In one place, a descendant of the Vikings rode a ship such as Lief never dreamed of; from another, one of the descendants of the Caesars, and here an Apache rode a steed such as never roamed the plains. But they were warriors all. The hatch swung open, admitting a blast of Arctic air and a man clad in a heavy, fur-lined parka. He quickly closed the hatch and turned to the man in the pilot's couch. "O.K., Harry. I'll take over now. Anything to report?" "The heading gyro in the autopilot is still