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NASA Wants to Take the Blast Out of Sonic Booms
coondoggie writes to tell us that NASA and JAXA (the Japan Aerospace Exploration Agency) have announced a partnership to study the sonic boom. Hoping to find the key to the next generation of supersonic aircraft, the research will include a look at JAXA's "Silent Supersonic Technology Demonstration Program." "The change in air pressure associated with a sonic boom is only a few pounds per square foot -- about the same pressure change experienced riding an elevator down two or three floors. It is the rate of change, the sudden onset of the pressure change, that makes the sonic boom audible, NASA said. All aircraft generate two cones, at the nose and at the tail. They are usually of similar strength and the time interval between the two as they reach the ground is primarily dependent on the size of the aircraft and its altitude. Most people on the ground cannot distinguish between the two and they are usually heard as a single sonic boom. Sonic booms created by vehicles the size and mass of the space shuttle are very distinguishable and two distinct booms are easily heard."
Hmmph. I recommend reading Tom Wolfe's The Right Stuff, which contains much factual(and entertaining) data about test-flying in the era of the original space-race, to include much first-hand data about supersonic flying in the upper atmosphere(hint: it's much more dangerous than it sounds). Come on, Nasa & JAXA: find some folks with the right stuff and concentrate on long-term space station and moon missions. Don't piss away our taxpayer dollars exploring something that's already well-known! Who gives a fuck if China has stealth and who gives a fuck of ours is better than theirs! Should we all go to war, we'll be fucked by nukes anyway. Can't we just have a healthy space-race(V 2.0) pissing contest?
How do you make an engine where the supersonic airflow doesn't damage the compressor parts? Carefully.
I think the answer involves less airplane and more engine. Theoretically a J-58 engine by itself could operate supersonically with minimal shock waves since it is designed to reflect the shock waves into the engine in a way that they are subsonic before touching moving parts. The tricky part is adding the parts of the airplane the give lift and space for pilots to sit.
Where is the fun in that. I kind of like hearing one of those guys step on it a little to hard over New Mexico and Texas.
Yeah, there goes my 20 million dollar plane.
I mean I never get to see them drop bombs, but at least I get to see them tag and make some booms every once and awhile.
He who said 1,000,000 monkeys on 1,000,000 typewriters would eventually type the great novel, never saw an AOL chat room
Well, there are *civilian* uses for not having a loud sonic boom, like, being able to fly one of those things over populated areas.
But it certainly sounds like mission creep for JAXA, which is supposed to be more focused on Gundam-style robots.
Information theory is life. The rest is just the KL divergence.
Actually, at supersonic speeds you wouldn't hear it coming anyway because it would arrive before the sound anyway.
I live in the Edwards Air Force Base restricted air space, so we here many sonic booms in any given week, mostly from small fighter jets. In every instance the double boom is clearly audible, unless it's a tail-less spacecraft like SpaceShipOne. Whenever we hear a single boom, it is blasting going on at the nearby CalPortland Cement Plant limestone quarry or the gold mine.
Sometimes the booms are so loud the windows shake and things rattle around. We all love it because that's why we're here. But reducing the boom signature is an important area of research, so 'normal' folks can have supersonic airliners going overhead without disturbing their chiuahua's sleep patterns. That's why the concord only flew ocean routes. It would be nice to have supersonic transport between LA and New York.
--Mike
A supersonic plane is already pretty stealthy sound-wise until its already gone over you. The Mach cone extends behind the vehicle so that you'll only hear it after its passed you, at which point if you care that its there its probably too late.
The big advantage would be to allow supersonic or hypersonic flights over continental landmasses. While it doesn't help the main issue of economics, it opens the business possibilities for cross country high-speed flights. Where I see this really opening up possibilities is hypersonic flight (M > 4~5) since the drag drops back down to subsonic levels, making fuel economy on par with the current crop of jet liners. Of course all the hypersonic combustion (scramjet) issues and the heating issues are still uhh, very non-trivial. I hate to know what a fleet of jets with titanium tipped, actively-cooled wings would cost.
Uh oh...
It sounds like moose and squirrel were thwarted. Unfortunately for the Russians Comrade Badenov developed capitalistic streak and did not deliver formula on to glorious Air Force
You either believe in rational thought or you don't
The last thing NASA needs is the USAF's Guile to come after them.
But Guile didn't really yell "Sonic Boom". At that sample rate it sounded more like "Phonic Poo". You'll have to wait for an article about phonic poo to repost your comment.
The state you are in while your HEAD is detached... - wait, what?
They've been working on this for a while, actually: See - http://www.nasa.gov/vision/earth/improvingflight/supersonic_jousting.html That particular project was wrapped up.. but maybe the plan to expound upon it =)
And supersonic air travel did not pay when oil was $20 a barrel, how can it ever pay at $120 ?
And there seems to be some insurmountable obstacles in softening up a sonic boom-- you've already exhausted all options by traveling faster than the air can move out of the way....there's no t much wiggle room or time left.
I remember when the SR-71 set the transcontinental speed record in the late 1970's. (They have since improved on it a little.) The boom was quite loud and clearly double, and I was impressed at how much energy was wasted by it, given that I was 30-40 km away, and that it made the same boom across the entire country. That flight was a little under a km / sec average velocity.
That's why, unless there is some real drag breakthrough, I think that rocket planes are the way to truly fast passenger travel. One ballistic impulse of 7 km / sec or so to get up above the atmosphere and on your way is 50 times the energy requirement of the SR-71 to get to maximum speed, but that would get you across the Pacific in 30 - 40 minutes and use less energy than a Mach-3 aircraft, which would take 2 or 3 hours for the same trip. Plus, except at re-entry, a rocket plane has no sonic booms.
So the shuttle goes boom boom?
It goes "ba-boom". The two booms are far enough to be perceived as distinct but still close enough together to be one event.
Now if it knocks over something metallic it goes "ba-boom, CHING!"
(Thank you, thank you. I'll be here all week...)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
You seem to be labouring under the common misconception that a sonic boom is caused when an object "breaks the sound barrier". As long as an object is moving through the air at greater than the speed of sound it will create a shock wave (cone shaped, think of a boat wake rotated in 3-d) behind it. As the object flies by you, the shock wave passes you and you hear the "sonic boom" So the answer is yes, bullets have a sonic boom.
None of them can see the clouds; The polished wings don't care.
The sound when you fire the gun is from the expansion of the heated gasses after the bullet leaves the barrel. It has nothing to do with the bullet.
Supersonic bullets (for there are subsonic ones too) make shock waves, just like anything else going supersonic. They do produce a little sonic boom, too. From most accounts that I've read, it sounds like a small "crack!" as said bullet travels by. In order to observe this, I expect that you need to be a nontrivial distance from the gun that fired it, so that the bullet could pass over and leave its boom before the sound from the firing reaches you.
Public safety announcement: Please, kids, don't try this at home. Intentionally standing anywhere in front of the business end of a gun being fired is a bad idea and makes you a moron at best. Being the idiot on the other end, pointing and firing said gun while a person is there is downright criminal (except in very specific circumstances, like legitimate self-defense). If you must, set a cheap camera or microphone up. I'm all for the private ownership and (responsible) use of firearms... but please don't do something stupid.
Now you know... and knowing is half the battle.
The meek may inherit the earth, but the strong shall take the stars.
Also, how are you sure that the aircraft you claim to have seen were indeed supersonic? I've heard a real one (and many recreated F-18 and Concorde ones in Gulfstream's sonic boom demo trailer), you definitely notice it.
The meek may inherit the earth, but the strong shall take the stars.
There was supposed to be an earth shattering kaboom!