Background Boeing had in the past studied a
blended wing body design, but found that passengers did not like the theater-like configuration of the mock-up; the design was dropped for passenger airliners, but retained for military aircraft such as
aerial refueling tankers.
McDonnell Douglas developed the blended wing concept in the late 1990s, and Boeing presented it during an annual Joint
AIAA/
ASME/
SAE/ASEA Propulsion Conference in 2004. The McDonnell Douglas engineers believed their design had several advantages, but their concept, code named "Project Redwood", found little favor at Boeing after their 1997 merger. 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. The blended wing body (BWB) concept offers advantages in structural, aerodynamic and operating efficiencies over today's more conventional fuselage-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. These advantages are achieved at the expense of a multitude of disadvantages that make the concept impractical for airline use.
X-48 Boeing Phantom Works developed the blended wing body (BWB) aircraft concept in cooperation with the NASA
Langley Research Center. In an initial effort to study the flight characteristics of the BWB design, a remote-controlled propeller-driven blended wing body model with a 17 ft (5.2 m) wingspan was flown in 1997. The next step was to fly the 35 ft (10.7 m) wide X-48A in 2004, but the program was canceled before manufacturing. Research at Phantom Works then focused on a new model, designated X-48B, two examples were built by
United Kingdom-based Cranfield Aerospace, a division of
Cranfield University. Norman Princen, Boeing's chief engineer for the project, stated in 2006: "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 had a wingspan, weighs , and was built from composite materials. It was powered by three small
turbojet engines and was expected to fly at up to and reach an altitude of . The X-48B was an 8.5% scaled version of a conceptual span design.
Wind tunnel testing on a wide blended wing body model was completed in September 2005. After the wind tunnel testing, the vehicle was shipped to NASA's
Dryden Flight Research Center at
Edwards Air Force Base to serve as a backup to X-48B Ship 2 for flight testing. The X-48C has its vertical stabilizers moved inboard on either side of the engines, and its fuselage extended aft, both to reduce the aircraft's noise profile; it was to be powered by two JetCat turbines, each producing of thrust. The X-48C was instead modified to use two Advanced Micro Turbo (AMT) turbojet engines in 2012. Following flight testing of the X-48C in April 2013, Boeing and NASA announced future plans to develop a larger BWB demonstrator capable of
transonic flight. ==Operational history==