Re: space elevator

["DarkDAVE" <darkdave3000@xxxxxxxxxxx>]

> roational period of the far point must be 24 hours. No problem, the
> adverts say, we put an asteroid in geosync. An *asteroid*?

incorrect, not in Geo sync, but 100,000kms, which is over 3 times the
distance of geosync, perhaps you were reading from a amateur journalist, but
the professional papers say 100,000 kms. And it doesnt have to be an
asteroid, could be a space station, the centrifugal force there would create
artifical gravity and allow slingshots to other planets.

Also you dont need a yahoo id to access the space elevator yahoogroups, it's
on public access mode. The links that werent working were these ones because
of word wrap, just select the entire link and paste them in your browser
address box.

http://www.space.com/businesstechnology/technology/space_elevator_021120.htm
l
http://www.space.com/businesstechnology/technology/space_elevator_001226.htm
l

> No problem they say, we'll keep the cable permanently in tension by
> cunningly moving the asteroid out and using the cable to accelerate it
> inwards at the required rate. Now you're proposing to accelerate an
> asteroid at, say, one metre per second ad infinitum. What happens when
> there's a break? Oops, lost the asteroid.

If you do research on the actual cable being proposed you wouldnt say that.
It is carbon nanotubes, like diamond it is made of carbon atoms and like
diamond it is very tense and very light per unit length. Also robot prowlers
will be continuosly sent up the cable to re-enforced and repair it with
additional ribbons of carbon nano tubes.

> Next problem: what good does this geosync rope do you? Can you climb up it
> as they say? No. Of course not. You're exterting that force on the anchor
> at the far end. That anchor now can no longer be an asteroid, it must be a
> rocket that pulls back at the same force you extert. Energy saving over
> putting the satellite on a rocket: nil.

I assumed there would be thrusters on the anchor, however i was told this is
not even needed, something about the anchor stealing momentum from the earth
which becomes negligable, ask the space elevator guys at yahoogroups, once
again, its public.

> What about low earth orbit? You can't just jump off at 200km, as you'll
> fall straight back down. You need to achieve orbital velocity. What's the
> proportion of a rocket that lifts the satellite to 200km relative to the
> proportion that accelerates it to orbital velocity at 200km? Plus this
> cannot be done instantaneously, so you're still carrying fuel for lift
> work as well.

The elevator would be designed more for slingshotting payloads to other
planets rather than Low Earth Orbit destinations, ofcoarse geo sync orbital
destinations would be very easy to achieve also.
However if one wanted to put the payload in Low Earth Orbit, they could
carry enough fuel just to get the payload to the correct orbital velocity
(horizontally) and drop out of the elevator slightly higher than the
destined height, as the payload drops, the thrusters can take it to the
required speeds.

> All things considered, I just don't see how it can possibly work.

Join the space elevator group and ask those questions again, just copy
paste, and you will get volumes of prepared answers and links. Do this if
you are truely keen to find the truth about this ofcoarse :)

You have to read the profesional journals, not just the journalist websites,
they contain errors.

David

-- 
Orbiter discussion list:
- mail orbiter-request@firedrake.org with subject "unsubscribe" to leave
  or ask the listmaster (@firedrake.org)
- archives at http://lists.firedrake.org/orbiter/