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Effect of Edward's space elevator on private space travels?

Posted by: Ekkehard Augustin - Tue Jun 29, 2004 7:20 am
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Effect of Edward's space elevator on private space travels? 
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Post    Posted on: Thu Jul 01, 2004 8:06 am
bad_astra wrote:
Even assuming straight up at 200mph and not taking into account accelleration and deceleration, and disembarking (for the sake of simplification) 22000miles, that's a pretty long trip.

How do you maintain (let alone build) a 22000 mile suspension-bridge (a suspension bridge is the closest analogy I could agree with) that has to endure erratic and multi-variant weathering near its base, constant radiation, possible induction of electrical current by the earth's magnetic field, orbital debris (traveling at 5 miles per second, or something ... fast anyway) and presumably frequent use?

I've tried to read up on them (beanstalks), but there is a lot of argument both for and against their use ... it seems like the possibility of such a fantastic* method for reaching orbit is still in the air (so to speak).

*As in it seems like fantasy. But I know literally nothing about them, so I'll just ask my question in the spirit of honest enquiry.

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Post    Posted on: Thu Jul 01, 2004 8:22 am
Please refer to www.niac.usra.edu/studies/. There are placed documents by which Edwards explains how to handle weather conditions and satellite orbits crossing the elevator. The last will be handled by moving the point of surface the elevator is anchored on. This point will be at sea near the ecuadorian coast - a platform swimming on the ocean and because of this moveable.

Perhaps other ways may be found to handle the crossing of orbits - may be a subject private spacecrafts can handle.



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Post    Posted on: Thu Jul 01, 2004 8:55 am
Actually, in that document (which is dated July 2000, got anything newer?) it appears that the space tether starts at 160 miles above the earth, then stretches up to a ... hotel :lol: (sorry, it just strikes me as funny) ... at 775 miles. It's cool and everything, but there isn't anything about the sort of elevator that bad_astra mentioned.

It raises some questions though. What is a hoytether or hoytape design? This is supposed to somehow be resistant to micrometeorite impacts, but what exactly is it?

To deal with space junk they propose using "traffic control" ... erm, ok I guess they will have to move the tether because space junk is notoriously recalcitrant about taking orders from space traffic controllers.

some future space traffic controller wrote:
STC: "Hey spacejunk #36753, be advised you are going to strike the tether, please change your direction."

SJ36753: "Screw you pal, I'm going where I'm going, so YOU can just get out of my way."


That's going to be annoying.

No mention of a sea base.

He wants to use graphite fiber to build it?

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Post    Posted on: Thu Jul 01, 2004 9:30 am
Yes, the documents are from 200 and 2001. But the articles and reports in the german newspaper seam to be based on further researches Edwards has done. May be the NIAC homepage isn't up to date yet.

I suppose new and better articles to be read in journals and newspapers the next coming weeks - Scientific American and its german edition "Spektrum der Wissenschaft" and the german newspaper "DIE WELT".



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Post    Posted on: Thu Jul 01, 2004 12:15 pm
The hard part of gettin into space is getting past the lower end of Earth's gravity well, which is pretty strong. The gravitic effect of an Earth-size mass at earth's surface exerts a force sufficient to accelerate any massive object by 9.82 m/s^2 towards its center. However, at one more Earth radius (circa 6800 km up), that force is greatly lessened (since gravity's pull is quadratic in relation to the distance tbetween masses). So if you can just get out a little bit, you already save whole stack of energy trying to get free from Earth's gravity. As such, a 'space elevator' os a grand concept.

As to moving up and down the elevator: Wear and tear and friction against the elevator is only an issue if the elevator car actually touches it. Magnetic train rail technology has the answer: The elevator car can be held at a few centimeters of distance from the tether, and propelled upward by a magnetic current. This allows the car to travel as fast as the energy can be provided to overcome gravity, without much if any loss to friction. Basically, it's the first few km of travel that will be expensive, due to them taking place within the atmosphere. Once you're above the first 100 km, no biggie. And given the 'floating tether' concept I described earlier, the first hundred might not be the elevator's problem at all. Radiation belts aren't a problem (assuming an equatorial placement of the tether) for about the first Earth radius (just under 6800 km), either, and by that time, an elevator car might be moving very fast indeed.

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Post    Posted on: Thu Jul 01, 2004 12:57 pm
Awesome, a magnetic rail ... wait a second wouldn't that make it (as a conductive length) a giant lightning rod? That would be bad, no?

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Post    Posted on: Thu Jul 01, 2004 4:57 pm
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How did the apollo missions get though the radiation belts?


VERY QUICKLY


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Post    Posted on: Thu Jul 01, 2004 5:32 pm
At what altitude can you get into earth orbit just by falling?

How about a "short" space elevator that goes from the highest part of the atmosphere you can fly a non rockett powered aircraft to the lowest altitude at which you can get into orbit using the earths gravity.

There is a way to do that--right? Use the earths gravity to accelerate yourself into orbit?

That elevator would take you past the most expensive parts of the journey into space.

Btw could you deflect space radiation using electromagnets?


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Post    Posted on: Thu Jul 01, 2004 5:32 pm
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As to moving up and down the elevator: Wear and tear and friction against the elevator is only an issue if the elevator car actually touches it. Magnetic train rail technology has the answer: The elevator car can be held at a few centimeters of distance from the tether, and propelled upward by a magnetic current.


Do you think Mag-lev trains hover over thin air? If an elevator is made, it will be extremely thin, composed of carbon nano-tubes stretched to near limits of their tensile strength. Where do you propose to put the supporting structure (track magnets, power cables, etc) - and how will the elevator itself respond to the millions/billions tonnes of added mass that will add? What will the mag-lev elevator car actually "push" against?

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Post    Posted on: Thu Jul 01, 2004 7:30 pm
Texan wrote:
At what altitude can you get into earth orbit just by falling?

How about a "short" space elevator that goes from the highest part of the atmosphere you can fly a non rockett powered aircraft to the lowest altitude at which you can get into orbit using the earths gravity.



And what would the elevator be attached to? A space elevator works because it has a counterpoise about 56,000km away from earth.

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There is a way to do that--right? Use the earths gravity to accelerate yourself into orbit?


No.


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Post    Posted on: Thu Jul 01, 2004 8:05 pm
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There is a way to do that--right? Use the earths gravity to accelerate yourself into orbit?


I think you can use it only to get back to earth... as example you can't use darkness to create light...
Some spacecrafts used it to turn and to speed up.. but only when they are already in space...

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Post    Posted on: Thu Jul 01, 2004 9:52 pm
bad_astra wrote:
Texan wrote:
At what altitude can you get into earth orbit just by falling?

How about a "short" space elevator that goes from the highest part of the atmosphere you can fly a non rockett powered aircraft to the lowest altitude at which you can get into orbit using the earths gravity.



And what would the elevator be attached to? A space elevator works because it has a counterpoise about 56,000km away from earth.

Quote:
There is a way to do that--right? Use the earths gravity to accelerate yourself into orbit?


No.


Basically the only way a space elevator cable will realistically work is if it goes all the way to geostationary earth orbit and is counter balanced with either an equal length of ribbon going outward from there or the equivalent weight on a shorter outgoing cable. Without being geostationary it would burn up in the atmosphere. Shorter tethers will become very useful for other things but not actually getting into space from the ground.


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Post    Posted on: Thu Jul 01, 2004 11:29 pm
it's not realistic, or at least won't be for a VERY long time, but i'll refer you to the unreal tournament level "morpheus", where you fight in low grav on the tops of 12-mile-high buildings, constructed from basically a whole hell of a lot of really really strong carbon nanotubes. while the requisite technology for such a structure is probably at least 100 years away, i'll say that, in addition to being one hell of an apartment building, that (or something taller) would also be a good way of getting stuff from the ground to an altitude where it could be launched with basically no gravity or atmosphere for resistance, and could be landed on too. maybe 200 years from now you'll be able to buy a ticket on the Armadillo Mk. 11ty billion launching from the 20-mile tokyo galaxyscraper (what it's called in UT) to anywhere in the solar system.

oh almost forgot, at those altitudes, radiation from a nuclear engine would be trivial, so pollution wouldn't matter even if it was stuff that'd wipe out whole ecosystems on earth, and you wouldn't have to use chemical engines. obviously in that time frame antigravity could be around, and if so it'd be irrelevant.

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Post    Posted on: Thu Jul 01, 2004 11:59 pm
TJ wrote:
Basically the only way a space elevator cable will realistically work is if it goes all the way to geostationary earth orbit and is counter balanced with either an equal length of ribbon going outward from there or the equivalent weight on a shorter outgoing cable. Without being geostationary it would burn up in the atmosphere. Shorter tethers will become very useful for other things but not actually getting into space from the ground.
You only burn up in the athmosphere if you go really fast at relatively low altitude (i.e. typically below 100 km). Since we've had recent proof that attaining these 100 km is fairly doable cheaply, we could easily assume that a lifter could be built to take cargo to this altitude. So if we have a tether that starts at just over 100 km altitude, and then has an orbital center much further out, giving it a relatively low orbital velocity (perhaps in the few hundreds of km/h, projected to Earth's surface), we have a platform orbiting at low speed at low altitude, which is completely reachable by a much lower energy exertion than reaching a real orbit. From this low platform, then, the cargo can be lifted upwards, into a location from which higher orbits are attainable with less energy exertion - in short, have an elevator to cross the 'hard part' of getting to space. It would go from perhaps 100 km to an orbital center of perhaps 30,000 km (I haven't checked the orbital velocity of that altitude just yet), with a counterweight at an suitable distance further out. It's quite doable.

As for the problem of infrastructure, it would be there anyway. You need to have a way the elevator can 'crawl' up or down the tether anyway if you want to use it for somethoing sensible. I just suggested that magnetic propulsion could be one that reduces wear and tear on the cable.

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Post    Posted on: Fri Jul 02, 2004 12:51 am
ahh.. of course if it were moving through the atmosphere AND orbiting this would generate alot of stress on the elevator.....

ALSO it might make some of the countries below unhappy if it was obiting through their airspace. There are some orbits which might be more politcally feasible.

But yes, if you were going slow enough it might work....

AND there has to be a way to maneuver your spaceship into earth orbit by "falling"

You go up to a high altitude on the elevator - say 2000 miles, I don't know if that is high enough to work, fire your rocketts so you "fall" to the side of earth and get enough speed to go into orbit


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