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.

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.

Titan IV-A flew with steel-cased solid UA1207 rocket motors (SRMs) produced by Chemical Systems Division.

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 followed by the disastrous explosion of another in 1986 due to a SRM failure.

In 1988–89, The Ralph M. Parsons Company designed and built a full-scale steel tower and deflector facility, which was used to test the Titan IV Solid Rocket Motor Upgrade (SRMU).

To evaluate the magnitude of the thrust force, the SRMU was connected to the steel tower through load measurement systems and launched in-place.

A Space Shuttle would lift a lunar lander into orbit and then a Titan IV rocket would launch with a modified Centaur G-Prime stage to rendezvous and dock.

The plan required upgrading the Space Shuttle and Titan IV to use lighter aluminium-lithium alloy propellant tanks.

By the mid-1980s the United States government worried that the Space Shuttle, designed to launch all American payloads and replace all unmanned rockets, would not be reliable enough for military and classified missions.

Later renamed Titan IV,[18] the rocket would only carry three military payloads[19] paired with Centaur stages and fly exclusively from LC-41 at Cape Canaveral.

However, the Challenger accident in 1986 caused a renewed dependence on expendable launch systems, with the Titan IV program significantly expanded.

As of 1991, almost forty total Titan IV launches were scheduled and a new, improved SRM (solid rocket motor) casing using lightweight composite materials was introduced.

In 2014, the National Museum of the United States Air Force in Dayton, Ohio, began a project to restore a Titan IV-B rocket.

[25] After Titan 34D-9, extensive measures had been put in place to ensure proper SRM operating condition, including X-raying the motor segments during prelaunch checks.

The Titan's fuselage was filled with numerous sharp metal protrusions that made it nearly impossible to install, adjust, or remove wiring without it getting damaged.

The ISDS (Inadvertent Separation Destruct System) automatically triggered, rupturing the SRM and taking the rest of the launch vehicle with it.

At T+45 seconds, the Range Safety Officer sent the destruct command to ensure any remaining large pieces of the booster were broken up.

After a delay caused by the investigation of the previous failure, the 9 April 1999 launch of K-32 carried a DSP early warning satellite.

During the Centaur coast phase flight, the roll control thrusters fired open-loop until the RCS fuel was depleted, causing the upper stage and payload to rotate rapidly.