Design and development:
In fact, the original concept of a blended wing-body goes back to the jet bombers the Germans were designing at the very end of World War II. This concept was also developed at McDonnell Douglas in the 1990s, just prior to its merging into Boeing, and was presented during an annual Joint AIAA/ASME/SAE/ASEA Propulsion Conference in the US a few years ago. The McDonnell Douglas engineers were confident that their design had all the advantages mentioned, but their concept found no favor at Boeing. The most difficult problem they solved was that of ensuring passengers a safe and fast escape in case of an accident, since emergency door locations were completely different from those in a conventional aircraft.
In February 2007 Wired included the following in the article, Thinking Outside the Tube:
Ever since Boeing introduced the 707 in the 1950s, passenger jets have looked pretty much the same: long tubes with tails, engines mounted below the wings. That shape may one day be transformed into the graceful silhouette of a manta ray. In February, a 400-pound, 21-foot (6.4 m)-wide prototype of just such a bird will start practicing unmanned takeoffs, landings, and tricky slow-speed maneuvers at Edwards Air Force Base. Called the X-48B, it is a scaled-down model of a theoretical 500-ton, 240-foot (73 m)-wide blended-wing aircraft. Aeronautical engineers have long known that this design could be much quieter, more fuel efficient, and far roomier than a conventional cylinder. But recent advances—lightweight composite materials, fly-by-wire controls, sophisticated flight systems—have made building one of these planes more feasible. Commercial versions have been proposed—imagine a flying auditorium—but the X-48B is more likely to debut as a US military transport plane circa 2022."
The BWB concept reportedly offers greater structural, aerodynamic and operating efficiencies than today's more conventional tube-and-wing designs. These features translate into greater range, fuel economy, reliability and life cycle savings, as well as lower manufacturing costs. They also allow for a wide variety of potential military and commercial applications.
X-48
The Boeing Phantom Works is developing the blended wing body aircraft concept in cooperation with the NASA Langley Research Center. In a continuing effort to study the flight characteristics of the BWB design, a small remote-controlled model has been successfully flown. The next step was to fly the X-48A in 2004, which was to be built at NASA Langley, but that program was later canceled.
Boeing Phantom Works is focusing current research on a pair of models, called the X-48B, which were built under contract by Cranfield Aerospace in the United Kingdom. Norman Princen, Boeing's chief engineer for the project, said, "Earlier wind-tunnel testing and the upcoming flight testing are focused on learning more about the BWB's low-speed flight-control characteristics, especially during takeoffs and landings. Knowing how accurately our models predict these characteristics is an important step in the further development of this concept."
The X-48B has a 21-foot (6.4 m) wingspan, weighs 500-pound (230 kg), and is built from composite materials. It is powered by three small turbojet engines and is expected to fly at up to 120 kn (220 km/h) and reach an altitude of 10,000 feet (3,000 m).
NASA performed wind tunnel tests on Ship 1, an 8.5% scale model, at a facility shared by Langley and Old Dominion University in May 2006. After the wind tunnel testing, the vehicle was shipped to NASA's Dryden Flight Research Center at Edwards Air Force Base where it will serve as a backup to Ship 2 for flight testing. Ground testing at Dryden began in November 2006, to validate the aircraft's systems integrity, telemetry and communications links, flight-control software and taxi and takeoff characteristics. Flight tests began on July 20, 2007 - the first flight reached an altitude of 7,500 feet MSL (2,286 m) and lasted 31 minutes. The remotely-piloted aircraft was successfully stalled for the first time on 4 September, with fixed leading edge slats, a forward center of gravity, and 23-degree angle of attack (2° beyond the maximum coefficient of lift). Stall testing was repeated on 11 September with a NASA pilot at the console.
NASA and Boeing successfully completed initial flight testing of the Boeing X-48B on March 19, 2010. Fay Collier, manager of the ERA Project in NASA's Aeronautics Research Mission Directorate commented on the completion of the first phase of testing saying, "This project is a huge success. Bottom line: the team has proven the ability to fly tailless aircraft to the edge of the low-speed envelope safely." Following the installation of a new flight computer later this year, the X-48B will continue a new phase of flights tests that are to focus on additional parameter identification investigations. In addition, the team managing the project is also preparing a second hybrid wing body aircraft: the X-48C for future flight tests, which is intended to have a lower noise profile.
X-48C
Following a successful 80-flight test program, a modified version of the X-48B, the X-48C, is being prepared for flight test in 2011. The X-48C, to be converted from the second X-48B model, has the vertical stabilisers moved inboard, and its fuselage is extended aft, both in an attempt to reduce the aircraft's noise profile, and will be powered by two JetCat turbines producing 80 pounds-force (0.36 kN) thrust each.
Specifications (X-48B)
General characteristics:
(1) Crew: None
(2) Wingspan: 20 ft 5 in (6.22 m)
(3) Gross weight: 500 lb (227 kg)
(4) Powerplant: 3 × JetCat P200 turbojet, 52 lbf (0.23 kN) thrust each
Performance:
(1) Maximum speed: 136 mph; 219 km/h (118 kn)
(2) Endurance: 40 minutes
(3) Service ceiling: 10,000 ft (3,048 m)
