Re: space elevator

[David Henderson <orbiter@xxxxxxxxxxx>]

On Wed, 18 Dec 2002, DarkDAVE wrote:

> what about point number 5? u didnt comment on that, the idea of using mesh
> objects to act as chunks of 3d landscapes for individual sections of the
> planet sphere. Surely colision detection could be done for those objects?
> given that their smaller than the planet themselves.

I'm afriad that's not my area of expertise, so I didn't think a comment
useful.

> Regarding the space elevator, im not sure where youre coming from with your
> pesimism, are you saying it's not practical to SIMULATE it in orbiter? or
> are you saying it's not practical do implement it in real life?

Not a practical proposition in general. I've seen no realistic description
of dimensions and how you combat gravity.

> There has been extensive research done on the space elevator, and all the
> experts to my knowlege has agreed it's possible and withing man's reach.
> Only thing in dispute is the time frame to build it.

These are fantasy at best and corruption at worst. I'm not a member of the
yahoo group so those links don't work, but can you cite any credible paper
published in a peer-reviewed scientific journal?

I'll explain where I'm coming from:

In order to have a fixed point on the earth extending into oblivion, the
roational period of the far point must be 24 hours. No problem, the
adverts say, we put an asteroid in geosync. An *asteroid*?

Let's imagine, for example, the asteroid is indeed in geosync. We then
attach a (very heavy) cable to it. That cable isn't in geosync, so it
exerts a drag force on both the earth, and your asteroid. Most likely
result: broken cable, other likely result: asteroid now in decaying orbit.

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.

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.

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.

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

-- 
yours etc.                                             [gin.aibs.org.uk]
                                               Mobile:      07960 217459 
David.                             Work (Direct/Vmail): 020 8898 6565x38
d.henderson.96@cantab.net          Work (Main):            020 8893 3884




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