Airship to Orbit question

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Chance - 13 Dec 2005 21:22 GMT

I was reading about the airship to orbit idea, and how it is probably
impossible. This got me to thinking, are there any materials like
carbon nanotubes that could concievably be used produce a large volume
vacuum container or "balloon"? I recently asked one of those
ask-a-physicist sites and was told that an airtight "ballon" with a
volume of near vacuum should float even higher than a hydrogen balloon,
but that no existing materials are at the same time strong enough and
light enough to ever produce such a device. Such a device should be
much simpler and cheaper to create than a space elevator, and could
(hopefully) be mass produced. So is this is just a crazy idea, or is
it possible?

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beanstalkr - 19 Dec 2005 02:03 GMT

So is this is just a crazy idea, [[a vacuum-filled balloon]] or is

> it possible?

It's neither. It's not crazy and it's not possible with any balloon
current flight profile. Vacuum is cheaper than helium. But most people
don't realize the implosive force of one bar on a vacuum container. A
bar is 14.7 pounds per square inch, multiplied by the hundreds of
thousands of square inches on the surface of a large lifting tank.
So, the reinforced, honeycombed vacuum container would have to be
lifted to the stratosphere and then vacuumed-out where it could rise to
near space but not, of course, to space, which is a vacuum itself.
Similar to a two stage rocket, this would be a "two-stage balloon."
In practice, a partial vacuum would be drawn slowly during ascension
so as to maintain a safe pressure differential on the vacuum tank.

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David Given - 20 Dec 2005 15:06 GMT

> It's neither. It's not crazy and it's not possible with any balloon
> current flight profile. Vacuum is cheaper than helium. But most people
> don't realize the implosive force of one bar on a vacuum container. A
> bar is 14.7 pounds per square inch, multiplied by the hundreds of
> thousands of square inches on the surface of a large lifting tank.

It also doesn't help much --- hydrogen has about 1/18 the density of air at a
given pressure. Vacuum, of course, has 0/18 the density of air. So by using a
vacuum balloon, you end up making your life considerably more complex for only
an extra 6% boost in lifting capability.

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+- David Given --McQ-+

| dg@cowlark.com | Quidquid latine dictum sit, altum viditur.
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Chance - 21 Dec 2005 15:51 GMT

Thanks all for the replies. =-) I see, so the extra 6% boost doesn't
get you high enough to make the scheme practical. (if it was even
possible). So, what altitude would it be necessary to achieve in order
for electric propulsion to overcome drag?

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Space Forum / Space Flight / December 2005

Airship to Orbit question