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MIT and NASA Designing Silent Aircraft 176

Posted by samzenpus
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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MIT and NASA Designing Silent Aircraft

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  • by Anonymous Coward on Thursday November 20, 2008 @12:43PM (#25833689)
    It's called a balloon.
  • by liquidMONKEY (749280) on Thursday November 20, 2008 @12:45PM (#25833727)
    These aircraft will be silent, but deadly?

    Sorry, just had to sneak that in...
    • by CRCulver (715279) <crculver@christopherculver.com> on Thursday November 20, 2008 @12:52PM (#25833827) Homepage
      Yes, you'll know them by their vapour trails, but you won't hear them coming.
    • Re: (Score:3, Interesting)

      Don't expect your airport-side property values to rise just yet.

      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!
  • by Zebadias (861722) on Thursday November 20, 2008 @12:48PM (#25833779)
    Enclosed engines? That is not going to be as easy to maintain as the 'drop off' ones that currently sit under the wing.
  • by Shadow Wrought (586631) * <shadow...wrought@@@gmail...com> on Thursday November 20, 2008 @12:51PM (#25833811) Homepage Journal
    After all we've already had the "Whisper Jet." Of course anyone who's heard a 727 take-off knows that that is a relative term;-)
    • Re: (Score:3, Interesting)

      by WindBourne (631190)
      hehehe. My dad was air force. Ever heard a b-47 with a JATO pac take off? Makes the 727 a whisper jet. Even the DC8's (which were much noisier than 727 or 707). What was cool was to see the practiced take off for a squadron. something like 10-15 seconds apart. pitch black. My understanding is that only the lead could see anything. If an accident occurred on take off, my understanding is that it would be SEVERAL aircrafts collosion before it was realized that a problem had occurred.
      • Not doubting you, but I'm surprised. I thought turbulence problems from the vortexes coming off the lead aircraft made takeoffs that close quite risky.
  • But it seems like this is something the military would have already spent time and money on. Or would it be that they don't care if you hear them, they just want the stealth to avoid being 'seen' by radar at longer distances (which makes sense).
    • Re: (Score:2, Informative)

      by Warshadow (132109)

      Have you ever been on the ground when a B-2 is flying over? It's insanely quiet even at low altitudes. It's accomplished via an insanely simple method too. The exhaust is vented on the top side of the plane, so it does not resonate downwards as much.

    • by CompMD (522020)

      "Stealth" aircraft are quiet. I get buzzed by B2s rather frequently, since they are based only 90 miles from me. With four big, fully enclosed engines, the B2 is surprisingly quiet given how big it is.

  • by erroneus (253617) on Thursday November 20, 2008 @12:58PM (#25833917) Homepage

    "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.

    • Re: (Score:2, Funny)

      by jornak (1377831)
      The truth is out there.
    • Re: (Score:2, Insightful)

      by Sir_Lewk (967686)
      And the problem with setting an unrealistic goal but still achieving *some* progress is what?
    • 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

      • Re: (Score:2, Funny)

        by Conditioner (1405031)
        This idea was invented by Shampoo.
      • Well, I'd do some similar things, but I'd insist on putting those properlers above the wings, maybe we are thinking on different properlers (different sizes), but as I see it, putting them under the wing would decrease lift. By the way, exept for under the wings, there is no place where one couldn't gain by putting a propeler.

        Now, that would be a great design if it weren't for a few engineering troubles. The first, and most obvious one, is that big propelers are cheaper to produce, and, being noise an exter

      • by mccrew (62494)

        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.

        Could you explain this one? I would expect that you would have more lift by pushing the higher-speed air behind a propeller (higher speed = lower pressure by Bernoulli's equation) - one example of which was the Boeing YC-14 [wikipedia.org].

        I would expect that the only time you would have a lift benefit with the propeller centers below the wing would be when the aircraft is very close to the ground. Early versions of the 737 had problems with their thrust reversers because they were blowing too much air under the wing a

        • by MickLinux (579158)

          Well, as I remember, if you model an airplane propeller as a disk, then the air pressure slowly decreases from P-zero as you approach the disk from the front, then jumps up, and then again slowly decreases back to P-zero as you leave the disk behind.

          The air velocity along the propellar axis, on the other hand, steadily increases as you approach the disk, is approximately of zero slope as you cross the plane of the disk, and then decreases again.

          So what I am doing is taking advantage of the sudden jump in ai

      • The single biggest problem I see with your idea is simple - the larger the propeller/fan, the more efficient it is at moving air. By the same token, the fewer blades the more efficient.

        Secondary, even Lithium type batteries store a couple orders of magnitude less energy than hydrocarbons.

        Personally, I'd like to see cross-country high speed passanger(and cargo) rail.

      • 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.

        I don't think you quite understand the aerodynamics involved. By placing the props underneath the wing, you are actually reducing the pressure on the bottom of the wing, and therefore reducing lift. Bernoulli discovered a long time ago that the faster fluids flow, the lower the pressure. That's why the top of an airplane wing is curved -- the air flowing over the top of the wing reaches the trailing edge of the wing at the same time as the air flowing underneath the wing, but it is traveling a greater d

    • 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.

      • All the people that said "heavier than air craft will never fly" had never noticed that birds were heavier than air, and flew.

        All the people that said "aircraft cannot fly faster than the speed of sound" had never noticed that bullets flew faster than the speed of sound. The Bell X-1 was shaped after a 50-caliber bullet for exactly that reason.

        Getting into space was "Just a Small Matter of Engineering Improvement (TM)" over Chinese firework rockets.

        Anti-gravity, teleportation, or faster-than-light technolo

        • by deft (253558)

          Sure, but i wuoudlnt be suprised if they announce they have found a way to counter the sound waves, redirect them up, or something i've never heard of before.

          maybe propellers will always cause waves, but that doesnt mean we cant quiet them somehow with the right technology. I guess we'll know what 2 years and some funding can get us though eh? meet back here in 2 years :)

    • by dkleinsc (563838)

      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.

    • For a large bomber craft, its supprisingly quiet [youtube.com], especially if compared to something like a C5 galaxy [youtube.com]or C17 Globmaster [youtube.com], or even an F-18 [youtube.com] (well, it did have its afterburner lit).

      tm

    • by Deadstick (535032)
      "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.

      It did with this airplane: http://www.globalsecurity.org/military/systems/aircraft/x-26-pics.htm [globalsecurity.org]

      Not exactly a fighter or bomber, but it has interesting applications for reconnaissance.

      rj

    • "Silent" is a relative term, but the presumption is one that has noise levels approaching that of an automobile.

      Modern jets are already as quiet as that. Just listen to the average moron driving around with the automobile's mega stereo sound system cranked up.

  • Noise reduction from outside things like engine noise is always good. But can they also work out a way to make the plane quieter on the inside, too? Like, can they make it so we don't have to listen to that screaming baby in 7E, and can they shut up the annoying passenger in 13F that won't stop talking about his entire life story?
  • This is research money. In my understanding of the term, that means that the money is to be spent to try and find solutions that don't exist today. They might succeed, they might fail. Even if they succeed, there's no guarantee that the research will make it into a commercial product. That is true of all research. Furthermore, I don't see any comments that substantiate the vaporware tag. Shouldn't it be a requirement that if you're going to add a tag to an article you have to add a comment too?
  • About time... (Score:4, Insightful)

    by JoeMerchant (803320) on Thursday November 20, 2008 @01:44PM (#25834579)

    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.

    • The F22 is a stealth fighter wrt. radar cross section. But its twin F119 engines, each outputting 35000lbs. of thrust, are anything but silent.

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      Just a quick fyi, a supersonic aircraft outruns its own noise. You don't hear them coming.

      • by Chirs (87576)

        But your distant observation post can hear them and warn you...

      • Re: (Score:3, Insightful)

        by PitaBred (632671)

        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.

    • ...silent approach and supersonic response speeds?

      At the same time?

      • Key word: approach

        simple physics there, all supersonic approaches are silent, even the in the F86 [wikipedia.org] .

        What would be useful on a strafing run would be to fly at something just over stall speed and still sneak up on your targets....

    • Re: (Score:3, Interesting)

      by bendodge (998616)

      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. :(

    • Re: (Score:3, Interesting)

      by Shotgun (30919)

      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.

    • by Ihmhi (1206036)

      I live a couple miles away from Newark airport, so all of those improvements at cruising altitude wouldn't be worth crap to me honestly. Most of the planes are flying so low that I can see the bottle of Jack on the plane's dashboard.

      • I used to live 8 miles from MIA, and I thought it was bad, but walking 10 blocks south from my house I met the people who really suffered, they got the climb out blast pointed at them on over 1/2 of the northbound takeoffs.

        I moved 16 blocks north, not really to escape the noise just to get a bigger house that I could afford, and it was like another world - you could still hear them, but they were never too loud to talk over in a normal voice.

  • Quieter airplane? (Score:2, Informative)

    by CompMD (522020)

    See: Boeing 787.

    • Yet to fly, already 7 months past the date it was due to enter service - besides, its quietness isn't revolutionary, merely evolutionary since the much larger A380 already surpasses it in quietness.
  • by ZirbMonkey (999495) on Thursday November 20, 2008 @02:22PM (#25835141)

    It's about time that the stolen UFO technology currently being used in silent black helicopters is finally trickling down to private enterprise.

  • by dorfsmay (566262) on Thursday November 20, 2008 @02:24PM (#25835171) Homepage
    Gliders are near silent, and are aircrafts !
  • Efficiency is Key (Score:3, Insightful)

    by llZENll (545605) on Thursday November 20, 2008 @03:23PM (#25835991)

    The airlines could care less about noise, comfort, and environmental impact. If it saves them some gas then it may fly.

  • by Paracelcus (151056) on Thursday November 20, 2008 @04:11PM (#25836663) Journal

    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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