Space elevator - the ultimate brickwall

[greythanis]

The space elevator - why it won't work:<br />we all know the basics, a thread on the equator whose center of gravity is in geostationary orbit. here's the problem.<br />all sattelites avoid crashing into eachother either because they are at different altitudes, or because they are traveling at the same speed and therefore keep the distance between them constant at all times. now introduce a sattelite, traveling slower (geostationary) and covering ALL altitudes. All the sattelites are eventually going crash into the elevator, wrecking the economy, not to mention the elevator itself.<br />so from my point of view, let's keep the space elevator for mars shall we?

 

[josh_simonson]

On mars phoebos could hit it too, that's worse than a few small sats...

 

[Boris_Badenov]

2300 years ago what would a person have said about a steam engine (a Greek scientist developed one), when Jules Verne wrote 20,000 Leagues Under The Sea what did people say about an unlimited power source on a submarine?<br /> To say there will never be a Space Elevator is like saying life on other planets is impossible <img src="/images/icons/wink.gif" /><br /><br /> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[qso1]

crazyeddie:<br />Before any space elevator could be constructed,<br /><br />Me:<br />By the time we get a space elevator operational, we should have gotten a handle on the lower orbital debris hazards as you mentioned, removing it somehow. Debris at the top of the elevator would be minimal. Maneuvering should be left to the satellites rather than the elevator. I would think the elevator should be maneuvered as little as possible to avoid disturbing its inherant equilibrium and or stability for lack of better terms.<br /><br />And as you stated, I wouldn't call it impossible, although I'm still not convinced its practical considering the sheer size of it. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[barrykirk]

Using a Naval analogy.<br /><br />The George Washington Bridge HAS the right of way over all the barges and ships going up and down the river.<br /><br />For Spacecraft and spacestations, evenentually a protocal as to who has the right of way will have to be developed. I would think that a space elevator, if it is possible to build one would have the right of way.

 

[MeteorWayne]

That's kind of a specious argument though. There are few vessels that have the clearance above water to even come close to the GWB. In fact there may not be any, but I'll have to check. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vogon13]

(sorry to go off topic)<br /><br />Did you see the footage of the movable lift span bridge knocking the upper decks and stack off a largish ship in the St. Lawrence Seaway some years ago?<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>

 

[qso1]

BarryKirk:<br />if it is possible to build one would have the right of way.<br /><br />Me:<br />A good analogy and yes, the space elevator should have the right of way as it is less maneuverable as a whole than a satellite with thrusters. By its very design and nature, a space elevator has to remain on station. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[spacester]

See this 2.7 MB pdf or the corresponding html version and refer to the bottom of page 22.<br /><br />If the links don't work, google 'brad edwards niac' <br /><br />There was a much longer report available but I'm not immediately finding it. <div class="Discussion_UserSignature"> </div>

 

[JonClarke]

Phobos is a problem on Mars only if the surface end is located beneath the orbital track of the Moon. if it is located north or south of this then it is not a problem. If with a sub Phobos site, resonances could be induced that allow Phobos to pass.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[torino10]

I have always been more in favor of a flying space elevator concept. A cable aproximately 4000 kilometers long with the bottom end at an altitude of approximately 150 kilometers. <br />The advantages of a flying space elevator are numerous, most significant is that it could travel within the plane of the eliptic, unlike the ground to GEO , thus giving more release windows from the higher end to Luna and other destinations within the solar system. Another advantage is that the lower end will be accessable to most major cities twice a day from suborbital launch vehicles taking off from most major transportation hubs. This will encourage competiton in the suborbital market.<br /><br />Of course multiple flying space elevators may eventually be flown into the ground to Geo configuration if this is still desired.

 

[Boris_Badenov]

Are suggesting a suborbital vehicle launches, speeds to 2500 miles per hour, grabs the space elevator/ tether, and then accelerates to 18500 miles per hour in an instant? Lets see, 18500, minus 2500 equals 16000 miles per hour, divided by 9.81 equals about 1630 g’s. Think you could survive that? <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[nexium]

Hi Boris: You are mixing metric units with miles per hour. If the ribbon acellerates the space craft V=at at an average of 2g = 64.4 feet per second per second for 120 seconds = 2 minutes, The speed increases 7728 feet per second = about 5000 miles per hour; added to 5000 miles per hour = 10,000 miles per hour at an altitude of several hundred miles which qualifies as sub orbital speed. Humans can tolerate 5 or 10 g for several minutes, but even CNT with optimistic specs may fail. There may 2 or 3 additional g as the pay load is being towed in a circular path. We may have to use more than 4000 miles of rotating ribbon for 3 minutes and/or catch the end at faster than 5000 miles per hour. Neil

 

[publiusr]

Docking in LEO is a gentle affair. This is a flying wallenda trapeze act with a tether that can slice you in half.

 

[bdewoody]

Then show me even basically how it would be built. Like I said on another thread I can see how one would work if already there but for the life of me I can't see how it could be built, ie. the construction sequence like how do you hold it all up befre it's finished? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[barrykirk]

Essentially you unreel it from the center on out.

 

[bdewoody]

Unreel it from what? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[j05h]

>Unreel it from what? <br /><br />From a giant reel. I'd suggest at least part of a "rotovator" be electrodynamic so that it can provide it's own reboost.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[bdewoody]

Duuh,<br /><br />I mean what's holding the reel where? What's going to hold the reel in position while you are unwinding it and how do you get it there to unwind. Get my drift??? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[mrmorris]

<font color="yellow">"...electrodynamic so that it can provide it's own reboost"</font><br /><br />I'm staying out of the elevator issues on this thread. However, I thought I'd chime in on the tether issue. To my knowledge, there's been no proof that Electrodynamic Tethers (EDTs) will provide reboost. It's considered <b>possible</b>, but I have serious doubts.<br /><br />The problem is that the mechanics work this way -- a spacecraft has a multi-kilometer tether below it. Said tether is ferrous, and since the orbit is dragging it through Earth's magnetic field, an electrical potential exists just as happens in the wire windings of a generator. Just as an electrical motor and a generator are inverses (one converts mechanical energy to electrical -- the other electrical energy to mechanical), an EDT can <b>theoretically</b> do the same.<br /><br />To provide propellant-free deboost, the spacecraft would use the electricity generated by the Earth's magnetic field on the tether (i.e. pulling electricity *out* of the tether). This would create a drag which would pull the spacecraft downwards. I believe this would work exactly as expected.<br /><br />However, the 'reboost' concept is that the spacecraft <b>generates</b> electricity via solar panels and pumps it *into* the tether, thereby creating an upward vector that raises the orbit of the spacecraft.<br /><br />The problem lies to me in the fact that I have no problems whatsoever in 'pulling' on a rope to make a spacecraft come down. I simply can't understand how 'pushing' on a rope is going to make a spacecraft go up. Since the force vector is going to be spread evenly across kilometers of rope -- I don't see any way to 'stiffen' it such that this will have any positive effect at all on the spacecraft at the top. It may be that I've missed something in my reading and the tether for reboost potential will be 'above' the spacecraft -- but I don't beleive this to be the case.

 

[bitbanger]

"I don't see any way to 'stiffen' it such that this will have any positive effect at all on the spacecraft at the top."<br /><br />I believe what you are missing are the tidal effects of having the lower end of the tether closer to the planet. This is supposed (I'm not really knowedgeable here, I'm just parroting back what I've read) to provide the 'stiffening' that is needed.<br /><br />Also, you aren't really pushing the spacecraft up during reboost, you are increasing it's orbital speed. So if the lower end of the tether increases it's speed, then it will in essense be pulling the spacecraft along. This is also how the deorbit works. It doesn't pull down towards the planet, it retards the orbital speed.

 

[barrykirk]

Start with the reel in Geosynch orbit. Yes it takes a big rocket to get it there.<br /><br />Unreel with two lines. One going towards the earth and one going away from the earth.<br /><br />If done properly, if it can be done properly is another question, you should eventually end up with a space elevator.<br /><br />And I made it sound so easy...

 

[bdewoody]

What's going to make the line (wire made of unobtainium) go straight down to earth and not just trail out in a gradually decreasing orbit and eventually wrap around the planet, assuming it wouldn't break before then. I'm sorry but I don't think that would work. <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[vogon13]

It's a plumb bob.<br /><br />As automatic as gravity . . . . . <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>

 

[barrykirk]

It's called tidal force.<br /><br />If you had a satellite in the shape of a long rod. It would eventually orient itself so that it is pointing towards the center of the planet.