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

[Dan Clemmensen]

Adrian Tymes wrote:

>--- Dan Clemmensen <dgc at cox.net> wrote:
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>>Eugen Leitl wrote:
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>>>On Mon, May 24, 2004 at 09:45:18PM -0700, Johnius
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>>wrote:
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>>> 
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>>>> This thread reminds me of an invention of Win
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>>Wenger's
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>>>>that uses balloons to suspend a mass-driver for
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>>cheap
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>>>>space launches.  It occurs to me that several of
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>>you might
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>>>>have some great feedback about the idea...
>>>>What do y'all think?
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>>>It sounds like a really good idea... until you do
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>>the math, and realize that
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>>>LEO energy is all not about height, but about
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>>horizontal velocity component.
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>>>And that goes with 0.5*m*v^2.
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>>>So a ramp and a maglev stage (or a hypersonic
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>>airbreathing scramjet stage)
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>>>brings you much, much closer to LEO than any
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>>stratospheric balloon.
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>>>Latter have their own uses, though.
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>>If the idea works vertically, it should also work
>>horizontally. Start 
>>with a series of
>>vertically-oriented mass driver balloons to get the
>>payload into the 
>>stratosphere at
>>low velocity,
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>
>Or...use balloons as structural supports for a long,
>lower-altitude mass driver.  You'd need a really long
>(hundreds of kilometers) mass driver to accelerate to
>orbital speeds at human-tolerable levels (less than
>10G, preferably 2G or less), and inclining that at any
>decent angle (say, 10 degrees or more) means that the
>far end of the mass driver will also have to be
>hundreds (or at least many tens) of kilometers in the
>air.  (The 100s of km is a delta altitude from the
>start, but building up a hundred kilometers from
>ground level is actually far easier with today's
>technology than building down a hundred kilometers.
>Not that either one is easy.)  Instead of building
>large towers to support the higher sections, one could
>deploy them on airships.  Straight shot, and the tube
>can be (mostly) evacuated to minimize air drag, so
>overall more efficient than up-and-over.
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>  
>
The reason I suggested a horizontal shot in the stratosphere is to 
minimize drag. I'm not sure how the math works out, but my gut feeling 
is that the extra cost of hanging it in the stratosphere (bigger 
balloons to achieve the same lift) is more than compensated by the costs 
needed to overcome air friction at lower altitudes. Furthermore, a 
tropospheric system must withstand tropospheric weather, while a 
stratospheric system is fairly immune to weather by all accounts.  
'Real-estate" costs should be free, so the length of the mass driver is 
not a consideration, The weight is, of course. Again, I have not done 
the math, but I suspect the weight scales with the total power rather 
than the length. I contemplate a system of independent balloons, each of 
which accelerates the payload toward the next. The transferred momentum 
forces each balloon out of position as the payload passes. The balloon 
then uses a solar-powered ion drive to regain its position.