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View Full Version : Stairway to heaven? (Well, lift to space)



Lianachan
2005-Apr-27, 01:38 PM
http://cbs2.com/water/watercooler_story_116173449.html

Did Arthur C. Clark not suggest something like this a long time ago?

*sigh* Description of ACC edited out. Last thing I want to do is offend anybody. But I will say: i) it was satire and ii) I wasn't making allegations, I was reporting that there are allegations.

Amadeus
2005-Apr-27, 01:51 PM
What allegations and what have they got to do with that story?

[edited to remove quote]

Lianachan
2005-Apr-27, 02:43 PM
What allegations and what have they got to do with that story?

[edited to remove quote]

Nothing to do with the story at all. I just remember him suggesting that such a device might be a good way to get stuff into orbit cheaply at some stage in the future.

Fram
2005-Apr-27, 03:12 PM
Then why mention it (the allegations)? It's probably the best way to be certain that this thread will go off-topic very soon (if it hasn't done so already)...

Lianachan
2005-Apr-27, 04:54 PM
Then why mention it (the allegations)? It's probably the best way to be certain that this thread will go off-topic very soon (if it hasn't done so already)...

Just as part of my description of Arthur C. Clarke. Satire and all that.

I'm not banging on about it, and I'm not making people post off topic. If that's what people want to focus on, then that's their choice.

Nicolas
2005-Apr-27, 05:16 PM
If the thread is about space elevators (I couldn't open the article):

Some people here are working on design options and concepts. The materials needed are the largest problem. It is a nice concept (rather simple in essence), but some MAJOR breakthroughs are needed to construct it, especially in the materials and construction areas.

Sidenote: I would be very careful about such allegations (they must hurt very much if they're not true), especially if they don't really contribute to the subject at hand.

Van Rijn
2005-Apr-27, 09:13 PM
The space elevator is a really sexy idea and gets a lot of attention. It is, at best, a third or fourth generation transportation system: Something that you build with advanced technology when you have the traffic to make it useful. I am always annoyed that other types of momentum banks are usually ignored, though - while still not trivial to design many would be far easier to build (possibly with presently available materials) than a full scale space elevator. Look up the "rotovator" as one example.

I believe Charles Sheffield was the first science fiction writer to use a space elevator in a story. A novel followed that. At virtually the same time, Charles Sheffield and Arthur C. Clarke wrote novels about the concept. Sheffield's book was "The Web Between the Worlds" and Clarke's was "The Fountains of Paradise."

Nicolas
2005-Apr-27, 09:23 PM
What is the exact use of making a space elevator any higher than geostationary height?

Lianachan
2005-Apr-27, 09:31 PM
What is the exact use of making a space elevator any higher than geostationary height?

It's higher than geostationary? I didn't read it properly, and hadn't noticed that. I'd assumed it was precisely geostationary.

What problems would there be with, essentially, physically tethering a geostationary object to the ground? I don't mean technical and financial ones, I mean stress and structural ones. I would think it'd be pretty tricky to accomplish any time soon.

Van Rijn
2005-Apr-27, 10:08 PM
What is the exact use of making a space elevator any higher than geostationary height?

The most common design is essentially a cable under tension. Conceptually, you can start with a satellite in geostationary orbit and send one cable down to earth, the other up higher, to balance the mass. On the high end, you can shorten the cable by adding a "counterweight." However, if you extend the cable up far enough, you can use it to accelerate spacecraft to beyond earth's escape velocity.

There are alternate concepts. In theory, you could use a structure under compression, using active balancing to keep it from collapsing. Such a structure could (again in theory) be built up to only geostationary orbit. There is also the "space fountain" that is a completely dynamic (and probably insane) structure ...

Nicolas
2005-Apr-27, 10:13 PM
I had reasoned only upto the point of accelerating beyond geostationary altitude, but accelerating upto escape velocity (at larger heights) had slipt my mind. :)


Still I think building a really working space elevator is far ahead (though technology can be very rapid), even if that company says they'll start building nanotubes cable.

I'll wait and see.

Van Rijn
2005-Apr-27, 11:12 PM
Oh, I agree. There are a lot of problems to solve. The concept has been around a long time, but until carbon nanotubes, there was nothing that could do the job even in theory. If you tried to build a space elevator with high quality steel, at geostationary orbit the cable would be thicker than the earth! It is very similar to mass ratio versus specific impulse for rockets, and why you don't see many coal burning rockets.

So while it is now at least a real possibility, that is far from saying we can build one tomorrow. One thing for sure: If carbon nanotubes pan out, they will become very important on earth long before we build an elevator.

Here's a site that seems to have a good overview with a number of links:

http://encyclopedia.thefreedictionary.com/Space%20Lift

Makgraf
2005-Apr-28, 05:30 AM
Sheffield's book was "The Web Between the Worlds"
That was a bad book. Not ludicrously-terrible-so-bad-its-good bad just bad. Sheffield is probably one of the most disapointing sf authors for me. I read one of his short stories and was blown away. It was a great hard sf story about a team of superintelligent clones crashing an asteroid into a moon of Jupiter. Good characters, good action, good science and a twist ending. After reading it I rushed to the library and checked out all the Sheffield books I could find. I was so excited that I had possibly found a new favourite author. And the books were all pretty bad. :(

David Gerrold wrote a series about a space elavator that's excerpted on his website (http://www.gerrold.com/dingilliad-1/page.htm). It seems interesting enough (though instead of writing them he should've been finishing up his Chtorr series! Grr).

Van Rijn
2005-Apr-28, 10:18 PM
While "Web" was not one of his best books (and for that matter, I wasn't that impressed with Clarke's "Fountains of Paridise") Sheffield was one of my favorite hard science fiction writers. He presented some great ideas - in more than one case was either the first or one of the first to present a concept in a story (like space elevators and ZPE), and I really liked some of his characters. I, for one, miss him quite a bit (unfortunately, he died of a brain tumor in 2001).

tofu
2005-Apr-29, 09:08 PM
What is the exact use of making a space elevator any higher than geostationary height?

As a minimum, the center of mass must be at geostationary orbit. In practical terms, this means that you'll have a counterweight or else a lot more cable above geostationary. So point one is that every space elevator design has to go higher than geostationary.

As others have mentioned, building the elevator higher than that isn't wasted effort. A spacecraft released from the elevator above geostationary is instantly in an eliptical orbit. If you go high enough and release, you can go to the moon for free (well, you'll have to make a lunar orbit insertion burn). If you go higher still, you'll have earth escape velocity, and can go to mars for free.

It's a really great concept. It would make space travel so cheap, that it would change everything about our civilization. A space elevator would be a more important advance than electricity, or flight, or the wheel, or pretty much anything that I can think of.

And best of all, it would remove an important objection to nuclear power. You could take a small quantity of nuclear waste at a time up the elevator and fling it at the moon. Who cares if we radiate one little crater on the moon? I know, there are a lot of irrational people who will protest, but for the rest of us, this means that we can get rid of nuclear waste once and for all. The quantities of waste that we'd take up the elevator at any given time would be small enough that, if disaster struck, there wouldn't be enough radiation released to hurt anyone.

sarongsong
2005-Apr-29, 11:49 PM
...One thing for sure: If carbon nanotubes pan out, they will become very important on earth long before we build an elevator...A wee bit expensive, at this point in in time:
"...Carbon nanotubes are the reigning celebrity in the nanotechnology world. The spools of pure carbon are light, much stronger than steel, can conduct electricity or light, bend and flex back, and be produced with conventional equipment from the chemistry industry...Production also remains relatively limited...On the Web site of Carbon Nanotechnologies Inc., single-walled carbon nanotubes run $375 to $2,000 a gram."
NASA looks to carbon to lighten spacecraft (http://news.com.com/NASA+looks+to+carbon+to+lighten+spacecraft/2100-7337_3-5689207.html?tag=st_lh)
"...Mass production of nanotubes, however, remains a challenge. CNI plans to increase its manufacturing capacity to the point where the company can make 1,000 pounds of nanotubes a day by 2005. Right now, it can make only about a pound or two daily..."
The Stuff of Dreams (http://news.com.com/The+stuff+of+dreams/2009-7337_3-5091267.html?tag=nl)

Gullible Jones
2005-Apr-30, 12:07 AM
Also, short nanotubes would probably be very toxic.

Richard of Chelmsford
2005-Apr-30, 12:16 AM
http://cbs2.com/water/watercooler_story_116173449.html

Did Arthur C. Clark not suggest something like this a long time ago?

*sigh* Description of ACC edited out. Last thing I want to do is offend anybody. But I will say: i) it was satire and ii) I wasn't making allegations, I was reporting that there are allegations.

Arthur C. Clarke invented just about everything to do with modern space travel,..yes, including the space elevator.

It's a good idea and it would work, but you're in for a trip of 100 to 200 miles first off, aren't you?

Maybe better than riding the stack.

sarongsong
2005-Apr-30, 09:22 AM
April 28, 2005 (http://seattlepi.nwsource.com/national/221966_space28.html)
"...They [contestants] see the day when vehicles carrying cargo and humans will climb 62,000 miles high into space on a ribbon of carbon thinner than paper, powered by beams of pure light aimed ever upward from Earth...NASA has $400,000 in prize money...first-ever competition open to professional and amateur space fanatics alike...agency hopes eventually to offer millions of dollars in even larger competitions..."
Professional space fanatics? =D>

publiusr
2005-May-04, 07:52 PM
They need bigger rockets to put a good anchor up there:

www.liftport.com

Van Rijn
2005-May-04, 08:45 PM
What is the exact use of making a space elevator any higher than geostationary height?

As a minimum, the center of mass must be at geostationary orbit. In practical terms, this means that you'll have a counterweight or else a lot more cable above geostationary. So point one is that every space elevator design has to go higher than geostationary.


This is true of a tensile structure, but not of all possible space elevator designs. In theory, a design based on compressive forces could be built from the earth's surface and stop at geostationary orbit. At the very least, it would require active stabilization.

There is also the space fountain concept. (http://www.answers.com/topic/space-fountain) The space fountain today is like imagining modern computers in the vacuum tube era: You can imagine it, but you'd definitely want more reliable technology before you built it. On the other hand, you could build a space fountain for Jupiter. You couldn't build a tensile space elevator for Jupiter, even with perfect carbon nanotube cable.

Lurker
2005-May-04, 08:50 PM
Sorry... Sorry... NO Led Zeppelin in space!!! [-(


Denied!! :o

publiusr
2005-May-06, 09:54 PM
The Liftport people made Space Daily's headlines not long ago.

Wally
2005-May-08, 06:48 PM
Gotta wonder. . . god supposedly got pretty p.o'd when folks built the tower of babel. Gotta think this thing will really tick him off!!! :wink: