Vulcan Centaur#Versions and configurations

The Vulcan Centaur re-uses many technologies from ULA's Atlas V and Delta IV launch vehicles,{{Cite web |last=Boyer |first=Charles |date=January 6, 2024 |title=ULA: Most Vulcan Systems Have Atlas or Delta Heritage |url=https://floridamedianow.com/2024/01/ula-most-vulcan-systems-have-atlas-or-delta-heritage/ |access-date=October 25, 2024 |website=FMN News |language=en-US}} 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.{{rp|1-5}} It is built in the same Decatur, Alabama factory using much of the same manufacturing equipment, but is about {{Convert|0.3|m|ft|0|sp=us}} 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.{{Cite web |last=Clark |first=Stephen |date=May 21, 2021 |title=United Launch Alliance nears first fueling test on Vulcan rocket |url=https://spaceflightnow.com/2021/05/21/ula-nears-first-fueling-test-on-vulcan-rocket/ |access-date=June 8, 2021 |website=Space Flight Now}} 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.{{Cite journal |last=Thunnissen |first=Daniel P. |last2=Guernsey, C. S. |last3=Baker, R. S. |last4=Miyake, R. N. |year=2004 |title=Advanced Space Storable Propellants for Outer Planet Exploration |url=https://trs-new.jpl.nasa.gov/dspace/bitstream/2014/37950/1/04-0799.pdf |journal=American Institute of Aeronautics and Astronautics |issue=4–0799 |pages=28 |archive-url=https://web.archive.org/web/20160310001026/https://trs-new.jpl.nasa.gov/dspace/bitstream/2014/37950/1/04-0799.pdf |archive-date=March 10, 2016}}{{Cite web |title=Blue Origin BE-4 Engine |url=https://www.blueorigin.com/engines/be-4 |url-status=live |archive-url=https://web.archive.org/web/20211001032523/https://www.blueorigin.com/engines/be-4 |archive-date=October 1, 2021 |access-date=June 14, 2019 |quote=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.}}

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.{{Cite news |last=Foust |first=Jeff |date=September 11, 2020 |title=ULA studying long-term upgrades to Vulcan |url=https://spacenews.com/ula-studying-long-term-upgrades-to-vulcan/ |url-status=live |archive-url=https://web.archive.org/web/20240108153126/https://spacenews.com/ula-studying-long-term-upgrades-to-vulcan/ |archive-date=January 8, 2024 |access-date=March 4, 2021 |work=SpaceNews |quote="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".}}

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.{{Cite tweet |number=1145765959593893888 |user=ToryBruno |title=Vulcan is configurable with 0 to 6 SRBs. 2 fairing lengths, the longer, 70 ft fairing having a massive 11,000 cuft (317 cu-m) payload volume |date=July 1, 2019}}{{Cite news |last=Rhian |first=Jason |date=September 23, 2015 |title=ULA selects Orbital ATK's GEM 63/63 XL SRBs for Atlas V and Vulcan boosters |url=http://www.spaceflightinsider.com/organizations/ula/ula-selects-orbital-atks-gem-6363-xl-srbs-for-atlas-v-and-vulcan-boosters/ |url-status=live |archive-url=https://web.archive.org/web/20160111043540/http://www.spaceflightinsider.com/organizations/ula/ula-selects-orbital-atks-gem-6363-xl-srbs-for-atlas-v-and-vulcan-boosters/ |archive-date=January 11, 2016 |access-date=September 25, 2015 |publisher=Spaceflight Insider}}

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 {{Convert|27200|kg|abbr=|sp=us}} to low Earth orbit (LEO),{{Cite web |date=March 2022 |title=ULA Rocket Rundown |url=https://www.ulalaunch.com/docs/default-source/rockets/atlas-v-and-delta-iv-technical-summary.pdf |access-date=June 27, 2024 |website=United Launch Alliance}} surpassing the Atlas V's maximum of {{Convert|18,850|kg|abbr=on|sp=us}} with a single core and five GEM boosters,{{Cite web |title=Atlas V |url=https://www.ulalaunch.com/rockets/atlas-v |access-date=December 10, 2022 |publisher=United Launch Alliance}} and approaching the {{Convert|28,790|kg|abbr=on|sp=us}} capacity of the three-core Delta IV Heavy.{{Cite web |date=June 4, 2013 |title=Delta IV Launch Services User's Guide – June 2013 |url=http://www.ulalaunch.com/site/docs/product_cards/guides/Delta%20IV%20Users%20Guide%20June%202013.pdf |archive-url=https://web.archive.org/web/20131014123330/http://www.ulalaunch.com/site/docs/product_cards/guides/Delta%20IV%20Users%20Guide%20June%202013.pdf |archive-date=October 14, 2013 |access-date=October 31, 2020 |publisher=United Launch Alliance |pages=2–10, 5-3}}

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.{{Cite web |date=January 9, 2024 |title=Beyond Gravity Celebrates the Successful Launch of ULA's Vulcan Centaur Rocket |url=https://www.beyondgravity.com/en/news/beyond-gravity-celebrates-successful-launch-ulas-vulcan-centaur-rocket |access-date=December 13, 2024 |website=Beyond Gravity |language=en}}

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.{{Cite tweet |number=770579558726668288 |user=torybruno |title=@A_M_Swallow @ULA_ACES We intend to human rate Vulcan/ACES |first=Tory |last=Bruno |access-date=August 30, 2016}}

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.{{Cite web |last=Shalal |first=Andrea |date=May 21, 2015 |title=Lockheed-Boeing rocket venture needs commercial orders to survive |url=https://news.yahoo.com/lockheed-boeing-rocket-venture-needs-commercial-orders-survive-205416832--finance.html |archive-url=https://web.archive.org/web/20150723052732/https://news.yahoo.com/lockheed-boeing-rocket-venture-needs-commercial-orders-survive-205416832--finance.html |archive-date=July 23, 2015 |website=Yahoo! News}}{{Cite news |last=Avery |first=Greg |date=October 16, 2014 |title=ULA plans new rocket, restructuring to cut launch costs in half |url=http://www.bizjournals.com/denver/blog/boosters_bits/2014/10/exclusive-ula-plans-a-new-rocket-restructuring-to.html |url-status=live |archive-url=https://web.archive.org/web/20170315142232/http://www.bizjournals.com/denver/blog/boosters_bits/2014/10/exclusive-ula-plans-a-new-rocket-restructuring-to.html |archive-date=March 15, 2017 |access-date=November 14, 2014 |work=Denver Business Journal}} 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.{{Cite news |last=Erwin |first=Sandra |date=August 19, 2021 |title=National security launch in transition as Space Force waits for Vulcan |url=https://spacenews.com/national-security-launch-in-transition-as-space-force-waits-for-vulcan/ |access-date=June 16, 2024 |work=SpaceNews}}

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.{{Cite web |title=Blue Origin's BE-4 Engine Selected by ULA to Power Vulcan |url=https://www.blueorigin.com/news/blue-origin-s-be-4-engine-selected-by-ula-to-power-vulcan |access-date=November 17, 2024 |website=Blue Origin |language=en-US}} 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 {{convert|550000|lbf|kN|disp=flip|adj=on|lk=on}}-thrust BE-4 engines were to be used on a new launch vehicle booster.{{Cite news |last=Ferster |first=Warren |date=September 17, 2014 |title=ULA To Invest in Blue Origin Engine as RD-180 Replacement |url=https://www.spacenews.com/article/launch-report/41901ula-to-invest-in-blue-origin-engine-as-rd-180-replacement |url-status=dead |archive-url=https://archive.today/20140918114236/http://www.spacenews.com/article/launch-report/41901ula-to-invest-in-blue-origin-engine-as-rd-180-replacement |archive-date=September 18, 2014 |access-date=April 17, 2015 |work=SpaceNews}}{{Cite news |last=Fleischauer |first=Eric |date=February 7, 2015 |title=ULA's CEO talks challenges, engine plant plans for Decatur |url=http://www.decaturdaily.com/news/ula-s-ceo-talks-challenges-engine-plant-plans-for-decatur/article_8ba49046-af4a-11e4-97ef-ff58591d43fc.html |url-status=live |archive-url=https://web.archive.org/web/20170612024028/http://www.decaturdaily.com/news/ula-s-ceo-talks-challenges-engine-plant-plans-for-decatur/article_8ba49046-af4a-11e4-97ef-ff58591d43fc.html |archive-date=June 12, 2017 |access-date=April 17, 2015 |work=Decatur Daily}}

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.

In 2015, ULA announced the Vulcan rocket and proposed to incrementally replace existing vehicles with it.{{Cite news |last=Gruss |first=Mike |date=April 13, 2015 |title=ULA's Vulcan Rocket To be Rolled out in Stages |url=http://spacenews.com/ulas-vulcan-rocket-to-be-rolled-out-in-stages/ |access-date=April 17, 2015 |work=SpaceNews}} 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.{{Cite news |last=Ray |first=Justin |date=April 14, 2015 |title=ULA chief explains reusability and innovation of new rocket |url=http://spaceflightnow.com/2015/04/14/ula-chief-explains-reusability-and-innovation-of-new-rocket/ |url-status=live |archive-url=https://web.archive.org/web/20150417032046/http://spaceflightnow.com/2015/04/14/ula-chief-explains-reusability-and-innovation-of-new-rocket/ |archive-date=April 17, 2015 |access-date=April 17, 2015 |publisher=Spaceflight Now}}

Through the first several years, the ULA board of directors made quarterly funding commitments to Vulcan Centaur development.{{Cite news |last=Gruss |first=Mike |date=March 10, 2016 |title=ULA's parent companies still support Vulcan ... with caution |url=http://spacenews.com/ulas-parent-companies-still-support-vulcan-with-caution/ |url-status=live |archive-url=https://web.archive.org/web/20240108152603/https://spacenews.com/ulas-parent-companies-still-support-vulcan-with-caution/ |archive-date=January 8, 2024 |access-date=March 10, 2016 |work=SpaceNews}} {{As of|2018|10}}, 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.{{Cite news |last=Erwin |first=Sandra |date=October 10, 2018 |title=Air Force awards launch vehicle development contracts to Blue Origin, Northrop Grumman, ULA |url=https://spacenews.com/air-force-awards-launch-vehicle-development-contracts-to-blue-origin-northrop-grumman-ula/ |url-status=live |archive-url=https://archive.today/20181011074001/https://spacenews.com/air-force-awards-launch-vehicle-development-contracts-to-blue-origin-northrop-grumman-ula/ |archive-date=October 11, 2018 |access-date=July 28, 2020 |work=SpaceNews}}

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.

In September 2015, it was announced BE-4 rocket engine production would be expanded{{clarify|serial "production" is years away; does this just mean build a few extra development engines? or what? |date=December 2024}} to allow more testing.{{Cite news |date=September 10, 2015 |title=Boeing, Lockheed Differ on Whether to Sell Rocket Joint Venture |url=https://www.wsj.com/articles/boeing-lockheed-differ-on-whether-to-sell-rocket-joint-venture-1441933638 |url-status=live |archive-url=https://web.archive.org/web/20170415201056/https://www.wsj.com/articles/boeing-lockheed-differ-on-whether-to-sell-rocket-joint-venture-1441933638 |archive-date=April 15, 2017 |access-date=September 12, 2015 |work=THE Wall Street Journal}} The following January, ULA was designing two versions of the Vulcan first stage; the BE-4 version has a {{cvt|5.4|m}} diameter to support the use of the less dense methane fuel.{{Cite news |last=de Selding |first=Peter B. |date=March 16, 2016 |title=ULA intends to lower its costs, and raise its cool, to compete with SpaceX |url=http://spacenews.com/ula-intends-to-lower-its-costs-and-raise-its-cool-to-compete-with-spacex/ |url-status=live |archive-url=https://archive.today/20160317125310/http://spacenews.com/ula-intends-to-lower-its-costs-and-raise-its-cool-to-compete-with-spacex/ |archive-date=March 17, 2016 |access-date=March 19, 2016 |work=SpaceNews |quote=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.}} In late 2017, the upper stage was changed to the larger and heavier Centaur V, and the launch vehicle was renamed Vulcan Centaur.{{Cite news |last=Erwin |first=Sandra |date=March 25, 2018 |title=Air Force stakes future on privately funded launch vehicles. Will the gamble pay off? |url=https://tools.wmflabs.org/makeref/ |url-status=live |archive-url=https://web.archive.org/web/20150821031330/http://tools.wmflabs.org/makeref/ |archive-date=August 21, 2015 |access-date=June 24, 2018 |work=SpaceNews}} In May 2018, ULA announced the selection of Aerojet Rocketdyne's RL10 engine for the Vulcan Centaur upper stage.{{Cite web |last=Tribou |first=Richard |date=May 11, 2018 |title=ULA chooses Aerojet Rocketdyne over Blue Origin for Vulcan's upper stage engine |url=http://www.orlandosentinel.com/news/space/go-for-launch/os-united-launch-alliance-rocket-aerodyne-vulcan-20180511-story.html |url-status=live |archive-url=https://web.archive.org/web/20180513060411/http://www.orlandosentinel.com/news/space/go-for-launch/os-united-launch-alliance-rocket-aerodyne-vulcan-20180511-story.html |archive-date=May 13, 2018 |access-date=May 13, 2018 |newspaper=Orlando Sentinel}} That September, ULA announced the selection of the Blue Origin BE-4 engine for Vulcan's first stage.{{Cite press release |title=United Launch Alliance Building Rocket of the Future with Industry-Leading Strategic Partnerships – ULA Selects Blue Origin Advanced Booster Engine for Vulcan Centaur Rocket System |date=September 27, 2018 |publisher=United Launch Alliance |url=https://www.ulalaunch.com/about/news/2018/09/27/united-launch-alliance-building-rocket-of-the-future-with-industry-leading-strategic-partnerships |access-date=October 5, 2018 |url-status=live |archive-url=https://web.archive.org/web/20181006075150/https://www.ulalaunch.com/about/news/2018/09/27/united-launch-alliance-building-rocket-of-the-future-with-industry-leading-strategic-partnerships |archive-date=October 6, 2018}}{{Cite news |last=Johnson |first=Eric M. |last2=Roulette |first2=Joey |date=September 27, 2018 |title=Jeff Bezos' Blue Origin to supply engines for Vulcan rocket |url=https://www.reuters.com/article/us-blue-origin-ula/jeff-bezos-blue-origin-to-supply-engines-for-vulcan-rocket-idUSKCN1M70UM |url-status=live |archive-url=https://web.archive.org/web/20180928044934/https://www.reuters.com/article/us-blue-origin-ula/jeff-bezos-blue-origin-to-supply-engines-for-vulcan-rocket-idUSKCN1M70UM |archive-date=September 28, 2018 |access-date=September 28, 2018 |work=Reuters}} 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.{{Cite news |last=Foust |first=Jeff |date=October 25, 2018 |title=ULA now planning first launch of Vulcan in 2021 |url=https://spacenews.com/ula-now-planning-first-launch-of-vulcan-in-2021/ |url-status=live |archive-url=https://web.archive.org/web/20240108152604/https://spacenews.com/ula-now-planning-first-launch-of-vulcan-in-2021/ |archive-date=January 8, 2024 |access-date=November 11, 2018 |work=SpaceNews}}{{Cite tweet |number=954054070821670912 |user=jeff_foust |title=Tom Tshudy, ULA: with Vulcan we plan to maintain reliability and on-time performance of our existing rockets, but at a very affordable price. First launch mid-2020. |date=January 18, 2018}}

In August 2019, the parts of Vulcan's mobile launcher platform (MLP) were transported{{Cite tweet |number=1158856939532505088 |user=ToryBruno |title=Mighty Atlas is not the only thing rolling at the Cape today. Check the new Vulcan MLP arrival. |date=August 6, 2019}} 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 {{cvt|3|mph}} on rail bogies, standing {{cvt|183|feet}} tall.{{Cite tweet |number=1158865233173237761 |user=ULAlaunch |title=The MLP will transport #VulcanCentaur Vertical Integration Facility to SLC-41 using heritage undercarriage dollies used for Titan III, Titan IV and #AtlasV and will move at 3 mph. #VulcanCentaur |date=August 6, 2019}} In February 2021, ULA shipped the first completed Vulcan core booster to Florida for pathfinder tests ahead of the Vulcan's debut launch.{{Cite web |date=February 4, 2021 |title=Three rockets depart factory aboard RocketShip |url=https://www.ulalaunch.com/explore/blog-detail/blog/2021/02/04/three-rockets-depart-factory-aboard-rocketship |url-status=live |archive-url=https://web.archive.org/web/20210205103445/https://www.ulalaunch.com/explore/blog-detail/blog/2021/02/04/three-rockets-depart-factory-aboard-rocketship |archive-date=February 5, 2021 |access-date=February 6, 2021 |publisher=United Launch Alliance}} Testing continued proceeded with the pathfinder booster throughout that year.{{Cite web |title=Vulcan: Pathfinder fueling tests planned |url=https://blog.ulalaunch.com/blog/vulcan-centaur-pathfinder-fueling-tests-planned |url-status=live |archive-url=https://web.archive.org/web/20220407062657/https://blog.ulalaunch.com/blog/vulcan-centaur-pathfinder-fueling-tests-planned |archive-date=April 7, 2022 |access-date=April 11, 2022 |website=blog.ulalaunch.com}}{{Cite web |title=Vulcan: First demonstration of launch day completed |url=https://blog.ulalaunch.com/blog/vulcan-centaur-first-demonstration-of-launch-day-completed |url-status=live |archive-url=https://web.archive.org/web/20220414190345/https://blog.ulalaunch.com/blog/vulcan-centaur-first-demonstration-of-launch-day-completed |archive-date=April 14, 2022 |access-date=April 24, 2022 |website=blog.ulalaunch.com}}

In August 2019, ULA said Vulcan Centaur would first fly in early 2021, carrying Astrobotic Technology's Peregrine lunar lander.{{Cite news |last=Chow |first=Denise |date=February 4, 2023 |title=Bigger, faster, farther: A batch of new rockets is set to blast into space this year |url=https://www.nbcnews.com/science/space/bigger-faster-farther-batch-new-rockets-set-blast-space-year-rcna65014 |url-status=live |archive-url=https://web.archive.org/web/20230204183708/https://www.nbcnews.com/science/space/bigger-faster-farther-batch-new-rockets-set-blast-space-year-rcna65014 |archive-date=February 4, 2023 |access-date=February 14, 2023 |publisher=NBC News}}{{Cite web |date=August 19, 2019 |title=Astrobotic Selects United Launch Alliance Vulcan Centaur Rocket to Launch its First Mission to the Moon |url=https://www.ulalaunch.com/about/news/2019/08/19/astrobotic-selects-united-launch-alliance-vulcan-centaur-rocket-to-launch-its-first-mission-to-the-moon |url-status=live |archive-url=https://web.archive.org/web/20190819204709/https://www.ulalaunch.com/about/news/2019/08/19/astrobotic-selects-united-launch-alliance-vulcan-centaur-rocket-to-launch-its-first-mission-to-the-moon |archive-date=August 19, 2019 |access-date=August 19, 2019 |publisher=ULA Launch}}{{Cite web |last=Neal |first=Mihir |date=June 8, 2020 |title=Vulcan on track as ULA eyes early – 2021 test flight to the Moon |url=https://www.nasaspaceflight.com/2020/06/vulcan-2021-moon-flight/ |url-status=live |archive-url=https://web.archive.org/web/20200609190037/https://www.nasaspaceflight.com/2020/06/vulcan-2021-moon-flight/ |archive-date=June 9, 2020 |access-date=June 9, 2020 |website=NASASpaceFlight.com}} By December 2020, the launch had been delayed to 2022 because of technical problems with the BE-4 main engine.{{Cite web |date=December 17, 2020 |title=Bezos' Blue Origin to deliver first flight-ready rocket engines next summer |url=https://www.reuters.com/article/us-space-exploration-blueorigin/bezos-blue-origin-to-deliver-first-flight-ready-rocket-engines-next-summer-ula-ceo-idUSKBN28S0I8 |archive-url=https://web.archive.org/web/20201222022831/https://www.reuters.com/article/us-space-exploration-blueorigin/bezos-blue-origin-to-deliver-first-flight-ready-rocket-engines-next-summer-ula-ceo-idUSKBN28S0I8 |archive-date=December 22, 2020 |access-date=December 20, 2020 |website=Reuters}}{{Cite report |url=https://www.gao.gov/assets/gao-21-222.pdf#page116 |title=Weapon Systems Annual Assessment |date=June 8, 2021 |publisher=US Government Accountability Office (GAO) |page=106 |id=GAO-21-222 |quote=...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. |access-date=June 23, 2021 |archive-url=https://web.archive.org/web/20210624201648/https://www.gao.gov/assets/gao-21-222.pdf#page116 |archive-date=June 24, 2021 |url-status=live}} 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.{{Cite tweet |number=1405701313040732161 |user=Free_Space |title=Debut launch of @ulalaunch Vulcan slipping to 2022 as customer @astrobotic needs more time to prep Peregrine lunar lander. "Covid presented a lot of problems for the entire space supply chain," CEO John Thornton tells @aviationweek "We're just doing the best we can." |author=Irene Klotz}}{{Cite news |last=Roulette |first=Joey |date=October 10, 2022 |title=United Launch Alliance's debut Vulcan mission slips to 2023 -CEO |url=https://www.reuters.com/lifestyle/science/united-launch-alliances-debut-vulcan-mission-slips-2023-ceo-2022-10-10/ |url-status=live |archive-url=https://web.archive.org/web/20221010221557/https://www.reuters.com/lifestyle/science/united-launch-alliances-debut-vulcan-mission-slips-2023-ceo-2022-10-10/ |archive-date=October 10, 2022 |access-date=October 11, 2022 |publisher=Reuters}} 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.{{Cite web |last=Foust |first=Jeff |date=June 24, 2023 |title=First Vulcan launch further delayed for Centaur modifications |url=https://spacenews.com/first-vulcan-launch-further-delayed-for-centaur-modifications/ |url-status=live |archive-url=https://web.archive.org/web/20240108152617/https://spacenews.com/first-vulcan-launch-further-delayed-for-centaur-modifications/ |archive-date=January 8, 2024 |access-date=June 24, 2023 |website=Spacenews}} In October 2023, ULA announced they aimed to launch Vulcan Centaur by year's end.{{Cite web |last=Foust |first=Jeff |date=October 24, 2023 |title=ULA sets Christmas Eve launch date for first Vulcan Centaur |url=https://spacenews.com/ula-sets-christmas-eve-launch-date-for-first-vulcan-centaur/ |url-status=live |archive-url=https://web.archive.org/web/20240108152601/https://spacenews.com/ula-sets-christmas-eve-launch-date-for-first-vulcan-centaur/ |archive-date=January 8, 2024 |access-date=October 24, 2023 |website=SpaceNews}}

File:Peregrine launch (cropped2).jpg

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.{{Cite web |last=Foust |first=Jeff |date=January 8, 2024 |title=Vulcan Centaur launches Peregrine lunar lander on inaugural mission |url=https://spacenews.com/vulcan-centaur-launches-peregrine-lunar-lander-on-inaugural-mission/ |url-status=live |archive-url=https://web.archive.org/web/20240108153201/https://spacenews.com/vulcan-centaur-launches-peregrine-lunar-lander-on-inaugural-mission/ |archive-date=January 8, 2024 |access-date=January 8, 2024 |website=Spacenews}}{{Cite web |last=McCrea |first=Aaron |date=January 8, 2024 |title=Vulcan successfully launches Peregrine lunar lander on inaugural flight |url=https://www.nasaspaceflight.com/2024/01/vulcan-launch-peregrine-inaugural-flight/ |url-status=live |archive-url=https://web.archive.org/web/20240108153003/https://www.nasaspaceflight.com/2024/01/vulcan-launch-peregrine-inaugural-flight/ |archive-date=January 8, 2024 |access-date=January 8, 2024 |website=NASASpaceFlight.com}}

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.{{Cite web |date=January 9, 2024 |title=Update #8 for Peregrine Mission One |url=https://www.astrobotic.com/update-8-for-peregrine-mission-one/ |url-status=live |archive-url=https://web.archive.org/web/20240112151659/https://www.astrobotic.com/update-8-for-peregrine-mission-one/ |archive-date=January 12, 2024 |access-date=January 12, 2024 |website=Astrobotic}}

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.{{Cite web |date=August 14, 2019 |title=SNC Selects ULA for Dream Chaser® Spacecraft Launches: NASA Missions to Begin in 2021 |url=https://www.ulalaunch.com/about/news/2019/08/14/snc-selects-ula-for-dream-chaser-spacecraft-launches |url-status=live |archive-url=https://web.archive.org/web/20190814190202/https://www.ulalaunch.com/about/news/2019/08/14/snc-selects-ula-for-dream-chaser-spacecraft-launches |archive-date=August 14, 2019 |access-date=August 14, 2019 |publisher=ULA Launch}} The SNC Demo-1 was scheduled for launch no earlier than April 2024.{{Cite web |last=Irene Klotz |last2=Garrett Reim |date=October 25, 2023 |title=ULA Sets Dec. 24 As Target Date For Vulcan's Debut |url=https://aviationweek.com/aerospace/commercial-space/ula-sets-dec-24-target-date-vulcans-debut |url-status=live |archive-url=https://web.archive.org/web/20231228155038/https://aviationweek.com/aerospace/commercial-space/ula-sets-dec-24-target-date-vulcans-debut |archive-date=December 28, 2023 |access-date=January 11, 2024 |website=Aviation Week Network}}

After Vulcan Centaur's second certification mission, the rocket will be qualified for use on U.S. military missions.{{Cite web |last=Jeff Foust |date=January 5, 2024 |title=Vulcan on the pad for its first launch |url=https://spacenews.com/vulcan-on-the-pad-for-its-first-launch/ |access-date=January 8, 2024 |website=Spacenews}} {{as of|August 2020}}, Vulcan was to launch ULA's awarded 60% share of National Security Space Launch payloads from 2022 to 2027,{{Cite web |title=Contracts for August 7, 2020 |url=https://www.defense.gov/News/Contracts/Contract/Article/2305454/ |url-status=live |archive-url=https://web.archive.org/web/20200920110521/https://www.defense.gov/Newsroom/Contracts/Contract/Article/2305454/ |archive-date=September 20, 2020 |access-date=August 9, 2020 |publisher=U.S. DEPARTMENT OF DEFENSE}} {{PD-notice}} but delays occurred. 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".{{Cite news |last=Erwin |first=Sandra |date=May 20, 2021 |title=With ULA's new rocket Vulcan behind schedule, Space Force agrees to let Atlas 5 fill in |url=https://spacenews.com/with-ulas-new-rocket-vulcan-behind-schedule-space-force-agrees-to-let-atlas-5-fill-in/ |url-status=live |archive-url=https://web.archive.org/web/20240108153127/https://spacenews.com/with-ulas-new-rocket-vulcan-behind-schedule-space-force-agrees-to-let-atlas-5-fill-in/ |archive-date=January 8, 2024 |access-date=May 22, 2021 |work=SpaceNews}} For similar reasons, the Kuiper Systems prototype flight was moved to an Atlas V rocket.{{Cite news |last=Clark |first=Stephen |date=August 7, 2023 |title=Amazon shifts launch of its first Internet satellites to Atlas V rocket |url=https://arstechnica.com/space/2023/08/amazons-first-internet-satellites-will-launch-on-atlas-v-rocket-not-vulcan |url-status=live |archive-url=https://web.archive.org/web/20230807164939/https://arstechnica.com/space/2023/08/amazons-first-internet-satellites-will-launch-on-atlas-v-rocket-not-vulcan/ |archive-date=August 7, 2023 |access-date=August 7, 2023 |work=Ars Technica}}

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.{{Cite web |last=Erwin |first=Sandra |date=May 13, 2024 |title=ULA could fly dummy payload on next Vulcan launch if Dream Chaser is delayed |url=https://spacenews.com/pentagon-urges-ula-to-fly-dummy-payload-on-next-vulcan-launch-if-dream-chaser-is-delayed/ |access-date=May 14, 2024 |website=SpaceNews |language=en-US}} Bloomberg News reported in May 2024 that United Launch Alliance was accruing financial penalties due to delays in the military launch contracts.{{Cite news |date=May 14, 2024 |title=Lockheed-Boeing Alliance Hit With US Fine for Launch Delays |url=https://www.bloomberg.com/news/articles/2024-05-14/lockheed-boeing-alliance-hit-with-us-penalties-for-launch-delays |access-date=May 15, 2024 |work=Bloomberg}} 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."{{Cite news |last=Davenport |first=Christian |date=May 13, 2024 |title=Pentagon worried its primary satellite launcher can't keep pace |url=https://www.washingtonpost.com/technology/2024/05/13/pentagon-worried-ula-vulcan-development/ |access-date=June 28, 2024 |work=Washington Post |language=en-US |issn=0190-8286}} 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.{{Cite web |last=Decker |first=Audrey |date=June 26, 2024 |title=ULA owners add 'review team' after Pentagon airs concerns about launch schedule |url=https://www.defenseone.com/threats/2024/06/ula-owners-add-review-team-after-pentagon-airs-concerns-about-launch-schedule/397690/ |access-date=June 28, 2024 |website=Defense One}}

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.

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.{{Cite web |last=Berger |first=Eric |date=March 26, 2025 |title=With Vulcan’s certification, Space Force is no longer solely reliant on SpaceX |url=https://arstechnica.com/space/2025/03/at-long-last-the-space-force-has-certified-the-vulcan-rocket/ |access-date=March 27, 2025 |website=Ars Technica |language=en-US}}

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.{{Cite news |last=Berger |first=Eric |date=May 22, 2025 |title= The Pentagon seems to be fed up with ULA’s rocket delays |url=https://arstechnica.com/space/2025/05/the-pentagon-seems-to-be-fed-up-with-ulas-rocket-delays/ |access-date=May 23, 2025 |work=Ars Technica}}

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 ({{cvt|15.5|m}}) or L for Long ({{cvt|21.3|m}}).{{Cite web |title=Vulcan Centaur |url=https://www.ulalaunch.com/rockets/vulcan-centaur |url-status=live |archive-url=https://web.archive.org/web/20210225185355/https://www.ulalaunch.com/rockets/vulcan-centaur |archive-date=February 25, 2021 |access-date=March 3, 2021 |website=ulalaunch.com}} For example, "VC6L" would represent a Vulcan first stage, a Centaur upper stage, six SRBs and a long-configuration fairing. 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.

Starting in late 2025, ULA plans to upgrade the Centaur upper stage with the RL10C-X engine which will have a fixed nozzle extension and offer slightly increased thrust and specific impulse, offering minor improvements to payload capacities.{{Cite web |title=Vulcan Centaur Cutaway Poster |url=https://www.ulalaunch.com/docs/default-source/rockets/vulcancentaur.pdf |url-status=live |archive-url=https://web.archive.org/web/20221222061600/https://www.ulalaunch.com/docs/default-source/rockets/vulcancentaur.pdf |archive-date=December 22, 2022 |access-date=September 25, 2019 |publisher=ULA}}

The payload capacity of Vulcan Centaur versions are:{{Cite web |date=October 2023 |title=Vulcan Launch Systems User's Guide |url=https://www.ulalaunch.com/docs/default-source/rockets/2023_vulcan_user_guide.pdf |url-status=live |archive-url=https://web.archive.org/web/20240416234106/https://www.ulalaunch.com/docs/default-source/rockets/2023_vulcan_user_guide.pdf |archive-date=April 16, 2024}}

;Notes

{{notelist}}

These capabilities reflect NSSL requirements, plus room for growth.{{Cite web |last=Space and Missile Systems |date=October 5, 2018 |title=EELV LSA RFP OTA |url=https://www.fbo.gov/utils/view?id=e2c583b4a02911ba7f59eff384b38664 |url-status=dead |archive-url=https://web.archive.org/web/20190203062442/https://www.fbo.gov/utils/view?id=e2c583b4a02911ba7f59eff384b38664 |archive-date=February 3, 2019 |access-date=June 22, 2019 |quote=table 10 of page 27}}

A Vulcan Centaur with six solid rocket boosters can put {{convert|27,200| kilogram}} into low Earth orbit, nearly as much as the three-core Delta IV Heavy.

{{transcluded-section|List of Vulcan launches}}

{{#section-h::List of Vulcan launches|Launch history}}

{{#section-h::List of Vulcan launches|Future launches}}

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.

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.{{Cite news |last=Henry |first=Caleb |date=November 20, 2019 |title=ULA gets vague on Vulcan upgrade timeline |url=https://spacenews.com/ula-gets-vague-on-vulcan-upgrade-timeline/ |url-status=live |archive-url=https://web.archive.org/web/20240108152615/https://spacenews.com/ula-gets-vague-on-vulcan-upgrade-timeline/ |archive-date=January 8, 2024 |access-date=June 20, 2020 |work=SpaceNews}}

{{Main|Advanced Cryogenic Evolved Stage}}

The ACES upper stage—fueled with liquid oxygen (LOX) and liquid hydrogen (LH{{sub|2}}) 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,{{Cite web |date=April 13, 2015 |title=America, meet Vulcan, your next United Launch Alliance rocket |url=http://www.denverpost.com/business/ci_27905093/america-meet-vulcan-your-next-united-launch-alliance |url-status=live |archive-url=https://web.archive.org/web/20150417171804/http://www.denverpost.com/business/ci_27905093/america-meet-vulcan-your-next-united-launch-alliance |archive-date=April 17, 2015 |access-date=April 17, 2015 |newspaper=Denver Post}} 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. A senior executive at ULA said the Centaur V design was also heavily influenced by ACES.{{Cite news |last=Erwin |first=Sandra |date=April 7, 2021 |title=Bruno: The next big thing for ULA is a long-endurance upper stage |url=https://spacenews.com/bruno-the-next-big-thing-for-ula-is-a-long-endurance-upper-stage/ |url-status=live |archive-url=https://web.archive.org/web/20240108153037/https://spacenews.com/bruno-the-next-big-thing-for-ula-is-a-long-endurance-upper-stage/ |archive-date=January 8, 2024 |access-date=July 7, 2021 |work=SpaceNews}}

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.

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.{{Cite news |last=Klotz |first=Irene |date=July 20, 2022 |title=ULA Refines Plan To Reuse Vulcan Rocket Engines |url=https://aviationweek.com/defense-space/budget-policy-operations/ula-refines-plan-reuse-vulcan-rocket-engines |url-status=live |archive-url=https://web.archive.org/web/20220721013617/https://aviationweek.com/defense-space/budget-policy-operations/ula-refines-plan-reuse-vulcan-rocket-engines |archive-date=July 21, 2022 |access-date=July 21, 2022 |work=Aviation Week}} Before 2022, ULA intended to catch the engine section using a helicopter. ULA estimated this technology could reduce the cost of the first-stage propulsion by 90% and 65% of the total first-stage cost. Although SMART reuse was not initially funded for development, from 2021 the higher launch cadence required to launch the Project Kuiper mega constellation provided support for the concept's business case.{{Cite web |title=The Space Review: A megaconstellation megadeal |url=https://www.thespacereview.com/article/4367/1 |url-status=live |archive-url=https://web.archive.org/web/20220414180623/https://www.thespacereview.com/article/4367/1 |archive-date=April 14, 2022 |access-date=June 8, 2022 |website=www.thespacereview.com}} 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.

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.{{Cite tweet |number=1285290783931858944 |user=torybruno |title=By demand of the Internet, here is the uncropped picture of the #MarsPerseverance flip flops. Just a model. Related to a routine, ongoing trade study. Nothing more. |first=Tory |last=Bruno}}

{{Portal|Spaceflight}}

{{div col}}

• Heavy-lift launch vehicle
• Comparison of orbital launch systems
• {{annotated link|OmegA}}
• {{annotated link|New Glenn}}
• Falcon 9
• Falcon Heavy
• Ariane 6
• H3

{{div col end}}

{{reflist|1=30em}}

{{notelist}}

{{Commons category|Vulcan (rocket)}}

• {{Official website|www.ulalaunch.com/Products_Vulcan.aspx|Official ULA Vulcan page}}
• [https://www.youtube.com/watch?v=xTTkrxVR_20 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.
• [https://www.ulalaunch.com/images/default-source/default-album/vulcan_expanded_engineannc.jpg?sfvrsn=7a758ea8_0 A current ULA Vulcan with 5.4 m Centaur image]

{{United Launch Alliance}}

{{Expendable launch systems}}

{{US launch systems}}

{{Reusable launch systems}}

Category:United Launch Alliance space launch vehicles