tiny paintings wrote:Nice

Make a few windows dark and it'll look much better.

Actually, the subtle light and dark pattern agrees with what's behind the windows: Not individual rooms but annular walking and sight-seeng areas. What I suggested to CoffeeBot is making the windows a bit bigger and rectangular, and to make the light inside whiter.

Just for the public record, I'm speechless about the job CoffeeBot's done. Not only did he seem to read my mind about details I left out in my original drawing, but he actually solved some engineering issues I had. And he must be "in the zone" or something: I stated in a note in my drawing that the outer casing also served as a heat-radiating surface for engine cooling. And did not specify material.

The obvious material I should have specified, barring "isometal" would have been titanium. And it so happens that when you heat up titanium in the presence of oxygen it forms thin layers of varius oxides, not just one; giving it a subtle "rainbow" appearance. Well, the "metal" pattern CoffeeBot created for texturing just happens to have that very look

Almost chilling!

Not to speak of the sporty paint job, which makes the space elevator suddenly feel like the every-day occurrence it should feel like 1000 years from now; --just like we look at commercial airliners today and make nothing of it to the point of "caring" about the paintings on them as much as the plane itself. Wonder if an "spaceliner" logo might not be fitting as well, say "

ALBATROSSpace" or whatever

Anyhow, maybe someone here with more knowledge of materials can answer this nagging question for me: "How fast can we go?"

The elevator car has a fusion engine, so energy is not the problem; but rather how fast rollers can spin.

The general issue is, for Earth, GEO is 43,000 km up; --bit longer than the distance around the equator (40,000 km). If we averaged Mach 10 (3.3 km/sec) 43,000/3.3=13,030sec=217minutes= 3.6 hours. Of course, in single player mode we can just compress the trip time and show a little movie, but time compression doesn't square up with multiplayer, in general, as CoffeBot pointed out to me. Not that there couldn't be fellow travellers to meet, magazines to read, or other things to do during the trip...

But the question remains, how fast can we realistically go?

(By the way, the car would slow down to below mach speed before entering the atmosphere, we already decided; that's why the aerodynamic shrouds aren't there anymore; they were originally intended to allow supersonic penetration.)

My finger calculations are as follows:

If the rollers are, say, 1 meter in diameter, outer perimeter is 3.1415 meters.

Mach 10, or 3300 m/s divided by 3.1415 = 1050 revolutions per second = 63,000 RPM. Fighter jet engines I believe spin at like 100,000 RPM, and there the blades have to contend with hot exhaust as well as centrifugal force, so, seems to me it would be no rocket science to have this baby go at mach 20 even. But my question remains, can we go mach 50 or 100? "How fast can we go, realistically?"

EDIT:

One possible material for the rollers would be --again-- nanotubes, embedded in some epoxy, perhaps; would make the roller material so light and strong we might even be able to spin them at 1 million RPM and go Mach 150. In terms of acceleration, Mach 150 = 50,000 m/s. At 0.3 G it would take 4 hours and 40 minutes, so we are acceleration limited.

Okay, let's take it back to Mach 50:

330 m/s * 50 = 16,500 m/s

16,500 / 3.3 m/s^2 = 5000 seconds = 83.3 minutes = 1 hour, 23 minutes.

Distance travelled = 1/2 a t^2 = 0.5 * 3.3 * 25 * 10^6 = 41,250 km, so we'd better turn the equation around:

d = 1/2 a t^2 therefore t = sqrt( 2 * d / a ) where d is 43,000km/2, so,

half-time = sqrt( 2 * 0.5 * 43 * 10^6 / 3.3 ) = sqrt( 13M ) = 3600 seconds = 60 minutes = 1 hour accelerating to mid-point, another deccelerating to the finish.

I'd say this is our hard limit: 2 hours.

Why 1/3 of a G acceleration?

Because towards the end of the descent, decceleration is added to gravitational weight, and the cables would not be designed to take too much more weight than the car itself. Just economics: If you made the ribbons stronger, you'd probably want to send more cargo up or down, rather than increase the acceleration.

Finally, using the numbers above, maximum speed would be reached at mid point along the trip, and it would be equal to 3600 seconds times the acceleration of 3.3 m/s^2 = 12 km/s = 720 km/minute = 43,000 km/h

= Mach 36.4; and our 1 meter diameter rollers are spinning at 3820 revs per second, or 229,000 RPM.