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.
In 2026, NASA selected the VC2 version of the launch vehicle as a candidate for human-rating, so it can support Boeing CST-100 Starliner launches after the last few Atlas V launch vehicles are used or aged out.
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 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 to low Earth orbit (LEO), surpassing the Atlas V's maximum of with a single core and five GEM boosters, and approaching the 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 -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.
Funding Through the first several years, the ULA board of directors made quarterly funding commitments to Vulcan Centaur development. , the US government had committed about $1.2 billion in a public–private partnership to Vulcan Centaur development, with plans for more once ULA concluded a National Security Space Launch contract.
By March 2016, the United States Air Force (USAF) had committed up to $202 million for Vulcan development. ULA had not yet estimated the total cost of development but CEO Tory Bruno said that "new rockets typically cost $2 billion, including $1 billion for the main engine". In March 2018, Bruno said the Vulcan-Centaur had been "75% privately funded" up to that point. In October 2018, following a request for proposals and technical evaluation, ULA was awarded $967 million to develop a prototype Vulcan launch system as part of the National Security Space Launch program.
Development, production, and testing In September 2015, it was announced BE-4 rocket engine production would be expanded to allow more testing. The following January, ULA was designing two versions of the Vulcan first stage; the BE-4 version has a diameter to support the use of the less dense methane fuel. In late 2017, the upper stage was changed to the larger and heavier Centaur V, and the launch vehicle was renamed Vulcan Centaur. In May 2018, ULA announced the selection of Aerojet Rocketdyne's RL10 engine for the Vulcan Centaur upper stage. That September, ULA announced the selection of the Blue Origin BE-4 engine for Vulcan's first stage. The first launch faced multiple delays due to developmental challenges with its new BE-4 first-stage engine and the Centaur second-stage. In October, the USAF released an NSSL launch service agreement with new requirements, delaying Vulcan's initial launch to April 2021, after an earlier postponement to 2020.
In August 2019, the parts of Vulcan's mobile launcher platform (MLP) were transported to the Spaceflight Processing Operations Center (SPOC) near SLC-40 and SLC-41, Cape Canaveral, Florida. The MLP was fabricated in eight sections and moves at on rail bogies, standing tall. In February 2021, ULA shipped the first completed Vulcan core booster to Florida for pathfinder tests ahead of the Vulcan's debut launch. Testing continued proceeded with the pathfinder booster throughout that year.
In August 2019, ULA said Vulcan Centaur would first fly in early 2021, carrying Astrobotic Technology's Peregrine lunar lander. By December 2020, the launch had been delayed to 2022 because of technical problems with the BE-4 main engine. In June 2021, Astrobotic said Peregrine would not be ready on time due to the COVID-19 pandemic, delaying the mission and Vulcan Centaur's first launch; further Peregrine delays put the launch of Vulcan into 2023. In March 2023, a Centaur V test stage failed during a test sequence. To fix the problem, ULA changed the structure of the stage and built a new Centaur for Vulcan Centaur's maiden flight. In October 2023, ULA announced they aimed to launch Vulcan Centaur by year's end.
Certification flights
On January 8, 2024, Vulcan lifted off for the first time. The flight used the VC2S configuration, with two solid rocket boosters and a standard-length fairing. A 4-minute trans-lunar injection burn followed by payload separation put the Peregrine lander on a trajectory to the Moon. One hour and 18 minutes into the flight, the Centaur upper stage fired for a third time, sending it into a heliocentric orbit to test how it would behave in long missions, such as those required to send payloads to geostationary orbit.
A failure in the Peregrine's propulsion system shortly after separation prevented it from landing on the Moon; Astrobotic said the Vulcan Centaur rocket performed without problems.
On August 14, 2019, ULA won a commercial competition when it was announced the second Vulcan certification flight would be named SNC Demo-1, the first of seven Dream Chaser CRS-2 flights under NASA's Commercial Resupply Services program. They will use the four-SRB VC4 configuration. The SNC Demo-1 was scheduled for launch no earlier than April 2024.
After Vulcan Centaur's second certification mission, the rocket will be qualified for use on U.S. military missions. , Vulcan was to launch ULA's awarded 60% share of National Security Space Launch payloads from 2022 to 2027, but delays occurred. The Space Force's USSF-51 launch in late 2022 was the first national security classified mission, but in May 2021 the spacecraft was reassigned to an Atlas V to "mitigate schedule risk associated with Vulcan Centaur non-recurring design validation". For similar reasons, the Kuiper Systems prototype flight was moved to an Atlas V rocket.