Delta IV Heavy

The Delta IV Heavy, also designated Delta 9250H, was an expendable heavy-lift launch vehicle and the largest member of the Delta IV family. It was developed by Boeing under the US Air Force Evolved Expendable Launch Vehicle program and later manufactured by United Launch Alliance after the program transferred to it in 2006. Its maiden flight on 21 December 2004 carried a boilerplate payload and ended in partial failure when cavitation in the liquid-oxygen lines shut the engines down early. The vehicle consisted of three Common Booster Cores, each powered by an RS-68 engine, with two serving as strap-on boosters on a central core. Notable missions included reconnaissance satellites for the National Reconnaissance Office, the first uncrewed Orion test in 2014 and the Parker Solar Probe in 2018. After the Space Shuttle retired in 2011 it was the most capable operational launch vehicle until the Falcon Heavy debuted in 2018. Its 16th and final launch came on 9 April 2024, and ULA Vulcan Centaur succeeded it.