Re: ballistic subterranean trains

From: Andrew Clough (
Date: Tue Sep 25 2001 - 15:56:52 MDT

Damien Broderick wrote:
>A year or so back, there was a brief discussion on the list of the
>sub-orbital dynamics of a vehicle connecting distant places via an
>evacuated tube under the ground (maybe along a chord), impelled by
>for a basically free ride. I'm putting this in an sf novel, but I had a
>drive-crash months ago that obliterated the saved messages, and the exi
>archive search engine isn't helping me (although I've tried 101 variants
>topic and names).
>I was under the impression that everyone here felt all such craft would
>anywhere in about 80 minutes; the only net site I've found on the topic
>gives an analysis arguing for 42 minutes and change.
>I'm wondering about the sensations of flying one of these babies.
>weight for the first half, a moment of free fall, then heavier? How much

I've run into this idea before, in Vinge's novel A Deepness in the
Sky. Was it inspired by this list, or vice versa? Anyway, assuming a
straight path, you won't feel any free fall. In fact, you'll always feel
at least some gravity, always perpendicular to the tunnel floor! Of course
you'd need a vacum in there, and some means of propulsion to overcome the
inevitable friction loss...or maybe just have the recieving station a
little lower...

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