# Why is the Busemann biplane not used?

A Busemann biplane greatly reduces wave drag It would allow a deeper, more efficient structure to support a wing with less wetted area and thus friction drag. It would seem trivial to tilt the biplane to produce lift. It looks like the next breakthrough after the supercritical airfoil.
So why do we not find this configuration in modern supersonic aircraft? Are there any prohibitive drawbacks?

• Flow choking at off-design conditions. Feb 10 at 13:50
• @OrganicMarble didn't prevent multi shock intakes from existing. All you need to do is deflect a control surface to narrow the inlet or widen the exit until the shock is sucked in. Feb 11 at 2:02
• I'm not the one who noticed the problem, I just learned about it back in the 1970s, so it is pointless to argue with me. If you had done any research before posting this question, you would have read about this problem. Feb 11 at 2:04
• @OrganicMarble I have read about it years ago Feb 11 at 2:56

it would seem trivial to tilt the biplane to produce lift

Apparently, this is where the entire structure of the Busemann biplane would begin to generate a whole new set of shockwaves while also (common to all biplanes) a lot more drag.

The concept appears to be more useful to help explain symmetrical supersonic shockwave patterns in inlets than as a mechanism for (efficient) supersonic flight.

Sonic "boom" mitigation strategies as seen here appear to be focused on directing the shockwave away from the ground and/or splitting it into many smaller waves instead of the classic N wave.

This can be visualized, 3 dimensionally, as trying to arrange a group of rocks in a stream (of non-compressable fluid) to produce as small a wave as possible.

The first step (obviously) would be to streamline the shape, as shown here. Beyond that one may try to have the sound waves cancel each other out or scatter in different directions. The "biplane" is but one of these concepts.

Others may be multiple (unstacked) wings and/or lifting bodies with greater Lift/Drag ratios and lower form drag. The problem remains creating a structure wide enough to hold a sufficient number of passengers for profitable operation.

The Boeing 2707 tried to solve this issue by taking the best available aerodynamic shape and scaling it to larger size.

A Busemann biplane produces massive friction drag, while creating no lift.

Even if modified to produce, optimistically, 1/2 the lift of a normal wing of the same span, it's still going to incur 4 times the friction drag.

This configuration is well-understood and widely used, for instance, in supersonic inlets. It's just not capable of replacing the fuselage (unless onion rings develop an aeronautical civilization) or the wings.