Compression lift

In the aerodynamics of the compression lift means a lift force during supersonic flight. The shock wave is exploited in the Mach cone.

The shock wave produced when the sound speed is exceeded; a matched it designed supersonic aircraft can fly by by smaller angle of attack and low induced drag.

History

The phenomenon of compression lift was described by the NACA engineers Clarence A. and Alfred J. Eggers Syvertson in 1956 for the first time. They studied the deviations from the ballistic curve at re-entry, and covered it, the principle behind the compression lift on.

Compared with planing boats

The compression lift is similar to planing boats, when a boat in planing conditions, the hull speed approaches, is slides onto the bow wave and thus lifted partially out of the water. When the aircraft is, however, difficult to implement, because the shock wave is formed only at supersonic flight, is distinctly arrow-shaped (see Mach shear cone), and also their opening angle changes greatly with speed. This makes it difficult to construct an aircraft that can win over a large speed range boost from the shock wave.

Technical implementation

In the North American XB -70 for the first time compression buoyancy was used in an aircraft. In this case, the shock wave generated by the air intake, under the wings. So could without additional air resistance during supersonic flight, the lift will be increased by 30 % .. In the XB -70, this was additionally supported by the wing tips when they were fully folded down by this generated an additional 5 % compression boost. The folded-down wingtips increased directional stability, so that one could use the XB -70 with a smaller side Round, than would otherwise have been possible. Only so you could achieve the desired low resistance and thus acceptable range at Mach 3.

In so-called lifting bodys the same principle is used for generating lift. Newer maneuverable reentry vehicle ( MARV - nuclear warhead ) use this effect to some extent to the direction of change within the atmosphere to make it more difficult to intercept and to increase the accuracy.

The developed never about the conception phase of the American project like an airplane taking off spacecraft Rockwell X-30 was also based on the compression boost.