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MIT and NASA Designing Silent Aircraft
Posted by
samzenpus
on Thu Nov 20, 2008 11:42 AM
from the Fly-the-silent-skies dept.
from the Fly-the-silent-skies dept.
Iddo Genuth writes "Researchers at the Massachusetts Institute of Technology Department of Aeronautics and Astronautics recently won a contract from the National Aeronautics and Space Administration to design quieter, more energy efficient, and more environmentally friendly commercial airplanes. The two-million-dollar contract from NASA is just an initial step in bringing green technologies to the sky."
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It's called a balloon. (Score:5, Funny)
Re:It's called a balloon. (Score:5, Interesting)
Parent
Re:It's called a balloon. (Score:5, Funny)
What I thought. My last university spent £2m getting one of the campus buildings into Second Life.
Parent
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I hate sitting in the back half of the cabin to the rear of the jet engines.
Look on the bright side, planes hardly ever crash tail first.
Actually, the tail section is one of the more lethal places to sit. Tail sections tend to fall off in collisions. Further, turbulence will be worse as you get further aft of the wings.
Re:It's called a balloon. (Score:5, Funny)
Or a slingshot.
Catapult?
Ballista?
Trebuchet?
Mankind can't consider itself advanced till we can send satellites to space using a trebuchet.
Parent
Re:It's called a balloon. (Score:4, Insightful)
Just so you know, 'catapult' is the category of all heavy leverage throwers. Onagers and trebuchets are catapults; slingshots are not; ballistas, being composed of two small opposing onagers, might be ("paracatapult"?).
Parent
Re: (Score:3, Funny)
That'll do.. Can we resume our Magic game now please?
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rj
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They've had this feature in black helicopters for over a decade. http://en.wikipedia.org/wiki/Black_helicopter [wikipedia.org] How else is the UN and the Federal government going to control every aspect of our lives?
So, you're saying... (Score:5, Funny)
Sorry, just had to sneak that in...
Re:So, you're saying... (Score:5, Funny)
Parent
Re: (Score:3, Interesting)
Despite strides in cleaner and quieter engine technology, there will still be many older planes flying without the retrofits.
Certain airports have restrictions on takeoff hours to quell the noise during bedtime hours but note that the same airports still must allow landings at all hours!
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Re:So, you're saying... (Score:5, Informative)
The prop tips on these airplanes reach transonic speeds at full power
Prop designs are tailored for a specific aircraft design and engine combination. Part of the requirement for prop selection is to avoid supersonic or even transonic speeds, even while at full throttle. The reason being, efficiency significantly falls off once a prop begins to reach transonic speeds, let alone supersonic speeds. It is so important to avoid these speeds, well, you now know the origin of the scimitar shaped prop.
In short, if you are flying any Cessna 185, 206 or 207 which has a prop reaching transonic speeds, your prop needs to be replaced as it has been overhauled too many times.
Parent
Engine maintance costs. (Score:4, Insightful)
Re:Engine maintance costs. (Score:4, Funny)
Oh, I hope not!
Parent
Been there, done that. (Score:3, Funny)
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I understand the idea (Score:2)
Jet tehcnology can't do it ever (Score:5, Informative)
"Silent" is a relative term, but the presumption is one that has noise levels approaching that of an automobile.
That simply is never going to happen. Moving air around to create thrust will always be noisy. Even if all engine noises are reduced to zero, the vibrations of the air moving at the extreme speeds we would expect will cause more than enough noise. The only way I can imagine to combat that fact would be to distribute the effect over very large areas... and even then, as the size of the air moving system approaches "too big to be practical" it would still likely be way to noisy.
Helicopter style systems would be more of the same.
They are going to go back to Roswell and Area-51 and figure out how the aliens did anti-gravity so we can have aircraft that fly with less thrust requirement.
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I can think how I'd do it. (Score:3, Interesting)
I'd put many smaller, distributed brushless electric-motors all along the wing, especially towards the wingtips.
In order to help increase lift based on pressure (active pressure differences), I'd place the propeller centers below the wing, rather than above the wing.
To counteract some of the loss of lift from wingtip vortex pressure losses, I'd make the propellers spin with the bottoms moving towards the fusilage.
In order to reduce explosion risk, I'd use Lithium-ion phosphate batteries.
I'd probably also ha
Wow dude, you just said never. (Score:2, Interesting)
Theres a whoooole lot of people that said never. As in; we were never supposed to fly, never supposed to break the sound barrier, never supposed to get to space, etc.
Noone said it would be easy, or that they have an idea how to do it. but thats why we do these studies.
Luckily people that don't like to say "never" work at NASA.
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Gliders aren't silent, but they're a heck of a lot quieter than your average airplane and well below the noise level of, say, a motorcycle.
The B2 is relatively silent (Score:3, Interesting)
tm
What about the inside? (Score:2)
I don't understand why this is tagged as vaporware (Score:2, Informative)
About time... (Score:4, Insightful)
Sure, they will never be silent, but they haven't been doing much improvement in the last 30 years. The old 707 engines were remarkably loud - going to turbo-fans made a big improvement, but I feel like they haven't made any further reductions since the "hush kits" of the late 1970s.
The entire Florida peninsula is severely noise-polluted from aircraft. Even when they are flying over at 30,000 feet, they're louder than the breeze in the trees, or an idling car engine, 6' away. If they can reduce the sound output to where the noise from a jet at cruising altitude is less than normal ambient noise in a suburban neighborhood, that would be a big accomplishment. I doubt they'll get it down to where you can't hear them while standing in a quiet field away from air-conditioners noise of passing cars - but they can try....
Also, don't forget the military aspect of this - F4 Phantoms were intimidating, but they certainly wouldn't sneak up on anyone, even if the person was deaf they could feel an F4 coming. F16s are a huge improvement, noise wise. I've never heard a stealth fighter in person, but I assume their noise signature could be reduced too. A fighter jet capable of silent approach and supersonic response speeds would have plenty of applications.
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The F22 is a stealth fighter wrt. radar cross section. But its twin F119 engines, each outputting 35000lbs. of thrust, are anything but silent.
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Also, don't forget the military aspect of this - F4 Phantoms were intimidating, but they certainly wouldn't sneak up on anyone, even if the person was deaf they could feel an F4 coming. F16s are a huge improvement, noise wise. I've never heard a stealth fighter in person, but I assume their noise signature could be reduced too. A fighter jet capable of silent approach and supersonic response speeds would have plenty of applications.
I disagree. The Phantom can most definitely sneak up on you from behind. I took pictures of it at an airshow recently. Taking a picture and immediately plugging my ears afterwards was quite a trick, since it was flying very low and I forgot earplugs. You see it coming and then at about 30 yards hissssBOOM! I'd call that sneaking up. You don't have time to do anything but dive. There was also an F22 on display, but nobody was considerate enough to fly it. :(
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If they can reduce the sound output to where the noise from a jet at cruising altitude is less than normal ambient noise in a suburban neighborhood, that would be a big accomplishment. I doubt they'll get it down to where you can't hear them while standing in a quiet field away from air-conditioners noise of passing cars - but they can try...
Attend a large (or military) airshow sometime. The US's newest military transport, the C-14 Globemaster, is absolutely eerie. A huge, lumbering aircraft that is close to silent for it's size.
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But they don't outrun radio or networks. If they're heard going over the coast, and the interior is on alert, they're boned. It's still better to be quiet, even if you are supersonic.
Black Helicopters (Score:4, Funny)
It's about time that the stolen UFO technology currently being used in silent black helicopters is finally trickling down to private enterprise.
s/Silent Aircraft/Silent powered Aircraft/ (Score:3, Insightful)
Efficiency is Key (Score:3, Insightful)
The airlines could care less about noise, comfort, and environmental impact. If it saves them some gas then it may fly.
Black helicopters in whisper mode.. (Score:4, Funny)
Are a paranoids wet dream, cloaked black helicopters in whisper mode are already following me everywhere I go, I know they're there because I don't see or hear anything, really!
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Didn't hear it coming neither!
Nobody ever thinks of us poor runway maintenance folk when designing their 400ton aircraft :(
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Tell me if you can hear this: Whoosh!
Sorry, couldn't resist. I don't mean to be insensitive to workers' hearing loss or any other physical or psychological effects.
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wonder if CA will try to pass a law making these jets have a noise generator so that the blind can hear them coming (you know like their trying to do with eletric cars)
Re:Silent... aircraft. Huh. (Score:4, Informative)
CA is not "trying" pass a law that would make electric cars have noise generators (it doesn't even makes sense to talk about a state "trying" to pass a law: an interest group might lobby a state for a law, but that's not the state trying anything.)
California rejected (the legislature passed and the governor, citing that the issue was appropriately handled at the federal level, vetoed) a bill that would create a study to committee to determine what the sound requirements were for the safety of the blind around quite vehicles and to investigate means of meeting those requirements.
Presumably, the findings on this could have been used in the future to support legislative proposals for requirements, if both sound types levels which provided notable safety benefits and reasonable means of meeting those were determined; they just as easily could have provided fuel to support the argument that the necessary sound levels would have other adverse effect, be unreasonably expensive, etc., against such a future proposal.
It's true that in many places, in the East Coast and in California, advocates for the blind have lobbied for requirements for noise generators (not just study of the issue), but that's very different from any particular state passing (or even "trying to pass") a law requiring that.
Parent
Re:Silent... aircraft. Huh. (Score:5, Funny)
the governor, citing that the issue was of paramount import for stealth in the imminent rise of the machines, vetoed
There we go, fixed that for you.
Parent
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Fairly large numbers of people are killed by internal combustion cars, even with all the noise they make; anything that addresses that will also address the safety of quieter cars, and given that for the foreseeable future cars that usually move with an engine running are going to far more common than those that don't, will probably provide vastly more public benefit for the same amount of effort.
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I don't see how efficiency can go down because noise and efficiency go hand in hand. Noise is caused by air turbulence, reducing air turbulence will increase efficiency.
Having said that, two million is a drop in the ocean for this sort of thing. How come the USA can spend trillions bailing out stupid bankers but only has a couple of million for this sort of thing?
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Maybe that's all we had left after bailing out the bankers? :-P
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My recollection of grad school is that it involves few bangs or bucks.
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The noise an airplane makes at its home base doesn't count. The noise it makes over an enemy position in the night does.
rj