Venturing in to space useless?

[Neddie]

The current estimate for a space elevator is moot - there are numerous barriers to construction, deployment, upkeep and stabilization which have not been overcome yet - and nobody can accurately estimate the theoretical costs or ensure that we can circumvent such limits.

[Zpock]

Still, bill gates isnt (or wasnt since he gave all his cash away) to have his own then.

And the Iraq war costed how much? 1 trillion/(uk billion)

Spread those 20 over 20, or 40 years even thats a reasonable timeframe for such an epic project and its not that much.

[Comp1337]

The current estimate for a space elevator is moot - there are numerous barriers to construction, deployment, upkeep and stabilization which have not been overcome yet - and nobody can accurately estimate the theoretical costs or ensure that we can circumvent such limits.

How is stabilization a problem for a hanging elevator? You start building it at geosynchronous orbit, and from there build both ways.
The deployment would be the problem. It is an investment towards getting that precious helium on the moon, or mass from asteroids however

[AF]

Wouldn't it be better to build straight down instead of from both ends? Otherwise you run into limits of stabilization on the ground based size which could be avoided in a hanging elevator built entirely from space.

[jcnossen]

If you build in one direction only its going to fall down because of the weight of the cable, or you need propulsion to move the station in the other direction. Which sounds a lot more complicated.

Stabilization is a problem because once the big string starts vibrating, there is hardly any practical way to lose its energy in a controlled way. And it can start vibrating easily because of the wind.

[AF]

If the cable falls down then your geosynchronously orbitting counterweight isnt far away enough and the centre of gravity of the tether is too low.

[Comp1337]

But starting construction both ways would be easier than building one way and pushing it as the work continues?

[Pxtl]

Another problem with the space elevator - I forget the math, but it will curve when a climber is using it.

[Comp1337]

Elaborate

[Zpock]

A climber? Some guy climbing up the cable into outer space?

[AF]

The curve of something going up may well be counteacted by the curve of on going down.

At the same time gravity will have an effect on the curvature of the elevator preventing major curvature of the tether outside what gravity dictates. Increased curvature can be avoided by adding a movable counterweight at the bottom of the tether. The counterweight can then move in order to cancel out major vibrations within the tether. Smaller counterweights can interact smaller vibrations along the tether.

To insist that any tether would not have movement of any kind is silly, even tall buildings sway and bend.

Right now the main obstacle is getting the counterweight in space to orbit and then deploying the tether itself from orbit.

Building from the ground up isnt feasable, without it being tethered to the counter weight the tether would fall over and plummet after several thousand feet.

I assume a small tether would be dropped from orbit after which machines would climb the tether and reinforce it from the top down to form the core, afterwhich large surrounding sections would be added to form the elevator shaft.

[Kloot]

It basically has to do with the Coriolis effect. Each part of the cable has a certain horizontal speed (ie. angular momentum) that increases with altitude. That means that any payload being lifted up along it also needs to gain the same momentum (which is borrowed from the Earth's rotation). The problem is that the climber initially moves slower than the cable and thus causes drag on it, so the cable gets bent at the point occupied by the climber creating extra stress.

[Comp1337]

It basically has to do with the Coriolis effect. Each part of the cable has a certain horizontal speed (ie. angular momentum) that increases with altitude. That means that any payload being lifted up along it also needs to gain the same momentum (which is borrowed from the Earth's rotation). The problem is that the climber initially moves slower than the cable and thus causes drag on it, so the cable gets bent at the point occupied by the climber creating extra stress.

Thanks, why didnt i think of that...
But that could, as AF said be countered by sending an equally heavy elevator-thingey downwards?

[AF]

Indeed although I suspect that might generate an s shape or create waves up and down the tether.

[Felix the Cat]

Presumably the elevator would be constructed of flexible material and its construction and operation would take that extra bending into account.

Alternatively, the "elevator car" itself could be given the means to accelerate itself in such a way as to minimize the bend in the elevator.

[manored]

Wouldnt something like a big cannon/catapult work better than a elevator? We would just need some sort of bullet-shaped ship to resist the forces... :)

the runaway speed on earth (it doesn't consider air viscosity) is 11Km/sec

now imagine the amount of power needed to impress such force momentum to a fairly decent mass (i'm too lazy to do the calcs atm)

now imagine that force applied, not just to the projectile, but to all it's content for the 1st dynamic principle

everything will arrive in space like broken eggs

speading the applied force over a protracted amount of time prevents to apply too much force in a particular moment

It doesnt really needs go gain all energy needed at a single moment I think. Something like a big elevator that starts slow but goes speeding up until the speed is enough for whatever reach the space would work I think.

Beside, the cannon could still be used to transport raw materials like stell, by molding the stell into a bullet.

[SwiftSpear]

There is no runaway speed for escaping earth for an elevator car on a space elevator.

The "runaway" speed for escaping earth refers to the speed nessicary for an object on ground right now to suddenly gain in order to break earths gravitational pull with no further assistance. Anything assisted doesn't need to reach a certain runaway speed, if you had enough rocket fuel you could slowly crawl up out of the atmosphere at 2 miles per hour.

[AF]

I think what he means is an elevator that didnt go all the way, accelerating the object untill it exceeded escape velocity after which it exits through an open roof and is flung into orbit.

However thats still got the same problem of getting up and down quickly in an orderly fashion. When your letters arrive from space you dont want to go travelling around the pacific to find them.

[Peet]

escape velocity

orbit

Two completely mutually exclusive concepts...lernphysicslozl, all of you

[manored]

I think what he means is an elevator that didnt go all the way, accelerating the object untill it exceeded escape velocity after which it exits through an open roof and is flung into orbit.

However thats still got the same problem of getting up and down quickly in an orderly fashion. When your letters arrive from space you dont want to go travelling around the pacific to find them.

Thats right what I meant. I think its the best imaginable solution right now. True that its not fast but the more important is being cheaper than the rest right? :)

Seending letters from space to earth is stupid. You could want to send other things tough. I think that some decent calculation to reduce the search area a bit could help :)