From: Charles Hixson (charleshixsn@earthlink.net)
Date: Tue Aug 27 2002 - 15:45:41 MDT
Jeff Davis wrote:
>Friends,
>
>...
>
>Rather than a support structure based on compression,
>consider an alternative based on tension.
>
>A half-cone (axially bisected) "balloon" lying
>flat--on the plane of bisection--with the launch tube
>mounted atop the "ramp"/dorsal spine of the balloon.
>The weight of the tube would depress and divide the
>dorsal spine, so that the tube would rest in the
>"dorsal saddle" between the (now two) parallel dorsal
>sub-spines. The cross section would look similar to
>the McDonald's Golden Arches.
>...
>
The problem here is that a balloon could hardly extend above the
atmosphere, which would limit your speed... but perhaps .. has anyone
calculated how much a large diamond balloon would weigh? It would need
to be strong enough to endure acceleration stresses, but that's limited
to the central core. It sounds implausible, but imagine a vertical tube
kept evacuated, except at the bottom, surrounded by a balloon of diamond
that's also kept evacuated (diamond's strong, but I don't know if it's
strong enough to make this trick work!). The interior tube is lined
with a rail-gun, but that's not the only acceleration mechanism. The
lower door to the inner tube is high enough to allow a complete launch
vehicle to be inserted into the inner tube. At launch time, the upper
and lower doors of the inner tube are opened, so air pressure is added
to the thrust of the rail-gun. Then the doors are closed again, and the
inner tube is again evacuated. The weight is largely born by the
surrounding diamond balloon, which is kept evacuated so that the weight
is reduced, while allowing diagonal struts for strength. (The balloon
wouldn't need to be weight neutral, but a skin over the struts would
need to exclude the outside air, providing a compressive force which
would tend to prevent any collapse.
I can't convince myself that this is sensible, but I can't convince
myself that it isn't. I'm clearly not a structural engineer. But it
might reduce the weight on the foundations / amount of strength. Maybe.
It does require constant pumping to maintain vacuum, so it might not be
worth it, even if it would work.
-- -- Charles Hixson Gnu software that is free, The best is yet to be.
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