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

[deimtee]

spike wrote:

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>>-----Original Message-----
>>From: extropy-chat-bounces at lists.extropy.org 
>>[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of 
>>Rafal Smigrodzki
>>Sent: Tuesday, June 09, 2009 10:51 PM
>>To: ExI chat list
>>Subject: Re: [ExI] Inflatable tower could climb to the edge of space
>>
>>I would think the main advantage of a big tower would be the 
>>option of installing a linear motor launcher inside.
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>>Rafal
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>Ja, actually I was thinking along the side.  spike
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If it supported itself though lifting gasses rather than inflated 
pressure, you could
have a low stress structure.
I would think a long tethered sectioned  tube, rising at an angle of 15 
to 20 degrees, of sufficient
diameter that you can sling a linear motor  underneath and still have 
sufficient tension
on the tether cables to keep everything straight.  
This should give you over 100 km of  accelerator length.   If you pull 5 
gees for that
long you should be up around 3 to 4 km/sec.
I haven't  done the math for it but I think that would be enough for 
Keith's pop-up-and-push
launches.  Certainly it would get you high enough to use a small 
efficient motor to circularize
the orbit.
Given the height and volume I think you would need to use hydrogen as 
the lifting gas.

If you started on top of a fairly high mountain you could drop the angle 
of climb, make the tube
much longer and have a higher exit velocity, while still keeping most of 
the travel up in the rarified air.

Spike, regarding your idea of pressurizing to 20 times atmospheric in a 
vertical tube, air has a mass
of ~1kg/m3 at  STP.  The mass of your column of gas is going to be (very 
roughly) 75 million tonnes,
with a footprint of over 100 tonne/m2. 
I don't want to be near that balloon if it bursts.  :)

-David