Space elevators?!?

that is a good link,

oli, so if a little motion was in play to keep up there would be no drag right?

peace.

 

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If you're in atmosphere there will be drag - the trick is offsetting the drag. The picture Singularity posted offsets the drag by adding velocity during the pickup.

 

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and by not being constantly in the atmosphere constantly I wonder with what speed it get's whiped through the atmosphere

 

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ok i think i understand how that works .


peace.

 

Bad news: No free lunch.

Going straight up from Earth surface to geostationary orbit requires many, many Joules. Because gravity is always pulling down.

Earth surface at Equator moving very roughly speaking 1,000 MPH. So any object on surface has angular momentum based on that speed. Object moving many, many, many thousand miles up to geostationary satelite has only tiny angular momentum. Geostationary satelite has momentum based on many, many, many thousand MPH more speed. For about 400 years momentum, including angular momentum, has been policed to be strictly conserved. So, object climbing up high spiral stair constantly must use Joules to keep up sideways speed. When object reaches high geostationary satelite, HONEST book keeper must confess that Joules used to keep up sideways speed plus Joules used to go straight up against gravity equals total amount of Joules used by clumsy old fashioned rockets.

Don't shoot me, I'm just the messenger. OK?

 

CANGAS,

Do u think that the speed of objects in near earth orbits is more that of geostationary orbits ?

 

I'm not CANGAS but sure

 

If u r so sure then what do u think about his comments ?

DO u think he should be shot at for it.

 

Message from whom, illuminati ?

 

Clumsy, old fashioned rockets have to carry their fuel and reaction mass with them. This means lifting a lot more than just the payload to begin with.

For example, to send 6 tonnes of satellite to geostationary orbit on an Ariane 5G rocket meant lifting 740 tonnes of extra stuff (including 630 tonnes of fuel and oxidizer) off the launchpad.


Climbing a cable has two advantages over rockets - firstly, no reaction mass is required. Secondly, the energy source doesn't need to be carried on board - energy can be supplied electrically through the cable.

This means that the same 6 tonne payload could be lifted to the same orbit at a cost of perhaps 30 tonnes of gasoline (assuming 20% efficiency).

 

Not only that, but with proper designing, you should be able to harness at least some of the potential energy of cars coming back down the cable and feed it back into the system.

P.S.
Another advantage is that the Elevator need not supply the energy needed to conserve angular momentum; that is borrowed from the Earth's own rotation (And given back to the Earth when a car comes down)

 

Yes.

Why do u have to ask this question?

 

From laws of physics. U know about laws of physics or only about crackpot things?

 

As usual, Pete's post fails to address the point.

 

If an orbit elevator has what is called in structural engineering terms a moment connection with the rotating surface of the Earth then J's post could be true in principle.

What J does not understand is that a tether hanging down from a geostationary satelite cannot possibly have a moment connection with the angular momentum of the surface of the planet.

J has too much to learn before being able to make a cogent post on this topic.

A rigid structure rising up from the planet surface can transfer the planet's angular momentum to the stair-climbing orbital wannabee.

A freely hanging tether suspended from a satelite CANNOT transfer ANY of the planet's angular momentum to the pilgrim. Except in the negative sense: the lesser angular momentum of the climbing pilgrim will retard the satelati, dragging it down and decaying its orbit.

Sorry, orbit wannabee, climbing up a hanging tether is NOT a free lunch, no matter what it looked like in an hallucination.

 

It directly addressed the point quoted, which was about energy.

Come on, honest bookkeeper, show us how to tidy the books

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A space elevator, in its final form, does not consist of a cable hanging from a satellite at geostat. To build a space elevator, you start at geostat orbit and build down. At the same time, you build up from geostat. This is to maintain the CoG of the entire structure at geostat. (otherwise it will drift out of position) This can be as simple as lowering a cable from geostat, while at the same time as letting out a cable upward. (tidal forces will ensure that the cable will extend outward.

Once the cable reaches the Earth, you anchor it. Now you start shifting mass from geostat orbit outward along the cable. When it reaches the other end it becomes the other anchor point. The end of the cable is traveling much faster than orbital speed for that altitude so the mass trys the fly away form the Earth. The cable keeps it from doing so and is under tension.

The mass is made large enough that even with a maximum load car climbing up the cable, the CoG of the entire structure remains above geostat orbit altitude. as long as the Cog of the Whole structure remains above this altitude, it behaves, not like an satellite in orbit, but like a rock being swung around in a circle on the end of a string.

As to angular momentum transfer goes:

As the car climbs the cable, it will want to lag behind the Earth's spin. but as it does so, the cable will no longer be perfectly vertical. The Earth will now pull forward on the slanted cable transfering some of its angular momentum to the Car. The cable will only slant while the car is climbing. Once the car reaches its destination, the system will go back to vertical with the car enjoiyng the extra angular momentum it recieved from the Earth.

So yes, a tether style space elevator still transfers angular momentum from the Earth to the rising car.

And a rising car will not pull down a properly counter-weighted tether style space elevator.

 

You guys are getting confused about what each is addressing in this thread. It started out discussing a space elevator anchored to the Earth, but near the end, the thread and CANGUS had begun discussing a tether connecting two orbiting satellites and not connected to the Earth. Pete and Janus58 started speaking of Earth momentum transfer in conjunction with an anchored space elevator again, but CANGUS was still speaking of a tether system with no anchor point on Earth's surface, thus no transfer of Earth's momentum.

There are huge engineering problems that may be impossible, or near impossible, to overcome to make either system practical even if money were not a consideration.

 

Hi 2inq,
In the post I responded to, CANGAS was talking about a climbing to a geostationary satellite from Earth's surface.

I agree with you regarding the engineering problems.