The Delta IV Heavy (Delta 9250H) was an expendableheavy-lift launch vehicle,the largest member of the Delta IV family. Following the retirement of the Space Shuttle in 2011,it was the most capable operational launch vehicle until the Falcon Heavy's debut in 2018. At the time of its retirement in 2024,it ranked third among active rockets in payload capacity..[3][4][5] Developed by Boeing and later manufactured by United Launch Alliance (ULA),it first flew in 2004. The Delta IV Heavy was retired after its 16th and final launch on 9 April 2024 and was succeeded by ULA's Vulcan Centaur rocket,which can offer similar heavy-lift capabilities at a lower cost with a single-core and six solid rocket boosters.[6][7]
The vehicle consisted of three Common Booster Cores (CBCs),each powered by an RS-68 engine. Two served as strap-on boosters attached to a central core. During ascent,all three engines ignited at liftoff,with the central engine throttling down partway through flight to conserve propellant before throttling up again after booster separation.[8][9]
A distinctive feature of Delta IV Heavy launches was the hydrogen-fueled ignition sequence,which often produced a large fireball that scorched the booster’s exterior surface.[10]
The Delta IV program was initiated by Boeing under the U.S. Air Force's Evolved Expendable Launch Vehicle program and was transferred to ULA in 2006. The Delta IV Heavy was developed as the most powerful configuration of the family,complementing the smaller Delta IV Medium.[11]
Its maiden flight on December 21,2004 carried a boilerplate payload and ended in partial failure when cavitation in liquid-oxygen lines caused premature shutdown of the engines,leaving the test article in a lower-than-intended orbit.[12] The rocket achieved its first fully successful operational flight in 2007 with the launch of the DSP-23 satellite,and subsequently deployed several reconnaissance satellites for the National Reconnaissance Office (NRO).
A 20.5-meter-long (67.2ft) carbon composite bisector payload faring was standard. The Delta IV with the extended fairing was over 62 meters (203ft) tall.
An aluminum isogrid trisector fairing, derived from a Titan IV fairing, was also available as an option.[20] The trisector fairing was first used on the DSP-23 flight.[21]
↑ The officially reported mass of 21,000 kg includes the Launch Abort System (LAS) which did not reach orbit, but excludes the residual mass of the upper stage, which did reach orbit.
↑ "ULA CEO Tory Bruno". twitter.com. Retrieved February 12, 2018. Delta IV Heavy goes for about US$350M. That's current and future, after the retirement of both Delta IV Medium and Delta II.
↑ "Mission Status Center". Spaceflight Now. Retrieved July 26, 2014. The ULA Delta 4-Heavy is currently the world's largest rocket, providing the nation with reliable, proven, heavy lift capability for our country's national security payloads from both the east and west coasts.
↑ "Launch Schedule". Spaceflight Now. October 27, 2020. Retrieved October 31, 2020.
↑ "Launch Mission Execution Forecast". 45th Weather Squadron - Patrick Air Force Base. October 30, 2020. Retrieved October 31, 2020. This article incorporates text from this source, which is in the public domain.
This template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future
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†† - no new orders accepted and production stopped
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