Futuristic biplane design eliminates sonic boom

[tarnoch]

Suwheet, hooda thunk it? Big fly in the ointment is it cant fly subsonic.





A throwback to early 20th Century aviation may hold the key to eliminating the sonic boom - at least according to researchers at MIT and Stanford University. Strongly reminiscent of biplanes still in use today, the researcher's concept supersonic aircraft introduces a second wing which it is claimed cancels the shockwaves generated by objects near or beyond the sound barrier.


In fact the idea is not a new one. The idea of a biplane to negate the sonic boom was proposed in the 1930s by aviation pioneer Adolf Busemann, also responsible for the idea of swept-wing aircraft.


Aircraft traveling at supersonic speeds cause shockwaves in the air around them. A first boom is caused by the rapid compression of air at the front of the plane, literally pushed together by the aircraft. A second is caused by the negative pressure left in the plane's wake - or rather, the rapid return to normal pressure that follows soon after. Though the two booms separate phenomena, they occur so close together that they they are usually perceived as a single sound. An aircraft in supersonic flight creates a continual boom as it goes.


And that's a problem. Sonic booms might be all part of the drama at an air show, but if you were to live under a supersonic flightpath in regular use, the novelty would likely quickly wear off. There are also the concerns of the effect of supersonic flight upon wildlife which might include shock or injury in the short-term, and wholesale habitat abandonment over time. It's no surprise, then, that a return of commercial supersonic flight is considered a doomed enterprise in certain quarters.


Adolf Busemann's design, known as Busemann's Biplane, features two wings with a triangular length-wise cross section. The points of the wings point towards each other so that the outer face of the wings is completely flat, parallel to the air passing over and under. The wings must be sufficiently far apart that the passage of air between isn't stifled. With this design, the first positive shock wave is created and reflected between the wings, filling the space created in the plane's wake, canceling the negative shockwaves and negating the sonic boom.


What's the catch? At sub-supersonic speeds, a Busemann Biplane doesn't produce sufficient lift under acceleration, undergoing considerable drag. The design is said to work perfectly at supersonic speeds - it's getting to them that is the trouble. So though there may be no sonic boom, there's no flight either.


But the joint MIT/Stanford research at least appears to confirm that Busemann's noise-canceling concept was sound. The study, which used computer simulation, demonstrated that the biplane concept exhibited "significantly less drag." Additional research at Tohoku University in Japan claims Busemann's concept is effective in reducing the intensity of shock waves at ground level by 85 percent.


Better yet, the MIT/Stanford team think they might have cracked the problem of lift at sub-supersonic speeds. Through an iterative processes, modeling differing design variations, the team has discovered that smoothing the wing's inner surface eases the passage of air between the wings. By additionally "bumping out" the outer edges of the two wings, the team has come up with a design it claims will fly below the speed of sound, and with half the drag of Concorde.


"If you think about it, when you take off, not only do you have to carry the passengers, but also the fuel, and if you can reduce the fuel burn, you can reduce how much fuel you need to carry, which in turn reduces the size of the structure you need to carry the fuel," said Qiqi Wang, assistant professor of aeronautics and astronautics at MIT. "It's kind of a chain reaction."


The MIT/Stanford team is now pursuing a 3D model to address other practicalities in flight, with the hopes of approaching a static, optimized design. In contrast, the Japanese concept, identified by Wang, would change shape during flight to adapt to supersonic speeds.
Sources: MIT, Tohoku University, via Live Science

[figatova]

Russia working on quiet supersonic business jet

14 Mar 2012

A major Russian aeronautical research agency has launched preliminary design work for a quiet supersonic business jet that could fly over populated areas.

The Central Aerohydrodynamic Institute (TsAGI) will develop the preliminary design in partnership with several Russian companies, including aircraft manufacturer Sukhoi and engine maker NPO Saturn, TsAGI says.

An official conceptual image of the aircraft shows it with a long, pointed nose and as many as four engines mounted on top of the aft fuselage. The aircraft also features twin vertical tails and long, thin wings.

The goal of the project is to establish Russia's aeronautics industry as a technology leader in a potential new market for business aviation, TsAGI says.

Sergei Lyapunov, deputy director general of TsAGI, says the broad spectrum of industry and research organisations involved in the project is unprecedented in Russian aeronautics.

TsAGI says a preliminary assessment suggests the supersonic aircraft should generate the same noise level as future subsonic aircraft for the civil market. In addition to completing the design, the research team will also assess the "promising domestic engines" that could power the new aircraft.

The concept of a Russian supersonic business jet has been on the drawing board for decades. In the early 1990s, Sukhoi partnered Gulfstream to develop a design of the S-21. Sukhoi continues to list a "supersonic business jet" on its website as an ongoing project, without elaborating further. Tupolev has also proposed the Tu-444 supersonic business jet, advertising 4h flight times between Moscow and New York.

http://www.flightglobal.com/news/art...ss-jet-369505/

[tarnoch]

Originally Posted by figatova

http://www.flightglobal.com/news/art...ss-jet-369505/

Thats actually pretty cool looking, thanks for the addition.

[figatova]

I think there are several other projects, from Japan, Europe or Europe+America or + Japan, can't remember now but I did look it up some time ago.

[ThisisnotChad]

Russia built a "concorde" knockoff didn't they ?

[figatova]

Originally Posted by ThisisnotChad

Russia built a "concorde" knockoff didn't they ?

I wouldn't call it a Concorde knock off, but yeah, they did.

[seanjo]

Originally Posted by figatova

I wouldn't call it a Concorde knock off,

I would!

300px-RIAN_archive_566221_Tu-144_passenger_airliner.jpg

concorde_faster_than_a_speeding_bullet.jpg

[ThisisnotChad]

And the U.S. right ? Didn't they build one

[seanjo]

Originally Posted by ThisisnotChad

And the U.S. right ? Didn't they build one

A bomber...the Valkyrie.

North_American_XB-70A_Valkyrie_view_(top)_at_the_rollout_061122-F-1234P-015.jpg

[Tinbuk3]

An interesting concept.
I can recall when design was used to extend curled flukes on boats to reduce wake back in the 60's.
Glad to see design has progressed.