PRIMM, Nev., Oct. 8 - Fifteen robotic vehicles sprinted through the Nevada desert Saturday afternoon, closing in on a $2 million prize from the Pentagon meant to spur development of technologies for 21st century automated warfare. The vehicles were the survivors from an original starting field of 23 teams fielded by alliances of computer, automotive and aerospace companies, university researchers and others. The competition, called the Grand Challenge, was organized by the Defense Advanced Research Projects Agency, or Darpa, and was designed to tap into the talents of a wide range of researchers and innovators who might not otherwise be...