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View Full Version : Space Elevator rises closer to reality



NubiWan
2002-Mar-08, 02:45 AM
Tether Technology (http://space.com/businesstechnology/technology/space_tether_020306-1.html)

Free power to raise or lower, space craft's orbits. Perhaps the first real step toward a "Space Elevator." This is big stuff IMO.

<font size=-1>[ This Message was edited by: NubiWan on 2002-03-07 21:49 ]</font>

GrapesOfWrath
2002-Mar-08, 09:47 AM
I have one question. What is "touchy-feely physics" and is there a textbook?

ChallegedChimp
2002-Mar-08, 10:06 AM
Ouch GOW. Touche'

snicker...

Roy Batty
2002-Mar-08, 12:35 PM
Lol! 'touchy-feely physics' I laughed when i saw that.. i'm imagining quantum physicists with hands in an accelerater box fondling furry particles /phpBB/images/smiles/icon_smile.gif

Herrum! moving swiftly on, this looks like its using similar principles?
http://www.spaceref.com/news/viewpr.html?pid=7639

Phobos
2002-Mar-08, 05:41 PM
This is not that new an idea. Shuttle mission STS-75 had very good experimental results from a tether test.

What catches my imagination is the possibilty that nanotubes (extruded c60 molecules or "buckytubes") may actually be strong enough to support their own weight over virtually any length.

If the claim is true then we could start to imagine a space elevator where the elevating devices rises inside a hollow tube multiple miles long.

Sounds like science fiction but I am still listening for supportive/dismissive evidence.

Phobos

Azpod
2002-Mar-08, 07:30 PM
On 2002-03-08 12:41, Phobos wrote:
This is not that new an idea. Shuttle mission STS-75 had very good experimental results from a tether test.

What catches my imagination is the possibilty that nanotubes (extruded c60 molecules or "buckytubes") may actually be strong enough to support their own weight over virtually any length.

If the claim is true then we could start to imagine a space elevator where the elevating devices rises inside a hollow tube multiple miles long.

Sounds like science fiction but I am still listening for supportive/dismissive evidence.

Phobos


From what little I know on the subject, using nanotubes is the only way we even COULD build such a space elevator using today's technology. But rather than a giant hollow tube, it'd be a cable made of of trillions of these tubes chemically attached to each other, side by side. The cable would have to be extermely thick to support the weight of both itself and whatever we want to lift up the elevator, and long! It'd have to extend far enough past the geosynch orbit so that it would be stable as we hoist matter into geosynch orbit.

Of course, the biggest problem with the space elevator idea is that it cannot work with anything in near Earth orbit. A fleck of paint in NEO could cause considerable damage to the cable, and something larger would almost certainly shear it off. Granted, even with everything we have in NEO currently, the chance of collision is low, but if you consider what the cost would be if something did hit...

I think it's a great idea, but I don't see us or anyone getting all the nations agreeing to abandon NEO, and to clean up all the debris currently in NEO.

John Kierein
2002-Mar-11, 04:43 PM
If they don't put an ion gun at the end of the tether to allow the current to flow, it just might crumple up into a big ball. I've been somewhat peripherally involved in tethered satellites for some time. Even bid on building one once.

NubiWan
2002-Mar-28, 06:35 AM
An update with some specific interesting information, IMO, dealing with the Elevator's rise. It's nearer than me had thought.

Going Up (http://story.news.yahoo.com/news?tmpl=story&u=/space/20020327/sc_space/the_space_elevator_comes_closer_to_reality&cid=96)

Gsquare
2002-Mar-29, 05:38 PM
NibuWan,
The 'space elevator' is definitely in the realm of possibility, but it does not operate with any less energy than currently methods....the same amount of energy is required (maybe more in this case) to lift a certain mass against earth's gravity.
What it does is lower the impulse requirements so you can spread the energy over several days; i.e., much lower acceleration to get the payload up there; making it safer, more economical, etc.


I've been somewhat peripherally involved in tethered satellites for some time.

I thought the Nasa sponsored tether had breakage problems, etc. What was the net results?



the biggest problem with the space elevator idea is that it cannot work with anything in near Earth orbit. A fleck of paint in NEO could cause considerable damage to the cable, and something larger would almost certainly shear it off

Yea, not to mention terrorists flying into it!

G^2



<font size=-1>[ This Message was edited by: Gsquare on 2002-03-29 12:40 ]</font>

dapted
2002-Mar-30, 06:05 AM
OK Phobos, you asked for it.

Give me a break. Just put something in geostatioary orbit and "snake a cable down to earth" The cable has to be decelerated as it decends without imparting any force on the geostationary platform. Or you have to keep the platform in Geostationary orbit while in a much higher orbit. Thus you must have a hugh amount of thrust pushing you toward earth to maintain such an orbit and you must maintain this thrust all the while you are positioning ie: "snaking" the cable to earth. At the point where you finally make the connection the amount of thrust generated must be equal to the amount of strain the cable normally encounters to resist the centrifical force of the space anchor. Then as if that is not enough you have to accelerate an object as it goes down the cable and Accelerate it as it rises to space, to some point, then reverse it. Very confusing. This energy can come from rockets or it can come from kenetic energy stored in the space anchor and transfered as stress on the cable. I can't wrap my mind around how many billions of tons of mass it will take to keep the cable taught, let alone to keep it from bowing as it's payload accelerates or declerates its orbital velocity.

But assuming those smarter than I get it done, it becomes not only the vehicle of choice for taking things to space. Multiples of them become the vehicles of choice for rapid intercontinental travel. Any point up the tether becomes an space port, and shuttles carry passengers from one tether to the other.

What nonsense! But a lot of fun to daydream about.
We'll all be drinking that free bubble up and eatin that rainbow stew. Sing together now.

NubiWan
2002-Apr-03, 03:30 AM
Gsquare:
"I thought the Nasa sponsored tether had breakage problems, etc. What was the net results?"

It was an experiment to see if current could be generated with a tether from a spacecraft. It broke and was lost, but before it snapped, current was flowing...

Phobos
2002-Apr-03, 08:01 AM
Gsquare:
"I thought the Nasa sponsored tether had breakage problems, etc. What was the net results?"

It was an experiment to see if current could be generated with a tether from a spacecraft. It broke and was lost, but before it snapped, current was flowing...


I never heard the final conclusion, but it sounded like it worked too well, the tether overloaded and blew.

TinFoilHat
2002-Apr-03, 12:01 PM
On 2002-03-30 01:05, dapted wrote:
Give me a break. Just put something in geostatioary orbit and "snake a cable down to earth" The cable has to be decelerated as it decends without imparting any force on the geostationary platform. Or you have to keep the platform in Geostationary orbit while in a much higher orbit. Thus you must have a hugh amount of thrust pushing you toward earth to maintain such an orbit and you must maintain this thrust all the while you are positioning ie: "snaking" the cable to earth. At the point where you finally make the connection the amount of thrust generated must be equal to the amount of strain the cable normally encounters to resist the centrifical force of the space anchor.

If you extend two cables simultaneously - one down from the geosynchronous sattalite to the ground, and one up from the geosynchronous sattalite out into space - you never have to worry about providing any thrust at all. The center of mass of the entire arrangement stays in geosynchronous orbit, the weight of the lower cable is offset by the outward centrifugal force on the upward cable, and the entire system is perfectly stable all the way to when you attach the cable to the anchor point on the ground.

David Hall
2002-Apr-03, 12:22 PM
On 2002-04-03 07:01, TinFoilHat wrote:
[quote]
On 2002-03-30 01:05, dapted wrote:
Give me a break. Just put something in geostatioary orbit and "snake a cable down to earth" ...

Actually, you could also just make sure there's an equally massed counterweight on the other side of the stationary point. As you run the cable down, keep adding more mass to the other end.

I'm wondering about the current thing myself. I wonder just how much energy it would generate, and if it would be a problem or if it could be harnessed to provide free lifting engery for the elevators (and maybe more for the power-starved denziens down below).

Phobos
2002-Apr-03, 03:10 PM
If you extend two cables simultaneously - one down from the geosynchronous sattalite to the ground, and one up from the geosynchronous sattalite out into space - you never have to worry about providing any thrust at all. The center of mass of the entire arrangement stays in geosynchronous orbit, the weight of the lower cable is offset by the outward centrifugal force on the upward cable, and the entire system is perfectly stable all the way to when you attach the cable to the anchor point on the ground.


Thats how I understood things as well, but I don't beleive there is a need to greatly extend the cable above the geostationary orbit. Instead, a large mass (spacestation?) would probably be placed a little further beyond the geostationary orbit.

Also, whilst I thought that we could harness the energy from the tether I began to realise that as the cable is rotating with the planet it may not actually generate electricity (the tether experiment work like a dynamo, but if we have a cable passing from the ground through a geo-stationary point then that should greatly reduce power generation).

Jeff

Azpod
2002-Apr-03, 05:58 PM
I'm wondering about the current thing myself. I wonder just how much energy it would generate, and if it would be a problem or if it could be harnessed to provide free lifting engery for the elevators (and maybe more for the power-starved denziens down below).


Simple answer: none. The cables used in the shuttle experiements generated electricity because they were moving with respect to the Earth's magnetic field. This cable wouldn't be moving with respect to the Earth's magnetic field, so the total energy produced would be zero, or very close to it.

One other problem with carbon nanotubes does involve electricity, however: carbon nanotubes break down with high electrical current. If the cable gets stuck by lightning, it will disintegrate!

I think this problem can be overcome by making sure minimal current goes through the buckytubes themselves, but a giganitic lightning rod extending to the top of the stratosphere (or beyond) would add considerably to the weight of the cable on the near-Earth end of things.