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The Imminent Arrival of the Space Elevator

If you haven't already read the IEEE Spectrum article on Space Elevators that Glenn Reynolds has linked to twice (at Instapundit and now at Tech Central Station), you really need to.

In the article author Bradley Carl Edwards describes (with some nifty pictures) the process of building a Space Elevator in the near future - perhaps within 15 years. This guy is no idle dreamer. Edwards received a grant from NASA in 2000 to study the concept.

First, Edwards explains why we should build it:

It all boils down to dollars and cents, of course. It now costs about US $20 000 per kilogram to put objects into orbit. Contrast that rate with the results of a study I recently performed for NASA, which concluded that a single space elevator could reduce the cost of orbiting payloads to a remarkably low $200 a kilogram and that multiple elevators could ultimately push costs down below $10 a kilogram.

Let me make this personal. A kilogram is 2.2 pounds. That means it would cost $1,909,090 to haul my 210-pounds into orbit - never mind the cost of air, food, water or other necessities I would need to have with me. Edwards is talking about lowering that cost to $955. I'll spend that much flying my family to Disney World.

There's also the issue of safety. Riding to earth orbit atop an explosive rocket is a dangerous system that fails far too often to be acceptible for civilian transport.

Edwards explains the engineering challenges of a space elevator. The biggest hurtle has been developing a material strong enough to withstand the extreme forces involved. When I was a kid I read an article that described the building of a space elevator with an unknown material the author called "fictionite." We now know what "fictionite" is:

In 1991, Japanese researcher Sumio Iijima discovered carbon nanotubes. These are long, narrow, cylindrical molecules; the cylinder walls are made of carbon atoms, and the tube is about 1 nanometer in diameter.

In theory, at least, carbon-nanotube-based materials have the potential to be 100 times as strong as steel, at one-sixth the density.

The reduced density over steel is as important as the increased strength. Old space elevator ideas had us parking an asteroid in earth orbit just to support the massive weight of the system. Edwards doesn't think anything near that level of mass will be necessary.

And at this lower density the space elevator material would only have to be about 33 times the strength of steel.

This strength [carbon nanotubes have the potential to be 100 times as strong as steel] is three times as great as what is needed for the space elevator. The most recent experiments have produced 4-centimeter-long pieces of carbon-nanotube materials that have 70 times the strength of steel.

Once we are able to scale up production of sufficiently strong carbon nanotubes, Edwards believes we can put up a space elevator in steps:

0805spacf4.jpgAn initial "deployment spacecraft" and two smaller spools of ribbon massing 20 tons each would be launched separately into low-Earth orbit using expendable rockets. The deployment spacecraft and spools would be assembled together using techniques pioneered for the Mir space station and the International Space Station. The deployment spacecraft would then follow a spiral course out to geostationary orbit using a slow, but fuel-efficient, trajectory.

Upon arrival, the spacecraft would begin paying out the two spools side by side toward Earth. Meanwhile, the deployment spacecraft would fire its engine again, raising it above geostationary orbit. The spacecraft's motions would be synchronized with the unreeling cable so that the spacecraft would act as the counterweight to the rest of the cable: this would keep the center of gravity of the entire elevator structure in geostationary orbit [see illustration, "View From the Top"]. When the two halves of the ribbon reached Earth's surface, a special elevator car would be attached that would ascend the elevator, stitching the two side-by-side halves of the ribbon together. This initial system would have a 20-cm-wide ribbon and could support 1-ton climbers.

Other specialized climbers would then be sent up this initial ribbon, adding more small ribbons to the existing one. When one reached the far end of the elevator cable, the climber's mass would be added to the counterweight, keeping the elevator in balance so that its center of gravity would stay in geostationary orbit. After 280 such climbers, a meter-wide ribbon that could support 20-ton climbers would be complete.

The climbers, like most of the elevator system, would use off-the-shelf components wherever possible. One of the reasons the climbers would be so simple and have so much room for payload is that they would not carry power-generating equipment. Power would be delivered to climbers by lasers beaming 840-nm light from Earth onto an array of photovoltaic cells.

I think one last step would be in order. Once the first elevator ribbon is in place, another should be placed parallel to the first to allow climbers to ascend and descend simultaneously - a gondola to the stars.


Exciting stuff.

So what will it be? Will we see the space elevator soon or will it be another one of those rapidly emerging Past Futures?

BTW, interesting picture. I don't see a cable, only a laser beam. Is the elevator not finished or are we going to develop a way to send a gondola to the stars riding on a beam of light?

The reason my "Future Healing" story became a past-future was because I failed to imagine a better technology than tailoring CBE stem cells to a matching patient.

Short of Scotty beaming us up, what better way can there be for getting us and our cargo into orbit? That might be another failure of imagination on my part, but I kinda doubt it. :-)

Click on the picture of the space station for a larger view. The ribbon that the author is describing is very thin, but relatively wide. On edge you wouldn't be able to see it at all, certainly not at the distance of that station picture. You would probably be able to see the ribbon on the side. I think that red line was the artist's compromise. Notice how the ribbon continues, almost invisibly, up from the station. The counter weight will be in a higher orbit.

Edwards spent some time covering some other problems that have to be overcome. Including security and weather.

Why not have the base of the elevator on an equatorial "Dark Sky Station?"


You would avoid a lot of problems with the weather and, I think, some security concerns. Also, it would be a shorter elevator. Therefore, it might be doable sooner.

Here's a artist's rendering of this kind of station:


It's part of JP Aerospace airship-to-orbit program.

Well to be honest, how much would it cost to be getting payloads up to 100,000 feet at the dark sky station? Plus the difficulty in keeping the ribbon taught at all times... I think part of the process is that it really requires the ribbon to be tethered to the earth as well as to the satellite.

At any rate, those numbers have been quoted before, but when pusfh comes to shove I really think that there will be a lot more additional costs involved. Much like the original shuttle was slated to launch every 2 weeks and cost millions instead of hundreds of millions, I think that it might be a bit to fanciful. Don't get me wrong, if someone makes it I'll sign up for a ticket, but I don't see it happening in the next 10 years.


It would be costly to get payloads up that high without a tether all the way to the ground - maybe too costly.

You would need a fleet of the lighter-air-lifters that JP Aerospace has in mind.

But I don't think that slack in the ribbon would be much of a problem. You could make the station heavier if needed by releasing some of its lighter-than-air gas.

I'm sure there are other technical problems with this kind of partial elevator I haven't considered.

Another idea: what if a Dark Sky station served as a half-way point on a complete ground-to-sky space elevator? It might prove useful to have a waystation enroute.

BTW, interesting picture. I don't see a cable, only a laser beam.

I can't speak for the image but you won't see much of the ribbon on the real one either - a meter wide, centimeters thick? You might well walk into it first.

You would avoid a lot of problems with the weather and, I think, some security concerns. Also, it would be a shorter elevator. Therefore, it might be doable sooner.

Not that much shorter - what, a few kilometers out of 60,000 plus? Weather isn't a problem where Edwards wants to put his elevator - it's dead calm there. You'd also complicate getting 'stuff' the ribbon to send it aloft - it might not be worth it from a cost/benefit point of view.


You might be right about the cost/benefit not being acceptible for a partial space elevator. And ChefQuix made the point that getting cargo up to 100,000 isn't free either.

But while a few kilometers out of 60,000 is not much, it would be a key few kilometers. Those kilometers would experience a significant higher load from earth's gravity and from the stress of weather - even in the Pacific.

Here's another idea I'd like to throw out. I've always heard that the only possible place for a space elevator is the equator. Why? Well, you need a geostationary orbit for an obvious reason - the base of the elevator can't be wandering around the planet. And a geostationary orbit has to be circular, equatorial, and match the earth's spin (geosynchronous).


But why couldn't a geostationary mass support two space elevators located equidistant from the equator? This would have to form an isosceles triangle with the apex immediately above the equator.


You could have one elevator servicing the American east coast counterbalanced by another for South America:

View image

Europe and Africa would probably team up as would Asia and Austrialia.

Obviously this is a second-generation project. This is the sort of thing that would be done years after a regular equatorial space elevator is put up.

Offsetting the anchor to the north or south would merely pull the counterweight a little in the same direction, with gravity pulling it back.  The elevator would achieve the advantage of being out of the orbital path of most debris that it drops.  A skyhook right on the equator would potentially meet with dropped debris on every orbit, and debris falling from on high meeting the skyhook near perigee could sever it.  The perigee of debris dropped from an offset skyhook would lie in the other hemisphere.


Of course this sort of elevator would be significantly longer (each leg would be longer than an equatorial system). That makes it more expensive.

It would have to withstand more force and it would be a longer climb. Still, having an elevator directly from New York into space might prove to be...useful.

Also, with the costs being this low, why couldn't we consider making it an alternative way to ship cargo, not just into space, but world-wide?

You could have a climber outfitted as a re-entry vehicle. Once in space, you could cheaply put it on a trajectory for any place on the planet.

Or, what about this:

View image

If you were using the offset elevator, you could send the cargo into space, or near space, and then transport it over a ribbon-bridge to the other leg and back down. Sort of a sky-rail system. If you had enough of these elevators up, the earth could be covered with a web of these sky-rails.

Rather, you could hit any spot on Earth that's covered by the orbit your cargo falls into (assuming you drop it from high enough that its perigee is well above the atmosphere).

I think you might have an issue with timeliness of delivery.  The concepts I've seen have talked about climb times of a week or so.  When you can fly halfway around the world in a day (and maybe for less energy cost), that sounds like a serious commercial handicap.

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