Vulcan Centaur is a heavy-lift launch vehicle developed and operated by United Launch Alliance (ULA). It is a two-stage-to-orbit launch vehicle consisting of the Vulcan first stage and the Centaur V second stage. Replacing ULA's Atlas V and Delta IV rockets, the Vulcan Centaur is principally designed to meet the needs of the National Security Space Launch (NSSL) program, which supports U.S. intelligence agencies and the Defense Department, but ULA believes it will also be able to price missions low enough to attract commercial launches. ULA began development of the new launch vehicle in 2014, primarily to compete with SpaceX’s Falcon 9 and to comply with a Congressional mandate to phase out the use of the Russian-made RD-180 engine that powered the Atlas V. The first launch of the Vulcan Centaur was initially scheduled for 2019 but faced multiple delays due to developmental challenges with its new BE-4 first-stage engine and the Centaur second-stage. The Vulcan Centaur conducted its first launch on January 8, 2024, carrying the Peregrine lunar lander as part of NASA's Commercial Lunar Payload Services program. Its second flight, conducted on October 4, 2024, as part of the U.S. Space Force's National Security Space Launch (NSSL) certification process, achieved its planned orbit despite the loss of a nozzle on one of the GEM-63XL solid rocket boosters, which resulted in reduced and asymmetrical thrust. Following a five-month review, the Space Force certified Vulcan for NSSL missions in March 2025. In February 2026, a second issue involving a solid rocket booster occurred, after which launches were paused pending investigation.
Description
The Vulcan Centaur re-uses many technologies from ULA's Atlas V and Delta IV launch vehicles, with an aim to achieve better performance and lower production costs. Also, unlike vertically integrated competitors like SpaceX and Blue Origin, ULA (itself a joint venture between Boeing and Lockheed Martin) relies heavily on subcontractors to build major components of the rocket. The Vulcan's first stage shares a common heritage with the Delta IV's Common Booster Core. It is built in the same Decatur, Alabama factory using much of the same manufacturing equipment, but is about 0.3 meters (1 ft) larger in diameter. The most significant change in the first stage is its use of liquid methane (liquefied natural gas) as fuel in two BE-4 engines developed by Blue Origin. Compared to the liquid hydrogen used on the Delta IV, methane is denser and has a higher boiling point, allowing for smaller, lighter fuel tanks. It also burns cleaner than the kerosene used in the Atlas V, reducing hydrocarbon buildup in engines, which would facilitate refurbishment under the proposed SMART reuse system. The rocket's second stage, the Centaur V, is an upgraded version of the Centaur III used on the Atlas V offering enhanced performance. It is powered by two RL10 engines from Aerojet Rocketdyne, fueled by liquid hydrogen. To further enhance payload capacity, the Vulcan Centaur can be equipped with up to six GEM 63XL SRBs (solid rocket boosters) from Northrop Grumman—a lengthened version of the GEM 63 SRBs used on the Atlas V. A single-core Vulcan Centaur with six SRBs delivers heavy-lift capabilities comparable to the larger and more expensive three-core Delta IV Heavy. With a single core and six GEM boosters, the Vulcan Centaur can lift 27,200 kilograms (60,000 lb) to low Earth orbit (LEO), surpassing the Atlas V's maximum of 18,850 kg (41,560 lb) with a single core and five GEM boosters, and approaching the 28,790 kg (63,470 lb) capacity of the three-core Delta IV Heavy. Beyond Gravity provides additional components, including the interstage adapter, payload fairing, and payload attachment fitting, which secures the payload and fairings to the second stage until commanded to release. The company also supplies a heat shield to protect equipment. Designed to meet the National Security Space Launch (NSSL) program's requirements, the Vulcan Centaur is also designed to be capable of achieving human-rating certification, enabling it to carry crewed spacecraft such as the Boeing Starliner or Sierra Nevada Dream Chaser.
History
Background ULA decided to develop the Vulcan Centaur in 2014 for two main reasons. First, its commercial and civil customers were flocking to SpaceX's cheaper Falcon 9 reusable launch vehicle, leaving ULA increasingly reliant on U.S. military and spy agency contracts. Second, Russia's annexation of Crimea in 2014 heightened Congressional discomfort with the Pentagon's reliance on the Atlas V, which used the made-in-Russia RD-180 engine. In 2016, Congress would pass a law barring the military from procuring launch services based on the RD-180 engine after 2022. In September 2018, ULA announced that it had picked the BE-4 engine from Blue Origin and fueled by liquid oxygen (LOX) and liquid methane (CH4) to replace the RD-180 on a new first-stage booster. The engine was already in its third year of development, and ULA said it expected the new stage and engine to start flying as soon as 2019. Two of the 2,400-kilonewton (550,000 lbf)-thrust BE-4 engines were to be used on a new launch vehicle booster. A month later, ULA restructured company processes and its workforce to reduce costs. The company said that the successor to Atlas V would blend existing Atlas V and Delta IV with a goal of halving the cost of the Atlas V rocket.
Announcement In 2015, ULA announced the Vulcan rocket and proposed to incrementally replace existing vehicles with it. Vulcan deployment was expected to begin with a new first stage based on the Delta IV's fuselage diameter and production process, and initially expected to use two BE-4 engines or the Aerojet Rocketdyne AR1 as an alternative. The second stage was to be the existing Centaur III, already used on Atlas V. A later upgrade, the Advanced Cryogenic Evolved Stage (ACES), was planned for introduction a few years after Vulcan's first flight. ULA also revealed a design concept for reuse of the Vulcan booster engines, thrust structure and first stage avionics, which could be detached as a module from the propellant tanks after booster engine cutoff; the module would re-enter the atmosphere behind an inflatable heat shield.
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