SEOUL/TOKYO (Reuters) -North Korea's second attempt to place a spy satellite in orbit failed on Thursday after the rocket booster experienced a problem during its third stage, state media reported, as space authorities vowed to try again in October. The pre-dawn launch came in the first hours of an eight-day window that North Korea had given for the attempt. The nuclear-armed country has been seeking to place what would be its first military spy satellite into orbit, saying it eventually plans a fleet of satellites to monitor moves by U.S. and South Korean troops.