> Spike Jones wrote:
>
> > Nowthen, since we are talking about frictionless evacuated tunnels,
> > an acceptable solution would be to build the tunnels at a constant
> > depth of about 4.5 km. Such could theoretically be built. After
> > the car descends to that depth, regardless of the shape of the
> > path down there under these assumptions, it would be travelling
> > at about 300 meters/sec, so the trip from anywhere to anywhere
> > would be at speed about competitive with current airline travel.
> Party of Citizens wrote: Mag lev trains now travel > 300 mph. How fast
> would they travel in a
> vacuum tube? Why 4.5 km deep? Why not on the surface?
Party it was merely an entertaining mental exercise. We postulated
an evacuated frictionless tube since it would not need an electromotive
force to move the train. The train would fall to its destination. I
chose
a constant depth of 4.5 km since the train would be going about
300 m/sec at that depth, a perfectly arbitrary value for a cruise
velocity. Of course it is easy to drive a maglev train. But it is
cool to imagine getting there by gravity. spike
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