[extropy-chat] balloon stations at the edge of space

[Eugen Leitl]

On Sun, May 23, 2004 at 06:47:19PM -0700, Adrian Tymes wrote:

> Vacuum balloons happen to be a dream of mine I reality
> checked some time ago.  In theory, if one could get
> materials strong and light enough, one could make an
> expandable brick full of near-pure vacuum.  Imagine a

This has been thoroughly discussed on nanotechnology Usenet newsgroups of
yore.

> flexible covering, joined to an internal,
> size-adjustable support mechanism (say, telescoping
> support structs).  Shrink the supports (telescope the
> struts in), and pressure forces the covering inwards,
> resulting in less displacement and thus less lift.
> Reverse the process for more displacement and more
> lift (up to whatever the supports & covering can
> stretch to).

You could also use simple solar thermal management 
of the hull (electropigment, insulation) to change lift on classical
hydrogen/helium lighter than air vehicles. Or use active control of
pressurized compartments.
 
> It'd be difficult to do this even with today's most

Make that rather "impossible". Nanoscale smart materials currently don't
exist. You need machine-phase chemistry to build those.

> advanced materials, mainly due to the weight of the
> motors to adjust the support mechanism.  If one could
> afford to only adjust during the day, power could come
> entirely from lots of low-efficiency flexible solar

There's no reason why thin-film cells need to be low-efficiency.

> cells: surface area is practically unlimited for that
> specific application, though weight is a concern.
> 
> Vacuum, of course, doesn't leak unless the container
> is breached, and it'd be a simple matter to add a

In practice, there's outgassing, so you need pumps. 
In practice, you can make hydrogen from captured atmospheric 
water vapor, and replenish your leaks, using
onboard photovoltaics or beamed terrestrial power.

> small vacuum pump in case of small leaks (possibly,
> this would even be what - slowly - gives the balloon
> its initial vacuum, and just leave it in there in
> case of future problems).

All of it is feasible, if you have MNT. We don't have MNT, so lighter than
air vehicles are limited to gases buoyant in the atmosphere (of which
hydrogen is cheapest, but has a very unfortunate rap since that Hindenburg
thing).

I was pretty amazed that these balooning people thought they could ion
(plasma) thrusters (powered from ground with a powerful microwave source) 
to counteract drag, indeed enough to go orbital, all
within a few days (?!). At several Mach oxygen plasma will eat 
any lightweight plastic alive.

Otoh, you can carry payloads up to higher stratosphere within tether reach.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
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