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. 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.
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". 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. After Vulcan's first launch in January 2024, developmental delays with the
Dream Chaser led ULA to contemplate replacing it with a mass simulator so Vulcan could move ahead with the certification required by its Air Force contract.
Bloomberg News reported in May 2024 that United Launch Alliance was accruing financial penalties due to delays in the military launch contracts. On May 10, Air Force Assistant Secretary
Frank Calvelli wrote to Boeing and Lockheed executives. "I am growing concerned with ULA's ability to scale manufacturing of its Vulcan rocket and scale its launch cadence to meet our needs", Calvelli wrote in the letter, a copy of which was obtained by the
Washington Post. "Currently there is military satellite capability sitting on the ground due to Vulcan delays." In June 2024, Bruno announced that Vulcan would make its second flight in September with a
mass simulator with some "experiments and demonstrations" to help develop future technology for the Centaur upper stage. Vulcan Centaur lifted off on the second of two flights needed to certify the rocket for future NSSL missions at 11:25 UTC on October 4, 2024. Approximately 37 seconds into the launch, the
nozzle on one of the
solid rocket boosters (SRB) fell off resulting in a shower of debris in the exhaust plume. Although the SRB continued to function for its full 90-second burn, the anomaly led to reduced, asymmetrical thrust. This caused the rocket to slightly tilt before the
guidance system and main engines successfully corrected and extended their burn by roughly 20 seconds to compensate. Despite the anomaly, the rocket achieved an acceptable orbital insertion. Despite achieving certification, military officials have expressed sharp dissatisfaction with Vulcan's performance during its protracted development. In written testimony to the
House Armed Services Committee in May 2025, Major General
Stephen G. Purdy, said that the program had performed "unsatisfactorily" in the previous year. He noted that the slow transition from the retired Atlas and Delta vehicles to Vulcan had delayed four national security launches, hindering the completion of Space Force objectives. Purdy said that, moving forward, United Launch Alliance must "repair trust" and demonstrate greater accountability. In February 2026, a second issue involving a solid rocket booster occurred, after which launches were paused pending investigation. == Versions and configurations ==