Lunar elevators

On Wed, 24 Nov 2004 02:52:01 -0000, victoriatangoman
wrote:
> --- In spacesettlers@yahoogroups.com, Ian Woollard
> wrote:
> > Hmm. Lunar Elevators:
>
> > http://www.universetoday.com/am/publish/lunar_space_elevator.html
>
> > Seems to be easier to install than a mass driver. You build it on the
> > earth and it deploys down from L1. A few hundred tonnes a year
> > capacity, and easy to expand up. Solar powered; maybe even gravity
> > powered! (with some work, picking a rock off the moon and dumping it
> > into Earth orbit can liberate energy).
>
> I'm sold but with some mnor variations. I think the case for a
> rotating lunavator is a tad more compelling.

Maybe, although there are complications with a lunar rotovator that
aren't present with a beanstalk to the same degree or at all. For
example, a rotovator stretches every time it goes down to the surface
which can make for a wild ride, it's highly orbitally unstable
("MASCONS"), and you probably need to expend propellent just to keep
it going.

Beanstalks are probably safer. There are concerns with micrometeorites
cutting it, but hoytether concepts probably help with that. And
beanstalks are nearer the state of the art.

> Touchdown along 3-7 lunar
> equator locations. Lunar orbital stabilizing mechanisms. Less Mass.

Actually, I think it may be more mass; this guy is suggesting a lunar
beanstalk weighs in at under 7 tonnes.

> Less length.
> http://www.tethers.com/papers/CislunarAIAAPaper.pdf
>
> But if for some reason those reasons are not compelling enough then a
> stationary model is still better than the rocketry approach. Don't
> forget the Hans Moravec version as well.
>
> Recall my post 2 years ago, "Boostrapping in 60 Easy Steps" was
> heavily reliant on a 3 stage rotating tether system.
>
> I think that one can make a strong case, in terms of mass payback,
> that landing material on the moon via lunavator is more efficient than
> using rockets. Even taking an equal amount of mass off of the moon
> seems trivial, but beyond these limits I think your reference to the
> lunavator becoming a mass driver replacement starts to walk on thin
> ice because of the volume limitations.

No, not really. The elevator can be as heavy/thick/capable as you
want. They're suggesting ratios of >30:1 launched mass:beanstalk mass
per year. That's thousands of tonnes if you want it, or more

> The mass driver is designed to
> move a lot of volume and doesn't need to be stabilized with
> countervailing mass shipments.

A beanstalk doesn't need that either.

> Lunavator = getting bases set up, delivering equipment, delivering
> staff and supplies.
>
> Mass Driver = getting tonnes of material into orbit

Mass Driver == complicated, dangerous, expensive, one way, *small* payloads
Beanstalk == cheap, passive, bidirectional, *big payloads*

But the world isn't necessarily either-or. A beanstalk might be a good
way to lower mass driver components to the moon for example. It
enables mass drivers if they turn out to be a good idea.

> TangoMan

--
-Ian Woollard

"In theory there is no difference between theory and practice, but in
practice there is."
"a society in which people can do and say what they want will also
tend to be one in which the most efficient solutions win" - Paul
Graham