Vacuum Dirigibles a Stupid Idea ?

Michel Van

Michel Van

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Wat is lighter than Air ?

Nothing !

better say a Vacuum
in 1670 Francesco Lana de Terzi had that Idea for a Balloons with Vacuum inside 4 big copper sphere.
Francescp%20Lana%20-%20Airship.jpg

of course the Technology of 17 century was not ready for this.
and with 21 century Technology ?
hh19.jpg


or is this still a stupid Idea?

source
http://airshipworld.blogspot.com/2007_09_01_archive.html
picture
http://www.rusring.net/~levin/levin3d/dz.htm
 
Michel Van said:
or is this still a stupid Idea?
Click to expand...

Pretty much, yes. Structures used to contain light lift gasses, hydrogena nd helium, are in *very* slight tension, sinc ehte gas pressure within is pretty much the same as the surrounding atmosphere. But a vaccuum chamber has a fairly high delta-P... and in the *wrong* direction. The structural weight required to hold the thing together would be massive.

Think of it this way: You can put fairly high pressures into a plastic 2-liter bottle. Several atmospheres worth, I believe. But if you simply try to suck the air out with your lungs, it will collapse. The internal or external structure required to keep the bottle from collapsing would weight a lot more than the bottle itself. That's because when pressurized the plastic is in tension... a stress that causes the plastic to want to straighten out. But when depressurized the plastic is now in compression, which works agaisnt straightening out the plastic.
 
Think of it this way: moving from helium to hydrogen:

Weight of air per liter at STP = 1.20 gr/l
Weight of helium per liter at STP = 0.18 gr/l
Net lift per liter of helium at STP = 1.03 gr/l

Weight of air per liter at STP = 1.20 gr/l
Weight of hydrogen per liter at STP = 0.09 gr/l
Net lift per liter of hydrogen at STP = 1.11 gr/l

So only a measily 8% increase by moving to a gas that is twice as light but a lot more flammable. Moving from hydrogen to vacuum gives:

Weight of air per liter at STP = 1.20 gr/l
Weight of vacuum per liter at STP = 0.00 gr/l
Net lift per liter of vacuum at STP = 1.20 gr/l

Or just another measily 8 8% increase by moving to something flammable to something that needs a pressure vessule that is *very* difficult to make very light.
 
Well, I was right to make a quick search. Considers the following - Los Alamos, so not exactly a fringe scientist working in his garage.



According to Beaux’s calculations they need a sphere of at least 1.4 meters in diameter for the ratio of material to vacuum to be sufficient for liftoff.
Click to expand...

My mind is completely blown (lame pun assumed)

I knew aerogel as a wonder stuff to catch asteroid dust for NASA, but this is rather unexpected.

Who wants to shoot down the idea ? (another lame pun, assumed again)

Francesco Lana de Terzi
Click to expand...

What a posthumous revenge that would be, for this man (half joking)
 
Totally impossible; one m3 of vacuum has a lift capacity of 1.2 kg-force or 11.8 N; a vacuum steel one m3 cube must weigh less than 1.2 kg to keep a lift capacity in a one bar atmosphere. But the atmospheric pression on each of the six sides of that steel (or any other material) cube is 10 tons, or 60 tons fr the six sides of a one m3 cube. A sphere is a better form but can't stand that difference between lift capacity and atmospheric pression forces.

Even the first fuselages of the DH Comet couldn't stand more than 2 years of commercial flight under a difference of 0,6-0,7 bar between the cabin and the outside (8000-10000m). OK here the metals work under traction constraints versus compression for an hypothetical vacuum lift machine.

During the 20's MM. Vaujean and Gargiulio proposed a rarefied air. dirigible. That project was based on 3 volumes placed inside each other to minimize the differences of pressure and their action on the internal walls of these volumes.
From AirMagazine Février-mars 2009
 

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Archibald said:
Well, I was right to make a quick search. Considers the following - Los Alamos, so not exactly a fringe scientist working in his garage.





My mind is completely blown (lame pun assumed)

I knew aerogel as a wonder stuff to catch asteroid dust for NASA, but this is rather unexpected.

Who wants to shoot down the idea ? (another lame pun, assumed again)



What a posthumous revenge that would be, for this man (half joking)
Click to expand...
Very interesting search
For more precisions
Approaching air buoyancy in aero/cryogel vacuum vessels (Journal Article)
 

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