Half a croissant, on a plate, with a sign in front of it saying '50c'
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buoyant space elevator

forget super-strength materials, build lite
  [vote for,

This is a hybrid of two technologies that have been proposed here, space elevators and vacuum balloons. Most space elevator concepts I've heard of involve the use of super strong materials that can support their own weight for hundreds of miles.

I'm thinking, why not build lite? Attach vacuum balloons around the circumference of the elevator at regular intervals and build the elevator itself from super lite materials. This takes care of the lower half that exists within the atmosphere. As for the upper half that extends into the vacuum of space, well, your on your own.

But it doesn't necessarily have to be used for a space elevator either. Even a skyscraper could utulize this idea. Iimagine such a structure would be made from a very strong, woven material that is air tight and inflated (think spacehab module for ISS). This wouldn't be some soft cushiony surface, but a very tough one that you could scrape your knuckles across and would have a fair amount of rigidity to it. The bouyancy of the vacuum balloons would keep it from buckling.

These balloons, in turn, would be anchored using kevlar cords to prevent the structure from swaying.

Anarch, Jun 25 2003

howstuffworks... http://www.howstuff...com/question194.htm
...talking about vacuum balloons. Not sure about the science at the end, though. [st3f, Oct 06 2004, last modified Oct 17 2004]

A more complete source on vacuum balloons http://www.aoi.com.au/ideasbank/5813.htm
[DrCurry, Oct 06 2004, last modified Oct 17 2004]

Armando Iannucci has something to say... http://www.telegrap...ue&_requestid=13088
Numbers 1, 5,6,7 are relevant.The rest are for Fun.
Daily Telegraph Friday 27th June. Learn Guys! [cloudface, Oct 06 2004, last modified Oct 17 2004]

Another dumb vacuum balloon idea http://www.halfbake..._20Vacuum_20Balloon
Why wasn't that one [marked–for–deletion] too? [DrCurry, Oct 17 2004]

More vacuum balloons http://www.halfbake...er-than-air_20solid
[bungston, Oct 17 2004]

(?) Similar idea via blimp http://www.halfbakery.com/idea/elevator
This is pretty close to what I suggested below; one track instead of a series. [cloudface, Oct 17 2004]


       Attaching balloons to the space elevator will actually make it less stable, due to the increased drag in high altitude winds. Moreover, putting a vacuum in a balloon will not gain you very much over using hydrogen or helium, while adding insurmountable containment issues.
DrCurry, Jun 25 2003

       Could someone please post a link to a "vacuum balloon"? Please?
phoenix, Jun 25 2003

       So kevlar, but no super-strength materials?
Shz, Jun 25 2003

       Kevlar, yes, but not for supporting the structure. Just for anchoring it against wind drag.
Anarch, Jun 25 2003

       sp: buoyant. [admin: spelling changed in title]   

       DrC: Are you claiming an MFD on the grounds that you don't particularly like the idea, or do you have a real reason?   

       Anarch: I fear that wind-shear may be the downfall of this idea (picture small child with balloon in high wind). How about putting the buoyancy inside the structure?
st3f, Jun 25 2003

       doesn't phoenix have a valid point?
po, Jun 25 2003

       st3f: vacuum balloon magic. Except that one could use conventional balloons to support the weight of the lower end of a space elevator, so this idea probably ought to stand despite its daffy mechanics.
DrCurry, Jun 25 2003

       May I enquire as to what happens in the upper atmosphere. Surely there is a collossal change in air resistance/temperature that will cause even greater 'drag' and severely compromise any balloon (vacuum or otherwise)
gnomethang, Jun 25 2003

       DrC: For vacuum balloons to work, we need material with a strength to weight ratio that we are unlikely to achieve for a long time. They are also unlikely to ever have any advantages over lighter than air balloons. That doesn't make them magic. Just a little silly.   

       po: What would that be?   

       gnomethang: any lighter-than-air device has an altitude at which it will become neutrally buoyant. So, there comes a point when they stop going up.
st3f, Jun 25 2003

       Yeah, right, sorta like anti-gravity. A Wibni, then (since people have been proposing this since Lana).
DrCurry, Jun 25 2003

       Nah. The theory of a vacuum balloon is that the inside weighs nothing. If the shell containing the vacuum weighs less than the air it displaces then it floats. That's all. No magic. The tricky bit is making a shell that is *very* strong, *very* light, completely airtight and doesn't seed any atoms to the vacuum it contains. (link)
st3f, Jun 25 2003

       Yeah, forcefield magic.
DrCurry, Jun 25 2003

       [st3f] That was not the nub of my gist.
I was rather more worried about calibration, stress and material selection about this point rather than the usual what 'goes up' problem.
I still don't think it will fly.
gnomethang, Jun 25 2003

       //I was rather more worried about calibration, stress and material selection...// You and me both.
st3f, Jun 25 2003

       Nice idea, several people had it already, but the material to build the baloons from is not around yet. In my own calculations Sapphire came the closest, but it was still about 500 times too heavy.   

       Perhaps something made from nanotubes could do the job, if they ever can be produced in large neough quantities.   

       The contraption may not look like a baloon. In my calculation it looked more promising to make an internal structure of 4 bars crossed (diagonals of a cube) and cover them with a thin super strong foil. The foil could be plain plastic reinforced with nono-tube-wire (if you have any of that).
kbecker, Jun 25 2003

       I like the idea of vacuum balloons, and balloons filled with the Eighth Barsoomian Ray, but hydrogen is very nearly as good, as pointed out above. Regarding the wind issue - zeppelins, dirigibles and other airships are able to deal with winds by virtue of their propellors. Instead of a bunch of inert little balloons, why not moor the space elevator to stacked zeppelins? When a wind came up, they could just compensate. In addition, you could pull up the whole contraption and motor around with it, if there were a need for a space elevator somewhere else. I think the "build light" idea for a space elevator is a decent concept and worthy of consideration, not extra bones. Too bad I missed the croissant rich days of 2001.   

       I have thought of a process for the top of the space elevator, but will post it separately as it is compatible but completely different from the buoyant elevator idea.
bungston, Jun 25 2003

       I think I bought an eighth of Barsoomian Ray back in high school.
thumbwax, Jun 26 2003

       I second what [Bungston] said with a few modifications.   

       1) Arranging the lifting balloons in the form of dirigibles is a good idea to reduce some of the wind drag as well as provide manuverability, but because the wind speeds in the upper atmosphere are very fast, compensating entirely with the dirigibles would require a lot of energy. I think it might be better to make the tether a bit stronger (and maybe some secondary tethers going down at a 45 degree angle supported with more dirigibles) to bear some of the wind load. If it was possible to make the tether strong ehough, we could even generate some enegy from the high winds.   

       2) I don't see any difficulties with the space end of the tether using this idea. Since the lower section of the cable is self supporting, the part of the cable hanging from geosyncronous orbit into the atmosphere is lighter, so the part swinging out beyond the orbit can be lighter by the same amount. The strength requirement for the whole cable is reduced by [anarch's] idea.   

       Other thougths: It seems we might want a tube running up the cable providing hydrogen to the dirigibles since hydrogen does leak out lowly and we want the space elevator to be permanent. Another option might be to produce the hydrogen in place by electrolysing condensation using power sent up the cable. Or we could always just keep hauling cylinders of gas up the cable. Would we really want to use hydrogen rather than helium? That seems potentially dangerous unless we can be sure there will be no ignition sources.   

       And speaking of ignition sources, what about lightning? The tether would need a pretty thick ground wire to avoid being vaporized during a lightning strike. I guess a ground wire might only need to go up to abot 40,000 feet or so. I assume there wouldn't be a problem with lightning once above cloud level. Maybe have helium balloons at lower altitudes where lightning is a possibility and hydrogen balloons at higher altitudes.
scad mientist, Jun 26 2003

       Ah, the charming and wacky vacuum balloon idea again. What you need to win an Ig Nobel with this is a nifty way to fill your balloons with free vacuum. A really good vacuum is mighty expensive, you know. Since your elevator reaches into space anyway, it would be a simple matter to run a vacuum hose from the top, where there’s lots of excellent free vacuum, all the way to the bottom, where there is a dearth of vacuum, and voila, you can fill up your balloons for free. Well, I know that you’re going to say that vacuum is so light that it won’t want to go down the tube. But no problem, you just put a few fans in the line to blow in down. See?

And if you really want to get fancy, consider a hot vacuum balloon.
pluterday, Jun 26 2003

       Heated Hoover. Burning Bissell. Kindled Kirby. Overheated Oreck. Enraged Eureka. Reddened Rainbow. Hot vacuums, all.
bristolz, Jun 28 2003

       [bristolz] What about me!? You forgot me!
Anarch, Jun 29 2003

       Forget the elevator, keep the zeppelins. That is, forget the part of the elevator in-atmosphere. You simply hang separate pieces of a linear accelerator track (or tube, or pathway) from higher and higher aerostats until you run out of buoyancy. That avoids most of the problems of structure, although you might need another orbiting tether to catch your payload once it got out of the atmosphere. Timing is everything: Your payload is fired or lofted or powers itself up through the discrete tethered (or untethered) sections of track until it runs out of air at a high altitude (and, hopefully, high deltervey.)
cloudface, Sep 24 2003

       "... your on your own" NO - "you're on your own"   

       (contraction "you're" is short for "you are.")   

       Isn't this obvious?
gargantua, Jun 12 2004


Pluterday has an excellent idea here: a vacuum pipeline to space, with vacuum fans to hurry the vacuum down. I say bottle space vacuum and sell it.

<itinerate salesman> Get your real space vacuum here! You...yes, YOU, I’m talking to YOU. Your lad there looks rather puny. <leans down, leering> Hey boy, getting any action? <laughs, addressing the crowd now, which has grown> Bet the girls aren’t knocking down his door! <snickers> How about trying Dr. Braun’s monster member maker? Uses real space vacuum. Pop the top, slip it over your son’s member quick (be real quick now, before all that vacuum gets out!), and watch it grow and grow and grow!
ldischler, Jun 12 2004


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