 It began as a backup ICBM project in case the SM-65 Atlas was delayed.It was a two-stage rocket operational from early 1962 to mid-1965 whose LR-87 booster engine was powered by RP-1 and liquid oxygen.The ground guidance for the Titan was the UNIVAC ATHENA computer, designed by Seymour Cray, based in a hardened underground bunker.