This article is about the American Vulcan Centaur launch vehicle by ULA. Not to be confused with the Russian Vulkan conceptual launch vehicle or the European Vulcain rocket engine. For other uses, see Vulcan (disambiguation).
United Launch Alliance launch vehicle
Vulcan Centaur
Vulcan Centaur in VC2S configuration ahead of its maiden flight
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.[18]
The Vulcan Centaur had a near perfect first launch on January 8,2024,carrying the Peregrine lunar lander,the first mission of NASA's Commercial Lunar Payload Services program. Its second launch,a NSSL certification flight,took place on October 4,2024,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. Following a five-month review of the launches,the Space Force certified the Vulcan for NSSL missions in March 2025.
Description
The Vulcan Centaur re-uses many technologies from ULA's Atlas V and Delta IV launch vehicles,[19] 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.[10]:1–5 It is built in the same Decatur,Alabama factory using much of the same manufacturing equipment,but is about 0.3 meters (1ft) 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.[20][21] 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.[22][23]
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.[24]
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.[7][25]
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 (60,000lb) to low Earth orbit (LEO),[26] surpassing the Atlas V's maximum of 18,850kg (41,560lb) with a single core and five GEM boosters,[27] and approaching the 28,790kg (63,470lb) capacity of the three-core Delta IV Heavy.[28]
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.[29]
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 9reusable launch vehicle,leaving ULA increasingly reliant on U.S. military and spy agency contracts.[31][32] 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.[33]
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.[34] 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.[35] Two of the 2,400-kilonewton (550,000lbf)-thrust BE-4 engines were to be used on a new launch vehicle booster.[35][36][37]
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.[32]
Announcement
In 2015,ULA announced the Vulcan rocket and proposed to incrementally replace existing vehicles with it.[38] 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.[38] 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.[39]
Funding
Through the first several years,the ULA board of directors made quarterly funding commitments to Vulcan Centaur development.[40]As of October2018[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.[41]
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".[40] In March 2018,Bruno said the Vulcan-Centaur had been "75% privately funded" up to that point.[42] 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.[41]
Development,production,and testing
In September 2015,it was announced BE-4 rocket engine production would be expanded[clarification needed] to allow more testing.[43] The following January,ULA was designing two versions of the Vulcan first stage;the BE-4 version has a 5.4m (18ft) diameter to support the use of the less dense methane fuel.[21] In late 2017,the upper stage was changed to the larger and heavier Centaur V,and the launch vehicle was renamed Vulcan Centaur.[42] In May 2018,ULA announced the selection of Aerojet Rocketdyne's RL10 engine for the Vulcan Centaur upper stage.[44] That September,ULA announced the selection of the Blue Origin BE-4 engine for Vulcan's first stage.[45][46] 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.[47][48]
In August 2019,the parts of Vulcan's mobile launcher platform (MLP) were transported[49] 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 3mph (4.8km/h) on rail bogies,standing 183ft (56m) tall.[50] In February 2021,ULA shipped the first completed Vulcan core booster to Florida for pathfinder tests ahead of the Vulcan's debut launch.[51] Testing continued proceeded with the pathfinder booster throughout that year.[52][53]
In August 2019,ULA said Vulcan Centaur would first fly in early 2021,carrying Astrobotic Technology's Peregrine lunar lander.[37][54][55] By December 2020,the launch had been delayed to 2022 because of technical problems with the BE-4 main engine.[56][57] 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.[14][58][59] 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.[60] In October 2023,ULA announced they aimed to launch Vulcan Centaur by year's end.[61]
Certification flights
Launch of the Peregrine lunar lander on Vulcan Centaur's first flight
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.[62][63]
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.[64]
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.[65] The SNC Demo-1 was scheduled for launch no earlier than April 2024.[66]
After Vulcan Centaur's second certification mission,the rocket will be qualified for use on U.S. military missions.[67]As of August 2020[update],Vulcan was to launch ULA's awarded 60% share of National Security Space Launch payloads from 2022 to 2027,[68] 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".[69] For similar reasons,the Kuiper Systems prototype flight was moved to an Atlas V rocket.[70]
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.[71]Bloomberg News reported in May 2024 that United Launch Alliance was accruing financial penalties due to delays in the military launch contracts.[72] 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."[73] 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.[74]
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.[75][76]
The nozzle anomaly added to the already extensive process required to certify the Vulcan for NSSL missions. Following a five-month review,the Space Force certified the Vulcan on March 26,2025.[77]
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.[78]
Versions and configurations
ULA has four-character designations for the various Vulcan Centaur configurations. They start with VC for the Vulcan first stage and the Centaur upper stage. The third character is the number of SRBs attached to the Vulcan—0,2,4 or 6—and the fourth denotes the payload-fairing length:S for Standard (15.5m[51ft]) or L for Long (21.3m[70ft]).[79] For example,"VC6L" would represent a Vulcan first stage,a Centaur upper stage,six SRBs and a long-configuration fairing.[79] The Vulcan Centaur with two or six SRBs is the standard offering,with the zero and four SRB variants offered on a mission-unique basis.[2]
Starting in late 2025,ULA plans to upgrade the Centaur upper stage with the RL10E engine which will have a fixed nozzle extension and offer slightly increased thrust and specific impulse,offering minor improvements to payload capacities.[2][16]
Capabilities
The payload capacity of Vulcan Centaur versions are:[2][80]
These capabilities reflect NSSL requirements, plus room for growth.[4][81]
A Vulcan Centaur with six solid rocket boosters can put 27,200 kilograms (60,000lb) into low Earth orbit, nearly as much as the three-core DeltaIV Heavy.[24]
Maiden flight of Vulcan Centaur and Vulcan Centaur VC2S Configuration. Certification-1 mission, the first of two launches needed to certify the rocket for National Security Space Launch (NSSL) missions. Payload from Celestis, demonstrated engine restart capability of the Centaur upper stage delivering multiple payloads to different orbits. The Peregrine payload failed in transit to the Moon, precluding a landing attempt, due to reasons unrelated to the launch vehicle.[83]
Certification-2 mission, the second of two launches needed to certify the rocket for NSSL missions. Originally scheduled to carry the first flight of Dream Chaser; however, due to schedule delays with Dream Chaser, ULA flew a mass simulator with experiments and demonstrations of future Centaur V technologies.[84][85] Approximately 37 seconds into the launch, the nozzle on one of 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 nominal orbital insertion,[75][76] with the Space Force praising the launch and "the robustness of the total Vulcan system".[86] The nozzle anomaly was attributed to a manufacturing defect in a insulator located inside the nozzle.[87]
USSF-106 mission.[88] Maiden flight of Vulcan Centaur VC4S Configuration.[89][90] First NSSL mission for Vulcan Centaur.[91] Carried Navigation Technology Satellite 3 (NTS-3), an experimental spacecraft to test technologies for next-generation GPS satellites.
Future launches
Future launches are listed chronologically when firm plans are in place. The order of the later launches is much less certain.[92] Launches are expected to take place "no earlier than" (NET) the listed date. As of August2025[update] ULA are "aiming for about two launches per month across its Atlas and Vulcan fleets in 2025 and 2026", but a total of nine launches in 2025.[93]
Military communications satellite. Maiden flight of the Vulcan Centaur VC2L configuration. Protected Tactical Satcom prototype payload. The PTS payload will fly on dedicated Northrop Grumman built ESPAStar-HP satellite bus.
ULA plans to continually improve the Vulcan Centaur. The company plans to introduce its first upgrades in 2025, with subsequent improvements occurring roughly every two to three years.[1]
Since 2015, ULA has spoken of several technologies that would improve the Vulcan launch vehicle's capabilities. These include first-stage improvements to make the most expensive components potentially reusable and second-stage improvements to allow the rocket to operate for months in Earth-orbit cislunar space.[108]
The ACES upper stage—fueled with liquid oxygen (LOX) and liquid hydrogen (LH2) and powered by up to four rocket engines with the engine type yet to be selected—was a conceptual upgrade to Vulcan's upper stage at the time of the announcement in 2015. This stage could be upgraded to include Integrated Vehicle Fluids technology that would allow the upper stage to function in orbit for weeks instead of hours. The ACES upper stage was cancelled in September 2020,[38][109] and ULA said the Vulcan second stage would now be the Centaur V upper stage: a larger, more powerful version of the Dual Engine Centaur upper stage used by the Atlas V N22.[24][108] A senior executive at ULA said the Centaur V design was also heavily influenced by ACES.[24][110]
However, ULA said in 2021 that it is working to add more value to upper stages by having them perform tasks such as operating as space tugs. CEO Tory Bruno says ULA is working on upper stages with hundreds of times the endurance of those currently in use.[110]
On August 28, 2025, in an infographic by ULA posted by Tory Bruno, a variant of Centaur V was referred as "ACES", this time standing for "Advanced Centaur Endurance Stage". Few details were provided about this updated ACES concept, other than a mention of "Smart Propulsion", which was not further explained[111]
SMART reuse
A method of main engine reuse called Sensible Modular Autonomous Return Technology (SMART) is a proposed upgrade for Vulcan Centaur. In the concept, the booster engines, avionics, and thrust structure detach as a module from the propellant tanks after booster engine cutoff. The engine module then falls through the atmosphere protected by an inflatable heat shield. After parachute deployment, the engine section splashes down, using the heat shield as a raft.[112] Before 2022, ULA intended to catch the engine section using a helicopter.[112] ULA estimated this technology could reduce the cost of the first-stage propulsion by 90% and 65% of the total first-stage cost.[39][112] Although SMART reuse was not initially funded for development,[108] from 2021 the higher launch cadence required to launch the Project Kuiper mega constellation provided support for the concept's business case.[113] Consequently, ULA has stated that it plans to begin testing the technology during its launches of the satellite internet constellation, with timing of the tests to be agreed upon with Amazon, the developer of Project Kuiper.[1]
Vulcan Heavy
In September 2020, ULA announced they were studying a "Vulcan Heavy" variant with three booster cores. Speculation about a new variant had been rampant for months after an image of a model of that version popped on social media. ULA CEO Tory Bruno later tweeted a clearer image of the model and said it was the subject of ongoing study.[24][114]
LEO Optimized Centaur
During the Vulcan Cert-2 mission broadcast on October 4, 2024, ULA announced plans to develop a "LEO Optimized Centaur", scheduled to launch aboard a Vulcan in 2025.[115] On August 28, 2025, it was revealed that this Centaur V variant, now designated CV-L, is 1.94m (6ft 4in) shorter than the original Centaur V, now renamed CV-HE (Centaur V High Energy). Unlike the CV-HE, which uses a hydrolox-fueled reaction control system (RCS), the CV-L will employ a hydrazine-fueled RCS.[111]
1 2 de Selding, Peter B. (March 16, 2016). "ULA intends to lower its costs, and raise its cool, to compete with SpaceX". SpaceNews. Archived from the original on March 17, 2016. Retrieved March 19, 2016. Methane rocket has a lower density so we have a 5.4 meter design outside diameter, while drop back to the Atlas V size for the kerosene AR1 version.
↑ "Blue Origin BE-4 Engine". Archived from the original on October 1, 2021. Retrieved June 14, 2019. We chose LNG because it is highly efficient, low cost and widely available. Unlike kerosene, LNG can be used to self-pressurize its tank. Known as autogenous repressurization, this eliminates the need for costly and complex systems that draw on Earth's scarce helium reserves. LNG also possesses clean combustion characteristics even at low throttle, simplifying engine reuse compared to kerosene fuels.
1 2 3 4 5 6 Foust, Jeff (September 11, 2020). "ULA studying long-term upgrades to Vulcan". SpaceNews. Archived from the original on January 8, 2024. Retrieved March 4, 2021. "ACES work has its fingerprints in our new version of Centaur, the Centaur 5 we're fielding with Vulcan. Those studies five, eight years ago certainly served us well, and it put us on a good path forward here for the evolution of our upper stages. We will continue to evolve our upper stage to meet the needs of the market going forward".
↑ Weapon Systems Annual Assessment(PDF) (Report). US Government Accountability Office (GAO). June 8, 2021. p.106. GAO-21-222. Archived(PDF) from the original on June 24, 2021. Retrieved June 23, 2021. ...a U.S. produced rocket engine under development for ULA's Vulcan launch vehicle is experiencing technical challenges related to the igniter and booster capabilities required and may not be qualified in time to support first launches beginning in 2021.
↑ "Contracts for August 7, 2020". U.S. DEPARTMENT OF DEFENSE. Archived from the original on September 20, 2020. Retrieved August 9, 2020. This article incorporates text from this source, which is in the public domain.
↑ Space and Missile Systems (October 5, 2018). "EELV LSA RFP OTA". Archived from the original on February 3, 2019. Retrieved June 22, 2019. table 10 of page 27
ISPCS 2015 Keynote, Mark Peller, Program Manager of Major Development at ULA and Vulcan Program Manager discusses Vulcan, October 8, 2015, Key discussion of Vulcan is at 12:20 point in video.
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