Titan IV

Titan IV was a family of heavy-lift space launch vehicles developed by Martin Marietta, later built by Lockheed Martin Space Systems near Denver, Colorado, and flown by the United States Air Force from 1989 to 2005. It was the last of the Titan rocket family that began with the Glenn L. Martin Company in 1958, and it was created to launch Space Shuttle class payloads for the Air Force after the Shuttle proved too unreliable for military and classified missions. The vehicle combined two large solid-fuel rocket boosters with a two-stage liquid-fueled core burning Aerozine 50 and nitrogen tetroxide, and could fly with no upper stage, the Inertial Upper Stage or Centaur. Launched from Cape Canaveral and Vandenberg, it was retired in 2005 over operating cost and toxic propellants, and replaced by Atlas V and Delta IV.