The dynamics of a space elevator are pretty interesting. It sounds like a simple concept, but when you look at the specifics you’ll see why they haven’t been built yet.

The “anchor” of the elevator (i.e. the center of mass) has to be, by definition, in geosynchronous orbit. That’s 22,000 miles (35.000 Km) straight up. Put another way, the elevator shaft would wrap almost completely around the globe at the equator. Remember that all of the mass of the elevator structure has to be balanced by an equal mass further out. Of course, the structure itself must be exceedingly light for something even as strong as nanotubes to support it while the “ballast” on the up-orbit side can be a small asteroid.

You may not get motion sick, but you’d probably be bored. Even if the elevator car could travel at 1,000 MPH (1.600 Km/hr), that’s a 22 hour trip, not counting stops at other levels. That’s also, you’ll notice, faster than the speed of sound at sea level. Of course, if you hold it down to “only” 100 MPH at first, you’ll be out of all appreciable atmosphere in less than an hour. Rather than a spaceship, the space elevator would be analogous to taking a train trip across the US or all of Europe 100 years ago.

Gravity is interesting as well. Not counting the initial acceleration of the elevator, you’re at 1 g at the start of your journey. At the last stop, the net gravity is, of course, zero, so you can pick any value in between that you want to experience. It’s been suggested that Icarus-style human flight (with wings strapped to your arms) is possible for the average person at about 1/10 g.

The entire way up you’ll feel a sideways acceleration as well since at ground level you are traveling about 1,000 MPH (160 Km/hr) sideways with the Earth, but when you reach your destination, the orbital velocity is about 5,800 MPH (9.300 Km/hr). All that sideways velocity has to be added as you ascend. The faster you go up, the stronger this acceleration will feel.

For a great description of how this all works, try Clarke’s “Fountains of Paradise.” He also did an extensive description in “3001″ where the Earth was being surrounded by a complete ring at geosynchronous orbit connected by several elevators down to the surface.

- Jack

“Microgravity? Given that the Earth’s radius is about 6400 km, it seems to me that going 100 km above the surface would only reduce your weight by about 3%… unless I’m missing something here.”

That’s why it’s called micro gravity, not zero gravity. The fact is that anywhere near the Earth, particularly in Low Earth Orbit, you are in a gravitational field strong enough to feel its effects. However, if you are either orbiting the Earth or on a parabolic trajectory in this field, you are effectively freefalling. Due to Einstein’s equivalence principle and all that, you can (almost) rightly consider yourself to be in a region free of gravitation, in so far as there is no experiment or observation that you could do in sufficiently small an area over sufficiently small a time period that could tell you definitively whether you were freefalling in a gravitational field or in empty space far from any sources of gravitation.

I say ‘almost’ in the last paragraph, because if you relax the “sufficiently small an area over sufficiently small a time period” part, you could in theory perform experiments that could detect whether tidal effects are present, and hence determine whether you were in a gravitational field or not. Hence, if you are, it is called microgravity not zero gravity. You feel weightless, but subtle effects still exist.

http://www.news9.com/global/story.asp?s=10806368
http://en.wikipedia.org/wiki/Rocketplane_Limited,_Inc.

Virgin Galactic appears to be the real deal for this sort of thing. Their flights will be out of New Mexico.

Piffle. I could totally do this, and I’m not even considered rich by Obama. I merely live within my means and invest. Of course it would mean abandoning my plans for early retirement, and I really do not want to do that, so no go for me. I’m like Mike @#24 above. I’l wait for a better deal on a longer trip.