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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?
Actually, at supersonic speeds you wouldn't hear it coming anyway because it would arrive before the sound anyway.
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.
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.
It's got nothing to do with military vs. civilian. Airliners depressurize occasionally. But they fly low enough that simple airmasks can suffice while the pilots do an emergency descent into the range of breathable atmosphere. You fly high enough and an airmask isn't gonna do the trick anymore.
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