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why is it so hard to make an elevator in to space???

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kappee

Guest
everybody's looking at lasers to help create a cheap way to lift us off the ground how about the old fashion way of wires. Isn't there a way of keeping a rocket junctioned in space with 500 miles of cable. Come on now we create enough trash to circle the earth and moon's orbit in a week. It would be easy for them to just create a magnetic lift along the tethered wire. Or is there something i'm missing here.
 
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CalliArcale

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That, plus the sheer amount of material required. The start-up demands for a rocket program are a lot smaller, so though it might cost a lot in discarded components in the long run, it's acheivable in the short run.<br /><br />But yeah, the technology really isn't there yet for the kinds of cables you'd need. Nanotubes will probably be the way to go, but so far they can't get them longer than a few inches. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>
 
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najab

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Well, first thing it would have to be longer than 500 miles. An object in orbit at 500 miles will move relative to the Earth's surface. You really don't want the bottom of your elevator to be going around the world every 2 1/2 hours - firstly it would be moving very fast and the end would likely burn up from the friction, and secondly it might hit things (birds, planes, mountains, etc)!<p>The solution to this problem is to put the top end of the cable in a geostationary orbit - in this orbit the cable would not move relative to the Earth. The geosynchonous point for the Earth is about 22,000 miles up. So we need a cable that's 22,000 miles long, rather than 500 miles.<p>Now think about the cable. We start with a steel cable that was strong enough to put an elevator on, about an 1/2 inch thick. Well, the volume of that cable (1/2 inch * 22,000 miles) is about 1.2x10<sup>9</sup> cubic inches. Steel weighs about 4.5oz/ cu inch. So our cable weighs about 154,000 tons. Looks like we'll need a thicker cable. Which would mean a heavier cable. Which would require a thicker cable.<p>That's the problem - we haven't yet found a material strong enough that we get out of the repeating thicker, stronger, thicker loop.</p></p></p>
 
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the_ten

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I wonder if I'm the only one who thinks the 'space cable' idea is.... corny.
 
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propforce

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Please don't do this during lunch time. I laugh so hard that my stomach hurts .... <div class="Discussion_UserSignature"> </div>
 
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mikejz

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Whats corny is that the price of space cable kept going up, so I switched to satellite
 
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najab

Guest
Methinks you need to slow down and read my post again. The point I was making that we can't build a SE with any extant material - substitute Kevlar for steel and it still works out as impossible. Until we get a material with a high enough tensile strength, we ain't gonna build a SE.
 
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arobie

Guest
And the problem with Carbon Nano-Tubes is that we can only create them on a nano scale to get the required strength.<br /><br /> I read sometime ago that someone figured out how to create them like 3 feet at a time, but the strength wasn't strong enough. If they work on that idea and get the strength up, then we could possibly be in bussiness. We would then have to ability to build the elevator in the near future but then we would need a company or person with enough money or investors willing to build it.
 
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meteo

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I belive the problem is not only the length of CNT's,there is also the problem of embeding them in a material. If my memory serves me the problem is as the percent CNT goes up it becomes more difficult to chemically bond the CNT to the material you embed it in, like polypropylene. We need to go from a couple percent CNT combined in a usable material/usable size to 50%.<br /><br />However, all this assumes a space elevator that connects to the ground. The strength requirements enter the doable range for a LEO-up space elevator or a lunar one.
 
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nhcatsteve

Guest
You need to consider that the entire mass of a cable to geo-synchronous orbit is not relevant, because there's effectively no gravity that far out. Also, the first 80,000 feet (about 15 miles) could be lifted with a huge kite, tethered in an area with consistently stiff high-altitude winds (which do exist). <br /><br />With this considered, perhaps one of the many existing polymers with far greater tensile strength than steel could do the job, even without carbon nanotubes. Am I missing something here? Why aren't we already doing this?!?
 
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bobvanx

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> Am I missing something here?<br /><br />Yep, you're thinking like a land-based creature. Which most of us are.<br /><br /> />there's effectively no gravity that far out.<br /><br />If you were a space-based creature, you'd know that gravity DOES go that far, and farther. The reason the space elevator has to be strong is that it's spinning once every 24 hours. Doesn't sound like much, but it's really, really long and the forces are going up really quickly. The place on the cable at GEO feels weightless, but the other two ends feel the full force of gravity and the dynamic system. That force gets transmitted as tension through the entire structure.<br /><br />A rotating tether in LEO could be built with today's materials. It would orbit every couple of hours, and it could spin at a rate which had the descending tip dipping into the very top of atmosphere moving at merely supersonic velocities.<br /><br />A scaled-up SS1-class vehicle could "dock" with the end of the tether. You'd have a minute or two to complete the maneuver.<br /><br />Then the tether's rotation would lift the ship up, and you'd feel quite a good G-force. Undock at the top of the rotation and you've got the velocity to go to GEO. Undock when you're at the bottom and you're 4,000 miles from where you started.
 
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mental_avenger

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<font color="yellow"> everybody's looking at lasers to help create a cheap way to lift us off the ground </font><br /><br />Excuse me? Everybody? I don’t know what bubble you have been living in, but that technology simply cannot provide enough thrust to be of any use, and even then it is only viable within the Earth’s atmosphere.<br /> <div class="Discussion_UserSignature"> <p style="margin-top:0in;margin-left:0in;margin-right:0in" class="MsoNormal"><font face="Times New Roman" size="2" color="#ff0000"><strong>Our Solar System must be passing through a Non Sequitur area of space.</strong></font></p> </div>
 
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mental_avenger

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<font color="yellow"> because there's effectively no gravity that far out. </font><br /><br />Only if you are in stable orbit. If you were not in orbit, but rather sitting in space above Earth at 22,000 miles, you would very quickly accelerate towards Earth at a high velocity.<br /><br /><font color="yellow"> Also, the first 80,000 feet (about 15 miles) could be lifted with a huge kite, </font><br /><br />It is highly unlikely that a multi-billion dollar project would trust their tether to a high flying kite. Also, 15 miles out of 22,000 is hardly worth the risk.<br /><br /><font color="yellow"> With this considered, perhaps one of the many existing polymers with far greater tensile strength than steel could do the job, even without carbon nanotubes. </font><br /><br />The problem is that the “classical” space elevator, anchored on the Earth on one end, and counter balanced on the other end, would experience tremendous tension forces. The tension forces would be equal to the combined weight of the tether from any point along its length, to the end. That applies to both the Earth end and the counter balance end. That is why such a tether would be tapered from the middle towards both ends. The middle would experience the most tension.<br /><br /><font color="yellow"> Why aren't we already doing this?!? </font><br /><br />1. We don’t have strong enough materials.<br />2. The initial investment would be very high.<br />3. It is a difficult concept to sell to investors.<br />4. The possibility of damage due to natural causes (extreme weather, orbital debris) would make it risky.<br />5. The vulnerability to terrorist attack would make it very risky.<br /> <div class="Discussion_UserSignature"> <p style="margin-top:0in;margin-left:0in;margin-right:0in" class="MsoNormal"><font face="Times New Roman" size="2" color="#ff0000"><strong>Our Solar System must be passing through a Non Sequitur area of space.</strong></font></p> </div>
 
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exoscientist

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Ultralong single-wall carbon nanotubes.<br />http://www.nature.com/cgi-taf/DynaPage.taf?file=/nmat/journal/vaop/ncurrent/abs/nmat1216.html&dynoptions=doi1096137264<br /><br />Extra-long carbon nanotubes set new record<br />20 September 2004<br />http://nanotechweb.org/articles/news/3/9/12/1<br /><br />A longer strand of tiny tough stuff.<br />http://www.lamonitor.com/articles/2004/09/17/headline_news/news03.txt<br /><br /><br /> The researchers claim to have developed a method that can produce arbitrarily long nanotubes. They've produced 4cm long single-walled nanotubes so far.<br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>
 
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bobvanx

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>It might be best if the elevator only comes to the edge of the atmosphere<br /><br />I like this idea. Since the tether is in reality an orbital tension structure, and if SWCNT (single wall carbon nano tubes) ribbon is as strong as we suspect it might be, then this lower end could easily be a wide flat "airport."<br /><br />It would add the cost of flying cargo to the 'port, but since it uncouples the tether from the surface, it adds a layer of security. It also adds a measure of steerability so you could induce beneficial oscillations to vibrate the tether out of the way of known space debris.<br /><br />The working conditions would be tough, requiring personnel to wear environmental suits. But that's actually a benefit: we'd get some much needed experience in how to run an operation with lots of people in a near-space like environment. From supplying oxygen to protecting against radiation, even to how long it takes to cycle in and out of habitat space and work space, it could be a valuable dataset fro when we start building stuff on Luna.
 
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