- 23 Jul '06 12:54So you have the technology to build a space elevator and you want to know what the velocities will be vs orbital velocity and escape velocity at several altitudes, like at what altitude can you step off and be in orbit and what altitude can you step off the cable and be at or above escape velocity? Don't just google in the answer, try to figure it out yourself. And what is the longest you can make the elevator, what are the constraints? The ones discussed on the net are about 100,000 kilometers high. Why? Why not 200,000 Kilometers or 400,000 Kilometers?
- 23 Jul '06 16:33

Well clarke is famous for the geosyncronous orbit but he actually did not originate the idea, it was done decades before, not sure who, I just heard that somewhere. But There are several questions here. I guess the 400,000 km distance question has been answered, it would be a bummer slamming into the moon, eh!. Hmm, so why can't we just connect the earth and the moon with a bloody cable then? You would problably have to have a humungus tower on the north pole instead of the equator but why not? Can you imagine what that would do for the environment of the moon? A friggin highway to the moon. Now there is thought!*Originally posted by FabianFnas***Just for information - the Moon is 384,000 km away...**

I think the answer has to do with a certain mr Arthur Clarke, the famous Science Fiction writer. Am I right? - 24 Jul '06 02:10Actually it was suggested in 1722 by Joseph Louis LaGrange while studying the famous 3-body problem of Newtonian mechanics. The LaGrange points are solutions to Newton's equations of orbital motion where an object of neglegible mas can be placed and stay motionless inreference to the other 2 bodies. There are currently a number of objects at the Langrange points(5) between the Earth and Sun. Checkout the Wikipedia.
- 24 Jul '06 03:14

Well I doubt it was 1722 since he was born in 1736 but there is no doubt of his greatness as a mathemetician. I don't see any mention of geosynchronous orbits in the Lagrange bio's I read, of course Lagrangian points are attributed to him like you said. Are you going to tackle the questions I raised? What altitude are you on a space elevator where you can step off and be at orbital velocity and what altitude are you on a space elevator where you can step off and be going at least escape velocity?*Originally posted by oldrunner55***Actually it was suggested in 1722 by Joseph Louis LaGrange while studying the famous 3-body problem of Newtonian mechanics. The LaGrange points are solutions to Newton's equations of orbital motion where an object of neglegible mas can be placed and stay motionless inreference to the other 2 bodies. There are currently a number of objects at the Langrange points(5) between the Earth and Sun. Checkout the Wikipedia.** - 24 Jul '06 03:42You're right of course. It was 1772 my tired fingers doubled up wrong. To your point about the altitude - I believe 26,200 miles would be the orbital point. I'll have to do some thinking about the other though. Some constraints on the construction would seem to be the strength and weight of the cable.
- 24 Jul '06 03:50

You are off about 4000 miles, its 22K miles and change. You may have been thinking about the distance from the center of the earth, THAT is 26K up and we normally think about the distance above the earths surface but all the calculations have to be done from the vantage point of the center of the earth, I think anyway.*Originally posted by oldrunner55***You're right of course. It was 1772 my tired fingers doubled up wrong. To your point about the altitude - I believe 26,200 miles would be the orbital point. I'll have to do some thinking about the other though. Some constraints on the construction would seem to be the strength and weight of the cable.** - 25 Jul '06 02:25No takers? Come on, its not THAT hard! One hint: the escape velocity at any given orbital velocity is the orbital velocity times the square root of two, so at geosych, about 22400 miles up (26400 miles from the center of the earth, approx.) the orbital velocity works out to about 1.9 mps or about 3 kM/sec. So times 1.414 gives you a velocity needed of 4.3 Km/sec assuming you are already in a stable orbit around 36,000 km up. So you are actually on a long rope and you are still going up. At what point do you start to be able to jump off the rope and never come down? Hint: it's a lot less than 100,000 Km.
- 25 Jul '06 21:23 / 1 edit

As far as I know, geosync is 22400 above the surface of the earth. Here is an article about it:*Originally posted by ThudanBlunder***In fact, it is 22,236 miles from the centre of the Earth.**

http://liftoff.msfc.nasa.gov/academy/rocket_sci/satellites/geo-high.html

It claims 22,241 statue miles up. Add to that the distance to the center of the earth, 3986 miles and you come up with 26227 miles from the center of the earth.

Where do you get the 'In fact' part?

Hey thud, long time no type! - 26 Jul '06 03:41

Well you know it and I know it but I don't see any answers here! PM with yours so you don't spoil the fun!*Originally posted by ThudanBlunder***Hi sonhouse.**

Yeah, you are right.

It's actually quite easy to work out using Kepler's 3rd Law.

What was that other puzzle site? I haven't been there in about 3 computers. They still didn't figure out my last problem! - 26 Jul '06 15:27

Then you have to look harder. We've been discussed the geosync orbits for a while. That's the answer.*Originally posted by sonhouse***Well you know it and I know it but I don't see any answers here!**

Do I have to write it out? Isn't it enough to hint the anser? So you know that I know?

I don't like to spoil the fun for the others...