Space Elevators

>For an elevator weighing 1 tonne this is a force of 4 newtons (about
the same as the weight of 4 apples, except sideways).<

With thousands of miles of leverage, four apples' weight is a whole
lot of torque: There's no way the structure can resist the torque
of even such a trivial load by sheer stiffness; it has to behave as
a flexible string. A stretched string is going to vibrate, even if
the applied force is small, unless it has damping. What do the
dampers weigh? Where are they in the plans?

And that's four Newtons per ton being lifted -- how many thousands
of tons do you have to be lifting at a time to make the elevator
worth building? It has to have huge throughput to pay for itself,
and each payload takes a substantial length of time to climb.

I should admit that I haven't looked into elevators in much detail,
due to the scarcity of unobtanium. But maybe nanotubes will do, in
which case I'll have reason to look more closely at the rest of the
specs.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> On 04/02/06, 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?
>
> http://en.wikipedia.org/wiki/Space_elevator#Angular momentum, speed
> and cable lean
>
> Incidentally you can can calculate the Coriolis acceleration from
the
> climb speed and the angular momentum of the Earth.
>
> a = -2 w * v
>
> where w = 2PI/(24*60*60)*
> and say speed is 200km/h so: v = (200,000/3600) m/s
>
> a = 0.004 m/s^2
>
> compare this to 10 m/s^2 due to gravity.
>
> For an elevator weighing 1 tonne this is a force of 4 newtons
(about
> the same as the weight of 4 apples, except sideways). She kinna
takeit
> kaptain!
>
> > 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?
>
> See coriolis.
>
> > 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
> > a mountaintop.
> >
> > --- In spacesettlers@yahoogroups.com, "Ryan" wrote:
> > >
> > > To the many readers:
> > > Recently, i have been studying the potential possibilty of a
space
> > > elevator. I came across this article on SPACE.com:
> > >
www.space.com/businesstechnology/technology/space_elevator_020327-
> > 1.html
> > >
> > > Now what i'm looking for is, the views and opions of all of
you.
> > I'm
> > > looking to compile a report that can be sent to pro-space
lobbist
> > > groups. Later i will disclose my findings from other groups and
> > also
> > > describe the pro's and cons that many people believe.
> > >
> > > In all reality, if space travel is to become the essence of the
> > > future, we must continue to focus on the first stage. The first
> > > stage would be to solve the problem of launching tons of
equipment
> > > into space, which in turn, would be used to launch towards
other
> > > planets. Also we must focus on the funding.But if the heads of
the
> > > goverment, the goverment of many countries, do not fix their
> > > thoughts we will never escape the earths natural orbit. For
> > example,
> > > since the goverments develpment of the space shuttle, we have
not
> > > spent more than 1% of the United States budget on the NASA
space
> > > program. It is now a fact of life, that if space travel is to
> > become
> > > a common practice, an affordable program that can be used by
upper
> > > middle class, that it must switch from goverment programs, to
> > > private organzations. I have thought long and hard about a
company
> > > that one day i will create called SpaceMed. It would be a
company
> > > that focused on the enhanced abilty to create medicines in
space.
> > > The ability to create chemical bonds that are free-floating
> > without
> > > any ties to gravity. That alone would bring in millions of
dollars
> > > of research money from countries that wished to send
astronuats to
> > > space but did not have the finanical abilty to do so. Using
lunar
> > > soil and the commisioning of many companies, we could create
lunar
> > > glass. The chemicals of the glass,essential just lunar dust
that
> > has
> > > been excavated, after being melted, would be turned into glass
> > > hundreds time stronger than bullet proof glass. This is
because of
> > > the benefits of the lower gravity. In the inner rotating hubs
of
> > > station, crystals could be developed to be used in computer
> > systems.
> > > After careful but inexpensive manufactoring processess the
> > crystals
> > > could be used to create computers that were faster and more
> > powerful
> > > than ever before. All of this extra's would be fueled by the
> > > excitment of the publc. Not once in history had a private firm
> > taken
> > > such a bold chance. I can tell you, without doubt that
> > millionares,
> > > senators, and other wealthy men and women would line up for a 5
> > > million dollar, 4 night stay at the tourism center located in
the
> > > outside rotating hub. This price may seem high, but at one time
> > men
> > > payed 20 million. Every part of my program is feasible but the
> > only
> > > possible way to open the space market to everyone would be
build a
> > > space elevator. A elevator that could lift 50+ tons and a space
> > > transportation vechicle. Without a space elevator the rising
cost
> > of
> > > propellant would continue to raise the cost of space travel.
The
> > > elevator could use a system of hydro-bouys that over the
courst of
> > > one week, develped the power needed to lift a
> > shuttle/transportation
> > > vechicle into space in a week. That would put it always on a
week
> > > schudele. The passengers can then depart later on 6 days later
and
> > > use a electromaganet propelled propulsion system that can take
the
> > > passengers to space in under a day.
> > >
> > > What i've been getting at is the possiblity of the economic
stand-
> > > point of all of the space settlers goals. To get into space you
> > must
> > > first prove to the public the possibilties and the potential of
> > > space. It's the same for a basketball player or a t.v. show.
> > Before
> > > the production company will finance a movie, they poll the
public,
> > > then place advertising and see what the public's reaction is.
Then
> > > they will film and play the pilot program. The same would apply
> > for
> > > my program. I don't know if anyone is interested, but i would
> > gladly
> > > describe the methods of the transportation vechicle, with or
> > without
> > > a elevator. There are many way to do it, so not one way may be
a
> > > sure fire way to do it. Srry if there are spelling mistakes in
the
> > > post, or if it was to long. I have watched the group for 2
months