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Is 'Harbenite' now possible?


Fidcal
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Just reached one of the books in the Pellucidar series where a fictitious material called Harbenite is used to build an airship. The author reasoned that since the lightest element is hydrogen the only way to go lighter is a vacuum. But of course, any structure that could withstand the pressure of the atmosphere against a vacuum would be far heavier than hydrogen. The author proposed a new super strong, super light, metal called Harbenite that could meet the need. No such solid material seems possible but I am now wondering if a special structure could.

 

Suppose a honeycomb of carbon nanotubes or buckyball structure. Somehow it would have to be foamed within a vacuum and I don't know how that might be done. I wonder if in theory it might produce a material structure that is lighter than hydrogen volume for volume? Imagine an airship supported by a giant balloon consisting entirely of a carbon nanotube shaped vacuum foam. It would not leak. I don't think it would be dangerously combustible - surely not like hydrogen anyway but whether it could burn like a metal scouring pad I don't know. If its outer surface could ignite then there might be a huge area in contact with the oxygen in the air. Hopefully its own material would suck heat away and extinguish itself faster than it could burn through to new layers. Only the outer layer would ever be combustible if at all seems likely to me. Actually, the material might be a super heat insulator.

 

I wonder what volume would be needed to support one man? Perhaps a large back pack could enable mankind to take another great leap?

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Many of the things you talk about is in a material already available:

 

http://en.wikipedia.org/wiki/Aerogel

 

 

I happen to have a nice piece right here (of my own manufacture :wub: ).

Incredibly lightweight, though not full of vacuum.

 

For comparison:

The H2 you talk about has a D of about 90 grams per m³ under normal pressure.

Air has about 1300 grams per m³.

 

So, for purposes of generating lift normal H2 is quite good compared to vacuum (density 0) already - not so much would be

gained by using something better.

 

However, like wikipedia says, the record low density solid is an aerogel of about 1000 g/m³ - that thing will float/rise in air.

But such an aerogel is very brittle and unstable.

 

About your idea with nanotubes or graphene :

As a lifting body such a material would have not only to withstand the pressure/strain on its "vacuum enclosing cells"; a huge problem would probably be diffusion of gases through the material because of the pressure gradient , spoiling the vacuum.

I work in the OLED/organic electronics development in Saxony, and there are considerable problems of keeping "air" (not just the usual components, there are more "sneaky" ones like noble gases, He,H,NO2,CH4,CO...) out of those circuits/materials with organic membranes (glass/metal seals are of course of no use, organic electronics are meant to be used as rolled displays and so on).

 

So, a solid material that has buoyancy in air is feasible - in more than one way probably.

But even nanostructured carbon is a huge shot short from making such a stuff mechanically very stable.

Vacuum-light AND very tough combined is not even in far sight anywhere, I think.

 

Maybe other know more, however; I spy Sotha was a chemist too ?

"Good people do not need laws to tell them to act responsibly while bad people will find a way around the laws." - Plato

"When outmatched... cheat."— Batman

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It just occurred to me that one way to approach a vacuum foam might be to bubble up the material in an extremely low pressure hydrogen tank. Each cell would still contain hydrogen but at extremely low pressure. However, from what you are saying there would be leakage. I guess these nano structures are still just structure and do not produce sealed cells. Maybe I was hoping they are so small that molecules of air cannot pass in through the gaps.

 

OK, Take 2. The above is constructed then placed inside a high vacuum chamber where the low pressure hydrogen leaks out over a period leaving a reasonable vaccum inside the structure. Next the whole material structure is sprayed with a vacuum sealant on the outside. These mushrooms are great :P

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Maybe other know more, however; I spy Sotha was a chemist too ?

 

Yep, I'm a chemist and I'm especially interested in nanotechnology.

 

And I've fiddled with gels too, altough not aero-ones.

 

Like said, creating a nano structure with vacuum inside, which could withstand the pressure difference and which would be non-leaking would be impossibly tricky. Think about the practical considerations: how do you suck vacuum into your nano cells? You should have some kind of stimulus responsive nanodevice, which you first open, then you enable vacuum, and then close the device. And then hope it would keep the vacuum.

 

It is much easier to prepare a microstructure with trapped gas.

 

Also if the idea is to prepare a 'safe' device which would not explode like H2, this vacuum material probably wouldn't solve this. If a huge amount of such cells would be destroyed at the same time.. It could be used to prepare a cool implosion bomb.

Clipper

-The mapper's best friend.

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Are nano structures really this weak? My understanding was that carbon nanostructures are the strongest structures known. Perhaps it is the foam structure that is not strong and there is some other form of nano structure that would be better? Anything that could trap pockets of vacuum should do.

 

Another approach: the one in Pellucidar, is not to make the whole structure out of foam but to produce super strong braced plating to form ultra light vacuum tanks.

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Are nano structures really this weak? My understanding was that carbon nanostructures are the strongest structures known. Perhaps it is the foam structure that is not strong and there is some other form of nano structure that would be better? Anything that could trap pockets of vacuum should do.

 

Another approach: the one in Pellucidar, is not to make the whole structure out of foam but to produce super strong braced plating to form ultra light vacuum tanks.

 

Well, nanofibers are really strong in the direction of the fibre. Perpendicular to the fiber, mechanical properties are of course weaker. Think about graphene, for example.

 

And then there is the problem of foam. You can easily achieve a foam with polymeric materials (styrox for example) or foaming liquids (mmhh, beer), but it's difficult to see how you could form an airtight foam of carbon nanotubes or nanospheres. That's why I was thinking of an individual micro to nanocontainer, which you could will with gas. Vacuum is even more difficult.

Clipper

-The mapper's best friend.

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But if we go back to the numbers:

Air - 1300

Hydrogen - 90

vacuum - 0

 

The difference between Hydrogen and vacuum is only about 7% increase in lift, not such a big deal. If the main point is to make it safe from fiery explosion, I guess that's another matter, but Helium is right around 180, so it's just another 7% worse but completely safe already.

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Ever since Vonnegut's "Ice Nine" fictional molecules\crystals have been compelling to me as well Fidcal. In fact, ice is an example of a crystalline structure that has a lower matter to vacuum density.

 

To achieve the result you originally described you would need to make an ice-like structure from a very light element. They have actually gotten close to making solid hydrogen in recent experiments if I recall correctly. Anything that is significantly heavier, eg. metal, would probably be too heavy. So your main problem is that these lighter "ices" need to be ultra-cooled but there may be a way around this:

 

1) Create a small MEMS scale LASER entanglement device.

2) Create an enormous spherical molecule around this device

3) Entangle the key bonding atoms in the structure to a stronger bonding metal atom in the entanglement device

4) Inflate the structure by bonding other external biasing molecules around it (see "Strained Silicon")

5) Use energy pumped into the entanglement to keep the structure together in-spite of being stretched to near or beyond it's breaking point.

 

Steps 1 and 2 are currently beyond our technological capability but not for long I suspect. Even without the MEMS device, perhaps creating something like bucky-balls and stretching the structure ala Strained Silicon would yield some interesting materials (although lighter-than-air would be unlikely?).

 

At one time in my life, I thought about creating a science-fiction novel about the above MEMS example where the device was controlled in a scheme similar to DRM and would cause any material it was incorporated into to self-destruct at the behest of the big companies that controlled them. People would eat food with this structure in it and it would become incorporated into their bodies so that the big companies could kill dissidents simply by disabling the MEMS inside of people. It could also be used to create the molecules infinitely more unstable than any current chemical explosive and anti-corporate freedom-fighters would use this to their advantage...

Edited by nbohr1more

Please visit TDM's IndieDB site and help promote the mod:

 

http://www.indiedb.com/mods/the-dark-mod

 

(Yeah, shameless promotion... but traffic is traffic folks...)

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  •  
  • Aircraft makers are constantly trying to shave < 1% of the weight of aircraft so 7% is a big deal.
  • Hydrogen needs a metal structure and surrounding skin to contain it so that needs including in any weight comparison. This vacuugel is its own structure.
  • Helium is becoming an endangered species I think I ready recently.
  • Hydrogen and helium leak and have to be replaced and their container maintained and liable to damage and serious sudden leakage. Assuming a vacuugel were stable and strong then it might have a shell go right through and it would just leave a hole; the remainder would still be lighter than air vacuugel.
  • Hydrogen is very flammable = dangerous. I doubt it will ever be used in airships again. So we're talking helium which is 14% + structure heavier than ... than what? We still have not defined the weight of vacuugel. I do not know how much is vacuum and how much carbon and still be structurally sound.

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  • Aircraft makers are constantly trying to shave < 1% of the weight of aircraft so 7% is a big deal.

1 or 7% is a big deal in terms of saving money on fuel, but probably not a big deal in terms of lifting orders of magnitude more like you'd need to do in an airship. The crazy airship idea in fiction that I liked involved type II superconductors excluding the magnetic flux of the earth, but that's also pretty crazy. Very light superconductors only levitate a few inches away from an extremely powerful magnet, so you probably wouldn't be able to levitate thousands of feet using the relatively weak magnetic field of the Earth.

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On Mars (Barsoom) Burroughs uses an even stranger idea than that. He used the Barsoomian eighth ray which streams out from Mars "constituting a force of repulsion of gravity" stored in small tanks for buoyancy and a radium engine for propulsion. :)

 

Since hydrogen is out we are talking helium so 14%. It seems to me that if you could make your airship able to carry 14% more freight or passengers then that would be a big deal. But as I say, it could be better or worse than that because the structure weight has to be taken into account, aluminium girders versus carbon nano material.

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H, cool thread.

 

As for the "vacuum foam", I too think that would be incredible tricky to manufacture. If you use some sort of gas, you can use pressure to push it into the foam bubbles. But with vacuum, you would need to suck the molecules out of whatever is enclosing the foam.

 

However, even if you don't change the lifting gas, just making the airframe lighter (by using f.i. metal foam instead of solid metal) would be an advantage.

"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." -- George Bernard Shaw (1856 - 1950)

 

"Remember: If the game lets you do it, it's not cheating." -- Xarax

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I don't know that foam is the right word or the right way to assemble this nano material. But if it is I've already described one method to make it contain a near vacuum. That is you bubble up extremely low pressure hydrogen inside a vacuum chamber. What you get is foam containing a near vacuum with a few molecules of hydrogen inside.

 

If, however, the nano material has to be micro-assembled then do it inside a vacuum chamber.

 

Or if, as Stumpy says, it can be grown then grow it inside a vacuum chamber.

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I don't know that foam is the right word or the right way to assemble this nano material. But if it is I've already described one method to make it contain a near vacuum. That is you bubble up extremely low pressure hydrogen inside a vacuum chamber. What you get is foam containing a near vacuum with a few molecules of hydrogen inside.

 

If, however, the nano material has to be micro-assembled then do it inside a vacuum chamber.

 

Or if, as Stumpy says, it can be grown then grow it inside a vacuum chamber.

 

Yeah, but have you accounted for the fact that for every m³ of vacuum, you also have some material to hold the vacuum there? If that material is more than the material you would need f.i. to hold helium, than your advantage (vacuum vs helium) might be less or even gone.

"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." -- George Bernard Shaw (1856 - 1950)

 

"Remember: If the game lets you do it, it's not cheating." -- Xarax

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Yes. :P

 

So we're talking helium which is 14% + structure heavier than ... than what? We still have not defined the weight of vacuugel. I do not know how much is vacuum and how much carbon and still be structurally sound.

 

 

But as I say, it could be better or worse than that because the structure weight has to be taken into account, aluminium girders versus carbon nano material.

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Yes. :P

 

Yeah, but you should be able to atleast estimate it. How big is a nano-tube? How big is a buckyball? You would need some pretty "light" material that consists of nothing but vacuum and a few atoms.

 

Wikipedia says the record for Aerogel is 1 mg/cm3, while air is 1.2 mg/cm3. So it would already float? I am not sure if the "1mg/cm³" includes just the solid material of the aerogel (I think it does, tho). So how would that compare to helium with 0.1786 g/L? Would the aerogel still weighting more than helium?

"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." -- George Bernard Shaw (1856 - 1950)

 

"Remember: If the game lets you do it, it's not cheating." -- Xarax

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Yeah, but you should be able to atleast estimate it. How big is a nano-tube? How big is a buckyball? You would need some pretty "light" material that consists of nothing but vacuum and a few atoms.

 

Wikipedia says the record for Aerogel is 1 mg/cm3, while air is 1.2 mg/cm3. So it would already float? I am not sure if the "1mg/cm³" includes just the solid material of the aerogel (I think it does, tho). So how would that compare to helium with 0.1786 g/L? Would the aerogel still weighting more than helium?

 

Converting the units, 0.179 g/L = 0.179 mg/cm^3. So the answer is that Helium is still much less dense than currently achievable aerogel, by a factor of about 6. The weight of outer skin to hold a large volume of helium is pretty negligible, since the outer skin is a thin surface, and surface area goes as R^2 while volume (total amount of Helium within a container of that size) goes as R^3.

 

You could imagine trying to build a skin out of a sturdy material like carbon nanotube fibers or graphene, and evacuating the inside. That's going to weigh much less than a porous material. But as others have pointed out, even if it could withstand the 14 psi pressure differential, you only get a boost of 14% going from He to vaccuum. And having a huge volume ready to implode at any time doesn't sound very safe to me. :)

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Converting the units, 0.179 g/L = 0.179 mg/cm^3. So the answer is that Helium is still much less dense than currently achievable aerogel, by a factor of about 6. The weight of outer skin to hold a large volume of helium is pretty negligible, since the outer skin is a thin surface, and surface area goes as R^2 while volume (total amount of Helium within a container of that size) goes as R^3.

 

You could imagine trying to build a skin out of a sturdy material like carbon nanotube fibers or graphene, and evacuating the inside. That's going to weigh much less than a porous material. But as others have pointed out, even if it could withstand the 14 psi pressure differential, you only get a boost of 14% going from He to vaccuum. And having a huge volume ready to implode at any time doesn't sound very safe to me. :)

 

Thanx for putting in words what I had in mind :) The idea of having a "vacuum gel" sounds intriguing because it would be more safe than a vcauum container (no blowing up) or helium container (no leaking), but if it is heavier by a factor of X (X > 1.0) than its not very useful.

 

But I am also thinking on aircraft, if you could manufacture a stable, but lightweight "foam", and use this to replace aluminum or carbon fibers, then that would be a huge benefit. As I understand it, tho, f.i. aerogel can easily shatter. However, maybe you could take an aergoel, and "bond" a plastic sheet on either side, so you get a scratch-resistant, and so on material sandwich. Hm, yummy! :D

"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." -- George Bernard Shaw (1856 - 1950)

 

"Remember: If the game lets you do it, it's not cheating." -- Xarax

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