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Author Topic: What technology do we need to build a space elevator?  (Read 4221 times)

Ronald Salkin

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Ronald Salkin  asked the Naked Scientists:
   
What technological/engineering advanced would be necessary for humans to build a space elevator?  Or to bring a small asteroid into orbit where its materials could be used for space-based construction?  And are there any other viable alternatives to radically reduce the cost of space-based structures such as habitable environments, solar-power-gathering satellites, etc?
 
Thanks much,

Ron S


What do you think?
« Last Edit: 26/03/2011 20:30:03 by _system »


 

Offline JMLCarter

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What technology do we need to build a space elevator?
« Reply #1 on: 27/03/2011 00:59:50 »
Space elevator:
The main issue is a material that can form a rope 100km long and still support its own weight does not exist. Perhaps something will come up, though.

Moving Asteroids:
Near Earth Objects (NEOs) present a very serious threat to the planet and there is some serious research being conducted to identify them all and to develop technologies that can move them. Moving them out of the way is a step towards moving them into orbit for their resources, but things haven't gotten that far. Techs include attaching solar sails and ion drives, and I suppose I have to admit nuclear missiles - but it's not a great option.

Space Habitat:
A private organisation Bigelow Aerospace has developed an inflatable space habitat from a NASA project. The have had a prototype in orbit filled with photos from sponsors - no people have ever used one though.
 

Offline imatfaal

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What technology do we need to build a space elevator?
« Reply #2 on: 28/03/2011 14:10:00 »
Ronald & JMLC - Getting a strong tether is much of the problem; but JML has underestimated the scale of the trouble.  To be in geosynchronous orbit the tether needs to be around 35,000 km long! 
 

Offline Geezer

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What technology do we need to build a space elevator?
« Reply #3 on: 28/03/2011 18:18:25 »

The main issue is a material that can form a rope 100km long and still support its own weight does not exist.


As Matt points out, it would need to be just a tad longer than that. However, this is mitigated to some extent by the fact that a lot of the tether will be practically weightless.
 

Offline JMLCarter

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What technology do we need to build a space elevator?
« Reply #4 on: 28/03/2011 18:30:47 »
There's also some solutions that do not tether to the ground, but hang into the atmosphere; this allows them to move and the top end to be in a lower orbit. An aircraft is used to get to the bottom of the tether.
 

Offline Geezer

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What technology do we need to build a space elevator?
« Reply #5 on: 28/03/2011 19:21:11 »
There's also some solutions that do not tether to the ground, but hang into the atmosphere; this allows them to move and the top end to be in a lower orbit. An aircraft is used to get to the bottom of the tether.

In that situation, I would think the speed of the tether travelling through the atmosphere would create so much drag that the satellite would fall out of orbit. The aircraft would also have to go really, really fast to catch up with the tether.

Maybe it would work if the satellite and the tether were well beyond the Earth's atmosphere, but then you would need something like the Space Shuttle to get to the end of the tether.

I wonder if we could stand the problem on its head and run a tether from the Moon to a satellite in orbit around the Earth? Then you could run an elevator between the satellite and the Moon. The weight of the tether might even be a non-issue.
 

Offline Phractality

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What technology do we need to build a space elevator?
« Reply #6 on: 29/03/2011 05:11:13 »
To be in geosynchronous orbit the tether needs to be around 35,000 km long! 

Actually, it needs to be quite a lot longer, still. Geosynchronous orbit is 35,786 km above mean sea level, or 42,164 km from the center of the Earth. For the thickest and strongest part of the rope (or ribbon) to be at geosynchronous orbit (where the tension is greatest), there has to be a counterweight far beyond that. Depending on the mass of the counter weight, it could be anywhere from 60,000 to 200,000 km from Earth.

The minimum tensile strength requirement is about 62 Gpa (Gigapackard Gigapascal). That's nearly 20 times stronger than Kevlar. But the strenght to weight ratio is what counts, and CNT is about 10% lighter than Kevlar. Progress is being made on developing CNT (carbon nanotubes) which, theoretically, should be strong enough. Multiwalled CNT strands, a few microns long, have been measured at 63 Gpa. Single walled CNTs should be stronger, still. A similar fiber, boron nitride nanotubes, has been produced with a tensile strength nearly 1 Tpa (terapascal). So there is hope, yet, that the space elevator is doable. In the near term, there are many applications for CNT other than the space elevator, so market forces will continue to drive R&D.

But should we build it? What if a piece of space junk should come along and snap it? Depending on how high up it snaps, it might produce a permanent ribbon all the way around the equator. This would be a hazard to shipping, and it would enrage environmentalists who throw a tantrum when somebody drops a gum wrapper in the forest.

Another problem with CNT is the potential health risk if tiny amounts are inhaled. It may turn out to be worse that asbestos. Careless manufacature, accident or a terrorist act could release tons of the fine, indistructible fibers into the atmosphere, where they could float for years. They might float in the oceans for millennia. That could reduce Chernobyl to a footnote in the history books.
« Last Edit: 29/03/2011 06:45:16 by Phractality »
 

Offline Geezer

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What technology do we need to build a space elevator?
« Reply #7 on: 29/03/2011 05:58:00 »

is about 62 Gpa (Gigapackard)


Unless you are talking about a really big US automobile, I think you might mean 62 GPa (gigapascals)
 

Offline Phractality

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What technology do we need to build a space elevator?
« Reply #8 on: 29/03/2011 06:47:31 »

is about 62 Gpa (Gigapackard)


Unless you are talking about a really big US automobile, I think you might mean 62 GPa (gigapascals)

No wonder I had trouble Googling it. Is there a unit of measure named Packard?
 

Offline imatfaal

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What technology do we need to build a space elevator?
« Reply #9 on: 29/03/2011 13:54:39 »
Phrac - extended cable as counter-weight is a fairly recent addition to the idea - but you are right in what you say.  the added benefit is that you could just let a ship fling off the end of the cable if you wanted to launch it into space.  And I like the packard - now you just have to decide what it quantifies
 

Offline Heikki Rinnemaa

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What technology do we need to build a space elevator?
« Reply #10 on: 29/03/2011 17:32:09 »
Hi.

One idea is vacuum-object,,

Hmm,,vacuum clothes,,then can fly like butterfly,,:)

One idea is mayby use earth magnet-flow,,which rise up at middle of equator,,that is my thought of that magnet-flow,,idea is here

http://www.thenakedscientists.com/forum/index.php?topic=37473.0

magnet-flow elevator,,:)

 

Offline briligg

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What technology do we need to build a space elevator?
« Reply #11 on: 04/04/2011 20:17:58 »
Phractal alluded to the issue of space junk snapping the cable. That is actually a really big issue, because with the amount of junk up there, never mind meteors from elsewhere, the calculation show the cable would probably be hit every year on average. You can make the cable a wide enough ribbon to allow a struck patch to still be structurally sound, or deploy some sort of protection system along the entire length. You would also need a repair system. These things raise the price of the project hugely, they would be a large percentage of the expense.

I'm going to bring up the matter of a space fountain here, because it is a competing design very few people know about, which is perhaps why the question i asked about it is getting limited interest.
http://www.thenakedscientists.com/forum/index.php?topic=38397.msg350683#msg350683
The space fountain concept has been fleshed out and the numbers have been crunched enough to show it is just as viable as a space elevator. Probably more so: protecting it from space debris would be a minor issue, as the favoured design is only 200km tall. No major breakthrough is required to construct one, all the technology exists - although clearly the engineering challenges would be huge. The cost of construction would be vastly reduced, compared to the cost of a space elevator, because it can be built from the ground up.

A space fountain is an active structure - it is held up by the energy in the system, more than by material strength. Basically, the transfer of energy from an electromagnetically accelerated stream of iron pellets to the structure by magnetic interaction holds the tower aloft. The pellets travel through a tube containing a vacuum, and are held away from the tube wall magnetically. The pellets are redirected and accelerated at the top and bottom of the tower by a loop of electromagnets. At the top, redirecting the pellet stream causes an upwards force to push on the electromagnets. Along the length of the upward stream of pellets are 'electromagnetic drag devices' that harvest the kinetic energy of the pellet stream, with the net result of an upward force being transfered to the structure, and electricity being produced to power the coil guns on the downward stream of pellets. The coil guns accelerate the downward stream, which also transfers an upward force to the structure.

According to calculation by Roderick Hyde, of Lawrence Livermore National Laboratory, once the system has been fully powered up, careful management of the transfer of the energy in the pellet stream, electromagnetically, would allow the system to be entirely self-sustaining, except for the energy lost through inefficiencies in the equipment. Thus, once in operation, the energy input required to maintain the tower  wouldn't be a major burden.

http://en.wikipedia.org/wiki/Space_fountain
http://www.orbitalvector.com/Orbital%20Travel/Space%20Fountains/Space%20Fountain.htm
« Last Edit: 04/04/2011 20:38:05 by briligg »
 

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What technology do we need to build a space elevator?
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