Futuristic Biplane Design Eliminates Sonic Boom 140
Zothecula writes "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."
Re:The problem. (Score:3, Interesting)
False. For example, when I was building a supersonic rocket, I thought of using a Busemann biplane to decrease drag drastically in the supersonic regime. However, the stabilizing function of fins on a rocket is a result of the lift they produce at nonzero angles of attack. As a result, the rocket would have no stability, and would consequently fail to launch (alternatively, I could have used gyroscopic stabilization, but putting anything in the path of the exhaust tends to be highly dangerous, so I went with a super-light rocket).
Re:Solving the worng problem (Score:5, Interesting)
Concorde flight time from JFK to Heathrow was closer to 3 hours. And among a very wealthy (or expense accounted) class it was very popular (just not quite popular enough).
But remember that the biggest impediment to the success of Concorde might have really been that it only made sense to fly JFK Heathrow and JFK de Gaulle. Because of this, few planes were built, eliminating any economies of scale of building or even maintaining them. Also eliminating the possibility of follow-on models -- as it is often the subsequent models where the manufacturer finally gets it "right".
The reason this is announcement is a big deal, therefore, is that it potentially fixes Concorde's achilles heel -- that it was only allowed to go full speed over water, and didn't have the range to go over water any further than NY to Europe. This plane could fly over land, and have a longer range -- opening the possibility of many more city-pairs, many more sales, therefore economies of scale.
Having said that, barring a magic bullet like "engineers figure out sure-fire way to make a Mach-2 passenger jet at only 50% higher cost per passenger mile with limited up-front development risk", you are correct that no one is going to spec billions to see if they can make the thing work. Concorde was cool, but a financial boondoggle for Britain and France. Boeing thought about making a (relatively) efficient Mach-0.95 jet, but at the cost of a dramatic departure from traditional airliner design. They decided the risk was too great and went with the more traditionally-shaped 787.
We're stuck at Mach-0.85 until another government decides to underwrite the development costs. There's just too much risk for a private corporation to take on. They could spend billions and have it just not work.
The one possibility for this tech, however, is for a really high-end private jet. A guy like Burt Rutan might be able to put together a skunk-works-style prototype of the thing, and then sell copies at a few hundred million a piece. At that price, could probably sell a half-dozen around the world.
(Note: current passenger jets can reach top speeds above Mach-0.9, but typical cruising speed is right around Mach-0.85.)
Re:No sonic boom? (Score:5, Interesting)
And of course the shock-wave itself causes some major control issues as you pass through the barrier itself, at least as I understand it, as well as creating a huge amount of drag. That is a large reason they had so much trouble breaking the barrier in the first place: the planes would lose control as they passed through it and crash.
Yep. There were two big problems with control. The first was that as you move from subsonic to supersonic, the center of lift would move. The aircraft was balanced for controllability at subsonic flows, but when you passed from subsonic to supersonic, the aircraft became unstable and would either crash or break up. The second problem was that the control systems were easily manipulated by the pilot at subsonic speeds, but the shock wave created at the control surface hinge was too great for a human to overcome -- pilots literally weren't strong enough to push the control surfaces against the shock wave until engineers developed all-flying tail surfaces (stabilators rather than elevators). Overcoming drag was basically just a problem of developing a powerful enough engine.