Supersonic Bi-Directional Flying Wing is a novel concept suggested by Prof. Gecheng Zha at University of Miami for supersonic airplane to achieve zero or very low sonic boom, low supersonic wave drag, and high subsonic performance. The SBiDir-FW planform is symmetric about both longitudinal and span axes. For supersonic flight, the planform will have low aspect ratio and high sweep angle to minimize wave drag and remove sonic boom. For subsonic mode, the airplane will rotate 90deg in flight and the sweep angle will be reduced and the aspect ratio will be increased substantially. In simple words, we like the airplane to be slender for supersonic high speed flight. For low speed such as at take-off/landing, we like the airplane to have wide wing span with high aspect ratio. Conventional supersonic airplane compromises for low and high speed and ends up being unable to optimize both. The SbiDir-FW is promising to remove the conflict. The same concept can also apply to hypersonic (M>5) one-stage to orbit vehicles.

With the same sweep angle and lifting surface area of a conventional wing-tube configuration, SBiDir-FW configuration is 41% longer and the aspect ratio is 50% smaller. Furthermore, the flying wing configuration uses the whole body length (the maximum possible length) as the airfoil chord to distribute the lift and use the whole body area as lifting surface, which results in ultra high slenderness, minimal shock strength to minimize wave drag, and minimized compression wave coalescing in mid-field to form a smooth Sine wave shape ground over-pressure signature with very low sonic boom instead of a N-wave. The ultra-slenderness at supersonic is translated to very high aspect ratio at subsonic speeds by rotating 90?. Hence the configuration has favorable aerodynamic performance in the whole flight envelop from low to high speed.

The preliminery CFD simulation shows that it obtains smooth ground sonic overpressure of 0.3psf with L/Dp = 16 at Mach 2.0. The ground pressure signature is not the N shape wave with two impulsive shock waves, but is in a smooth sine shape wave, which means no sonic boom. For more information, please visit the SBiDir publication site .

SBiDir-FW is at its infant stage and a longterm research and development needs to be done to make it become mature technology. Imagine to fly from New York to Los Angeles in 2 hours instead of 6 hours, New York to Tokyo in 4 hours instead of 15 hours. The research has been funded by NASA and FCAAP.