Space Elevator in 15 years?

[Dis]

Drose has a point. Who will be the first couple to do it in the space elevator? That's a record many people would want to get.

[:) Smiley]

15 years is based on technical considerations. Throw in political and economic ones and it's anyone's guess.

[Urban Ranger]

Originally posted by DanS
On the other hand, a ribbon would have a high surface area and really low terminal velocity. This would seem to make it rather safe from the doomsday scenarios offered by DRose.

Why on earth do you need a cable that long?

[MrFun]

Originally posted by Dr Strangelove


And you're just the man for the job.

Actually, I thought Lazarus smells bad without farting?

[Dis]

Originally posted by Urban Ranger


Why on earth do you need a cable that long?

in this case the cable has to be long enough to "balance" things out. The end has to have enough centrifugal force on it to keep the ribbon taut.

[:) Smiley]

Even if the cable won't damage the Earth, it'd still suck for those riding the elevator at the time. Doesn't make it any less cool though.

[DanS]

Even if the cable won't damage the Earth, it'd still suck for those riding the elevator at the time.

Yes, their terminal velocity might be quite a bit higher.

[Urban Ranger]

Originally posted by Dissident
in this case the cable has to be long enough to "balance" things out. The end has to have enough centrifugal force on it to keep the ribbon taut.

The other end of the cable should be anchored.

[Dis]

I'm talking about the space end. There is nothing to anchor it to.

[KrazyHorse]

Originally posted by Urban Ranger




The other end of the cable should be anchored.

To what? You definitely need to put your "anchor" further away than geosynchronous orbit (~40 000 km IIRC)

And the closer your anchor is to geosynchronous the more mass you need to put there. It's a simple question of requiring that the net force on the upper part balances out the net force on the lower end.

[KrazyHorse]

Originally posted by Dissident
I'm talking about the space end. There is nothing to anchor it to.

The sugestion I've heard for anchoring the space end is to put a huge hunk of mass on the end somewhere above geosyncronous orbit. That would provide a counterbalance to the mass below. But the minimum possible length would be the height of geosyncronous orbit. Making it exactly this height would require an infinite anchoring mass.

[Hagbart]

Originally posted by Immortal Wombat
That's arguable.

15 years is somewhat optimistic, shall we say. And of course, once we have built it, it'll break or fail or something. And being stuck in a lift 10 miles above the earth for 18 hours while the engineers try to fix things - that wouldn't be much fun.

I don't think it's intended for people (it would be exciting tho), but as a cheap way for launching satelites and stuff into orbit.

[KrazyHorse]

Let's see now. In the accelerating reference frame of the rotation of the earth, the "force" a mass m experiences is equal to m * (GM/(r^2) - r*w^2) (downward) with M the mass of the Earth, r is the distance from the centre of the Earth to the mass and w is the angular frequency of the Earth's rotation i.e. 2Pi/24hours (assuming you put all these in the right units)

Now, say we assume that we have a material with a maximum (mass) tensile strength of s (s is gotten by dividing the cross-sectional tensile strength t by the mass density p so s = t/p and thus has units of Newton*metres/kilograms = metres^2/seconds^2).

Say that we want to hold up a maximum car mass of m. This makes the bottom of the cable required have a linear mass density of u0 = m/s*(GM/R0^2 - R0*w^2) where R0 is the radius of the Earth.

[Dis]

Originally posted by KrazyHorse


The sugestion I've heard for anchoring the space end is to put a huge hunk of mass on the end somewhere above geosyncronous orbit. That would provide a counterbalance to the mass below. But the minimum possible length would be the height of geosyncronous orbit. Making it exactly this height would require an infinite anchoring mass.

that's why you make it longer.

The figure I heard was twice the height of geosynchronous orbit.

[DanS]

KH is a show-off.