Space Elevator Discussion

[Legendary Emu]

I don't know if it's just me, but I get depressed when I read about space elevator and similar concepts because the first part is really neat and shows how useful it would be, and then you read about the limitations and how much it won't happen in this century, then it hits you like a rotating skyhook.

So maybe this thread could be about space elevators and similar concepts like orbital airships and floating launch points in the sky.

[Aethon]

Lets start with the moon.

http://www.space.com/24919-lagrangian-elevator-to-the-moon-is-it-possible-video.html#ooid=xoamN5cDq2m4yhdpiPbcpCmZNxmJa-w2 (Takes a while to load and play but is worth the wait)

http://www.space.com/24905-moon-elevator-lunar-exploration-liftport.html

Edited December 3, 2014 by Aethon

[Mazon Del]

I actually almost worked for those guys a bit. Liftport is a pretty cool group.

[Tex_NL]

Please. Not again. This has been discussed here multiple times already and the result have always been the same: it's a pipe dream. It requires technology and materials far beyond what we have. And by the time we finally do have the resources required to actually build and maintain one it has outgrown it's usefulness. By that time there will most likely be far easier ways to achieve orbit.

[Albert VDS]

I wouldn't call a Space Elevator a pipe dream, as it theoretically possible and we as a whole could work towards making it a reality.

The only stumbling block is money.

Space Elevator Threads need videos of Arthur C Clarke talking about them:

[Nibb31]

The only stumbling block is money.

...And technology.

The only stumbling blocks are money and technology.

...And purpose.

Oh bugger! Amongst the only stumbling blocks are: money, technology, and purpose.

...And political will.

Oh screw that. Nobody expects the Spanish Inquisition.

[lajoswinkler]

The only stumbling block is money.

And you're wrong. The materials needed are vastly beyond out scientific understanding of materials science. It's not even about technology.

[Bill Phil]

Chances are, that any same government would realize that building an Earth-to-orbit-to-moon-and-beyond logistics would be way cheaper. Then you can start building things in space with asteroid resources, and the only Earth launches would be humans and some specialized cargo.

So, by the time the tech becomes available, or the money, we have other (cheaper) options.

[zilfondel]

This was posted last July, by one of the world's largest and most advanced and successful civil/infrastructural/architectural engineering firms. For reference, they have worked on the UK's High Speed 1, 2nd ave Subway, Heathrow Terminal 5, China's CCTV HQ, the Gherkin building, and honestly hundreds of other projects. Many of these are multi-billion dollar projects involving decades long timetables.

Anyway...

http://thoughts.arup.com/post/details/362/coming-soon-space-elevators

An elevator should reduce the cost of getting into space to about $220/kg for an estimated build cost of $20 billion. It is difficult to predict how much of a difference a reduction of two orders of magnitude on the launch costs will make to the space industry and society, but it is likely to be as significant. Today the aerospace industry carries over three billion passengers and $6 trillion of goods a year. This means that the cost of a space elevator is about the same as one day’s air freight.

and

I’m not the only one who thinks space elevators could soon be viable. NASA is researching and promoting enabling technologies such as the power beam and tether climb challenges and the Tokyo-based Obayashi Corporation has announced plans to build an operational space elevator by 2050. There are also plans by Liftport, an American company, to build a smaller elevator on the Moon by 2025.

While we have not quite got all the technology in place, and there are still engineering challenges to be overcome, the space elevator has nearly arrived.

Edited December 4, 2014 by zilfondel

[Bill Phil]

It's not as practical as you would think. Large success leads to large exaggeration. And support, etc. If someone put all the details, ALL the details, and explained it, then sure, I would say okay. But, 20 billion is very optimistic. It would be over budget in the end. It's inevitable. And the bigger the project, and the more crazy the idea, the more time it takes. So it doesn't seem in any way practical unless you already have an orbital infrastructure. But then there's almost no reason.

Plus, how much power would it take to operate those elevators? I assume you want a lot of payload. You'll also need propellant anyways, to keep it stable as it wobbles around.

Now, the real question isn't construction price or payload cost per kilogram, but what matters is the upkeep cost. It's a huge structure ( HUGE, that's why it's so expensive), and it will be hit by debris and micrometeorites. The total upkeep cost will be ginormous compared to the construction cost. It's useless for all orbits except GEO, unless you want to use a decent amount of your payload mass as propellant to get it from GEO to LEO.

So, the company that'll run it will have to increase costs to insure the upkeep, and they want a profit. So from many standpoints, not just technically, it's impractical.

If any of this is completely incorrect, please pint me to sources. Thanks.

[Helix935]

my question is where would we set up these space elevators, what locations exactly because i know that Arthur C. Clarke foresaw that one prime location would be in Sri Lanka but i still need to know if there are other prime locations for them being set up on Earth

[Iskierka]

Space elevators will never exist because they interfere with normal space operations too much.

The vast majority of satellites are in low and medium earth orbits, and in ones that do not perfectly resonate with geosynchronous. And a majority of those -need- to be there, either for observation resolution, ping times on communication, or various other reasons. If you built a big elevator going up through their orbits, you'd have to write off tens of billions of hardware offering hundreds of billions in terms of business, with no way to replace them as the elevator cannot provide the same functionality.

And that's before considering the cost of protecting or repairing the elevator from damage from these satellites, and before even considering HOW you'd build one of these things. I recently came across an interesting concept where three orbital elevators were linked by a low/medium-orbit ring that they forced ferromagnetic fluid through at high velocity, similar to a launch loop, reducing the structural load on the towers by supporting them partway, but it still offers no solution to lost orbits, construction methods (it may have less static load but you still need to put it together), and it creates different structural requirements at the antipodes to the towers.

If you want to put something in orbit with cables and electrical power, launch loops are the way to go. Non-interfering with orbits, possible with current materials technology, access all orbits unlike a space elevator. The idea of a vertical object you simply climb isn't going to happen.

[kerbiloid]

Alcubierre mini-scooters are much more realistic, I guess.

Even if build such monstrous construction, any cargo still would require almost the same energy (kinetic + potential) as if just launch it.

And it's much easier to send it by a microwave ray if you don't want to place a reactor just aboard.

So, the only question: is it easier to build a 70000 kilometers high whip-shaped building or just to create an arcjet or plasma nozzle with high ISP and low fuel consumption.

[magnemoe]

Space elevators will never exist because they interfere with normal space operations too much.

The vast majority of satellites are in low and medium earth orbits, and in ones that do not perfectly resonate with geosynchronous. And a majority of those -need- to be there, either for observation resolution, ping times on communication, or various other reasons. If you built a big elevator going up through their orbits, you'd have to write off tens of billions of hardware offering hundreds of billions in terms of business, with no way to replace them as the elevator cannot provide the same functionality.

And that's before considering the cost of protecting or repairing the elevator from damage from these satellites, and before even considering HOW you'd build one of these things. I recently came across an interesting concept where three orbital elevators were linked by a low/medium-orbit ring that they forced ferromagnetic fluid through at high velocity, similar to a launch loop, reducing the structural load on the towers by supporting them partway, but it still offers no solution to lost orbits, construction methods (it may have less static load but you still need to put it together), and it creates different structural requirements at the antipodes to the towers.

If you want to put something in orbit with cables and electrical power, launch loops are the way to go. Non-interfering with orbits, possible with current materials technology, access all orbits unlike a space elevator. The idea of a vertical object you simply climb isn't going to happen.

Yes, stuff in lower orbit would be an problem, more some as then an space elevator makes economical sense you would have magnitudes more stuff in orbit.

One idea who is pretty realistic is to put the end on an ship, this way you could move the lower part of the elevator to get away from stuff in orbit.

Launch loops has the problem that they are pretty hard to take offline for service.

[-Velocity-]

As I noted before, space elevators are much easier to build on other bodies in the solar system than on Earth. So they might end up being very useful- for getting things into space from a lunar mining operation, or putting things into orbit from the surface of Mars. Both the Moon and Mars, our top colonization targets, are favorable for building space elevators. Mars has low gravity plus a high rate of spin, which makes it easy to achieve the necessary centrifugal force on the tether required to overwhelm gravity and maintain tension. The Moon, on the other hand, spins much more slowly but has such weak gravity that a space elevator is possible there too. Mars has the problem though of having a moon (Phobos) that crosses below geostationary orbital altitude, so we'd have to deal with that somehow- possibly by just putting the base of the Martian elevator on rails on a track a few dozen kilometers long, so that it could just dodge Phobos when a collision would otherwise result. At least, that would be my first proposal.

[Bill Phil]

Or just don't build a space elevator and use high altitude space-guns.

[Albert VDS]

...And technology.

The only stumbling blocks are money and technology.

...And purpose.

Oh bugger! Amongst the only stumbling blocks are: money, technology, and purpose.

...And political will.

Oh screw that. Nobody expects the Spanish Inquisition.

As far as I know the main contender for the ribbon material is carbon nanotubes. We know how to make them in small amounts, research "only" needs more money to find a way to make larger quantities.

It's purpose is to make launches cheaper, a few hundred dollars to just get into space is a good deal.

Political will is always a problem for everything.

[Mazon Del]

Specifically what we need is the ability to produce arbitrarily long multi-walled carbon nanotubes. We are getting better with this as time goes on. I believe we are in the near-inch range for length.

[Iskierka]

It's questioned whether even indefinitely long nanotubes will be strong enough, and how to anchor and repair them is a major problem.

[SargeRho]

Space Elevators on Earth might never happen, but what about other bodies? Mars, The Moon, etc.

I read that a Mars elevator could be built with current materials.

[Mazon Del]

It's questioned whether even indefinitely long nanotubes will be strong enough, and how to anchor and repair them is a major problem.

It isn't much questioned that they would be strong enough, and anchoring isn't much of a question either. But repairing them is a bit of one. I've heard two ideas on this topic.

Idea 1: Attempt to utilize the tendency of CN to 'reconnect/repair' themselves and provide a car that occasionally goes up and down the ribbon spraying out the same sort of tiny-CN we see now. Might work, but also isn't likely to be very good for people breathing the air downwind. Unfortunately CN is as bad as asbestos in your lungs.

Idea 2: The primary driver in all cost estimates for space elevators is the cost of launching the materials into space. Once you get one up, the cost of adding more drops dramatically. It would of course still be very expensive, but largely a small fraction of the first. Given this, the idea ends up being that once the first is done, set up at least one more at staggered intervals (the second one like 3-5 years later, third one 3-5 after that, etc). Once the first one starts reaching degradation levels where it is time to decommission it, you can demolish it in a variety of safe ways and then just rebuild another at its location.

[Bill Phil]

Space Elevators on Earth might never happen, but what about other bodies? Mars, The Moon, etc.

I read that a Mars elevator could be built with current materials.

Yeah, but we actually have to get everything there. That's not easy...

[Tex_NL]

Space Elevators on Earth might never happen, but what about other bodies? Mars, The Moon, etc.

I read that a Mars elevator could be built with current materials.

And WHY is it feasible with current technology? Because it is already easy to lift off due to the low gravity.

Yes, it is probably possible to build a space tether on the moon but you don't have to. Building and maintaining one is still way more expansive than a conventional launch.

[GoSlash27]

Our government is spending $1.50 for every $1.00 they collect and inflating the money supply just to keep operating at current levels. "Only" $20 Billion dollars?? When was the last time you heard of a public works project that *didn't* exceed it's initial estimates by at least a factor of 10? And of course once you get it started, it's impossible to kill it no matter how obvious it is to everyone that it's a boondoggle.

Setting aside the (not inconsequential) fact that it's impossible with current tech, How many tons of material would you have to orbit in order to make this cheaper than what we're doing now?

Space elevators are awesome... if you love shiny theoretical space toys and can't balance a checkbook. For the rest of us, they're a disaster waiting to happen.

[SargeRho]

And WHY is it feasible with current technology? Because it is already easy to lift off due to the low gravity.

Yes, it is probably possible to build a space tether on the moon but you don't have to. Building and maintaining one is still way more expansive than a conventional launch.

Using electricity to move things into orbit is going to be cheaper than using methane and oxygen I think.