The modifications to the Busemann's Biplane design reported in this article have proven that it is possible to design a modified Busemann's Biplane wing design that actually produces lift at supersonic speeds. Is it then possible to fly the same plane at hypersonic speeds of say Mach 10 (and ground speeds of above 10,000 km/h)? What are the other technical limitations?

The engines can achieve it and the air frame could be cooled, is noise once again an impediment at those speeds? Are there any effects on the human body for flying that fast given gradual acceleration? What about fuel, is it fuel efficient? Do we have a type of fuel that could power today's engine designs at those speeds given the complexities of using hydrogen?


2 Answers 2


Why Mach 10? Would Mach 3 or 4 not be enough? See here and here and here for the complications which arise at higher speeds.

The linked article is full of misrepresentations - of course will the Busemann biplane create lift at sub-supersonic speed (what is that, anyway? I read it as subsonic speed). Give it a proper subsonic airfoil and it will do so just like any other biplane, and even with the trapezoidal airfoil it will do so, albeit with more drag. It will also create lift and drag if operated at a proper angle of attack below its design speed (maybe that is meant by sub-supersonic speed, but the author never clarifies that).

Busemann biplane

Busemann biplane as shown in the linked article (source)

Did you note that the shock lines in the graph only occur between the two wings? That means that on the outer surfaces you will only see ambient pressure. The pressures internally cancel each other, and the result is that the Busemann biplane will not create any lift at its supersonic design speed in order to do its magic. As soon as it starts to create lift, it needs to create shock waves on the outside which will invariably be audible. That the researchers at Tohoku claim them to be 85% weaker is easy if they omit to mention to what they compare it.

Now look at the bulky passenger compartment on the top wing. This is clearly not optimised for supersonic travel (please compare it to the fuselages of the Concorde or the Tu-144 to get an idea what works).

No, this article is just utter nonsense.

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    $\begingroup$ Most things are 85+% quieter than the Tunguska event. $\endgroup$
    – UIDAlexD
    Commented Sep 20, 2017 at 17:59
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    $\begingroup$ 85% of all statistics are made up... oh, never mind. $\endgroup$
    – FreeMan
    Commented Sep 20, 2017 at 20:48
  • $\begingroup$ Sorry, this answer is woefully out of date and does not even understand why the Space Shuttle had a blunt nose. $\endgroup$ Commented May 27, 2020 at 7:35
  • $\begingroup$ @RobertDiGiovanni Recent Mach 5-7 scramjet test vehicles have all had blunt noses, for exactly the same reason as the Shuttle. The SR-71 maxed out around 1,000 mph slower. $\endgroup$ Commented May 27, 2020 at 9:25
  • $\begingroup$ Yes, they have no other choice due to thermal effects, which also makes propulsion problematic. It may work, being cost effective for commercial application may be another story. $\endgroup$ Commented May 27, 2020 at 11:18

The idea is certainly valid.

Busemann's original design could not generate lift, but modern variations can. Here are just three recent papers on how it can be done:

Wave drag has two causes, one due to the bulk or form of the plane and the other due to the lift generated.

The Busemann concept can eliminate form shock drag but not that due to lift. Busemann's original geometry eliminated all wave drag and hence also lift. Modern Busemann type designs can create lift, with its associated shockwave, while still eliminating much or all of the form drag, thus achieving considerable improvements in efficiency over conventional designs. They can also allow adequate performance over a range of speeds and angles of attack. The three papers linked explore different ways of achieving all this; some use variable geometry.

But Mach 10 cruise is less likely. We do not yet have the materials or airbreathing engines to achieve even half that for sustained flight. Moreover Mach 10 cruise requires extreme altitudes and it can be more economic to go for a conventionally-winged ballistic/suborbital spaceplane which maintains its cruise segment of the journey in empty space. The acceleration of any airborne vehicle can be limited to a level comfortable for the particular passengers, although varying gee levels can affect the economics.

Whichever approach is taken, to avoid overheating at hypersonic speeds above Mach 5 the fuselage nose would have to be bluff like the Space Shuttle rather than pointed like Concorde.

On engines and fuels, the only airbreathing technologies in the offing for these speeds are the scramjet and the airbreathing rocket (principally SABRE). For different technical reasons, both these are likely to be restricted to hydrogen fuel.

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    $\begingroup$ Interesting to note it may work holding the "wings" at 0 AOA and using the fuselage as the lifting surface at supersonic speeds. At subsonic speeds the wings could be used conventionally. With the amount of thrust required, one could consider vectoring it up too. $\endgroup$ Commented May 27, 2020 at 11:24
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    $\begingroup$ Not a bad idea, that. Certainly better than the concept, studied during XB-70 Valkyrie development, for detachable outer wing sections which dropped away for supersonic cruise! $\endgroup$ Commented May 27, 2020 at 11:28
  • $\begingroup$ Dropped or just tilted down? Imagine landing that thing without the outer section of the wings, approach and landing speeds would be insane... $\endgroup$
    – Jpe61
    Commented May 27, 2020 at 21:24
  • $\begingroup$ @Jpe61 The final version tilted them down, where they enhanced the waverider effect. But landing with empty fuel tanks is less stressful on the wings than takeoff at full laden weight. For more see en.wikipedia.org/wiki/North_American_XB-70_Valkyrie#WS-110A $\endgroup$ Commented May 28, 2020 at 8:43
  • $\begingroup$ Oh, now I see what you mean. The Valkyrie that actually flew never had jettisonable wingtips as I recalled, but one of the early proposals did. Interesting! $\endgroup$
    – Jpe61
    Commented May 28, 2020 at 22:01

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