[ExI] Inflatable tower could climb to the edge of space

spike spike66 at att.net
Tue Jun 9 05:21:49 UTC 2009

> -----Original Message-----
> From: extropy-chat-bounces at lists.extropy.org
> [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of
> Damien Broderick
> Sent: Monday, June 08, 2009 8:10 PM
> To: ExI chat list
> Subject: Re: [ExI] Inflatable tower could climb to the edge of space
> At 07:16 PM 6/8/2009 -0700, spike wrote:
> > > I still don't see how you can light up a rocket engine at the top
> > > (let alone the bottom) and not set the sucker on fire.
> >
> > > What am I missing?

There isn't enough atmosphere to support combustion at 30km.

> >
> >You would need release the rocket and have a cold gas
> thruster to push
> >away slightly from the tower to eliminate damage upon ignition.
> Aren't those birds held down when they're ignited, and only
> released when they're already burning like crazy? Isn't the
> thing likely to tumble if you wake it up in midair?
> This method requires the whole craft to be hauled up to 20 or
> 30 or 100km, unless the tube is largely evacuated and it
> launches somehow from the ground without setting everything
> alight. I suppose if you drag it up empty and fuel it through
> pipes pumped by a monster motor at the bottom...
> Damien Broderick

With the proper control authority, via thrust vector control, swivel
nozzles, intertial gyros, advanced digital control algorithms and such, even
a tumbling rocket can be straightened and made to fly pointy end first.  We
can do that with current military technology; it is not near the technical
challenge of creating a really tall inflatable tower. 

I haven't done the calculations on the inflatable tower notion, but my
intuition tells me it would allow the tower to go higher than without the
internal pressure.  I am imagining a cone structure, perhaps a km diameter
at the base, gradually tapering upwards, 30km or so.

It could be constructed in sections: assume a km diameter base, 200 meters
high, so about about 994 meters diameter at 200 meters height, where we
would construct an enormous hemispherical dome.  The first section would
then be pressurized partially, and structural strength added to the dome
until it was at about 20 atmospheres.  Then the second piece would be
constructed up to 400 meters and a diamter of about 988 meters, a new dome
at that height, pressure gradually added to the second section, until the
first and second sections are in equilibrium.  Then the first dome could be
removed, for it would no longer serve any purpose.

This successive dome building, pressurizing the new section and removing the
previous dome would continue all the way to the top, which would be in
equilibrium at a mere 19 atmospheres (or one less than the bottom section in
any case.)  At the very top would actually be an enormous pulley, over which
a single cable would be used to haul the rocket to the top.  This rocket
would have two swivel nozzles which could be used to direct the force of the
thrust outward away from the tower.

I haven't actually seen this version of the idea, and don't know if it is
anything like what Jeff proposed so many years ago.  Do let me perform some
honest BOTECs and return when I know what the hell I am suggesting, for
other obligations, such as fatherhood and husbandhood, demand my immediate




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