Futuristic Biplane Design Eliminates Sonic Boom

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."

Comments

Re:The problem.

[Icyfire0573]

I read the article, so I know that they fixed that by taking the old design which had no lift, ran it through a ton of simulations and found a design which has the lift necessary to fix this. It's not like people never discover new things.

Re:Would would want . . .

[X0563511]

... only if:

1. When you have an orgasm, everyone within a few miles felt it, but you didn't
2. Instead, you only got a light shudder

Re:The problem.

[Chuckstar]

The MIT team is not using an adaptive wing. As described by Icyfire0573 above "...they fixed that by taking the old design which had no lift, ran it through a ton of simulations and found a design which has the lift necessary to fix this."

There is a team in Japan that is using an adaptive wing. Depending on exactly how the Japanese team's wing adapts, that could be an impediment to use in a commercial airliner. Thinking about current airliner designs, the wing surface shape is modified by flaps and slats, but the core load bearing structures of the wings (spars and the connection points to the airframe) remain fixed. I would be wary of a swing-wing design for commercial air, for instance, but something similar to flaps/slats would theoretically be no more of a safety risk than today's (incredibly safe) designs.

In addition to safety, there is also the simple fact that fewer moving parts would be cheaper to build and maintain.

Re:No sonic boom?

[jamstar7]

One of the problems with the Concorde was, they weren't allowed to fly at supersonic speeds across the US because of the booms. So, supersonic London to LA was flat out of the question. From what I understand, a lot of other countries followed suit, outlawing supersonic flights in their airspaces. Without the speed advantage, the Concorde was a low passenger fuel hog that turned into a hanger queen and eventually got grounded and decommissioned. Fix the sonic boom problem, get fuel economy as a bonus, and we just might see the Concorde II in our lifetimes. LA to Melbourne in under 14 hours? COOL!!!

Re:The problem.

[HornWumpus]

E and F engine rocket kits are supersonic. Not much more then an Estes.

I'm pretty sure some of the 3 stage Estes rockets can go supersonic on 2 Ds and a C. They lose their fins when they do though. I never did find anything but one of the fins.

Re:The problem.

[pittance]

The Busemann biplane came up when we did supersonic aero in University back in '98 or '99 and it was always stated to be an impractical wing design because, at the supersonic zero boom/zero wave drag condition, it couldn't produce lift; this doesn't stop it being useful for other things like shells etc. where you don't mind zero supersonic lift if you can get low drag

The diagrams in the article seem to look like that condition in supersonic flow where the "inner" surfaces interfere favourably with each other to cancel wave drag and have the upper and lower surfaces with no incidence to the flow so they produce no shock waves.

Supersonically it should still produce lift quite happily if you angle it so there is incidence to the flow but I think that it should then produce wave drag and booms... For example I can't see from the article how, in a lifting condition, the shock wave from the compression of the supersonic flow on the undersurface (which produces the compression & higher pressure that helps lift the wing) could be cancelled out without having another wing underneath that; then you have the same problem with the undersurface of that wing & then you're in a "it's wings all the way down" problem.

Conventional 'low boom' solutions (like the Gulfstream/NASA "quiet spike") all tend to shape the nose of the aircraft to reduce the suddenness of the pressure increase across the shock wave but they aren't able to eliminate it...

It could be that they've found a case where they can get low wave drag/boom while still producing some lift and also getting decent subsonic lift/drag - that would be really interesting...

Re:The problem.

[element-o.p.]

With a zero degree angle of attack your aircraft with any amount of thrust will fall...

Are you sure about that? I think you confused "angle of attack" with "coefficient of lift."

There are airfoil designs (basically, any asymmetric airfoil) that will produce lift at an AoA of zero degrees. If lift is non-zero, then the only question is how fast does an aircraft need to be going to generate enough lift to overcome weight at a zero-degree angle of attack?

Also, just to be pedantic, the balancing act is between lift, weight, thrust and drag. Lift is related to AoA so I'll concede that you basically covered that force, but you completely neglected to mention drag above.

Re:No sonic boom?

[AmiMoJo]

Actually the banning of sonic booms was more political than based on reality. Boeing had pretty much given up on their supersonic passenger aircraft and the French/British design looked set to rule the long distance market.

Concord was still an impressive aircraft, cutting flight times to the US down to five hours. Unfortunately it cost a lot to design, build and run, but had it not been effectively banned from many parts of the world those costs would certainly have come down with volume and improvements to the technology. Instead the supersonic passenger jet market was killed before it really started.

We have been promised radically new aircraft designs for decades but they never seem to come. In many ways Concord was the last big step forwards, everything after that was just a refinement of existing technology.