Supersonic Flight Without The Sonic Boom 311
fname writes "Here's a story from Spaceflight Now about a new test aircraft that can travel at supersonic speeds without triggering a sonic boom. The technology works by modifying the shape of the plane. Although it's been believed to be possible for a long time, this is the first actual flight test, barring black box projects I suppose."
Re:Why? (Score:3, Informative)
"They foresaw a way to solve the sonic boom problem, and to enable a generation of supersonic aircraft that do not disturb people on the ground."
Summary misleading (Score:5, Informative)
Re:Why? (Score:2, Informative)
First paragraph:
Re:Why? (Score:4, Informative)
if a SST can go supersonic without the boom, then development of new craft could take place, because new markets could open up...
Re:Why? (Score:5, Informative)
This is important because the main reason super sonic airplanes are not used more often for civils is because of the sonic boom. The sonic booms can be very loud and disturbs urban areas. The Concord, for example, had to wait to be very far away from populated areas before getting into super sonic speeds. This rwas costly, since the Concord was design to have optimal fuel efficiency at super sonic speeds.
Re:Why? (Score:5, Informative)
What the article doesn't say, but was reported in Aviation Week a few weeks ago, is that this technique (and certainly this airplane) only reduces sonic booms -- it doesn't eliminate them. This demonstration is to show people that the math is right; that the sonic booms can be reduced through shaping. It is still unclear whether it is possible to build a practical airplane with a tolerable (negligible) sonic boom. Perhaps this could be combined with other techniques (the Russians have been working with exciting a plasma in front of the airplane, for instance) and together you could get a minimal boom.
Probably the parent article was questioning the need for supersonic travel at all -- whether it's worth the cost. It will almost certainly be less fuel efficient than subsonic travel. Travel in general is less fuel efficient than staying home. Living is less fuel efficient than dying.
thad
Discovery Wings channel show touches on this (Score:5, Informative)
Rejected (Score:4, Informative)
Northrop [northgrum.com], working with the Pentagon [defenselink.mil] and NASA [nasa.gov] sucessfully tested a "quiet" supersonic flight [cnn.com] wednesday at California's Edwards Air Force Base [af.mil]. In the tests, an F-5E aircraft [primezone.com] with a modified nose section flew supersonically through the test range, shortly thereafter, an unmodified F-5E [af.mil] flew supersonically through the same airspace, with the sensors showing a clear reduction in the intensity of the sonic boom produced by the F-5E modified fuselage [primezone.com].
Re:Why? (Score:3, Informative)
Re:Guns? (Score:1, Informative)
But you'd probably run into many problems, hence they haven't done it?
Also, I'm not clear on this, but I suspect a silencer would slow a bullet enough that it wouldn't be supersonic, so that wouldn't be viable.
Plus using a coke bottle filled with anything to silence a gun would probably result in it exploding, most cobbled together silencers do so.
Old science (Score:3, Informative)
Re:Yes, but how? (Score:5, Informative)
Re:Why? (Score:1, Informative)
Sonic boom 101 (Score:-1, Informative)
For example, back in the 1970s, Richard Seebass from the University of Colorado in Boulder, worked out that you could virtually eliminate the sonic boom by making the nose of the plane blunt. This blunt nose would heat up the air in front of the plane, and would also stretch the bow shock wave out a long way in front of the plane. So there wouldn't be a sudden jump in pressure, that would give the offensive shock wave down on the ground. But H. K Cheng, a retired Aeronautical Engineer formerly with the Department of Aerospace Engineering at the University of Southern California, has a modern Star Wars version of this - it uses a laser to heat up the air in front of the plane.
In 2001, the United States Defence Advanced Research Projects Agency allotted some $70 million to three manufacturers to work out how to make supersonic planes more quiet. The companies (Boeing, Lockheed Martin and Northrop Grumman) are each trying different approaches.
John Morgenstern, an Aeronautical Engineer and expert in sonic booms from the Lockheed Martin Skunk Works in California, has come up with a very neat way of effectively blunting the nose of a plane. His design has a little flap that pushes forward from the nose of the aeroplane. Not only does it stretch out the shock wave coming from the nose, it also creates an extra bit of lift, which cuts the fuel consumption. In 1999, he published a patent with an even more daring design, which has a longer nose and a V-shaped tail.
Domenic Maglieri from Eagle Aerospace in Hampton Virginia has an even wilder design - a supersonic biplane. This would spread the lift over more surface area of wing, and so reduce the sonic boom. Heinz Gerhardt, an aeronautical engineer from Northrop Grumman in Los Angeles likes this idea so much that he has designed a family of supersonic biplanes.
At this stage, all the big companies are keeping quiet. But Gulfstream (which is funding its own research) reckons its supersonic business jet will be flying in around six years time, while the Russian Sukhoi Company reckons their supersonic bizjet will fly in 2010.
And of course, in the backs of their minds, the companies are all thinking of big supersonic jets that can carry a big number of people a big distance, and so generate big bucks. You see, for all of its speed, the Concorde has only a short range, which is fine for flying across the Atlantic, but hopeless for flying across the Pacific or around the Pacific Rim.
The new supersonic designs aim for a maximum overpressure of just 0.3 pounds per square foot.
But as well as new shapes, the new supersonic planes will need radically new engines. The Concorde engine is fine at Mach 2.2, but it's very thirsty and noisy on take-off and landing.
Rolls Royce, on the other hand, has decided to modify the existing giant engine that powers the Boeing 777 with 95,000 pounds of thrust. This enormous engine is bigger in diameter than the body of a Boeing 737. Rolls Royce want to remove the huge fan off the front, and in this form, it should just meet take-off and landing noise requirements.
These supersonic bizjets will still burn up a lot of fuel. But if you can afford a$160 million plane, the cost of a few extra tonnes of fuel will be no worry at all.
So once the supersonic flight industry loses the boom, business should start to bloom.
No QUANTITATIVE information at all. (Score:4, Informative)
The article doesn't give one single blessed number that would enable anyone to judge how effective the experiment was.
I'm not sure what the right measurement would be... decibels? sones? psi? pascal-seconds? Or average blood pressure increase in human subjects in Hgmm? But the article doesn't say.
Not even the usual marketing claim, like "42% less boom than traditional aircraft, yet still has that same great NASA 'look'"
Something about "We were all blown away by the clarity of what we measured" just doesn't do it for me.
Re:Why? (Score:3, Informative)
Your logic is refuted by the fact that Concorde was in service for almost 30 years -- it carried its first passengers in 1976. The technical failures of the Russian project have no bearing on Concorde.
in fact the original poster has a good point. Concorde failed to flourish economically largely because the US authorities refused it permission to fly supersonically over the continental USA. That meant it was automatically excluded from the longer routes, such as London-LA, where the timne difference from supersonic speeds would have made a revolution in business travel possible.
Even on regular jets it's possible to make it to NY and back on business in 24hr (leave London 9am, arrive NY around 11am, afternoon meeting, leave NY 10pm, arrive London 9am...) Concorde's extra speed on that route is basically just adding convenience and glamour. But London-LA in 3 hours instead of 10 would revolutionise business travel between Europe and the west coast. That's what BA and Air France were counting on to make the numbers work. Another result of the FAA ban on supersonic travel was that US airlines, naturally, would never buy the airline.
So basically, the FAA ban on supersonic travel in the US meant that Concorde was barred from its most profitable routes, and so was unattractive to most airlines. That's why it never made any money, either for its makers or for BA and Air France. And there's little doubt that the FAA ban -- while partly based on genuine concerns about noise -- was also in part a response to protect the US aircraft industry.
It's just ironic that the long-term effects of this strategy were to kill of Boeing's Sonic Cruiser, which it had pinned its hopes on as the airplane to beat Airbus (the descendant of the consortium that built Concorde). As a result, Boeing is reduced to relying on the 747 -- first flown in 1969 -- to compete with Airbus's new superjumbo.
Re:Old science (Score:5, Informative)
The examples are ATF, Eurofighter, Viggen, Suhoy S27 and later, so on so forth. All of these have shapes designed specifically to split the shockwave into a series of shockwaves to improve lift and maneuvrability at hypersonic speeds. As a result the noise is muffled as a side effect. From there to muffling it completely is just one step.
In btw, I am glad that it was done on the F5. It is the only US bird that has some resemblance of grace and beauty in the air.
Re:Guns? (Score:1, Informative)
I believe it can also use silenced ammunition
booms are continuous (Score:3, Informative)
A sonic boom isn't a one time deal when you crack the sound barrier. after you break it, the boom is continous as you fly over the ground. Thus if you travel supersonically over the entire width of texas, then the entire width of texas for that corridor your plane passes over will hear/feel the shockwave.
Re: Blatant Plagiarism Whore (Score:4, Informative)
Wow, you sure put a lot of effort into that reply. It must burn you to know that Karl S. Kruszelnicki Pty Ltd [abc.net.au] had the gall to blatantly plagiarise it and copyright it, no less.
Re:no. (Score:5, Informative)
Re:Where's the Earth Shattering Kaboom!?!? (Score:3, Informative)
It doesn't remove boom/New Scientist covered this (Score:5, Informative)
Supersonic vehicles actually generate two booms- one for the nose and one from the tail- that's why this has the nose glove and the modified tail.
Incidentally, the size of the boom is related to the size of the aircraft, military planes are much smaller and hence give much less problems.
Interestingly, Concorde's nose is sharp- this is aerodynamically efficient, but generates bad sonic booms- it would be much better to use a rounded nose from that respect. Detailed changes to the tail section (other than the ones shown here) can also greatly reduce the shockwave. If you've seen Thunderbirds, some of the airliners shown there are strongly reminiscent of the kinds of shapes that probably help out, (strangely enough, that's probably because they got fairly good advice when designing their models.)
I think that the vehicle shown in the photo has a compromise nose shape- it's sharp on top to give better aerodynamics, but rounded underneath to project a weaker sonic boom downwards. Atleast that's my take on what they've done- IANAA. (I Am Not An Aerodynamicist).
Quantifying the reduction in the sonic boom (Score:4, Informative)
The following URL says the peak pressure was reduced by one third, but there was very little difference in the sound of the boom on the ground. This was a better result than expected, since they did not expect to hear _any_ difference.
After all, this was _not_ an attempt to fly supersonically without generating a sonic boom, despite the misleading title of this thread. Instead, it was a (very successful) attempt to valid the CFD models used to design the aircraft nose modifications and predict the reduction of the pressure wave on the ground.
Now that they have proved that their method works, they can work on more noticeable reductions.
http://209.157.64.200/focus/f-news/973267/posts
Re:Concord (Score:4, Informative)
For starters, you don't have to "throw out" the Concorde as BA/AF are doing that for you. They even refused to sell one to Virgin Airways as Branson might find a way to make the flight profitable and would thereby kill BA/AF's hopes of pushing all of the Concorde folks into the 747 first class section.
There are two other reasons why you won't see the Concorde flying supersonic over the continental USA, with or without a sonic boom:
1) There are far too many other slow aircraft flying at or near Concorde altitudes. Considering the fuel costs involved in getting to supersonic speeds (max drag between 0.97M and 1.4M), the economics of trans-continental supersonic flight would require sterile airspace for end-to-end clearance. The lobby group for bizjet owners would never let that happen at their expense.
2) Even a reduced shock wave will have destructive powers if the aircraft is required to turn at supersonic speeds - the waves on the inside of the turn are concentrated toward a single point at which the N-wave would be amplified to an unacceptable level. Although it would be possible to structure straight-line routes between city pairs, the odds are pretty good that the flight would be unmanageable in terms of communication and coordination among ATC units.
Re: Sorry you are wrong - website (Score:2, Informative)
Re:Concord vs. U2, G5, Lr55 (Score:3, Informative)
Well, the 767/777 routinely fly as high as 41,000'. Lear and Gulfstream both reach into the mid-50's.
Concorde didn't actually spend much time at 60,000. A typical trans-Atlantic flight would start at 45,000 and then slowly climb as fuel weight was reduced, with only the last hour of supersonic flight above 55,000'. In the first half of any transcontinental flight it would be in the way of quite a few aircraft.
FWIW, the U2 is really the least of Concorde's problems as they generally fly between 65,000 and 70,000', well out of reach of Concorde.
Re:Concord (Score:4, Informative)
That's because you fly commercial like me, prole. OTOH, Gulfstreams and other long range bizjets cruise in the 50k' range. Check out 'specifications' at thus URL: http://www.gulfstream.com/g550/
And while the Concorde ends its flight at 60K, it starts at 50 and gradually climbs as the weight of used fuel is lost. So not only is it ripping along at high speed but also constantly changing altitude. Not the kind of wild behavior you want over the continental US where there are a lot of the aforementioned bizjets puttering around at less than half the speed.
Re:Why? (Score:3, Informative)
The engines that the Concord used where turbojets not the turbofans that airliners use now. To make matters worse the Concord used afterburners for take off. The amount of noise that that an afterburning tubojet makes compaired to tubofan of the same thurst is huge.
To not make a sonic boom over land is easy. Just do not fly supersonic. THe trick is to make an engine that is efficent at supersonic and subsonic speeds and that does not make too much moise or pollute too much.
Good luck.
Re:Why? What REALLY Killed the TU-146 (Score:3, Informative)
That isn't what killed the TU-146. It was their inability to get modern digital fuel controls that doomed that plane. The engines were also used on a major Russian bomber and no way in hell did the West plan to help that program.
And, btw, what caused the SST crash at the Paris airshow was the TU-146 pilot having to suddenly dodge a French fighter plane that was playing hide-and-seek in the clouds trying to get some spy photos of the SST. (Why they just didn't go back and use Concorde photos escapes me.) The Russian pilot had been assured that he had clear airspace for 10 miles. Dodging the French plane broke the spine of the TU-146. The French and Russians together covered this up for a long time -- each for their own reasons.
And yes, the French copped to this finally a few years ago.
Re:Why? (Score:3, Informative)
No, not even close. Try 1954 [boeing.com]. I know I've seen on TV why they stopped but I cannot find the reason now. Fear of ballistic missiles or bombers doesn't fly (pardon the pun) since telling missiles bombers and civilian airplanes apart was the main reason there even is a NORAD. It was their main operational task. Even built huge analog machines, complete with PPI:s and light pens in the fifties to cope with the burden.
Re:Summary misleading (Score:3, Informative)
At best, this will allow corporate execs to travel in small jets supersonically as they'll be the only ones who can afford it.