[LINK] Space lift to the stars is now more than a dream

[David Boxall]

On Mon, 09 Nov 2009 at 13:45:41 +1000 Lea de Groot wrote:
> ...
> Its been a while since I read up on it, but I think the elevator stops 
> at LEO - low earth orbit, and there isn't much that low; it burns up.
> Could be wrong, its been a while...
That may have been the case when the proposal was for a rigid structure. 
It was calculated that the necessary structure would weigh more than the 
whole planet. The proposal now is for a cable or belt, held taut by a 
counterweight. For that to work the counterweight must be well beyond  
geosynchronous orbit, hence the 97,000 kilometres mentioned in the article.

On Mon, 9 Nov 2009 at 15:43:38 +1100 (EST) grove at zeta.org.au wrote:
> ...
> I want to know how loud the "hum" will be from the resonating/vibrating
> cable(s).
Interesting question. The structure would be stationary relative to the 
planet's surface, but winds at altitude can reach speeds in the 
thousands of kilometres per hour, so there's considerable potential for 
vibration build-up. Current proposals mention a carbon nanotube fabric 
belt, which would tend to flutter. Interesting indeed.

The belt proposal posits an all-up weight of 300 tonnes. At one metre 
wide, that works out at around 30 grams per square metre (GSM). For 
comparison, most computer printers use 80-85 GSM paper. Any such belt 
would be very thin: practically invisible edge-on. I wonder what would 
happen to a bird that flew into that almost-invisible edge. Major paper-cut?
 
-- 
David Boxall                    |  When a distinguished but elderly
                                |  scientist states that something is
http://david.boxall.id.au       |  possible, he is almost certainly
                                |  right. When he states that
                                |  something is impossible, he is
                                |  very probably wrong.
                                                   --Arthur C. Clarke