Space Elevators

An lunar elevator may work or not, I don't know. But I'm
optimistic. Because it would have to be based on the tidal force
rather than a lunar-synchronous orbit, you wouldn't have the
coriolis/angular-momentum problem. The bottom of the main cable
would have to be at the nearest or farthest point from earth, unless
the base can bear a lot of tangential force -- but (and I hadn't
thought of this before googling it just now) you could have a side
cable curving off to some other location.

The only problem is damping vibrations, and with the ability to
apply a lot of excess tension I would expect that to be manageable,
even if you have recoil from an electromagnetic launch system at the
top. It could be a lot smaller than one on the lunar surface
because it wouldn't have to provide enough speed to climb the
gravity well. It could also be fairly long, supported like a
suspension bridge.

I don't know why I hadn't thought about a lunar elevator before, in
considering colony construction. It seems as though it might make
the moon a better source than asteroids for the materials it can
provide. I'm not seeing any reason to have a lunar elevator be a
couple hundred years off, if it turns out to have enough advantages
over a surface EM system to be done at all.

--- In spacesettlers@yahoogroups.com, Alexander Roderick
wrote:
>
> Space elevators are one of those projects that true believers think
> mankind's space efforts cannot even begin without. They fear, as
the Mars
> colony camp do, that any creedence given to a theory other than
theirs will
> give what little investment and research given to space
enterprizes will go
> to someone else, so they are sure to make their idea seem like the
only one
> that can work.
>
> Back in the 19th century, science fiction writers and theorists
were
> convinced practical powered flight couldn't happen without some
sort of
> anti-gravity device. We figured out how to beat it with brute
force. By
> the same token, there's no need to build an elevator to space any
more than
> there's an absolute need to build a railroad across the Pacific
Ocean (which
> in itself has some supporters, via a route across the Bering
Strait). Not
> to say it's impossible, just not truly neccessary at this stage.
If such a
> thing gets built, I see it happening as a test on a lower gravity
body
> first, like Mars or the Moon, before we risk something that
potentially
> dangerous on Earth, and it'll probably be a few hundred years into
the
> development of off-world habitation rather than at the beginning.
>
> -Al
>
> On 2/4/06, Dan Wylie-Sears wrote:
> >
> > I'm pessimistic about space elevators. I can't rule them out,
and I
> > would love it if they turned out to live up to the hopes of their
> > fans.
> >
> > But I haven't heard anything that convinces me anyone has worked
out
> > the details of, for example, vibrations in a string that long and
> > taut under realistic conditions. Then there's the question,
where
> > do you get your angular momentum? If you just lift a payload up
the
> > string, straight up, you haven't given it any angular momentum.
> > It's still only going fast enough to go around the earth's
> > circumference once per day, not fast enough to go around
> > geosynchronous orbit in the same length of time (or the
> > circumference at whatever height you've gotten it to as you've
> > lifted it partway). Or to put it another way, how do you offset
the
> > coriolis force as you lift your loads? If you're lifting mass
at a
> > constant rate, you could have the thing hanging at a slight
angle to
> > the west, so that the tension pulls it to the east. But then
your
> > base needs to be capable of resisting that tension, not floating
> > loose in the ocean as described in the linked article. And how
much
> > extra tension do you need, for how much capacity? Is that going
to
> > put you over the limit of your material strength-per-mass, for
some
> > moderate amount of payload-per-time? If your payloads don't go
up
> > completely uniformly, how does that put vibrations into the
system?
> > How much of an anchor do you need, to attach your base to the
ground?
> >
> > Space elevators may be great for Mars, though.
> >
> > By contrast, I'm optimistic about electromagnetic systems that
> > accelerate payloads at a few g though a tunnel and let them go
from