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.

It made its second launch, a NSSL certification flight, on 4 October 2024, which achieved an acceptable orbital insertion, despite the nozzle on one of the GEM-63XL solid rocket boosters falling off which led to reduced, asymmetrical thrust.

The Vulcan Centaur re-uses many technologies from ULA's Atlas V and Delta IV launch vehicles,[18] 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 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.

[19][20] 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.

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.

[39] As of October 2018[update], 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.

[46][47] In August 2019, the parts of Vulcan's mobile launcher platform (MLP) were transported[48] to the Spaceflight Processing Operations Center (SPOC) near SLC-40 and SLC-41, Cape Canaveral, Florida.

[51][52] In August 2019, ULA said Vulcan Centaur would first fly in early 2021, carrying Astrobotic Technology's Peregrine lunar lander.

[61][62] 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.

The Space Force's USSF-51 launch in late 2022 was be 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".

"[72] 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.

[73] Vulcan Centaur lifted off on the second of two flights needed to certify the rocket for future NSSL missions at 11:25 UTC on 4 October 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.

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.

The Space Force added that it was reviewing the launch data to determine Vulcan's suitability for future national security missions.

[74] Space Force Colonel James Horne later praised the launch and "the robustness of the total Vulcan system", with the USSF "knee deep in finalizing certification".

[4][79] A Vulcan Centaur with six solid rocket boosters can put 27,200 kilograms (60,000 lb) into low Earth orbit, nearly as much as the three-core Delta IV Heavy.

[107] A method of main engine reuse called Sensible Modular Autonomous Return Technology (SMART) is a proposed upgrade for Vulcan Centaur.