The Space Elevator

[Kyriakos]

Well, i was naming the branch of physics that deals with forces in the level normally dealt with by humans (ie non macrocosmic nor microcosmic). For example friction, increases of speed due to movements like free-fall or others that change an original state of balance, etc. The equations and identities in that part are also used in building (moreover quite a bit more cautiously here due to the region being highly seismic), so one has to suppose that those would be heavily used in the building of the parts of a space elevator, above those which are in our own atmosphere (but like i said - and asked for a reply - i have not read just how the elevator would be used, and it seems that it is argued it would merely position loads on orbit).

And the harmonic vibration indeed is a nasty scenario. And one i also have to doubt (granted, intuitively) we can calculate how to decisively cancel, due to the length of the project and other parameters resulting from the differences from a regular building. (Even today troops or other marching numbers always break formation when passing a bridge, case there is always the danger of causing this sort of vibration that keeps expanding, and in the end the bridge breaks into pieces).

 

[El_Machinae]

Oh, there are a lot of really serious concerns. Some of them look like they just need dedicated fixes. Some look like they might be nearly impossible. This is why I sign up to the Consortiums, because there are small pockets of really smart people who will work on these issues, if they just get a wee bit of help. The SE would be a game-changer, and it's not like there aren't a vast number of spinoff technological benefits.

The OP might also want to check out Liftport, whose idea of a Moon elevator might be a lot more feasible.

 

[peter grimes]

They already use seismic dampers in some buildings, so it's not as if there's the vibration damping is impossible.

Link to video.

 

[onejayhawk]

Oh, there are a lot of really serious concerns. Some of them look like they just need dedicated fixes. Some look like they might be nearly impossible. This is why I sign up to the Consortiums, because there are small pockets of really smart people who will work on these issues, if they just get a wee bit of help. The SE would be a game-changer, and it's not like there aren't a vast number of spinoff technological benefits.

The OP might also want to check out Liftport, whose idea of a Moon elevator might be a lot more feasible.

I was considering that yesterday.

Doing a colony in space turns out to be impractical for medical reasons. Our metabolism needs gravity plus radiation is high in space. It could be done, but a more logical place is the moon. A elevator on the moon could be built using current technology, with only mundane engineering issues. The approach offers a lot of advantages, while allowing a practical scaled test of the elevator design.

J

 

[El_Machinae]

Well, gravity can be simulated with rotation, and radiation is just a function of armoring (which takes weight and mass to get to orbit, mind you). Seriously, I've dropped a few terms you can use in google to get better sources with.

 

[onejayhawk]

Well, gravity can be simulated with rotation, and radiation is just a function of armoring (which takes weight and mass to get to orbit, mind you). Seriously, I've dropped a few terms you can use in google to get better sources with.

It could be done. Radiation shielding is a bigger issue. If you build a colony on the moon, just enlarge a cave. The crust provides radiation shelter and helps contain your atmosphere. The elevator provides the commute to zero G activities. It is still a lifetime away. most likely, but it is already doable.

I like a scaled down version of Ringo's Troy. In that he used a massive solar array to bore a pit in a nickle-iron asteroid. The pit was filled with comet snow and sealed. The array heated the whole thing to molten. The core of comet snow vaporizes. When the shell gets sufficiently malleable, the high pressure steam causes a bubble to form. In the book, the bubble grows to a almost ten kilometers in diameter, with a wall over a kilometer thick. Scale that down by 95% and you get a viable large habitat.

Thanks for pointing toward the consortium. I had been looking for this, but did not know the appropriate searchterms:
http://www.niac.usra.edu/files/studies/final_report/521Edwards.pdf

J

 

[El_Machinae]

Oops, I should have mentioned Edwards earlier on. His book (last decade) was pretty good.

He's a true believer, so he's got some bias, but it's still a good place to start in order to stay abreast of the conversation.

 

[aelf]

All have issues, but when the push comes, I suspect Sinapore to get one of the first two. It is too natural a location--large, technically sophisticated population

Nah, the population is only good for technical slave labour. Trained monkeys, basically.

 

[peter grimes]

Thanks for pointing toward the consortium. I had been looking for this, but did not know the appropriate searchterms:
http://www.niac.usra.edu/files/studies/final_report/521Edwards.pdf

Thanks for linking that! I'm more than half-way through, and it's fascinating. I love reading stuff like this.

Now I want to get the book which goes into a lot more technical detail.

 

[El_Machinae]

I really enjoyed Edward's book. I got dreamy stars in my eyes reading it.

 

[peter grimes]

So if I understand the Edwards report correctly, the crawler won't exert a downward force on the ribbon. It uses the ribbon to absorb angular momentum from the rotation of the earth.

The crawler is powered by a type of electromagnetic rocket, the electricity to power it is wirelessly beamed via anchor-based laser.

Thus the energy required for a launch is only the energy needed to move the mass of the crawler + payload a distance of ~35000km. The energy required to achieve orbital velocity is "free*", this is why a space elevator can provide dramatic cost savings for launches.

Sound about right?

*Free, in the sense that it's absorbed angular momentum translated from the ribbon

 

[Phrossack]

I'm still concerned about terrorism. There will always be jerks, and sooner or later someone will try to blow up the space elevator. It'd be easy to damage and hugely expensive to repair.

 

[peter grimes]

Why don't terrorists target Drilling Platforms? It's roughly the same level of technical ability.

Where the ribbon is anchored there's very little force - it's a movable platform, the weight of the ribbon is almost entirely counteracted (balanced) by the orbital anchor. The terrestrial base deals more with handling the ground operations than serving as a physical anchor.

Unless I've misread things, of course.

 

[hobbsyoyo]

^Which was one of the reasons i asked where the space elevator would actually be leading to. Some space station in eternal orbit around our planet? Something other than that? (seems less likely it would link to the moon, for example).

This kind of misses the point. It's not that the elevator is being built to get to a place, rather, it's that it is allowing humans to take things into orbit very cheaply and efficiently to then go other places. Once you've gotten into orbit, you're half way to practically everywhere in the solar system from an energy perspective.

That said, you would need a large 'anchor' at the space end of the tether. Some have suggested towing an asteroid into orbit to form the anchor. But in any case, it won't be an important destination itself likely, just a place to launch off from into deeper space.

I don't really see the use of it if it leads to a space station, cause obviously it would cost an enormous amount of money to make, it might not work with current technology, it could be prone to disasters, and if it gets ruined we would be stuck with a rather nasty tower orbiting our nasty little world :\

It will be enormously expensive likely, but it will also pay for itself multiple times over. In this instance, the Panama Canal analogy works pretty well I think.

Good gods.

We're better off looking for more efficient rockets, a space elevator's totally impractical.

Unfortunately, we're at the limits of what traditional chemical rockets can do. Companies like SpaceX claims they can bring down costs significantly, but they do so with new managerial practices, essentially. There isn't any additional 'efficiencies' from that their rockets can achieve, they basically just make them cheaper than others can. There are other options but many are politically untenable for launching rockets (various nuclear propulsion schemes) or are about as far off as space tethers (laser-based propulsion systems). And for the latter case, by the time they arrive we could likely build space tethers which in the end would be far more economical.

Why don't terrorists target Drilling Platforms? It's roughly the same level of technical ability.

Where the ribbon is anchored there's very little force - it's a movable platform, the weight of the ribbon is almost entirely counteracted (balanced) by the orbital anchor. The terrestrial base deals more with handling the ground operations than serving as a physical anchor.

Unless I've misread things, of course.

Yeah, I don't think terrorism would be a major concern for a tether. Not to say that anyone should be complacent about it, but an exclusion zone with air-defense and tight controls on who can come near/inside the facility should be sufficient. Of course, the magnitude of disaster of a potential successful terrorist attack on a space elevator far outpaces anything comparable. Even a nuke in terrorists hands would probably do orders of magnitude less damage than a falling cable that wraps around the earth at hypersonic speed.

 

[El_Machinae]

So if I understand the Edwards report correctly, the crawler won't exert a downward force on the ribbon. It uses the ribbon to absorb angular momentum from the rotation of the earth.

The crawler is powered by a type of electromagnetic rocket, the electricity to power it is wirelessly beamed via anchor-based laser.

Thus the energy required for a launch is only the energy needed to move the mass of the crawler + payload a distance of ~35000km. The energy required to achieve orbital velocity is "free*", this is why a space elevator can provide dramatic cost savings for launches.

Sound about right?

*Free, in the sense that it's absorbed angular momentum translated from the ribbon

The crawler will exert a downward force, but it won't be significant compared to the counter-weight. Or, if you put enough crawlers on the line to affect the counter-weight, the maths are pretty easy.

And yes, the major draw is that the sheer Energy required to get something to orbit (or further) is really quite easy to generate, and doesn't need to be explosive. Further, the vehicle needn't carry its own fuel to get from the atmosphere into LEO.

I'm still concerned about terrorism. There will always be jerks, and sooner or later someone will try to blow up the space elevator. It'd be easy to damage and hugely expensive to repair.

Well, repairing is one thing. I'd think that all stations would want a spare tether on board in case the primary tether is broken. This is an expensive piece of redundancy, but affordable overall (just like fire-escape stairs are technically 'expensive' when buildings a skyscrayper, but ehn). Terrorism will always be an issue, it's something that can be targeted by any long-distance flier. And it makes a great target. But, that aside, the risk of terrorism is the same whether it's 350 km or 35,000 km, really.

 

[onejayhawk]

You do not need a large mass at the top, much less an asteroid. This is not a string which is pulled tight by centripital force. The "string" is gravity. The tether is more akin to a climbing/rapelling line on the face of a cliff.

J

 

[El_Machinae]

I'm, uh, not sure what you're going for there. You might have a different conception of what I'm used to. Do you have a good schematic of what you're thinking of? Centrifugal force is a major component of the idea, except with the Moon Elevator.

 

[Core Imposter]

Whatever you are going to build the cable thingy out of its going to have to have an organic component. It has to be alive. Dynamic. Self replicating because it will have sense stress and adapt.

What do we have along those lines to work with?

 

[peter grimes]

That's not what the engineers who have looked into this say. Carbon nano-tubes embedded in a matrix is sufficient, assuming the nano-tube quality is high enough. And that's the key.

 

[IAM]

microbot centipeds

http://www.popsci.com/technology/ar...ven-times-its-weight-512-thermal-powered-legs