If all goes well, Monday will be the last day for mankind as a strictly terrestrial species. On Monday man will take up permanent residency in space, a dream for a generation of space sojourners and the stuff of science fiction for even longer. At the Russian-owned cosmodrome near Baikonur, Kazakhstan, three astronauts — Russians Yuri Gidzenko and Sergei Krikalyov and their American commander, Bill Shepherd — are in final preparations for their launch on Tuesday to the International Space Station, in orbit some 230 miles above Earth. The station is designed to last at least 10 years, but could last 25 or more, and then be replaced by a newer, bigger station. Expeditions to the moon or Mars may be launched from there.