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Delta IV Heavy
Variant of the Delta IV space launch vehicle From Wikipedia, the free encyclopedia
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The Delta IV Heavy (Delta 9250H) was an expendable heavy-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]
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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]
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History
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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).
The rocket was also used for two notable missions for NASA, Exploration Flight Test-1, the first uncrewed test of the Orion spacecraft in 2014,[13] and the Parker Solar Probe launch in 2018, which required an additional Star 48BV third stage to achieve its elliptical heliocentric orbit.[14]
Production of Delta IV Heavy hardware ended in May 2023,[15] with its last mission flying for the NRO on April 9, 2024.[16]
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Capabilities
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At liftoff, the rocket had a mass of approximately 733,000 kilograms (1,616,000 lb) and generated about 9,420 kilonewtons (2,120,000 lbf) of thrust.[17]
The Delta IV Heavy had the following payload capacities:[18][19]
- Notes
- Characteristic energy (C3) = −2 km2/sec2
A 20.5-meter-long (67.2 ft) carbon composite bisector payload faring was standard. The Delta IV with the extended fairing was over 62 meters (203 ft) 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]
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Launch history
- Common Booster Cores underperformed, lower orbit than planned
- plus Star 48BV upper stage (approx 2,100 kg)
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Comparable vehicles
Current:
- Long March 5 (geostationary transfer orbit)
- Long March 5B (low Earth orbit)
- Long March 7A (geostationary transfer orbit)
- Falcon Heavy
- Proton-M
- Vulcan Centaur
- Angara A5
- Ariane 6
- New Glenn
Retired or cancelled:
- Ariane 5 (retired)
- Atlas V Heavy (proposed, never developed)
- Saturn IB (retired)
- Titan III (retired)
- Titan IV (retired)
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