Space Elevators

[PFVA63]

Hi,

Here's an interesting link to an article on a Space Elevator conference that is currently underway.

Regards

PF

http://cosmiclog.msnbc.msn.com/archive/2008/07/18/1206845.aspx?GT1=43001

 

[Magnus von Thornwood]

Awesome...

Now I can catch this year's papers and presentations...I hope. Been following the Beanstalk now for about 7 years, so am always looking for the latest and greatest.

Thanks.

 

[samuelvss]

Hi,

Space Elevator conference that is currently underway.http://cosmiclog.msnbc.msn.com/archive/2008/07/18/1206845.aspx?GT1=43001

Is there anything about orbital tethers in canon?

Whether or not, what does anyone think of the implications of the technology's use in OTU?

 

[jfetters]

Is there anything about orbital tethers in canon?

Whether or not, what does anyone think of the implications of the technology's use in OTU?

I don't think there is anything outside of 2300. But as for the OTU, I think the economics of OTU fusion technology takes beanstalks out of the equations in most circumstances. There are exceptions, of course, but considering the levels of OTU technology, I would think that they would also be a huge target.

 

[veltyen]

I don't think there is anything outside of 2300. But as for the OTU, I think the economics of OTU fusion technology takes beanstalks out of the equations in most circumstances. There are exceptions, of course, but considering the levels of OTU technology, I would think that they would also be a huge target.

Not so much fusion - Grav removes the need. Anything that is a slow safe launch nixes beanstalks being useful. Even the high atmosphere balloon launch almost gets in the way.

 

[Gallowglacht]

Is there anything about orbital tethers in canon?

Whether or not, what does anyone think of the implications of the technology's use in OTU?

There is an adventure in an old White Dwarf set on a beanstalk on earth that was mostly built when grav tech was discovered, so they finished it as a tourist attraction.
I think thats as close as it gets.

 

[samuelvss]

Not so much fusion - Grav removes the need. Anything that is a slow safe launch nixes beanstalks being useful.

A couple of thoughts. One thing that the OTU and recent technological history has shown us is that newer, clearly superior, technologies often do not cancel out the old ones, but rather just take market share. Slug throwers and energy weapons are one example from canon, and trains and trucks are one from recent history.

Another is that old infrastructure may endure, for a while, into times when it would be inefficient to build it, but less efficient to replace it; also old infrastructure may find "lower" uses when its primary use is technologically anachronistic. The Canal du Midi, and other canals come to mind.

I agree, mostly, with the statements about grav/fusion supplanting the need for beanstalks. But the basic weight and tether of a beanstalk represents quite an investment. Grav can fly stuff to orbit, and can, expensively, park it for a while below orbit. How's this for a techno-analogy: A beanstalk is to an air/raft what a freight train is to a lear jet. It's easier to operate one, and you can park it, free, anywhere along its' static (paid for) path.

One potential use: There are dangers and inefficiencies to entering a gravity well for commerce that could be conducted in orbit. If oceans of a world were the closest source of hydrogen to a high-capacity high port, then a pre-existing bean stalk might be the perfect pipeline route. Even though labor is pretty cheap in the OTU, this use would probably leverage pre-existing infrastructure.

Another potential use: A hotel that could be "parked" at the ideal atmosperic level for the weather, view, sports usages, etc.

These, I imagine at TL9 or so.

Another possible use, a pipeline down into a gas giant.

What others?

 

[epicenter00]

It's really difficult to justify space elevators vs. grav technology (though grav and fusion tech and how it's handled is one my pet peeves about Traveller OTU). I don't know if it's as much as comparing rail vs. trucks as it is comparing chipped stone knives vs. drop-forged steel.

Beyond quaintness, there'd be no good reason in Traveller to build a Space Elevator once you have the tech - and grav and miniature fusion become available extremely early in the OTU. I'd argue that the materials tech for elevators would be a TL9 or TL10 development. However, in the standard Traveller tech scale, grav tech becomes available at TL9. Using a vehicle with Grav powered by Cheap Fusion Power is better in every way - it's cheaper, more reliable, safer, faster, and more flexible. You might find weird hybrids in the OTU - like a space elevator with grav-assisted cars at early TL9 because grav tech isn't refined enough to the handwavium levels or fusion reactors are still too big so the power is piped up the elevator or down (solar).

It would be one of those stages of technological development that would be skipped by any colony. Think of many nations in the Third World that aren't bothering with wired telephone service and exchanges and all - they're just going straight from no telephone service to cellphone without the expensive and vulnerable telephone infrastructure - the benefits of that stage of technological development just don't make up for the drawbacks.

 

[samuelvss]

Using a vehicle with Grav powered by Cheap Fusion Power is better in every way - it's cheaper, more reliable, safer, faster, and more flexible.

I am skeptical.

I would agree that grav is more flexible, as a lear jet is more flexible than a train. How it is safer I fail to see. If you have power failure in an elevator, you have brakes. If you have power failure in a grav vehicle......

Arguably, the reliability of fusion power, particularly at higher tech levels, is such that that is never an issue. I believe there are enough instances of power plant failure in canon to conclude that it might (possibly) sometimes occur.

Once fusion power becomes 100.000% reliable, then one reason to build an orbital tether would cease. When does that occur?

At what TL is it possible to build an air/raft that cannot be crashed? It's pretty hard to crash an elevator. Likewise, a pipeline is a bit harder than a tanker to crash. A grav vehicle is using power whenever it is in the air. It is also using, if we accept the ideas of Book 8, a skilled operator. In order to use a freely maneuverable grav platform 24/7/365, one needs 4 operators, working roughly a 40 hour week. To operate an elevator, you need regular maintenance, which presumably every mechanical system would need.

If grav/fusion are available at TL 9, and beanstalks are, then concurrent development is conceivable.

Quaintness is likewise not to be sneezed at. Until recently, the economics of long distance passenger rail were such that it was almost always cheaper and quicker to fly on a long trip (and safer by your reckoning). Yet folks would shell out money to take the train. Indeed, some people do not like to fly.
Market share may change radically, but technologies seldom fizzle completely; extant infrastructure is used while it endures and its use and maintenance is cheaper than the capital investment needed for replacements.

It is economical to use horses for logging in a few niches. It is likewise economical to heat with wood split with an axe. My 16' dining room table, which I commissioned for $1000 about 10 years back, was built by a man with no electricity in his home or shop.

 

[Supplement Four]

Is there anything about orbital tethers in canon?

JTAS covered a world in the Solomani Rim with arcologies that reached out to orbit...I think....it's been a long time since I read it.

 

[veltyen]

At what TL is it possible to build an air/raft that cannot be crashed? It's pretty hard to crash an elevator.

Air/raft crashes. Occupants killed. Maybe someone unluckily gets landed on.

Elevator crashes. Planetary ecosphere annihilated. An elevator might be 100,000 km long, and the last stretch impacts the ground at approximately free space speeds (on earth that's between 7 and 10 km/s).

Yes. Elevators crash less often, however the risk difference is significant.

 

[samuelvss]

Elevator crashes. Planetary ecosphere annihilated. An elevator might be 100,000 km long, and the last stretch impacts the ground at approximately free space speeds (on earth that's between 7 and 10 km/s).
.

I actually had imagined the elevator as the moving part, not the stationary part. Train tracks don't crash. Trains crash.

The elevator is in fact in contact with the shaft, and has mechanical failsafes. You are talking about the tether/beanstalk itself parting, which presumably doesn't happen from loose lug nuts. There is a difference between an elevator falling (essentially doesn't happen these days) and the building falling. If there is any chance of this parting occurring absent something on the order of an astroid strike then the technology is not feasible, which indeed it may not be!

 

[Magnus von Thornwood]

Actually...

Space Elevators using tethers, as envisioned by NASA here on old Terra, won't fall, they'll launch out into space, i.e. fall up. They did some study on this, though again it depends on where the tether is severed, some will probably fall back down, but for the most part it just floats up, up and away...could be an interesting way to launch a slow ship too.

 

[far-trader]

My limited recollection of it is the beanstalk is balanced, but perhaps a safety measure would be to have some positive tug on it so that if it did separate at ground level it would go up not down.

A separation at the ground would result in it going nowhere (if it was balanced), excepting for air resistance (and I'm not sure just what that would do to it, whip it around some I'd guess (be a hazard to ground and air), air-drag (and impacts) might be enough to pull the whole thing from orbit in time).

A separation anywhere above the ground will result in the part above the break going into space (with a speed dependent on the break point and mass, and perhaps not with sufficient speed to attain escape velocity in which case it crashes later, after making life in orbit hell for months or more). The part below the break will fall to the ground trailing (I think) the rotation of the world (to the West on Earth).

Of course I could be misremembering and/or misunderstanding some of it

 

[samuelvss]

I would agree with far-trader. The really key point that veltyen makes is that if you have a break far enough up there, you've got a huge amount of kinetic energy.o:

I think it falls strait down, subject to atmospheric conditions, though. It already has the rotational inertia.

 

[far-trader]

I think it falls strait down, subject to atmospheric conditions, though. It already has the rotational inertia.

Good point, I had not considered that. I wouldn't think the air would influence it much, depending on what we're talking here (ribbon thin carbon nanotube for light lifts to heavy multi-strand cable) it could just pretty much coil up on the anchor point. The stories I can think of all iirc have it laying out though.

 

[Kaveman Koder]

"An elevator might be 100,000 km long"

That seems very long to me...

Earths atmosphere extends 800 km, around 90% of the atmosphere by weight lies in the lowest 15 km.

I guess it depends the depth of the atmosphere and other science stuff beyond me:rofl:

 

[samuelvss]

That's why Kavemen never reached escape velocity!:rofl:

To get to a geosynchronus orbit from Terra, that's 36,000 km above sea level. But, the weight needs to be a bit farther out so the climber does not pull it down.

A great little link: http://en.wikipedia.org/wiki/Space_elevator

Some wiki is crap; some is gold; some is crap with nuggets...

 

[Peter Schutze]

the bottom portion would likely settle to Earth with less force than a sheet of paper due to air resistance on the way down

the upper portion of any cable that fell to Earth would burn up in the atmosphere

these are obviously not the mega strong cables disaster stories revolve around ..... but since mars doesnt have a decent atmosphere

 

[veltyen]

the bottom portion would likely settle to Earth with less force than a sheet of paper due to air resistance on the way down

the upper portion of any cable that fell to Earth would burn up in the atmosphere

these are obviously not the mega strong cables disaster stories revolve around ..... but since mars doesnt have a decent atmosphere

Since we are talking about theoretical objects then this is conjecture anyway.

"mega strong cables" are exactly what a beanstalk/elevator would involve. They need to be stupidly strong to account for minor eddying in the cable. They also need to be quite resistant to friction heat effects (burning up on reentry) due to normal friction on the cable in normal operation.

A similar strength to a cable strung accross the pacific that had no supports except at either end. That case has almost no gravitational potential energy in comparrison though.