Space Elevator | Eclipse Phase

Thu, 2010-07-08 09:21

#2

nezumi.hebereke nezumi.hebereke's picture

Re: Space Elevator

Imagine it like this. There's a 100 pound rock on the ground. You have to lift up the rock and put it on the top shelf. So you put your legs underneath and *hoooist* it up, sweating and heaving, and tuck it in where it belongs. Now there's another rock. You do it again. Each time you're exerting a lot of energy lifting that darn thing up, and fighting against gravity. Now imagine we attach a pulley to your ceiling. Through that pulley we run a rope, with a bucket on each end. Now put your rock up. The first rock, you can either hoist it up like before, OR you can put it in the bucket and pull on the other side to bring it up (which might be easier), so there's a win there. You get your rock up to the bookshelf. Now you need to put your second rock up. So you put that rock in the bucket on the ground. Going up to the bookshelf, you realize you have 100 pounds of old D&D stuff you need to burn anyway, so you put that in the bucket now by the ceiling. 100 lbs countered by 100 lbs is round about 0 lbs (plus friction, of course). So when you lift the giant rock, you aren't hoisting 100lbs, you're lifting what feels like maybe 10lbs. That's a lot easier! Third rock comes up, you toss in 40 lbs of your wife's stuff. She doesn't need it. The rock is still only 60 lbs, as far as you're concerned. Easy! A space elevator works on the same basic concept. On Earth, you load up rocket fuel, water, food, finished goods, etc. On the space side, you put in zero-g manufactured goods, mined products, maybe some space garbage, or just rocks for ballast. Now, instead of sending up a rocket which is 90% fuel and 10% what you actually need (VERY pricey), you are sending up a space bucket which is maybe 30% 'fuel' and infrastructure, and 70% what you actually need. That adds up. A space elevator is unlikely to connect to the Moon. It'll connect to an orbital station. Ships can dock at the station and unload goods from other planets or space, and load up on goods from Earth or Mars. Since most space ships can't enter gravity, this saves them from having to have a shuttle. A space elevator also reduces construction costs. Again, stuff made to work only in zero-g is a lot cheaper to make, but stuff made on Earth will necessarily be made to survive 1g (or more, to manage escape velocities). Ship the pieces up into space, you can assemble them easily in space. Also do note that the top of the space elevator is held aloft because of the rotational speed of the planet. Ever pick up your kid by the ears and spin as fast as you can? What happens? The kid's feet rise off the ground and stay about even with his ears. That's because he's directly perpendicular to your axis of rotation. If you tried to hold the kid straight above you, spinning wouldn't keep him aloft - he'd just fall on your head. So any space elevators need to be close to the equator of the planet. Ideally, it's also a place where, if it crashes, it won't smash anything important.

Thu, 2010-07-08 11:17

#3

Eskapist

Re: Space Elevator

Oh, this was really helpful! Thanx a lot. I hope they will describe the mars elevater in more detail in sunward. Can't wait...

Thu, 2010-07-08 15:18

#4

cenrae

Re: Space Elevator

Heres some good links about space elevators the first has a cool video. http://www.spaceelevator.com/ http://en.wikipedia.org/wiki/Space_elevator

Fri, 2012-10-26 16:39

#5

LeZero

How high?

I'm reanimating this topic, Does someone know how high is the station at the end of the Earth's elevator? Is it into the barrier zone?

Fri, 2012-10-26 17:08

#6

CodeBreaker CodeBreaker's picture

I am not a scientist. Take

I am not a scientist. Take this at face value. The Space Elevators station end must be outside of the interdiction zone, at least by my understanding of the physics used. The anchor point of an Earth elevator must be, at minimum, beyond geostationary orbit. As far as I am aware the elevators in EP, at least those around Earth, use their terminal station as their anchor point. That means that the terminal station must be at or beyond 35,800km. According to Sunward the interdiction zone is focused on LEO, specifically between 300 and 350km. There are also hunter-killer drones between 400 and 2,000km. So as far as I am aware people should potentially be able to fly right on up to the elevator and hitch a ride down with some ease. However I doubt the space around the elevator terminal is left open. Lots of sensors pointed that way. Edit: Page 175 of Sunward. "As mentioned in Lack, the fiction piece at the beginning of the EP core rulebook, one of the space elevators on Earth remains intact. Though it is largely believed to be nonfunctional, this is a ruse. It is in fact deactivated, but a dedicated team with the proper planning and know-how could theoretically reactivate the climber shuttle cars. The spaceport station at the elevator’s terminus is well-guarded, and the elevator itself is actively protected from debris, presumably by the Planetary Consortium or whatever entity is keeping the elevator in repair. [b]The spaceport itself is far above the orbital altitude of the defensive cordon.[/b]"

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Fri, 2012-10-26 17:11

#7

LeZero

Thank you for your answer.

Thank you for your answer. I think about making my campaign starting on Earth, and the players would have to escape from Earth. I'm exploring all the options which could occur to the PC, so I would assume they could use the elevator to go away.

Mon, 2012-10-29 01:36

#8

RustedPantheress RustedPantheress's picture

One issue: The killsats are

One issue: The killsats are watching, and motion up or down the elevator is easy to see (unless the entire structure is enclosed). And the Consortium has a vested interest in making sure that no survivor (or anybody that knows of survivors) gets off the planet. Because can you imagine what would happen if the public knew that there were survivors down there?

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Mon, 2012-10-29 04:39

#9

Smokeskin

CodeBreaker wrote:

CodeBreaker wrote:
The Space Elevators station end must be outside of the interdiction zone, at least by my understanding of the physics used. The anchor point of an Earth elevator must be, at minimum, beyond geostationary orbit. That means that the terminal station must be at or beyond 35,800km.

I don't know if that is what you mean by anchor point, but the center of mass of the entire system - cable, counterweight, elevator, payload - must be outside of geostationary orbit. I can't remember if the EP terminal station is at the end of the cable, but it doesn't have to be.

Mon, 2012-10-29 10:05

#10

RustedPantheress RustedPantheress's picture

It is, there's no point at

It is, there's no point at having an elevator cable that continues past the station. Waste of resources. So station=anchor point.

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Somebody is using bad science! Snark, facts, snark. Your body is corrupted: Cool, do more science to it. Your mind is warped: That's nice, want a cookie? What do we say to the God of Death? Not today!

Mon, 2012-10-29 14:28

#11

Arenamontanus Arenamontanus's picture

Actually, having a longer

Actually, having a longer elevator is useful. It allows you to launch things cheaply into higher orbits by dropping them off. If I remember the calculations right the benefit is measurable, but not enough to motivate a super-long extension. So it is likely that there is extra cable running a bit higher with an end-launch station.

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Mon, 2012-10-29 17:24

#12

OneTrikPony OneTrikPony's picture

The anchor point has to be

The anchor point has to be beyond geosyncronous orbit. The reason for this is that the whole cable orbits at the geosync period. all of the cable up to 35000km is orbiting at a speed [u]slower[/u] than a circular orbit for that altitude. Every meter of cable has an angular momentum that is less than the force of gravity acting on it. This means that all of the cable up to the geosynchronous station wants to fall out of the sky. That is the reason that an anchor is needed. It counter balances all of the cable below it, keeping things tight. The picture on the wiki page below will explane it better at a glance. http://en.wikipedia.org/wiki/Space_elevator [edit] Forgot to add that the station will be at geosynch because it needs to rendevous with ships that are also in geosynch orbit. If it's not, ships trying to dock will have to burn propl to catch up or slow down. this is also the reason that the lunar elevator runs on a track all the way around the moon. [/edit]

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Mon, 2012-10-29 21:09

#13

NewtonPulsifer NewtonPulsifer's picture

Warning: Switch of topic to

Warning: Switch of topic to terraforming That's a good tidbit about Luna's "tracked" space elevator that I had missed. You could use that track as an artificial planetary magnetic field. Mars only has twice the circumference of Luna , so building an artificial planetary magnetic field would be feasible by Luna's standard. Perhaps use a maglev train route?

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Mon, 2012-10-29 21:34

#14

Arenamontanus Arenamontanus's picture

NewtonPulsifer wrote:That's a

NewtonPulsifer wrote:
That's a good tidbit about Luna's "tracked" space elevator that I had missed. You could use that track as an artificial planetary magnetic field.

How? By running a current through it? A quick check with the formula for magnetic fields in current loops http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html suggests that we need 100 million Amperes to get an earth-like magnetic field. I don't think it is worth it - magnetic fields are overrated as radiation protection.

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Mon, 2012-10-29 22:14

#15

Quincey Forder Quincey Forder's picture

on elevators and planetary radiation shielding

I think that the elevator is closed, and the climber trains move up and down on track inside the tube, which I'd say is either transparents (diamond-like composites) or reflects the exterior through AR display The best examples of orbital lift, for me can be found in Gundam 00 and Zone of the Enders: Dolores, I. I believe both are aviable in DVD, on huluplus or Netflix. Another one is briefly shown in Kurau The Phantom Memory. By the way...how long is the trip surface-orbit, in EP? I remember that in Gundam 00, it took hours, long enough for Hallelujah Haptism to take a nap in his cabin. A good look for the climber train would be the Fall from Total Recall 2012. that stuff is like a 20 stories building going up and down You could very well redo a space version of the Orient Express Murder aboard an orbital elevator. A murder is commited and the stack of the victim is missing. Once the train reach Olympos or Prospect, the culprit could simply vanish. tick-tock, tick-tock... my question, on the radiation shileding is, if magnetic fields are overrated, what would be a viable solution for Mars?

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Mon, 2012-10-29 22:55

#16

NewtonPulsifer NewtonPulsifer's picture

100 million amps? Very do-able

Arenamontanus wrote:
How? By running a current through it? A quick check with the formula for magnetic fields in current loops http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html suggests that we need 100 million Amperes to get an earth-like magnetic field. I don't think it is worth it - magnetic fields are overrated as radiation protection.

Current "cheap" superconductor wire has a current density of 20kA/cm^2 (42kA/cm^2 for tape) So a 100 million amp cable is do-able with technology purchaseable today. In the lab they've already done 60 Million Amps per square centimeter using a nano-mesh. http://pubs.acs.org/doi/abs/10.1021/nl102584j Georgia Tech has achieved 100 million amps per cm^2 with graphene interconnects (not superconducting though). http://nextbigfuture.com/2009/08/graphene-has-current-carrying.html I don't see 100 million amps being a big deal with EP tech. EDIT: I should be clear the graphene is a short range interconnect, but it does show the possibilities.

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Tue, 2012-10-30 02:10

#17

OneTrikPony OneTrikPony's picture

I don't see this being a big

I don't see this being a big enough issue on Mars to bother uniting the Tharsis League and all the city states long enough to get it done. Might be a good idea for the inner Jovian moons tho. That is, if it's possible. Which cheep "superconductor" wire is currently carrying 20kA? And is it super conductor or semi-conductor? Sweet Links btw, Thanks

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Tue, 2012-10-30 02:43

#18

NewtonPulsifer NewtonPulsifer's picture

Magnesium diboride is the

Magnesium diboride is the cheapest superconductor out right now that I'm aware of. http://cmp.physics.iastate.edu/canfield/pub/pw0201.pdf Boron and Magnesium are both relatively cheap.

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Tue, 2012-10-30 07:22

#19

Arenamontanus Arenamontanus's picture

Remember that you need to

Remember that you need to cool that loop - even with room temperature superconductors the dayside of the moon is likely above the breakdown temperature (and when a big superconductor cable quenches things get *fun* - those amperes suddenly turn into heat). Doing something like this on Mars is harder, since you would need to cross the Quarantine Zone and geologically active environments (terraforming causes aquifer landslides). Plus, there is a lot of unoxidized iron dust in the environment. That cable is going to attract it like a magnet. It might be simpler to just coil a smaller circle around settlements.

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Tue, 2012-10-30 15:02

#20

NewtonPulsifer NewtonPulsifer's picture

Arenamontanus wrote:Remember

Arenamontanus wrote:
Remember that you need to cool that loop - even with room temperature superconductors the dayside of the moon is likely above the breakdown temperature (and when a big superconductor cable quenches things get *fun* - those amperes suddenly turn into heat). Doing something like this on Mars is harder, since you would need to cross the Quarantine Zone and geologically active environments (terraforming causes aquifer landslides). Plus, there is a lot of unoxidized iron dust in the environment. That cable is going to attract it like a magnet. It might be simpler to just coil a smaller circle around settlements.

Dayside of the moon isn't that hot; 100C, right? Just putting it in the shade of the skyhook rail would be enough. However, there is always covering it in something insulating (aerogel jacket) or highly heat conducting (carbon nanotubes). If it quenches and automatic failsafes don't dump the current in time, so what? Let it cool off and start it up again. It's not a huge deal if the artificial magnetosphere only has say a 98% uptime. Why would one need to cross the quarantine zone? Just go around it. Any of the issues you mentioned for Mars apply equally for laying power lines, fiber, and building trains; I'm sure it is done anyways. As to attraction of dust, I'm having trouble imagining why that is an issue.

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Tue, 2012-10-30 17:55

#21

Arenamontanus Arenamontanus's picture

NewtonPulsifer wrote:Dayside

NewtonPulsifer wrote:
Dayside of the moon isn't that hot; 100C, right? Just putting it in the shade of the skyhook rail would be enough.

Over a month the shadow shifts to the other side.

Quote:
However, there is always covering it in something insulating (aerogel jacket) or highly heat conducting (carbon nanotubes).

Insulators only slow heat conduction, they don't stop it it. Give enough time and the interior will be hot. Heat conduction and active cooling are required.

Quote:
If it quenches and automatic failsafes don't dump the current in time, so what? Let it cool off and start it up again. It's not a huge deal if the artificial magnetosphere only has say a 98% uptime.

Quenching is not gentle. (Videos online just show a lot of boiling helium rather than what happens when the stored energy goes off, since practically nobody currently does energy storage in superconductor coils, and when they do they are *very* careful) Let's see. 100 million amperes in a coil 1737 km in radius has an energy around (there are some issues with the inductance of Luna itself) 0.5*1.737e3*1e8^2=8.7e18 J. About ten times the energy released by Krakatoa, equivalent to a 2 gigaton explosion. Say goodbye to the skyhook rail, and quite possibly the skyhook (there are going to be some *fun* Lorenz forces here as the magnetic field implodes - and it is more or less connected to ground zero)... oh, and did I mention the EMP? Note the recent transformer failures: failsafes have a hard time being fast enough. And where do you dump those gigatons of energy? You cannot ground it, since it will vaporize the ground.

Quote:
Why would one need to cross the quarantine zone? Just go around it. Any of the issues you mentioned for Mars apply equally for laying power lines, fiber, and building trains; I'm sure it is done anyways. As to attraction of dust, I'm having trouble imagining why that is an issue.

I'm not saying it cannot technically be done, I am just saying it is not worth the effort. The benefit of a magnetic field is microscopic when you already have a radiation hardened infrastructure, and you need a megascale installation to maintain the field.

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Tue, 2012-10-30 21:34

#22

Arenamontanus Arenamontanus's picture

Arenamontanus wrote

Arenamontanus wrote:
Insulators only slow heat conduction, they don't stop it it. Give enough time and the interior will be hot. Heat conduction and active cooling are required.

Just had a neat idea, unrelated to the main topic. If you can change the insulation (for example by using a smart material, or an aerogel that can be flooded and emptied with hydrogen) you can use the long hot lunar day and the long cold night to your advantage. Insulate during the day, then let your heat escape during the night. Or vice versa. You can set up heat pumps and all sorts of fun tricks this way. Yes, for energy production direct photovoltaics are likely more efficient, but for lunar heat management cycling smart insulator/conductors plus heat storage tanks (water, salt or even hydrogen) are likely ideal.

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Tue, 2012-10-30 21:45

#23

OneTrikPony OneTrikPony's picture

I'm sure that thermal

I'm sure that thermal batteries are important on luna because of the length of the day. 14 days of night makes photovoltaic infrastructure and implementation problematic for everyone who isn't at the poles. I guess the major distribution infrastructure is already in place via the skyhook. But I think that thermal batteries are still imortant. I think there might be something I don't understand about what you're saying tho. As far as insulation goes; wouldn't putting up a sun shade be more effective as insulation than an envelope of hydrogen or water durring the day. Shade is pretty effective in Vacuum. (and you could fill your sun shade with phase change materials like water.)

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Wed, 2012-10-31 17:27

#24

NewtonPulsifer NewtonPulsifer's picture

Based on the grenade thread,

Based on the grenade thread, our limit of energy for about 6000 tons of superconducting cable is e14, not e18. So we'd be adding 10,000 times of that mass just to give it enough tensile strength. That definitely makes a planetary superconducting loop infeasible in terms of cost, unless you had some dual use for it (like as a power grid loop). I don't see the mere 40 million inhabitants of Luna needing 8.7e18 J on reserve :)

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"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto