The Biosphere simulator tilts in another direct, dreaming of a tilting sun and the never-ending horizon. Mars Is Beautiful, we fly forever, racing the sun, and down below us, the single Martian City, named Phoenix, runs its stripmall streets from coast to coast, pole to pole, ridge to ridge, golfcourse to golfcourse... the city that never sleeps.     I was assigned to Military Systems, where we built weapon systems trainers, making sure everything was as real as possible.