Cheaper, quieter and fuel-efficient biplanes could put supersonic travel on the horizon

Mar 16, 2012 by Jennifer Chu
Conceptual drawing of a supersonic biplane. Image: Christine Daniloff/MIT News based on an original drawing courtesy of Obayashi laboratory, Tohoku University

(PhysOrg.com) -- For 27 years, the Concorde provided its passengers with a rare luxury: time saved. For a pricey fare, the sleek supersonic jet ferried its ticketholders from New York to Paris in a mere three-and-a-half hours -- just enough time for a nap and an aperitif. Over the years, expensive tickets, high fuel costs, limited seating and noise disruption from the jet’s sonic boom slowed interest and ticket sales. On Nov. 26, 2003, the Concorde -- and commercial supersonic travel -- retired from service.

Since then, a number of groups have been working on designs for the next generation of supersonic jets. Now an MIT researcher has come up with a concept that may solve many of the problems that grounded the Concorde. Qiqi Wang, an assistant professor of aeronautics and astronautics, says the solution, in principle, is simple: Instead of flying with one wing to a side, why not two?

Wang and his colleagues Rui Hu, a postdoc in the Department of Aeronautics and Astronautics, and Antony Jameson, a professor of engineering at Stanford University, have shown through a computer model that a modified biplane can, in fact, produce significantly less drag than a conventional single-wing aircraft at supersonic cruise speeds. The group will publish their results in the Journal of Aircraft.

This decreased drag, according to Wang, means the plane would require less fuel to fly. It also means the plane would produce less of a sonic boom.

“The sonic boom is really the shock waves created by the supersonic airplanes, propagated to the ground,” Wang says. “It’s like hearing gunfire. It’s so annoying that supersonic jets were not allowed to fly over land.”

Double the wings, double the fun

With Wang’s design, a jet with two wings — one positioned above the other — would cancel out the shock waves produced from either wing alone. Wang credits German engineer Adolf Busemann for the original concept. In the 1950s, Busemann came up with a biplane design that essentially eliminates shock waves at supersonic speeds.

Normally, as a conventional jet nears the speed of sound, air starts to compress at the front and back of the jet. As the plane reaches and surpasses the speed of sound, or Mach 1, the sudden increase in air pressure creates two huge shock waves that radiate out at both ends of the plane, producing a sonic boom.

Through calculations, Busemann found that a biplane design could essentially do away with shock waves. Each wing of the design, when seen from the side, is shaped like a flattened triangle, with the top and bottom wings pointing toward each other. The configuration, according to his calculations, cancels out produced by each wing alone.

However, the design lacks lift: The two wings create a very narrow channel through which only a limited amount of air can flow. When transitioning to supersonic speeds, the channel, Wang says, could essentially “choke,” creating incredible drag. While the design could work beautifully at supersonic speeds, it can’t overcome the drag to reach those speeds.

Giving lift to a grounded theory

To address the drag issue, Wang, Hu and Jameson designed a computer model to simulate the performance of Busemann’s biplane at various speeds. At a given speed, the model determined the optimal wing shape to minimize drag. The researchers then aggregated the results from a dozen different speeds and 700 wing configurations to come up with an optimal shape for each wing.

They found that smoothing out the inner surface of each wing slightly created a wider channel through which air could flow. The researchers also found that by bumping out the top edge of the higher wing, and the bottom edge of the lower wing, the conceptual plane was able to fly at supersonic speeds, with half the drag of conventional supersonic jets such as the Concorde. Wang says this kind of performance could potentially cut the amount of fuel required to fly the plane by more than half.

“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,” Wang says. “It’s kind of a chain reaction.”

The team’s next step is to design a three-dimensional model to account for other factors affecting flight. While the MIT researchers are looking for a single optimal design for supersonic flight, Wang points out that a group in Japan has made progress in designing a Busemann-like biplane with moving parts: The wings would essentially change shape in mid-flight to attain supersonic speeds.

“Now people are having more ideas on how to improve [Busemann’s] design,” Wang says. “This may lead to a dramatic improvement, and there may be a boom in the field in the coming years.”

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User comments : 13

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roboferret
4.3 / 5 (8) Mar 16, 2012
This may lead to a dramatic improvement, and there may be a boom in the field in the coming years.


I thought the idea was to get rid of the boom ;)
Howard_Vickridge
5 / 5 (2) Mar 16, 2012
It's just got be a deliberate pun!. Dark too... the Concorde certainly went boom in a field. Sadly. A fact glossed in the intro describing Concord's demise.

The new wing sounds very promising.
antialias_physorg
2 / 5 (6) Mar 16, 2012
Over the years, expensive tickets, high fuel costs, limited seating and noise disruption from the jets sonic boom slowed interest and ticket sales.

The crash of one of the two in-service planes might have had something to do with it, too.

While biplanes have been proposed over and over for the past 30 years or so for commercial airliners they have never been built. Reasons include the added weight and structural complexities of two sets of wings (which means less cargo carrying capacity - and hence profit - as opposed to single wing aircraft). The other is that airports need to be able to handle the biplane design (e.g. terminals might need to be restructured) - which is a huge cost factor.
gurloc
4.8 / 5 (4) Mar 16, 2012
Concorde had been teetering on the edge of death for years, the crash was just the final straw. Its worth reminding people that the Concorde accident was not the fault of the Concorde but was caused by a piece falling off one of the flying garbage heaps that the US airlines call planes.

It would be nice to see the return of supersonic travel, especially if it could be made more affordable, 10 hour flights are not pleasant.
kcameron
5 / 5 (1) Mar 16, 2012
There's a better article with a picture on msnbc:
http://www.msnbc....SJ5__uQ0
33Nick
not rated yet Mar 16, 2012
The famous Concorde crash was due to a Continental or American Airline DC10's locking gear strut that fell at take off, was sucked in by the Concord's engines, which ripped the gas tank and started the fire. My uncle worked on the investigation. The Captain's effort were heroic, considering the disaster. Also, the Concord is the plane that suffered the least troubles in the history of aviation, if I remember well. Yes, the Concord was starting to have micro-fractions in its skeleton and it is still chartered today.

It would be nice to see a fast speed commercial plane again. My father took and told me the windows were hot, due to friction. Makes you dream...
Vendicar_Decarian
2.3 / 5 (3) Mar 16, 2012
Commercial Supersonic flight is a concept who's time never arrived and will never make sense when you can tellecommute at the speed of light.
KingDWS
4.5 / 5 (2) Mar 16, 2012
Commercial Supersonic flight is a concept who's time never arrived and will never make sense when you can tellecommute at the speed of light.


True but telecommuting doesn't have the same satisfaction as being to actually see or smell a place or wiggle your toes in the sand at the beach. Or telling someone to spin off face to face. :-)
kochevnik
Mar 16, 2012
This comment has been removed by a moderator.
Callippo
2 / 5 (5) Mar 16, 2012
In general, one kilowatt of energy in form of food requires two to ten kilowatts of energy to grow and produce. Why the people in developed countries believe, the whole process can suddenly work in the opposite way? Biofuels are made of corn or sugar cane. I very doubt, these fuels will get cheaper, when the soil becomes exhausted after few harvests for humus and minerals and the biofuel plantations will change into new deserts. Just because something is working few years after cutting down of tropical forests doesn't mean, it's a sustainable source.
Deadbolt
Mar 16, 2012
This comment has been removed by a moderator.
Skepticus
3 / 5 (2) Mar 17, 2012
Another so familiar rip-off from another Nazis scientist who where "persuaded" to move to United States to get the last drops out of his lemon. As the saying goes, history is written by the victors.
Au-Pu
1 / 5 (1) Mar 17, 2012
roboferet, that is what the article was about. A wing design that eliminates the sonic boom. As for most of the others they do have problems staying with an idea.
Are they all suffers of attention deficit disorder.
It certainly sounds as if they are.
roboferret
not rated yet Mar 18, 2012
roboferet, that is what the article was about. A wing design that eliminates the sonic boom. As for most of the others they do have problems staying with an idea.
Are they all suffers of attention deficit disorder.
It certainly sounds as if they are.


I think my joke made a sonic boom as it went over your head.
unknownorgin
not rated yet Mar 22, 2012
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