Delta IV Heavy

Orbital heavy-lift launch vehicle

The Delta IV Heavy (Delta 9250H) is an expendable heavy-lift launch vehicle, the largest type of the Delta IV family and the world's second highest-capacity rocket in operation. It is manufactured by United Launch Alliance and was first launched in 2004.

The Delta IV Heavy consists of a central Common Booster Core (CBC), with two additional CBCs as liquid rocket boosters instead of the GEM-60 solid rocket motors used by the Delta IV Medium+ versions. At lift off, all three cores operate at full thrust, and 44 seconds later the center core throttles down to 55% to conserve fuel until booster separation. The boosters burn out at 242 seconds after launch and are separated as the core booster throttles back up to full thrust. The core burns out 86 seconds later, and the second stage completes the ascent to orbit.