Vulcan Centaur

Vulcan Centaur is a heavy-lift launch vehicle created 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 second stage. It replaces ULA's Atlas V and Delta IV rockets. It is principally designed for the National Security Space Launch (NSSL) program, which launches satellites for U.S. intelligence agencies and the Defense Department, but will also be used for commercial launches.

ULA began developing the Vulcan rocket in 2014, largely to compete with SpaceX's cheaper, partially reusable rockets and to comply with a Congressional requirement to stop using the Russian-made RD-180 engine that powers the Atlas V. The first flight of the Vulcan Centaur was initially slated for 2019, but was delayed multiple times by developmental problems with its BE-4 engine and the Centaur upper stage. Vulcan Centaur launched for the first time on 8 January 2024 carrying Astrobotic Technology's Peregrine lunar lander, the first mission of NASA's Commercial Lunar Payload Services (CLPS) program.

Description
The Vulcan Centaur uses technologies from ULA's Atlas V and Delta IV launch vehicles, plus newer gear for better performance and lower costs. The Vulcan first stage is similar in size as the Delta family's Common Booster Core, allowing ULA to reuse manufacturing equipment.

It uses two BE-4 engines built by Blue Origin that burn liquid oxygen and liquid methane (liquefied natural gas). Methane burns cleaner than the kerosene used on Atlas, spewing less particle pollution and making it more suitable for engine reuse. Compared to the liquid hydrogen used on Delta, it is denser and has a greater temperature range, allowing fuel tanks to be smaller and lighter.

The second stage is the Centaur V, a larger and improved version of the Centaur III used on the Atlas, which is powered by two RL10 engines built by Aerojet Rocketdyne, fueled by liquid hydrogen and liquid oxygen. The first stage can be supplemented by up to six GEM 63XL solid rocket boosters built by Northrop Grumman.

Vulcan Centaur offers heavy-lift capabilities in the footprint of a medium-lift launch vehicle. With a single core and six GEM boosters, the Vulcan Centaur can lift 27200 kg to low Earth orbit (LEO). That is much more than the 18,850 kg that the Atlas V could lift to LEO with a single core and five GEM boosters, and nearly as much as the three-core Delta IV Heavy which could lift 28,790 kg to LEO.

Vulcan has been designed to meet the requirements of the National Security Space Launch program and is designed to achieve human-rating certification to allow the launch of a vehicle such as the Boeing Starliner or Sierra Nevada Dream Chaser.

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 2014, 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 550000 lbf-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 a proposing to incrementally replace existing vehicles with it. Vulcan deployment was expected to begin with a new first stage that was based on the Delta IV's fuselage diameter and production process, and initially expected to use two BE-4 engines or the 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 to be introduced 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 5.4 m 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. 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 3 mph on rail bogies, standing 183 feet 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 8 January 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 14 August 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 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". 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 10 May, 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 an “inert payload” plus some “experiments and demonstrations” to help develop future technology for the Centaur upper stage.

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 (15.5 m) or L for Long (21.3 m). For example, "VC6L" would represent a Vulcan first stage, a Centaur upper stage, six SRBs and a long-configuration fairing. The most powerful Vulcan Centaur will have a Vulcan first stage, a Centaur upper stage with RL10CX engines with a nozzle extension and six SRBs.

Capabilities
The payload capacity of Vulcan Centaur versions are:


 * Notes

These capabilities reflect NSSL requirements, plus room for growth.

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

Potential upgrades
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.

Long-endurance upper stages
The ACES upper stage—fueled with liquid oxygen (LOX) and liquid hydrogen (LH$2$) 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, 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.

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.

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 heatshield as a raft. 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 megaconstellation provided support for the concept's business case. Prior to 2022, ULA intended to catch the engine section using a helicopter.

Vulcan Heavy
In September 2020, ULA announced that they were carefully 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.