6 ms·

Vacuum airship

• dj_gitmo 12y ago
  This rail-bound tank was probably not designed with weight savings as a prime considerations. https://www.youtube.com/watch?v=Zz95_VvTxZM https://www.youtube.com/watch?v=Zz95_VvTxZM Still, this is a fascinating idea and I would love to see someone make a serious attempt at it.
  • panzi 12y ago
    Yeah, but as the Wikipedia article states: not even diamond is strong enough. So don't hold your breath.
• digikata 12y ago
  I wonder if a modern materials would let us build lift cells in this vein - maybe thin-skinned vessels filled with aerogel for structural support.
  • soperj 12y ago
    immediate thought was aero gel too. I wonder if graphene would be useful as well.
  • jcampbell1 12y ago
    > "This cannot even be achieved using diamond" The whole concept totally absurd. Helium is ~15% the density of air, so even if you created a material 100x stronger than diamond, it would only outperform helium by a tiny amount.
    • titanomachy 12y ago
      The helium in a balloon/dirigible is under pressure, so its density would be somewhat greater than 15% that of air. But point taken.
      • coryrc 12y ago
        No. It's always the same pressure as air. That's the point. It'll always be ~15%.
• jccooper 12y ago
  "His patent application was eventually denied on the basis that it was 'wholly theoretical, everything being based upon calculation and nothing upon trial or demonstration.'" He'd get that patent today. Little as it might avail him.
• valarauca1 12y ago
  Its a cool idea but as the post suggests air pressure on the vacuum spheres is a major problem. The crush force on the sphere will scale 40x the lift factor. So 1 gram of lift, 40 grams of crush. Once you reach scales of 10,000 kilograms you'll be dealing with keeping 400,000 kilograms of weight out of your vacuum.
  • shadowmint 12y ago
    Its worth noting that this force is not due to air preasure per se, but the difference in prrssure between the inner and outer volumes; if you can distribute the 'crush force' over a series of concentric partially pressured shells for example, the force is significantly reduced. ...not sure how it would apply to balloons, but its used in a number of things to contain high pressure on the inner ring.
    • valarauca1 12y ago
      Technically true, but then that weights more. So you change the mass to mass to lift ratio.
  • idlewords 12y ago
    The advantage over hydrogen at atmospheric pressure is really minor, too.
    • dredmorbius 12y ago
      Other than vacuum not burning.
      • idlewords 12y ago
        Yeah, your balloon just implodes at the speed of sound. In terms of disastrous outcomes, it's pretty much the same thing. Hydrogen explosions are scary, but the ball of flame also rises very quickly. Most of the people on the Hindenburg survived.
• idlewords 12y ago
  The linked articles from the 1887 New York Times are wonderful: "The means by which passengers will be landed en route is also in doubt. Some suggest that they will simply be dropped overboard and their luggage thrown after them, while others maintain that a coil of greased rope for the purposes of descent will be carried on each and every machine." Truly the Hyperloop of its day. http://query.nytimes.com/mem/archive-free/pdf?res=9904E7D81538E533A25757C1A9649C94669FD7CF http://query.nytimes.com/mem/archive-free/pdf?res=9904E7D815...
  • waps 12y ago
    This is a problem that every zeppelin faces too. They can't easily gain or lose height, because that would mean losing the gas they need to stay airborne. A vacuum ship that actually has a vacuum pump aboard would have the great advantage that it can easily change it's buoyancy using, say, electrical power. It could use this to change height, or compensate for being loaded with materials. Vacuum ships would actually be a solution to the zeppelin problem.
    • idlewords 12y ago
      A zeppelin could use compressor tanks to control its buoyancy in an exactly analagous way. Lots of details on how the problem was handled in practice here: http://en.wikipedia.org/wiki/Buoyancy_compensator_(aviation) http://en.wikipedia.org/wiki/Buoyancy_compensator_(aviation)
    • tsotha 12y ago
      There are multiple solutions to the "Zeppelin problem", as you call it, to the point that it's not much of a problem. If you had a powerful enough pump to create a reasonable vacuum it's far more powerful than the pump you need to compress helium if you need to lose buoyancy.
  • TezzellEnt 12y ago
    How does this compare at all to the Hyperloop?
    • 12y ago
• phkahler 12y ago
  I have wondered if such a thing could be designed for use in the upper atmosphere and dropped in from space. That would avoid the need to keep out the full atmosphere. But then so would pumping out the air as it gained altitude...
  • genwin 12y ago
    I like this thinking! Like dropping a beach ball into a swimming pool.
  • refurb 12y ago
    But if dropped into the upper atmosphere where there is little air pressure, it would sink until it got to an altitude where it's weight equaled the mass of the atmosphere it was displacing.
    • jjoonathan 12y ago
      That would be the point.
• olefoo 12y ago
  The major weakness of a vacuum airship is that a breach of the pressure hull will compromise the vacuum and thus the buoyancy. So any truly useful solution will require a number of independent vacuum cells. The strongest shape made of compressive members is a tetrahedron, if surfaced with an impermeable and inelastic membrane an evacuated aerostat could end up looking like http://www.theatlantic.com/video/archive/2012/01/a-gorgeous-floating-crystal-inspired-by-alexander-graham-bells-kites/251224/ http://www.theatlantic.com/video/archive/2012/01/a-gorgeous-...
• hacknat 12y ago
  14% advantage over helium makes it seem like it's not worthwhile. Am I missing something?
  • angersock 12y ago
    Helium is quite expensive, and a limited resource: http://www.popularmechanics.com/science/health/med-tech/why-is-there-a-helium-shortage-10031229 http://www.popularmechanics.com/science/health/med-tech/why-...
  • kansface 12y ago
    Helium is a finite resource- escaped Helium eventually leaves our planet forever; nuclear fusion will probably never produce sufficient helium for current industrial use.
• aaron695 12y ago
  Misses the point hydrogen is safer, easier, could be done today with existing tech for commercial travel (Already used a lot for scientific balloons) and pretty much has the same lifting power. (Also Helium is obviously currently is used in airships commercially with no real problems on top of a theoretical vacuum ship other than perhaps cost of balloon contents, which I'd guess is not the limiting factor anyway)
  • spiritplumber 12y ago
    A problem with Hydrogen is that it is very reactive -- that doesn't necessarily mean fire, but it does mean that any surface it comes into contact with will be affected. For example, you can't fill a latex balloon with hydrogen and expect it to last very long.
    • refurb 12y ago
      Hydrogen, at normal pressures, isn't that reactive at all if you ignore it's combination with oxygen.
• tsotha 12y ago
  This is an idea that seems interesting at first glance, but it's really not. What's important for lift isn't the absolute weight of the gas; it's the ratio of the weight of the lifting gas to the surrounding air. What that means is while hydrogen gives you about 1kg/m3 lift a perfect vacuum bottle only gives you about 1.3kg/m3. It probably wouldn't make sense even if we had the necessary exotic materials.
• lpmay 12y ago
  This reminds me of Buckminster Fuller's cloud 9 concept. His idea was that since volume scales so much more strongly than surface area for a sphere, if you make a larger and larger sphere you will enclose cubed more air for only squared more structure. Build a large enough sphere and heat the enclosed air a couple degrees above ambient and the entire structure would be buoyant, like a soap bubble with human breath in it. http://en.wikipedia.org/wiki/Cloud_Nine_%28tensegrity_sphere%29 http://en.wikipedia.org/wiki/Cloud_Nine_%28tensegrity_sphere...
  • ianbicking 12y ago
    "Geodesic spheres (structures of triangular components arranged to make a sphere) become stronger as they become bigger, due to how they distribute stress over their surfaces." I happened upon some Bucky Fuller stuff recently, and wondered just how large geodesic spheres have been made... and it's not particularly large. Which makes me wonder: is this really the whole story? What is the flaw in geodesic spheres that keeps them from being the basis of huge enclosed structures?
    • Synaesthesia 12y ago
      The difficulties of construction for one, and such large structures are vulnerable to buckling I would imagine.
    • deleted 12y ago
      [deleted]
• beloch 12y ago
  At atmospheric pressure, a given volume of hydrogen weighs approximately 7% (there is some variation with temperature) of an equivalent volume of air. All that is needed to contain hydrogen at atmospheric pressure is a membrane it can't pass through. The inwards force exerted on the membrane by the atmosphere is perfectly balanced by the outwards force exerted by the hydrogen gas. The only structural material required is for the purpose of harnessing the lifting power of the enclosed gas, providing an aerodynamic shape, etc.. Conversely, a vessel containing a vacuum must be built to withstand the 101,325 N/m^2 net inward force exerted upon it by the atmosphere that is not balanced by the outward pressure of the contents of the vessel. Consider, for a moment, what you would need to build a 1 m^2 coffee table out of if 20 elephants were to be able to stand on top of it at once. For the sake of argument, let's say that we had a magical material that would let us build a replica of the Hindenburg that is of equal weight to the original, only with vacuum vessels replacing the hydrogen bags. The Hindenberg contained 200,000 m^3 of hydrogen lift gas, weighing 1,798 kg and displacing enough atmosphere to provide a total lift of 25,850 kg, 10,000 kg of which were considered it's cargo capacity beyond the passengers it carried. This new version of the Hindenberg, despite being built with materials and techniques that are probably well beyond our current level of technology, would carry the same number of passengers and just 18% more cargo. For those of you who think that vacuum vessels are a lot safer than hydrogen, I'd like to remind you that the atmosphere surrounding 200,000 m^3 of vacuum provides a rather huge amount of potential energy waiting to be released. When vacuum vessels of a large size fail the resulting implosion can be both spectacular and devastating. https://www.youtube.com/watch?v=Zz95_VvTxZM https://www.youtube.com/watch?v=Zz95_VvTxZM
• ChuckMcM 12y ago
  These are fun (also in Diamond Age I believe) and I like how they are both impossible to create and there is a patent application on them :-) It is interesting to run the structure density vs the vacuum numbers. I always wondered if we would be able to make vacuum filled bucky balls out of carbon at some point.
• rotten 12y ago
  Does the vacuum have to be perfect? Maybe you can reduce the pressure on the surfaces, and therefore simplify the engineering, by leaving some air in there. I think it is an interesting idea that varying the internal pressure would change your lift. You only ever need "just enough" lift anyhow.
• m-i-l 12y ago
  Reminds me of an idea I had for lighter than air packing material. It was going to be something like over-sized bubble wrap filled with helium, or balloons you'd insert into the spaces and inflate with a helium canister. Seems a great idea at first, but then you do the maths, and think about the materials. Unfortunately the weight savings are likely to be so minimal they're unlikely to save on postage costs, and even if they did reduce postage they're likely to be outweighed by the cost of materials. Plus you later find out that lots of other people have had the same idea and posted on the internet about it.