Titan IV was a family of heavy-lift space launch vehicles developed by Martin Marietta and operated by the United States Air Force from 1989 to 2005. Launches were conducted from Cape Canaveral Air Force Station, Florida and Vandenberg Air Force Base, California. The Titan IV was the last of the Titan family of rockets, originally developed by the Glenn L. Martin Company in 1958. It was retired in 2005 due to their high cost of operation and concerns over its toxic hypergolic propellants, and replaced with the Atlas V and Delta IV launch vehicles under the EELV program. The final launch (B-30) from Cape Canaveral occurred on 29 April 2005, and the final launch from Vandenberg AFB occurred on 19 October 2005. Lockheed Martin Space Systems built the Titan IVs near Denver, Colorado, under contract to the US government. Two Titan IV vehicles are currently on display at the National Museum of the United States Air Force in Dayton, Ohio and the Evergreen Aviation and Space Museum in McMinnville, Oregon. Vehicle description The Titan IV was developed to provide assured capability to launch Space Shuttle–class payloads for the Air Force. The Titan IV could be launched with no upper stage, the Inertial Upper Stage (IUS), or the Centaur upper stage. The Titan IV was made up of two large solid-fuel rocket boosters and a two-stage liquid-fueled core. The two storable liquid fuel core stages used Aerozine 50 fuel and nitrogen tetroxide oxidizer. These propellants are hypergolic (ignite on contact) and are liquids at room temperature, so no tank insulation is needed. This allowed the launcher to be stored in a ready state for extended periods, but both propellants are extremely toxic. The Titan IV could be launched from either coast: SLC-40 or 41 at Cape Canaveral Air Force Station near Cocoa Beach, Florida and at SLC-4E, at Vandenberg Air Force Base launch sites 55 miles northwest of Santa Barbara California. Launches to polar orbits occurred from Vandenberg, with most other launches taking place at Cape Canaveral. Titan IV-A Titan IV-A flew with steel-cased solid UA1207 rocket motors (SRMs) produced by Chemical Systems Division. Titan IV-B The Titan IV-B evolved from the Titan III family and was similar to the Titan 34D. While the launcher family had an extremely good reliability record in its first two decades, this changed in the 1980s with the loss of a Titan 34D in 1985