A novel flying wing concept that in one configuration can fly supersonically and in another fly subsonically, has been awarded a study grant under NASA’s Innovative Advanced Concepts (NIAC) project.
Proposed by a team led by Gecheng Zha of the University of Miami’s Mechanical and Aerospace Engineering department, the bi-directional flying wing combines wing and fuselage shaping optimized for faster-than-sound and subsonic speeds in one platform. The Miami team says the design has “the potential to revolutionize supersonic flight with virtually zero sonic boom and ultra-high aerodynamic efficiency.”
The star-shaped aircraft’s planform is symmetric about both the longitudinal and span axes. For supersonic flight, the aircraft will fly in a direction in which the planform has a low aspect ratio and a high sweep angle to minimize wave drag and sonic boom. For subsonic mode, the aircraft rotates through 90 deg in flight and utilizes a more conventional planform.
Supersonic (Mach 1+) configuration is represented (upper) and subsonic (lower)
“The conflict of subsonic and supersonic aerodynamic performance of conventional fuselage-wing configuration is hence removed,” says Gecheng Zha (click here to see a presentation of the concept for potential use in UAVs in 2009). The team adds that preliminary CFD simulation for a business jet version of the design at Mach 1.6 and 2.0 indicate that the configuration is also virtually ‘boom-less.’ The report says at these speeds the design generates “no N-wave sonic boom on the ground at a high lift to pressure drag ratio L/Dp of 16. The superior supersonic aerodynamic performance is benefited from the sharp nose and ultra-slender body with a low aspect ratio of 0.33, which translates to a very high subsonic aspect ratio of 33 for high subsonic performance.”
The concept is powered by centrally-mounted twin turbofans which pivot around an axis point near the center of the aircraft. Details of the proposed transition phase from low to high-speed flight, and back again, are not discussed though the design team predicts low g-forces below one. Further work will include design refinement of a supersonic flying wing business jet configuration using CFD as well as mission analysis to study the concept’s feasibility. It will also include wind tunnel testing to verify the design’s supersonic aerodynamic performance and sonic boom signature.
The NIAC program is designed to nurture visionary ideas that “could transform future NASA missions with the creation of breakthroughs — radically better or entirely new aerospace concepts — while engaging America's innovators and entrepreneurs as partners in the journey.”