Space pier

Prompted by a posting by Bill Haught, I looked up space piers.

http://www.wisegeek.com/what-is-a-space-pier.htm

It seems to me that it's all very well talking about having a linear
accelarator on top of a 100km tower, but what kind of bending load does
this involve?

The base of the tower has to resist the entire torque. Even if the tower
could be made strong enough, what about the ground to which it's attached?

Sylvia.

This is getting rapidly over my head, but I think I sort of have an idea of
what you are refering to.

The pier curves with the Earth so that the track is always 100 km high.
Except perhaps if one wishes to start lower than 100 km and eject at
super-orbital velocity. Then the curvature of the track should match the
projectile's tendency to fly out.

When you get to high speeds the projectile/craft is lighter.

The towers would have to be built with light and strong materials. I
suppose maybe with a truss system you can do 70,000 ft with steel. I am
inclined to think it can be attached to ground in a way that will allow
ground to handle it.

In short, I'm inclined to think that outside of earthquakes and *maybe* high
winds that there shouldn't be a problem. I would think that if a jet or
tornado takes the whole thing down construction wasn't robust enough.

Comments from engineers?


"Sylvia Else" wrote in message
...
Prompted by a posting by Bill Haught, I looked up space piers.

http://www.wisegeek.com/what-is-a-space-pier.htm

It seems to me that it's all very well talking about having a linear
accelarator on top of a 100km tower, but what kind of bending load does
this involve?

The base of the tower has to resist the entire torque. Even if the tower
could be made strong enough, what about the ground to which it's attached?

Sylvia.

Sylvia Else wrote:
Prompted by a posting by Bill Haught, I looked up space piers.

http://www.wisegeek.com/what-is-a-space-pier.htm

It seems to me that it's all very well talking about having a linear
accelarator on top of a 100km tower, but what kind of bending load does
this involve?

The base of the tower has to resist the entire torque. Even if the tower
could be made strong enough, what about the ground to which it's attached?

Sylvia.

Look at the details. The thing would be a lot longer than it is tall
(more of an elevated track than a tower), several orders of magnitude
heavier than anything it throws, and made of diamond by using
(furiously-handwaved) molecular manufacturing processes. Torque is the
least of the problems. The biggest problem is that you couldn't point
it in any direction you wanted. This would limit its applicability to
the all-important problem of how to quickly deliver pizzas to any point
on Earth from a central location, and thus make it far more difficult
to line up the needed capital investment.

-michael turner
www.transcendentalbloviation.blogspot.com

"Michael Turner" wrote in message
ups.com...


Look at the details. The thing would be a lot longer than it is tall
(more of an elevated track than a tower), several orders of magnitude
heavier than anything it throws, and made of diamond by using
(furiously-handwaved) molecular manufacturing processes.

I do wonder why Josh only mentions diamond. I would think carbon fiber /
epoxy ought to do even for 100 km. towers. Ping engineers -- comments?


Torque is the
least of the problems. The biggest problem is that you couldn't point
it in any direction you wanted. This would limit its applicability to
the all-important problem of how to quickly deliver pizzas to any point
on Earth from a central location, and thus make it far more difficult
to line up the needed capital investment.


Or just put things in orbit so they are half way to anywhere in the universe
energy-wise. You can deliver pizzas if you wish.

Michael Turner wrote:

Sylvia Else wrote:

Prompted by a posting by Bill Haught, I looked up space piers.

http://www.wisegeek.com/what-is-a-space-pier.htm

It seems to me that it's all very well talking about having a linear
accelarator on top of a 100km tower, but what kind of bending load does
this involve?

The base of the tower has to resist the entire torque. Even if the tower
could be made strong enough, what about the ground to which it's attached?

Sylvia.


Look at the details. The thing would be a lot longer than it is tall
(more of an elevated track than a tower), several orders of magnitude
heavier than anything it throws, and made of diamond by using
(furiously-handwaved) molecular manufacturing processes. Torque is the
least of the problems. The biggest problem is that you couldn't point
it in any direction you wanted. This would limit its applicability to
the all-important problem of how to quickly deliver pizzas to any point
on Earth from a central location, and thus make it far more difficult
to line up the needed capital investment.

It talks about going up one of the towers. To my mind it would need a
lot of cross bracing, to the point that it looked more like a trestle
bridge.

http://en.wikipedia.org/wiki/Trestle

Sylvia.

In article ,
Sylvia Else wrote:

Prompted by a posting by Bill Haught, I looked up space piers.

http://www.wisegeek.com/what-is-a-space-pier.htm

It seems to me that it's all very well talking about having a linear
accelarator on top of a 100km tower, but what kind of bending load does
this involve?

The base of the tower has to resist the entire torque. Even if the tower
could be made strong enough, what about the ground to which it's attached?

You seem to be imagining a single tower. It's not; it's a whole series
of them, like a pier.

I agree, though, that you'd need both a large number of them to span 300
km, and a large mass of support struts or (more likely) cables in
between each pair of towers.

Sylvia Else wrote:
Prompted by a posting by Bill Haught, I looked up space piers.

http://www.wisegeek.com/what-is-a-space-pier.htm

It seems to me that it's all very well talking about having a linear
accelarator on top of a 100km tower, but what kind of bending load does
this involve?

The base of the tower has to resist the entire torque. Even if the tower
could be made strong enough, what about the ground to which it's attached?

The article cited does mention that, like a "space elevator", it would
require futuristic materials.

I do remember reading in a book discussing the V-2 rocket there was a
claim that the atmosphere became thin enough at 25 miles to permit
rockets to level off in their flight, instead of flying straight up to
avoid air resistance.

Thus, it seems to me that one could think in terms of an accelerator
with an exit point that was 40 km high instead of 100 km high.

Also, why have an elevator lifting things up to the 100 km level, and
then use the accelerator only to gain velocity? Why not simply tilt the
accelerator?

Still, though, while I think things can be made "easier" in one way,
another number given there gives me pause. I think that 10g is a bit
too much of an acceleration, since even conventional rockets to space,
such as the Space Shuttle, have dispensed with such high accelerations.
If 10g requires a 300 km long accelerator to reach a useful velocity,
at half the acceleration, it takes twice the time to reach the same
velocity, and the average speed is the same, so the length also
doubles.

So my idea of a cheap way into space that falls short of a space
elevator would be a giant ramp, perhaps 200 miles long, at its far end
25 miles high. Perhaps it could be built as an earthwork, using a very
gentle slope, and a dendritic network of buttresses? Or would even
solid granite flow like liquid when trying to create something so high?

John Savard

In article .com,
wrote:

Also, why have an elevator lifting things up to the 100 km level, and
then use the accelerator only to gain velocity? Why not simply tilt the
accelerator?

I imagine because otherwise, you're plowing through large masses of air
within the accelerator, with all the problems that causes. Unless of
course you evacuate the tube, but that's nontrivial.

However, just because you want something high and stationary in the
atmosphere doesn't mean you have to support it on huge towers. Why not
float it from huge balloons instead? Might as well make this mess of
air we're in work for us.

Still, though, while I think things can be made "easier" in one way,
another number given there gives me pause. I think that 10g is a bit
too much of an acceleration, since even conventional rockets to space,
such as the Space Shuttle, have dispensed with such high accelerations.

I think the first use for any such catapult system is going to be for
bulk cargo, not people. That means we can make it much shorter, and
also reduces the safety concerns, all of which translates to a cheaper
device. And we can still put it to a LOT of good use hefting things
like water into orbit. (Or properly-packaged solar cells, perhaps, if
we want to start our SSP economy with materials launched from Earth.)

So my idea of a cheap way into space that falls short of a space
elevator would be a giant ramp, perhaps 200 miles long, at its far end
25 miles high. Perhaps it could be built as an earthwork, using a very
gentle slope, and a dendritic network of buttresses? Or would even
solid granite flow like liquid when trying to create something so high?

I don't know, but it sounds like a truly gargantuan project. You're
talking about building a mountain three times taller than Everest.

Holding up a launcher from balloons would take a lot of very tall
balloons, but it still sounds a lot easier to me than building a
mountain that big.

Best,
- Joe

I covered this in one of my previous posts. The corrected version is
he

http://groups.google.com/group/sci.s...a8361600615baf
or
om


Joe Strout wrote:
In article .com,
wrote:

Also, why have an elevator lifting things up to the 100 km level, and
then use the accelerator only to gain velocity? Why not simply tilt the
accelerator?

I imagine because otherwise, you're plowing through large masses of air
within the accelerator, with all the problems that causes. Unless of
course you evacuate the tube, but that's nontrivial.

However, just because you want something high and stationary in the
atmosphere doesn't mean you have to support it on huge towers. Why not
float it from huge balloons instead? Might as well make this mess of
air we're in work for us.
- Joe

In article . com,
"Bill Haught" wrote:

I covered this in one of my previous posts. The corrected version is
he

http://groups.google.com/group/sci.s...d/1d0c34b5a390
f3a8/4ca8361600615baf?hl=en#4ca8361600615baf

Not as far as I can tell. Please quote the part that explains why
towers are preferable to balloon support.