Re: Technology: Rigid Airship

From: Adrian Tymes (
Date: Wed Apr 12 2000 - 20:11:25 MDT

Spike Jones wrote:
> I did some calcs on this today. Looks to me like the vacuum dirigible
> notion doesnt work out. If one uses only idealized assumptions regarding
> the strength of materials, and assumes assembling a spherical vacuum
> ship on orbit, ignoring how to lower the thing into the atmosphere, etc,
> then one sees that the mass of the atmosphere displaced increases as
> the cube of the linear dimension, but the mass of the sphere also increases
> as the cube, since the surface area increases as the square of the
> diameter and the thickness increases proportional to the diameter.
> Looks to me that even assuming a hollow diamond sphere, we
> still arent in the vacuum dirigible business. Dammit. {8-[ spike

For a strictly uniform sphere, perhaps. But if you get the walls
thick enough that the can withstand a few atmospheres' difference
between outside and inside, the only thing left as you go up in size is
structural stability...and maybe one could find a way to do that which
does not go up in mass as a product of surface area times sphere

Michael S. Lorrey wrote:
> I have a question for you two. I assume you are going at it from the angle of one big
> bag. What about some sort of foam or honeycombed type structure, with lots of really
> really small chambers?

Each chamber would have to float (or, at least, be within 1/2 bouyancy
of being able to float, assuming that adjacent chambers sharing walls
reduces overall mass by about 1/2). A really small chamber would
displace a really small amount of air, so it could only have a really
small amount of mass - probably not enough to contain vacuum even in its
own volume (though I would love to be proved wrong here).

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