Space elevator - the ultimate brickwall

[bdewoody]

I guess it will remain to be seen but from an engineering standpoint I still do not see how this would work. <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[rocketman5000]

if you have the reel in a GEO and start to unwind the upper and the lower portions of the ribbon at the same time it shouldn't drift from its location as the center of mass never changes

 

[docm]

Let's discuss the day proposed for the carbon ribbon reaches close proximity to the Earth. Our <i>highly conductive</i> carbon ribbon.<br /><br />On STS-75 3,500 volts at ~.5 amps (~1,750 watts) was generated when a tether was lowered 13 miles, cutting through Earths field lines. The tether fried where it contacted its payload bay deployment tower. <br /><br />In addition to the elevators ribbon generating a current by cutting through shifting field lines there is another source; the potential difference between the Earth and the ionosphere runs ~250,000 volts. <br /><br />Now imagine our elevators extremely long ribbon moving through the Earths field lines <i>and</i> the ionosphere and its constantly moving currents on the way down. It should acquire a significant potential. <br /><br />May I propose a ground attachment attempt on July 4th at dusk? <img src="/images/icons/tongue.gif" /> <br /><br />Now consider how affecting the ionosphere by shorting even a part of it could affect the weather patterns, which have recently been tied to current patterns in the ionosphere.<br /><br />Hmmmmm..... can you say "environmental impact statement"? <div class="Discussion_UserSignature"> </div>

 

[vogon13]

A cable fixed at GEO and extending upwards and downwards won't cut many lines of flux . . . . .<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>

 

[docm]

Because the cable won't move much once attached, but on the way down you can bet it'll be moving around cutting what lines are there many times. Not to mention the relative motion of the field lines themselves.<br /><br />Unless both are near stationary, and you can bet against that, it will acquire a big charge and that doesn't take into consideration that 250kv potential from the ionosphere.<br /><br />Current? Don't have a clue but I sure wouldn't want to be there when tha ribbon comes down.<br /> <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

throw enough money at any technically feasible idea and you can make it work. Apollo is testimony to that

 

[vogon13]

<i>Geostationary</i> earth orbit?<br /><br />Capiche?<br /><br />I reiterate, how many lines of flux get cut by a conductor rotating in sync with the rotating lines of flux?<br /><br /><br />???<br /><br /><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>

 

[nexium]

While it is desirable to dispose of space junk, the orbits are known for nearly all the LEO = low Earth orbit junk larger than 10 centimeters and an increasing percentage over one centimeter or over one gram. The lower end of the space elevator ribbon will be attached to an anchor ship, which will move about ten kilometers, to insure a miss by a kilometer or two. It is expected that this movement will be made several times per week to insure that the ribbon misses both satellites and space junk. The ribbon will be about one meter wide and somewhat like a fish net, so only about 1% of the strength will be lost when millimeter size junk tears though the ribbon at high speed. Damaged spots will be repaired typically within hours. For more details www.liftport.com click on forums near the bottom of the page. Neil

 

[nexium]

A space craft will lift about 20 tons of starter ribbon on a reel to an altitude of about 91,000 kilometers = 60,000 miles. It will start to unreel the ribbon a bit below GEO altitude, so that end falls slowly toward Earth. When the space craft reach an altitude of about 91,000 kilometers, it and the empty reel will become a counterweight, otherwise the ribbon needs to be almost 200,000 kilometers long to keep the center of weight at GEO altitude. Neil

 

[nexium]

Most of that 13 miles of tether is likely standing vertically in an eliptical LEO. The average orbital speed is about 17,000 miles per hour, so it does cut some flux lines even though the orientation is less than optimum. If we attach another length of conductive tether with an ion engine on the bottom end, the tether can be made to tumble end over end. This is called a bolo. With high tip speed, and the correct orientation, the bottom tip will be moving only a few thousand miles per hour with respect to Earth's equator. A pay load can be attached to this slow tip with the help of a suborbital rocket, and released a few minutes later at about the highest altitude. The payload speed has been increased by several times, which can take the payload most anywhere in the inner solar system. Some of the electricity to run the ion engine can likely come from cutting magnetic lines of force as the ion engine optimizes the orbit and increases the tip speed. Part of the time the curent may be reversed to aid in getting higher tip speed and optimum orbit. Neil

 

[rocketman5000]

sounds a bit like perpetual motion. <br /><br />One of the 3 commandments is don't break the second law of thermodynamics

 

[josh_simonson]

No perpetual motion, the space elevator or electrodynamic tether just steals energy from the earths rotation. Over millions of years of use the day might become measurably longer and cause a huge debate like global warming is now. I believe an electrodynamic tether in a retrograde orbit would actually push against the earth such that the earth spins faster, so perhaps in 10 million years we will have to end our 'addiction to using the earths spin to help get to orbit' and develop 'alternative launch systems' to aleviate 'human induce day-lengthening', with all the horrors that an extra 10 minutes of sleep every night would cause... <img src="/images/icons/wink.gif" /> <br /><br />I'm more of a fan of rotovators than space elevators. I don't think a 100,000 km bus trip up a cable is all that practical. The material science demands for a rotovator are far less too.

 

[mithridates]

I do like the idea of a space elevator but with all the logistics involved I think JP Aerospace's method is a lot better if we're looking for a nice stable way to get from the surface of the Earth to orbit without having to use chemical rockets.<br /><br />The technology would still be useful though - later on it would certainly be the best method to use if we decide to mine a rapidly spinning asteroid some 20 km in diameter or so. Some asteroids spin around so fast they actually change in shape quite a bit.<br /><br />Actually now that I think about it that could also be a really destructive weapon too. -_- <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[spacelifejunkie]

Idaho Space Materials claims to have a breakthrough in CNT production and purity.<br /><br />http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=104&STORY=/www/story/10-26-2006/0004460130&EDATE=<br /><br /><br />SLJ

 

[barrykirk]

Cool....<br /><br />I'd still bet that we will be building space tethers long before an elevator.