On August 7, 2011, NASA and Boeing successfully flew their experimental X-48C aircraft over NASA’s Dryden Flight Research Center at Edwards Air Force Base in southern California. The flight, a first for the X-48C aircraft, lasted nine minutes and climbed to an altitude of 5,500 feet before landing.
Designed by Boeing and built by Cranfield Aerospace Limited of Cranfield, England, the prototype X-48C promises to be the future of fuel efficient, quieter aircraft capable of significantly longer distance flights. The remotely-piloted aircraft is actually an 8.5 percent scale model of an eventual full-size heavy-lift vehicle with a 240-foot wingspan and a range of 11,000 miles, which Boeing hopes to see flying in the next 15-20 years.
The biggest difference between the X-48C and present day aircraft is its revolutionary triangular look, a Blended Wing Body design (BWB). The BWB concept is essentially a cross between a flying-wing design and a conventional aircraft, merging the aircraft’s wing and body into one structure. The design offers potential customers long-term fuel efficiency, more fuel capacity, and noise reduction benefits. The aircraft’s profile allows air to pass over it more efficiently compared to present day planes, allowing for lower drag and better lift, which the X-48 team expects will equate to a 20-30 percent improvement in fuel consumption when the final full-scale version of the X-48 is complete.
“We are very pleased to begin flight tests of the X-48C,” said Mike Kisska, Boeing X-48C project manager. “Working with NASA, we’ve successfully passed another milestone in our work to explore and validate the aerodynamic characteristics and efficiencies of the blended wing body concept.”
Tuesday’s flight may have been a first for the X-48C, but the prototype aircraft is actually an upgraded model of the former X-48B, which successfully performed 92 flights at Dryden between 2007 and 2010. The B model proved that a BWB aircraft could be controlled at low-speeds just as effectively as any present day conventional aircraft, and the changes made to create the C model will help engineers evaluate noise shielding designs applied to the airframe.
Video: The X-48 Blended Wing Body (BWB). Credit: Boeing/stealthb2777
The modifications made to the X-48C were geared specifically to noise-reduction. The wingtip winglets were relocated inboard next to the engines, and the aft deck was extended two feet to the rear. In addition, the new aircraft flies under the power of two 89-pound thrust turbojet engines, rather than the three 50-pound thrust jet engines used by the X-48B. The engines were also moved forward on the C model, above aft center, with the idea being that the sound from the twin jet engines will bounce up or to the sides, rather than down towards the ground.
Modifications made to the X-48C also change the aircraft’s handling qualities compared to the X-48B, so the project team developed flight control system software modifications, including flight control limiters to keep the aircraft flying within a safe flight envelope. With a wingspan of just over 20 feet and weighing in at about 500 pounds, the X-48C can reach an altitude of 10,000 feet and fly for 35 minutes at an estimated top speed of 140 miles per hour.
“We are thrilled to get back in the air to start collecting data in this low-noise configuration,” said Heather Maliska, X-48C project manager at NASA’s Dryden Flight Research Center. “Our dedicated team has worked hard to get the X-48C off the ground for its first flight and we are excited learning about the stability and control characteristics of this low-noise configuration of the blended wing body.”
The X-48 project team expects to fly the C model 20 times through the remainder of 2012. In addition to significantly reducing noise, upcoming flights this fall will help the X-48 team further develop methods to validate the design’s aerodynamics, with the goal of reducing drag through engine yaw control tests. Engine yaw control software in the X-48C’s flight computer will use asymmetric engine thrust to create yaw (nose left or right movements) for trim and for slow maneuvers.
Engineers will use the data collected from the X-48C flights and apply what they learn into the next prototype version, which Boeing expects will be human-piloted and have most of the capabilities that can be expected in the final full-scale version. NASA expects the next prototype to be ready for test flights in the next 4-5 years, with the final X-48 ready to hit the skies in the next decade. The X-48 could be used for a wide range of military and civilian applications, everything from aerial refueling and transport missions for the U.S. Air Force to commercial airline flights.
NASA’s Aeronautics Research Mission Directorate and Boeing are funding the X-48 technology demonstration research effort in support of NASA’s goals to reduced fuel burn, emissions and noise in the design of future aircraft. The Air Force Research Laboratory is also a member of the project team.
For more information about the Aeronautics Research Mission Directorate, visit: www.aeronautics.nasa.gov