Space Elevator?

What the heck is a "space elevator"?

In the UPI new release about Pres. Bush's bold new space initiative, it said
that the committee which layed out his new policy investigated everything
from snip to space elevators to snip, more stuff.


JD

"Joe Delphi" wrote in
ink.net:

What the heck is a "space elevator"?

Did you think of Googling first? There really is a lot of information on
this topic available on the web.

In the UPI new release about Pres. Bush's bold new space initiative,
it said that the committee which layed out his new policy investigated
everything from snip to space elevators to snip, more stuff.

It's a cable in geostationary orbit, extended down to the surface of the
Earth. The other end of the cable is either extended upward, or a
counterweight put at the end, such that the center of mass of the cable is
above geostationary orbit. This keeps the cable in tension.

This allows spacecraft to "climb" into orbit without using rockets. The
materials engineering challenges are immense, however.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

Well, I learn something new everyday. I am a technical person although I
don't work in the aerospace industry and, at first, I thought this was a
joke, I didn't know that people were seriously studying it.

I can imagine how it might work up to geo-sync orbit, but the website said
that people are also investigating how it can be used to lift payolads to
the moon and other planets - not sure how that would work.

JD



Jorge R. Frank wrote in message
...
"Joe Delphi" wrote in
ink.net:

What the heck is a "space elevator"?

Did you think of Googling first? There really is a lot of information on
this topic available on the web.

"Joe Delphi" wrote in
ink.net:

Well, I learn something new everyday. I am a technical person
although I don't work in the aerospace industry and, at first, I
thought this was a joke, I didn't know that people were seriously
studying it.

Not surprising; many people still consider it a joke. One of the biggest
obstacles is that no existing material is strong enough to construct one.
But a lot of folks have stopped laughing since the discovery of carbon
nanotubes, which shows some promise *if* it can be fabricated economically
in the quantities required, and can be integrated into a composite material
without losing too much of its theoretical strength. Another obstacle is
that the elevator would become a navigation hazard for low-orbiting
spacecraft, and may need the capability to "dodge" detectable space debris,
plus shielding to protect against undetectable space debris. This is
solvable, but far from trivial.

British SF author Arthur C. Clarke is a leading advocate of space
elevators. When asked when one might actually be built, he replied, "about
ten years after everyone stops laughing." Other sources give a different
number of years; they are probably all accurate quotes, given Clarke's
propensity for embellishing his own quotes as he ages.

I can imagine how it might work up to geo-sync orbit, but the website
said that people are also investigating how it can be used to lift
payolads to the moon and other planets - not sure how that would work.

A space elevator in geostationary orbit (GSO), by definition, rotates at an
angular velocity equal to that required by a spacecraft in GSO. Angular
velocity for a circular orbit decreases with altitude. So if a spacecraft
climbing a space elevator "jumps off" at an altitude below GSO, it will be
travelling too slow to remain at the jump-off altitude, and will wind up in
an elliptical orbit with apogee equal to the jump-off altitude, and a lower
perigee altitude (possibly lower than the surface of the earth, if it
doesn't climb high enough...).

On the other hand, if the space elevator extends significantly above GSO,
the spacecraft could continue to climb above GSO. If the spacecraft jumps
off above GSO, it will be travelling too fast to remain at the jump-off
altitude, and will wind up in an orbit with perigee at the jump-off point,
and a higher apogee altitude. If the jump-off altitude is high enough, the
spacecraft will be travelling faster than Earth escape velocity. Careful
choice of jump-off altitude and timing will result in a translunar or
interplanetary trajectory, though small propulsive corrections may still be
required afterward.

--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

In article ,
says...
"Joe Delphi" wrote in
ink.net:

Well, I learn something new everyday. I am a technical person
although I don't work in the aerospace industry and, at first, I
thought this was a joke, I didn't know that people were seriously
studying it.

Not surprising; many people still consider it a joke. One of the biggest
obstacles is that no existing material is strong enough to construct one.
But a lot of folks have stopped laughing since the discovery of carbon
nanotubes, which shows some promise *if* it can be fabricated economically
in the quantities required, and can be integrated into a composite material
without losing too much of its theoretical strength. Another obstacle is
that the elevator would become a navigation hazard for low-orbiting
spacecraft, and may need the capability to "dodge" detectable space debris,
plus shielding to protect against undetectable space debris. This is
solvable, but far from trivial.

British SF author Arthur C. Clarke is a leading advocate of space
elevators. When asked when one might actually be built, he replied, "about
ten years after everyone stops laughing." Other sources give a different
number of years; they are probably all accurate quotes, given Clarke's
propensity for embellishing his own quotes as he ages.

And Clarke is often an "eternal optimist."

For another view of space elevators, it's worth reading Kim Stanley
Robinson's "Red Mars." Not to give away too much of the plot, a space
elevator is not invulnerable, and the risks and costs of a structural
failure are worth considering.

Diane

"Diane Wilson" wrote in message
k.net...

much snipped

And Clarke is often an "eternal optimist."

For another view of space elevators, it's worth reading Kim Stanley
Robinson's "Red Mars." Not to give away too much of the plot, a space
elevator is not invulnerable, and the risks and costs of a structural
failure are worth considering.

And while KSR's elevator scene makes great imagery it has absolutely no
attachment in actual reality. Maybe at the time of the writing or in the
seventies when elevator cables needed to mega-giga-ton objects. But this is
the 21st century now and we have ideas about how to build real elevator
cables.

Nowadays elevator cables would be as dangerous as ticker-tape parades.

People, please do some research on the matter before making uninformed
comments in public.

http://www.liftport.com/pages/index....4a6d1c7628e060

http://www.isr.us/SEScienceFAQs.asp#2

http://www.isr.us/SEBEPFAQs.asp#4

Diane

Regards
Frank Scrooby
(who was awestruck by KSR's descriptions at least the first dozen times
round.)

"Joe Delphi" wrote in message link.net...
What the heck is a "space elevator"?

In the UPI new release about Pres. Bush's bold new space initiative, it said
that the committee which layed out his new policy investigated everything
from snip to space elevators to snip, more stuff.


JD

Stand on the equator. Look up. Your friend on a satellite at GEO
tosses a rope overboard. Once it hits the ground you swarm up it like
a monkey. Or if you're not into the week long climb, attach an
elevator car which will mechanically climb for you. Not as quick as a
rocket, but not as expensive either.

You can counterbalance the cable by attaching a large mass at GEO, or
by sticking a long bit of cable out past GEO. Climbers can zip out to
the end, and by judicious aiming, be flung into interplanetary space.

That is, of course, simplyfying greatly. But you you get the idea.

some links

Liftport - raising private venture money to build one
http://www.liftport.com/

Lif****ch
http://lif****ch.org/tiki-view_articles.php

Discussion Group


ISR - Think Tank working with NASA
http://www.isr.us/SEHome.asp