 m (35 ft) and was powered by three small Williams J24-8 turbojets. As of mid-2001, the plans called for a completion of the vehicle by the end of 2002, ground tests through 2003, and a first flight in 2004. However, problems in the development of the flight control system as well as changing priorities at NASA led to the termination of the X-48A program (probably in early 2002).
|X-48A (3% scale wind tunnel model)|
The cancellation of the X-48A was not the end of the NASA/Boeing BWB research. The project continued at a much reduced level, and in 2002 Boeing contracted Cranfield Aerospace (UK) to design and build a smaller (8.5% scale, with about 6.4 m (21 ft) wingspan) BWB model. This vehicle was eventually designated as X-48B in June 2005. In November that year, Boeing announced that two examples were built and are planned to be flown in 2006. NASA has already flown a smaller (3.7 m (12 ft) span) model of the X-48B in a wind tunnel. The U.S. Air Force is now also involved in the BWB program, since the AFRL (Air Force Research Laboratory) is listed as a participator in the X-48B development.
Extensive ground tests with the two X-48B vehicles at NASA's Dryden Flight Research Center began in late 2006. These tests validated engine and fuel system, battery endurance, the telemetry link, the flight-control software, and the aircraft's taxiing characteristics.
The first flight of the X-48B eventually occurred on 20 July 2007. The vehicle is controlled by a pilot on the ground, who sees video transmitted by a forward-looking camera in the aircraft. After the initial low-speed flights, higher-speed tests were performed in test phase II. The latter required some modifications to the X-48B to increase its maximum speed. Phase II flight tests eventually began in spring 2008. By April 2009, 50 X-48B flights had been completed successfully, and a follow-on test program is planned to explore the limits of the vehicle's flight envelope.
The X-48C is similar to the X-48B, but includes modifications to reduce the noise level. This includes reducing the number of engines to two, and adding two vertical fins to shield engine noise.
Data for X-48A/B/C:
|Wingspan||10.7 m (35 ft)||6.22 m (20 ft 5 in)||6.25 m (20 ft 6 in)|
|Weight||1130 kg (2500 lb)||225 kg (500 lb)|
|Speed||265 km/h (165 mph)||220 km/h (120 knots)|
|Ceiling||?||3000 m (10000 ft)|
|Propulsion||3x Williams J24-8 turbojet; 1.07 kN (240 lb) each||3x JetCat P200 turbojet||2x SPT15 JetCat Ducted Fan|
 "Blended-Wing-Body Sub-scale Aircraft Demonstrates
Flight Characteristics of new Design", McDonnell Douglas Press Release, 29 July 1997
 "The Blended Wing Body, A Revolutionary Concept in Aircraft Design", NASA, 2001
 Rob Coppinger: "X-48B scale model to fly next year", Flight International Magazine, 22 November 2005
 Joseph R. Chambers: "Innovation in Flight: Research of the NASA Langley Research Center on Revolutionary Advanced Concepts for Aeronautics", NASA, 2005
 Boeing Website
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