OT: About Space Elevators

[geoschmo]

A plane hitting the cable is going to do damage to the plane, but it's going to break the cable as well. The cable slicing through the plane and ramaining intact is just not going to happen. We can't even comprehend materials strong enough for something like that. By the time we can planes will be faster and made of stronger materials too, so the plane will still break the cable.

You aren't going to have thousands of miles of cable falling down though, and it's not going to wrap around the earth. If the cable is that long it could of course wrap around the earth, but that much cable wouldn't fall down.

While the cable may thousands or even tens of thousands of miles long, a break in the cable at above a couple hundred miles is not going to cause it to come crashing down. The reason is that at that length the mass of the cable itself will be enough to keep it in orbit. Remeber that this isn't like hanging a rope fom a branch of a tree. The cable isn't supported by the sattelite at the orbital end. The cable is in effect a sattelite itself.

A break anywhere in the lower couple hundred miles of cable would cause everything below that to plummet to the ground of course. And a couple hundred miles of cable is going to be a problem if it lands on something. But you can limit the risk by locating the ground end carefully.

The literature on the website Baron posted talks about putting the ground end on a mobile ocean platform, like what is used for deep ocean oil drilling. These aren't attached to the ocean floor. This sort of arangment could actually be moved to avoid low earth orbit sattelites and possible sever weather such as a hurricane.

EDIT: Something else I didn't consider, but the website mentions. Parts of the ribbon above a certain altitude falling down will burn up in the atmosphere. So actually you may not get more than 10 or 15 miles of ribbon on the ground, not the hundreds that I was thinking. And the ribbon is heavy in total, but streatched out any particular piece of it is very light. So as it falls that part that survives the trip through the upper atmosphere will be slowed by the lower atmosphere to around the speed of falling paper. You'd have a big cleanup job picking up miles of ribbon cable, but it won't have much physical impact even if it hits something on the ground.

Geoschmo

[ October 09, 2002, 13:13: Message edited by: geoschmo ]

[disabled]

My concern is what if they can't move it away from the hurricane in time.

A project like that is going to be measured in the hundreds of trillions price tag and with gov't buying, they'll make 2 and 3x the price.

I also think they will come up with a self-clibing mechanism to pull stuff up. Sure it's slower, but we can slap an italian sticker on it and say it's romantic.

[Mylon]

The idea behind the design is that the weight is held slightly past geosynchronus orbit so that the weight has a tendancy to fly away from the planet. The cable stops this and holds it in tension. An object climbing the cable effectively pulls the cable down, but since the cable has more inertia than the object, the elevator moves much, much more than the cable does. The tendancy of the weight holding the cable to fly away means that the weight has a constant influx of inertia to resist the tug of elevators. This inertia is probably at the cost of Earth's rotational speed, since it has to come from somewhere...

[geoschmo]

Originally posted by Mylon:
This inertia is probably at the cost of Earth's rotational speed, since it has to come from somewhere...

The principles of orbital mechanics do say that you are correct, but the total mass of the cable system in relation to the earth means the amount of change in the earth's rotation will be so infinesimally small they will be practically unmeasurable. In relation to the effect of the moon and the friction of tidal effects it will be for practical purposes nonexsistant.

[ October 09, 2002, 14:30: Message edited by: geoschmo ]

[geoschmo]

Originally posted by Hadrian Tyrael S. Aventine:
My concern is what if they can't move it away from the hurricane in time.

A project like that is going to be measured in the hundreds of trillions price tag and with gov't buying, they'll make 2 and 3x the price.

I also think they will come up with a self-clibing mechanism to pull stuff up. Sure it's slower, but we can slap an italian sticker on it and say it's romantic.

The estimates on the website are in the tens of billions actually. The main hurdle is designing the ribbon itself. Once that is done and the system is up and running, it could very easily pay for itself in a short time.

Well the ground unit can be placed in areas of historically low storm activity. And it can be moved to an extent, if the ground station is a mobile one. I would imagine that in the event of a particularly nasty storm, the cable could simply be disconnected and "Reeled up" out of danger. The ground station would just need to batten down and ride it out then.

Geoschmo

[Urendi Maleldil]

So it's actually a great space kite

[geoschmo]

Originally posted by Urendi Maleldil:
So it's actually a great space kite

Right, so all we have to watch out for are great space kite eating trees.