Will the climbers pull the space elevator toward Earth?

Status
Not open for further replies.
N

nexium

Guest
The space elevator described at www.liftport.com seems to be much the same as the Dr. Edwards elevator. The CNT = carbon nano tubes needs to be hundreds of times stronger than Kevlar for the starter ribbon to have a mass of 20 tons and the finished ribbon 200 tons. The climbers = lifters or elevator car will be only 5% to 10% of the total ribbon mass, so the total movement is rather small. Perhaps more important, nothing happens a few miles up the ribbon when a climber starts up the ribbon. The ribbon stretches locally due to the weight which is increased by the climber accellerating up the ribbon. The stretch transient travels up the ribbon at perhaps 500 kilometers per hour, so the climber could outrun it's own stretch transcent.<br />If my 500 kilometer per hour estimate is average, it is 200 hours before the far end starts to fall toward Earth. By then the climber is likely past GEO altitude, and is now pushing the ribbon away from Earth which partially cancels the pulling it was doing the first 36,000 kilometers. If the climbers stop at or before GEO altitude or leave the ribbon for destinations elsewhere in the solar system instead of parking at the far end as a counter-weight, there are acumulating problems keeping the ribbon from falling toward Earth. Over periods of weeks, it will require careful management of the transcients traveling on the ribbon. Over compensating can mean the ribbon is tryng too hard to move away from Earth which may break the ribbon due to excessive tension. This is an unlikely problem, unless telemetering gives bad data and/or humans make a bad judgement call or micro meteorites damages the ribbon just before a strong transcient arrives. Please embelish, refute and/or comment as I may have this wrong. Neil
 
V

vogon13

Guest
It seems the vibrations and elongation of the CNT would propagate at the speed of sound in the material. Probably much faster than 500 MPH.<br /><br />I don't know that anyone would have a climber go up that fast.<br /><br />IIRC, most of the space elevator designs have a mass on the high end, and my impression was, the entire system would be under tension. And the tension would have to exceed the mass of the climber.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
N

nacnud

Guest
Unless the climber was going to elsewhere in the soloar system why pass GEO? Just stop there and come back down.
 
B

brandido

Guest
I believe you are correct - based on some quick research, it looks like sound propogates in <b>[edit]</b> in steel <b>[edit]</b> the longitudinal direction at 6000 meters/second - given the strength of the CNT cable and the tension it is under, I would think it would be even higher. Based on a (conservative) use of the number for steel, the sound propates at 21600 Kilometers/Hour, far in excess of the speed of the climber, often considered to be around 200 kilometers/hour. <br /><br />And you are correct, the majority of Space Elevator designs currently under discussion have a mass at the far end, I believe in the tens of tonnes range.
 
Status
Not open for further replies.

Latest posts