> Artificial gravity. After the Mars shuttle has left Earth's atmosphere, the ship splits into two parts -- the passenger cabin and a counterweight, attached by a chain like so:
>
> o----:----o
>
> Next, you just rotate the two parts around the central part of the chain (the colon in the above diagram). Viola! Instant simulated gravity, no calcium loss.

And we'll get a whole bunch of sitcoms based around what would happen if the chain broke during the flight. :-}

Dar "Lost in Space" ien