SUPERSONIC BIPLANE - the resurrection of the biplane

Japanese computer model of a
commercial supersonic biplane

The biplane/triplane designs largely died out in the 1930's due to their inefficiency compared to monoplanes but we may very well see the rise of them again in the next decade or two. Recently, university teams in Japan and the United States are working on a supersonic biplane design conceived by aviation engineer Adolf Busemann in the 1930's. The concept produces a greatly reduced sonic boom and might mean the revival of commercial supersonic air travel.

Busemann's concept; as you can see,
it requires symmetrical wings

For Busemann's design to work, the plane's wings had to be in specific angles so shockwaves would destructively interfere as they left the wing cavity. The only problem was, even though the concept aircraft performs well in supersonic flight, it cannot fly at subsonic speeds. This is because the wings are symmetrical, which does not allow for the low-pressure/high-pressure difference between the top and bottom of the wings, respectively, to create enough lift. Also, when approaching supersonic speeds, the two wings create tremendous drag. Now, eight decades later, modern aviation engineering teams in opposite sides of the world are using computer simulations to improve upon Busemann's work and have come up with two different approaches to solve this drag problem.

The Japanese Tohoku University's research team is experimenting with a plane that has movable wings, eliminating the lift/drag problem in subsonic speeds. The US Stanford/MIT research team has come up with a stationary wing design but with greater wing separation to increase air flow, smoother inner wing surfaces, and curved out wing edges (reduces drag at supersonic speeds). At supersonic speeds, this model is even more flight efficient than the Concorde.


WHAT ARE SONIC BOOMS and why they are so detrimental to supersonic civilian planes

As a plane nears supersonic speeds, tremendous pressure builds up in front of the plane as air-pressure waves (created by the displacement of air by the plane) are compressed together. As the plane exceeds the sound barrier, these pressure waves combine to form shock waves that are similar to wake waves generated by a fast moving boat. The sonic boom is heard during the sharp release of pressure after the shock wave passes through. It is this loud sound that greatly annoys civilians and wildlife alike and is one of the main causes of the premature retirement of the Concorde and the subsequent avoidance for the development of newer supersonic passenger jets. Fortunately, it is possible that the supersonic biplane might breath life back into commercial supersonic air travel.