In 1984, the Titan IV development began under the US Air Force Complementary Expendable Launch Vehicle (CELV) program. The Titan IV, billed as assured access to space by the US Air Force, was first launched in 1989 specifically to carry large military satellites in the wake of the Challenger accident.  The new Solid Rocket Motor Upgrade (SRMU) provides increased payload capacity and improved safety, reliability, and launch site operability, while reducing cost per pound of payload. The SRMU features a three-segment design. Light-weight graphite composite cases coupled with the use of high performance propellant results in a 25 percent increase in lift capability. The number of critical field joints has been reduced from eight on a Titan IVA to two on the Titan IVB, with each field joint having redundant seals. Five full-scale static test firings qualified the motor design in 1993.  In 2005, the Titan IV was retired. The final launch (B-30) from Cape Canaveral AFS occurred on April 29 2005; while, on October 19, 2005, the final launch from Vandenberg AFB occurred.