h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

OK, I've corrected the geostationary altitude to 22,300 miles and, more importantly, have added the italics on 2001: A Space Odyssey.

Looks good to me

looks good to me too

Pimms

I'm intrigued by the 'time to get to orbit' discussion. Currently, you can't get from ground to orbit via NASA in less than 6 months, and that's if you are a secret military project. Yes, the Shuttle when it is flying, it goes up very very fast, but it doesn't launch very often at all. Any speed faster than once in 6 months would be a good speed! Time vs. expense is also interesting, Japanese car companies rely on slowly getting their cars across the ocean and planning way ahead of time and still make a nice profit. Any 20K km expanse can have room for more than one elevator car, so there can be lots of planning.

There's a lot of ocean at the equator. If we are positing a material that is strong and flexible enough to do what we are wanting here, why not anchor it to a platform (made of the same stuff) in the ocean? This would give you more possible sites, and also insulate the cable from wars and terrorism. Is a likely spot to anchor it really that rare?

I carefully said in the entry that suitable spots are not as common as you think without giving away the fact that I have no idea how man suitable spots there are.

I can't see any reason why it couldn't be in the sea myself. This would certainly make it very accessible to most nations of the world.

It would be harder to put it over the sea because you'd need a good stiff anchor in order to stop the 'rope' being whipped around by the atmosphere. Anchors are much, much easier to sink into the land.

This is a pretty decent entry - I've read a lot about space elevators and it's nice to see it in some layman's language.

One aspect you've glossed over somewhat is the fact that - after a period of equilibrium - a space elevator will be self-sustaining, energy wise. That is, there will be as much stuff coming down as going up, hence providing its own counter-balance.

B

I seem to remember reading Mr Clarke, either in the epilogue to 2061 or in 3001, envisaging the Space Elevator being built from huge diamond deposits flung around the solar system after Jupiter gets turned into a sun. Just a bit of trivia.

Clarke also wrote about a shuttle experiment where a cable was to be lowered down a looong way to check out the feasibility. Apparently it got stuck after a couple of miles. I've no idea if this is true or not but I've no reason to disbelieve the great Arthur C Clarke and it would make a nice footnote to the entry.

I enjoyed this entry and, having read it after all the italic bits and discussions about the US military industrial complex, I think it's ready.

Incidentally, for those who want the figures, the US spends around $400bn each year on defence, which makes the Pentagon richer than all but a dozen countries. Britain is one of the world's biggest defence spenders too, but it spends only a tenth of what the US does.

Hi Gnomon,
an interesting way to get a lot of mass cheaply "up there".

Actually I am a bit surprised Hoovooloo did not come screaming along after:
"The simpler explanation is to say that the centrifugal force caused by your circular motion cancels out the force of gravity pulling you downwards" See A597152 Centrifugal force.
A motion creating a force? I think this will have to be reformulated a bit.

A nitpick: a satellite will only stay above one point if it is launched in the right direction, otherwise it will quickly dispose of one or more other real geostationary satellites.

An alternative way for compensating for the weight of the cable would be to place the satellite further away, with a higher speed to keep a period of 24 hours.

There are also complications with the movements of the elevator. The mass going up or down at high speed will be subject to a probably not negligible Corriolis force (See A593273) which would change the orbital speed of the satellite and would require an even stronger (and heavier) cable.


More interesting notes about a space elevator can be found at
http://www.wikipedia.org/wiki/Space_elevator

Although, if you are going to include any of the above, it should be noted that it's Coriolis, not Corriolis.

B

I started with sattelites

Just to confirm what has already been said, Clarke did re-visit the idea of the space elevator in 2061 suggesting the diamond from the jupiter explosion as the material.

However, in 3001, he changed this to buckytubes - enlongated tubes of buckminsterfullerene - which are reported to have a greater tensile strengh then diamonds. If you could make the tubes long enough, or chain them together, or both, they would be the perfect material of the elevators (according to Clarke, anyway).


Geggs

Can't polymerise buckyballs.

I've tried.

B

A couple of notes:

About the following sentence: "Clarke positioned his elevator in the island of Sri Lanka, because of his love for the country. He glossed over the fact that Sri Lanka is not actually on the equator and needs to be for the elevator to work."

To be absolutely precise, Clarke set his elevator on a fictional island named Taprobane, which just happened to be exactly like Sri Lanka in every way except location.

I think you could mention some other books that feature space elevators. I would recommend Kim Stanley Robinson's Mars Trilogy, which has many detailed descriptions of a space elevator on Mars. And I would also mention Iain M. Banks' "Feersum Endjinn" which is set on the stump of a ruined space elevator; in Banks' novel, there are space elevators built on the mountain Chimborazo (on the equator in South America), on Mt Kilimanjaro (on the equator in Africa), and on a mountain in Borneo. Since the first two are both volcanoes, this seems somewhat implausible...

Hope this helps...

To be precise, Taprobane is the old name for Sri Lanka, so I think I am justified in saying Clarke set his book in Sri Lanka. He apologised himself for having moved it south, but said that it was worth it to make a good story.

Indeed he did - mea culpa.

Weren't there a few Heinlein books that had space elevators, too, come to think of it? Friday, for one, I believe.

I think it would possibly be worth linking to some of the startup companies that are working on this idea -- some of them have really good diagrams and whatnot that help illustrate the concept.

Do we need to include other launch technologies to make this entry balanced, since it is speculative and not absolute fact? I am thinking of one or two sentence commentaries about rockets, Space Shuttles, and improved resuseable vehicle, and superconducting launch rails (aimed permanently in the correct direction, sloping upwards).

I'm inclined to think we don't need to include other technologies. This is speculative, but it makes that clear in the entry. It doesn't claim to be the only way into space.

I'll try and dig out a few links to websites about the Space Elevator.

I don't intend to list a load of books which mention the Elevator. I concentrated on Clarke's book because the elevator was the sole subject of the book and because it was the book that introduced the concept to the world.

I've added a couple of links at the end.

It was with entries like this in mind that I requested the creation of the Smiley. Superb stuff - succinct, highly readable yet information-packed.

The only change I'd make is to put 'Star Trek' in italics at the beginning, but the Subs can fix that. Elevator going up!