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Centaur (rocket stage)
Centaur (rocket stage)
Centaur (rocket stage)
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Centaur
A single-engine Centaur III being raised for mating to an Atlas V rocket
ManufacturerUnited Launch Alliance
Used on
Current
Atlas V: Centaur III
Vulcan: Centaur V
Historical
Atlas-Centaur
Saturn I
Titan III
Titan IV
Atlas II
Atlas III
Shuttle-Centaur (not flown)
Associated stages
DerivativesAdvanced Cryogenic Evolved Stage (cancelled, not flown)
Launch history
StatusActive
Total launches273 as of October 2024[1]
Successes
(stage only)		254
Failed15
Lower stage
failed		4
First flightMay 9, 1962; 63 years ago (1962-05-09)
Centaur III
Height12.68 m (499 in)[2]
Diameter3.05 m (120 in)
Empty mass2,247 kg (4,954 lb), single engine
2,462 kg (5,428 lb), dual engine
Propellant mass20,830 kg (45,920 lb)
Powered by1 × RL10A, 2 × RL10A or 1 × RL10C
Maximum thrust99.2 kN (22,300 lbf), per engine
Specific impulse450.5 seconds (4.418 km/s)
Burn time904 seconds
PropellantLOX / LH2
Centaur V
Height
  • CV-L: 10.66 m (35 ft)
  • CV-HE: 12.6 m (41 ft)[3]
Diameter5.4 m (17.7 ft)
Empty massCV-HE: 7,100 kg (15,700 lb)[4]
Gross massCV-HE: 53,600 kg (118,200 lb)[4]
Powered by
Maximum thrust
  • RL10C: 203.6 kN (45,780 lbf)
  • RL10E: 214.6 kN (48,240 lbf)[7]
Specific impulse
  • RL10C: 453.8 s (4.450 km/s)
  • RL10E: 460.9 s (4.520 km/s)[7]
Burn timeCV-HE: 1,077 seconds[8]
PropellantLOX / LH2

The Centaur is a family of rocket-propelled upper stages that has been in use since 1962. It is currently produced by United Launch Alliance (ULA) in two main versions. The 3.05 m (10 ft) diameter Centaur III (also known as the Common Centaur) serves as the second stage of the retiring Atlas V rocket, and the 5.4 m (17.7 ft) diameter Centaur V is used as the second stage of the Vulcan Centaur rocket.[9][10] Centaur was the first rocket stage to use hydrolox propellant—liquid hydrogen (LH2) and liquid oxygen (LOX)—a high-energy combination well suited for upper stages but difficult to handle because both propellants must be stored at extremely low cryogenic temperatures.[11]

Characteristics

[edit]

Centaur stages are built around stainless steel pressure-stabilized balloon propellant tanks[12] with 0.51 mm (0.020 in) thick walls. It can lift payloads of up to 19,000 kg (42,000 lb).[13] The thin tank walls minimize mass, maximizing overall stage performance.[14]

A common bulkhead separates the LOX and LH2 tanks, further reducing weight. The bulkhead consists of two stainless steel skins separated by a fiberglass honeycomb, which limits heat transfer between the extremely cold LH2 and the comparatively warmer LOX.[15]: 19 

The main propulsion system consists of one or two RL10 engines made by Aerojet Rocketdyne.[12] The stage is capable of up to multiple restarts, constrained by propellant supply, orbital lifetime, and mission requirements. In combination with insulation on the propellant tanks, this enables Centaur to perform multi-hour coast phases and multiple engine burns for complex orbital insertions.[13]

The stage is equipped with a reaction control system (RCS), which also provides ullage.

On the Centaur III the RCS system consists of twenty hydrazine monopropellant thrusters, arranged in two two-thruster pods and four four-thruster pods. Approximately 150 kg (340 lb) of hydrazine is stored in two bladder tanks and fed to the thrusters by pressurized helium, which also supports some main engine functions.[16]

On some Centaur V stages, the hydrazine system is replaced with hydrolox thrusters supplied by gaseous propellants from the main tanks.[17][18]

Current versions

[edit]

As of 2025, two Centaur variants are in use: Centaur III on Atlas V,[19][20] and Centaur V on Vulcan Centaur.[21] All of the many other Centaur variants have been retired.[22][23]

Centaur III/Common Centaur

[edit]
Single Engine Centaur (SEC) stage

Common Centaur is the upper stage of the Atlas V rocket.[16] Earlier Common Centaurs were propelled by the RL10-A-4-2 version of the RL-10. Since 2014, Common Centaur has flown with the RL10-C-1 engine, which is shared with the Delta Cryogenic Second Stage, to reduce costs.[24][25] The Dual Engine Centaur (DEC) configuration will continue to use the smaller RL10-A-4-2 to accommodate two engines in the available space.[25]

The Atlas V can fly in multiple configurations, but only one affects the way Centaur integrates with the booster and fairing: the 5.4 m (18 ft) diameter Atlas V payload fairing attaches to the booster and encapsulates the upper stage and payload, routing fairing-induced aerodynamic loads into the booster. If the 4 m (13 ft) diameter payload fairing is used, the attachment point is at the top (forward end) of Centaur, routing loads through the Centaur tank structure.[26]

The latest Common Centaurs can accommodate secondary payloads using an Aft Bulkhead Carrier attached to the engine end of the stage.[27]

Single Engine Centaur (SEC)

[edit]

Most payloads launch on Single Engine Centaur (SEC) with one RL10. This is the variant for all normal flights of the Atlas V (indicated by the last digit of the naming system, for example Atlas V 421).

Dual Engine Centaur (DEC)

[edit]

A dual engine variant with two RL-10 engines is available, but only for launching the CST-100 Starliner crewed spacecraft. The higher thrust of two engines allows a gentler ascent with more horizontal velocity and less vertical velocity, which reduces deceleration to survivable levels in the event of a launch abort and ballistic reentry occurring at any point in the flight.[28]

Centaur V

[edit]
Centaur V stage on Vulcan Centaur rocket carrying Peregrine lunar lander

Centaur V is the upper stage of the Vulcan launch vehicle developed by United Launch Alliance (ULA) beginning in 2014 to meet the requirements of the National Security Space Launch (NSSL) program.[29]

Development

[edit]

ULA initially intended the Centaur V, an upgraded version of the Common Centaur,[30] to only be used on a interim basis until a transition to the Advanced Cryogenic Evolved Stage (ACES) planned after the first few years of flights.[23][31]

In late 2017, the company began development of Centaur V by accelerating elements of the ACES design, including a 5.4 meters (17.7 ft) diameter and advanced insulation. The Integrated Vehicle Fluids (IVF) system, which had been intended to extend on-orbit lifetime from hours to weeks, was omitted.[23]

Centaur V was designed to provide higher performance than the Common Centaur, fulfilling NSSL requirements and supporting the planned retirement of the Atlas V and Delta IV Heavy families. The stage was officially named Vulcan Centaur in March 2018,[32][33] and in May 2018 ULA selected Aerojet Rocketdyne’s RL10 engine over Blue Origin's BE-3. Each Centaur V uses two RL10 engines.[34]

In September 2020, ULA confirmed that ACES would no longer be developed and that Centaur V would remain Vulcan’s upper stage.[35] The company said that the initial versions of the Centaur V offers 40% more endurance and 250% more energy than the Common Centaur.[36]

Vulcan launched successfully on January 8, 2024, with Centaur V performing as planned on its maiden flight.[37]

Starting in late 2025, ULA plans to upgrade the stage with the RL10E engine, featuring a fixed nozzle extension and modest improvements in thrust and specific impulse, offering minor improvements to payload capacities.[6][38]

CV-L

[edit]

During the Vulcan Cert-2 mission broadcast on October 4, 2024, ULA announced a "LEO Optimized Centaur" variant, later designated CV-L, scheduled to debut in 2025.[39] CV-L is 1.94 m (6 ft 4 in) shorter than the baseline Centaur V, which was redesignated CV-HE (Centaur V High Energy). Unlike CV-HE, which uses a hydrolox RCS, CV-L returns to using a simpler hydrazine monopropellant RCS.[17]

ACES revival

[edit]

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.[17] Previously, Bruno has suggested that future upper stages could offer up to 600% more endurance than the Common Centaur.[36]

Current engines

[edit]

Centaur engines have evolved over time, and three versions (RL10A-4-2, RL10C-1 and RL10C-1-1) are in use as of 2024 (see table below). All versions utilize liquid hydrogen and liquid oxygen.[40]

Centaur engines
Engine Upper Stage Dry mass Thrust Specific impulse, vac. Length Diameter Ref
RL10A-4-2 Centaur III 168 kg (370 lb) 99.1 kN (22,300 lbf) 451 s (4.42 km/s) 2.29 m (7 ft 6 in) 1.17 m (3 ft 10 in) [41][42]
RL10C-1 Centaur III (SEC) 190 kg (420 lb) 101.8 kN (22,900 lbf) 449.7 s (4.410 km/s) 2.12 m (6 ft 11 in) 1.45 m (4 ft 9 in) [43][44][45][42]
RL10C-1-1 Centaur V 188 kg (414 lb) 106 kN (24,000 lbf) 453.8 s (4.450 km/s) 2.46 m (8 ft 1 in) 1.57 m (5 ft 2 in) [46]
RL10E-1 Centaur V 230 kg (510 lb) 107.3 kN (24,120 lbf) 460.9 s (4.520 km/s) 3.312 m (10 ft 10.4 in) 1.872 m (6 ft 1.7 in)

History

[edit]
Centaur stage during assembly at General Dynamics,[47] 1962
Diagram of the Centaur stage tank

The Centaur concept originated in 1956 when the Convair division of General Dynamics began studying a liquid hydrogen fueled upper stage. The ensuing project began in 1958 as a joint venture among Convair, the Advanced Research Projects Agency (ARPA), and the U.S. Air Force. In 1959, NASA assumed ARPA's role. Centaur initially flew as the upper stage of the Atlas-Centaur launch vehicle, encountering a number of early developmental issues due to the pioneering nature of the effort and the use of liquid hydrogen.[48] In 1994 General Dynamics sold their Space Systems division to Lockheed-Martin.[49]

Centaur A-D (Atlas)

[edit]
An Atlas-Centaur rocket (Centaur D stage) launches Surveyor 1
See also: Atlas-Centaur

The Centaur was originally developed for use with the Atlas launch vehicle family. Known in early planning as the 'high-energy upper stage', the choice of the mythological Centaur as a namesake was intended to represent the combination of the brute force of the Atlas booster and finesse of the upper stage.[50]

Initial Atlas-Centaur launches used developmental versions, labeled Centaur-A through -C.

The only Centaur-A launch on 8 May 1962 ended in an explosion 54 seconds after liftoff when insulation panels on the Centaur separated early, causing the LH2 tank to overheat and rupture. This version was powered by two RL10A-1 engines.[51]

After extensive redesigns, the only Centaur-B flight on 26 November 1963 was successful. This version was powered by two RL10A-3 engines.[51]

Centaur-C flew three times between 1964 and 1965,[51] with two failures and one launch declared successful although the Centaur failed to restart. This version was also powered by two RL10A-3 engines.[51]

Centaur-D was the first version to enter operational service in 1965 ,[51] with fifty-six launches.[52] It was powered by two RL10A-3-1 or RL10A-3-3 engines.[51]

On 30 May 1966, an Atlas-Centaur boosted the first Surveyor lander towards the Moon. This was followed by six more Surveyor launches over the next two years, with the Atlas-Centaur performing as expected. The Surveyor program demonstrated the feasibility of reigniting a hydrogen engine in space and provided information on the behavior of LH2 in space.[15]: 96 

By the 1970s, Centaur was fully mature and had become the standard rocket stage for launching larger civilian payloads into high Earth orbit, also replacing the Atlas-Agena vehicle for NASA planetary probes.[15]: 103–166 

An updated version, called Centaur-D1A (powered by RL10A-3-3 engines), was used on the Atlas-SLV3D came into use during the 1970s.[53][54][51]

The Centaur-D1AR was used for the Atlas-SLV3D and Atlas G came into use during the 1970s and 1980s.[55][51][56]

By the end of 1989, Centaur-D had been used as the upper stage for 63 Atlas rocket launches, 55 of which were successful.[1]

Saturn I S-V

[edit]
Main article: S-V

The Saturn I was designed to fly with a S-V third stage to enable payloads to go beyond low Earth orbit (LEO). The S-V stage was intended to be powered by two RL-10A-1 engines burning liquid hydrogen as fuel and liquid oxygen as oxidizer. The S-V stage was flown four times on missions SA-1 through SA-4, all four of these missions had the S-V's tanks filled with water to be used a ballast during launch. The stage was not flown in an active configuration.

Centaur D-1T (Titan III)

[edit]
A Titan IIIE-Centaur rocket (Centaur D-1T stage) launches Voyager 2

The Centaur D-1T (powered by RL10A-3-3 engines) was an improved version for use on the far more powerful Titan III booster in the 1970s,[51] with the first launch of the resulting Titan IIIE in 1974. The Titan IIIE more than tripled the payload capacity of Atlas-Centaur, and incorporated improved thermal insulation, allowing an orbital lifespan of up to five hours, an increase over the 30 minutes of the Atlas-Centaur.[15]: 143 

The first launch of Titan IIIE in February 1974 was unsuccessful, with the loss of the Space Plasma High Voltage Experiment (SPHINX) and a mockup of the Viking probe. It was eventually determined that Centaur's engines had ingested an incorrectly installed clip from the oxygen tank.[15]: 145–146 

The next Titan-Centaurs launched Helios 1, Viking 1, Viking 2, Helios 2,[57] Voyager 1, and Voyager 2. The Titan booster used to launch Voyager 1 had a hardware problem that caused a premature shutdown, which the Centaur stage detected and successfully compensated for. Centaur ended its burn with less than 4 seconds of fuel remaining.[15]: 160 

Centaur D-1T specifications

[edit]

The Centaur D-1T had the following general specifications:[58]

  • Diameter: 3.2 m (126 in)
  • Length: 9.6 m (31.5 ft)
  • Inert mass: 1,827 kg (4,028 lb)
  • Fuel: Liquid hydrogen
  • Oxidizer: Liquid oxygen
  • Fuel and oxidizer mass: 13,490 kg (29,750 lb)
  • Guidance:
  • Thrust:
  • Burn Capability: 3 to 4 burns
  • Engine: 2 x RL10A-3-3
  • Engine start: Restartable
  • Attitude control: 4 x 27 N (6 lbf) thrusters

Shuttle-Centaur

[edit]
Illustration of Shuttle-Centaur G‑Prime with Ulysses
Main article: Shuttle-Centaur

Shuttle-Centaur was a proposed Space Shuttle upper stage. To enable its installation in shuttle payload bays, the diameter of the Centaur's hydrogen tank was increased to 4.3 m (14 ft), with the LOX tank diameter remaining at 3.0 m (10 ft). Two variants were proposed: Centaur G‑Prime, which was planned to launch the Galileo and Ulysses robotic probes, and Centaur G, a shortened version, reduced in length from approximately 9 to 6 m (30 to 20 ft), planned for U.S. DoD payloads and the Magellan Venus probe.[59]

After the Space Shuttle Challenger disaster, just months before the Shuttle-Centaur had been scheduled to fly, NASA concluded that it was too risky to fly the Centaur on the Shuttle.[60] The probes were launched with the much less powerful solid-fueled Inertial Upper Stage, with Galileo needing multiple gravitational assists from Venus and Earth to reach Jupiter.

Centaur T (Titan IV)

[edit]
Centaur-T stage of a Titan IV rocket

The capability gap left by the termination of the Shuttle-Centaur program was filled by a new launch vehicle, the Titan IV. The 401A/B versions used a Centaur upper stage with a 4.3-meter (14 ft) diameter hydrogen tank. In the Titan 401A version, a Centaur-T was launched nine times between 1994 and 1998. The 1997 Cassini-Huygens Saturn probe was the first flight of the Titan 401B, with an additional six launches wrapping up in 2003 including one SRB failure.[61]

Centaur I (Atlas I)

[edit]
Main article: Atlas I

The upper stage of the Atlas I was the Centaur I stage, derived from earlier models of Centaur that also flew atop Atlas boosters. Centaur I featured two RL-10-A-3A engines burning liquid hydrogen and liquid oxygen, making the stage extremely efficient. To help slow the boiloff of liquid hydrogen in the tanks, Centaur featured fiberglass insulation panels that were jettisoned 25 seconds after the first stage booster engines were jettisoned.[62] Centaur I was the last version of the stage to feature separating insulation panels.

Centaur II (Atlas II/III)

[edit]
Main article: Atlas II

Centaur II was initially developed for use on the Atlas II series of rockets.[52] Centaur II also flew on the initial Atlas IIIA launches.[16]

Centaur III/Common Centaur (Atlas III/V)

[edit]
Main article: Atlas III

Atlas IIIB introduced the Common Centaur, a longer and initially dual engine Centaur II.[16]

Centaur III specifications

[edit]

Source: Atlas V551 specifications, as of 2015.[63]

  • Diameter: 3.05 m (10 ft)
  • Length: 12.68 m (42 ft)
  • Inert mass: 2,247 kg (4,954 lb)
  • Fuel: Liquid hydrogen
  • Oxidizer: Liquid oxygen
  • Fuel and oxidizer mass: 20,830 kg (45,922 lb)
  • Guidance: Inertial
  • Thrust: 99.2 kN (22,300 lbf)
  • Burn time: Variable; e.g., 842 seconds on Atlas V
  • Engine: RL10-C-1
  • Engine length: 2.32 m (7.6 ft)
  • Engine diameter: 1.53 m (5 ft)
  • Engine dry weight: 168 kg (370 lb)
  • Engine start: Restartable
  • Attitude control: 4 x 27 N (6.1 lbf) thrusters, 8 x 40 N (9.0 lbf) thrusters

Atlas V cryogenic fluid management experiments

[edit]

Most Common Centaurs launched on Atlas V have hundreds to thousands of kilograms of propellants remaining on payload separation. In 2006 these propellants were identified as a possible experimental resource for testing in-space cryogenic fluid management techniques.[64]

In October 2009, the Air Force and United Launch Alliance (ULA) performed an experimental demonstration on the modified Centaur upper stage of DMSP-18 launch to improve "understanding of propellant settling and slosh, pressure control, RL10 chilldown and RL10 two-phase shutdown operations. DMSP-18 was a low mass payload, with approximately 28% (5,400 kg (11,900 lb)) of LH2/LOX propellant remaining after separation. Several on-orbit demonstrations were conducted over 2.4 hours, concluding with a deorbit burn.[65] The initial demonstration was intended to prepare for more-advanced cryogenic fluid management experiments planned under the Centaur-based CRYOTE technology development program in 2012–2014,[66] and will increase the TRL of the Advanced Cryogenic Evolved Stage Centaur successor.[22]

Mishaps

[edit]

Although Centaur has a long and successful flight history, it has experienced a number of mishaps:

  • April 7, 1966: Centaur did not restart after coast — ullage motors ran out of fuel.[67]
  • August 10, 1968: AC-17. Centaur did not restart after coast — icing of the hydrogen peroxide supply lines.[68]
  • May 9, 1971: Centaur guidance failed, destroying itself and the Mariner 8 spacecraft bound for Mars orbit.[69]
  • April 18, 1991: AC-70. Centaur failed to restart (icing problem). Incomplete failure investigation initially stated that Centaur failed due to particles from the scouring pads used to clean the propellant ducts getting stuck in the turbopump, preventing start-up.[70]
  • August 22, 1992: AC-71. Centaur failed to restart (same icing problem as the prior incident).[70][71]
  • April 30, 1999: Launch of the USA-143 (Milstar DFS-3m) communications satellite failed when a Centaur database error resulted in uncontrolled roll rate and loss of attitude control, placing the satellite in a useless orbit.[72]
  • June 15, 2007: the engine in the Centaur upper stage of an Atlas V shut down early, leaving its payload — a pair of National Reconnaissance Office ocean surveillance satellites — in a lower than intended orbit.[73] The failure was called "A major disappointment," though later statements claim the spacecraft will still be able to complete their mission.[74] The cause was traced to a stuck-open valve that depleted some of the hydrogen fuel, resulting in the second burn terminating four seconds early.[74] The problem was fixed,[75] and the next flight was nominal.[76]
  • March 23–25, 2018: Atlas V Centaur passivated second stage launched on September 8, 2009, broke up.[77][78]
  • August 30, 2018: Atlas V Centaur passivated second stage launched on September 17, 2014, broke up, creating space debris.[79]
  • April 6, 2019: Atlas V Centaur passivated second stage launched on October 17, 2018, broke up.[80][81]
  • September 6, 2024: Atlas V Centaur passivated second stage launched on March 1, 2018, broke up.[82]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Centaur (rocket stage)

View on Grokipedia
from Grokipedia
The Centaur is a high-performance upper stage rocket developed by the , renowned for its use of (LH2) and (LOX) propellants, which provide exceptional for precise orbital insertions and deep space missions. First flown successfully in 1963, it has powered nearly 400 launches, enabling landmark achievements in planetary exploration, lunar landings, and satellite deployments. Development of the Centaur began in 1957 under General Dynamics/Astronautics Corporation for the U.S. Air Force, with NASA assuming management in 1959 through its Lewis Research Center (now NASA Glenn Research Center). The stage overcame early technical challenges, including cryogenic propellant handling, to achieve its inaugural successful flight on November 27, 1963, atop an Atlas booster. Key configurations include the original Atlas/Centaur, Titan IIIE/Centaur for heavy payloads, and a proposed Shuttle/Centaur variant that was canceled in 1986 due to safety concerns. Technically, early models measure approximately 30 feet in length and 10 feet in diameter, with a fueled weight exceeding 35,000 pounds, and are propelled by two Aerojet Rocketdyne RL-10 engines delivering a combined thrust of about 33,000 pounds. Centaur's propulsion system, utilizing the high-energy LH2/LOX combination, marked it as the first major U.S. rocket stage of its kind, enabling missions that reached every planet from Mercury to Neptune. Notable achievements include launching NASA's Surveyor lunar landers in the 1960s, which paved the way for Apollo; the Pioneer, Viking, and Voyager probes for interplanetary exploration; and more recent successes like the Cassini mission to Saturn in 1997 and the Curiosity Mars rover in 2011. It has also supported communications satellites such as ATS and Comstar, as well as observatories like OAO and HEAO. In its modern iterations, such as the Centaur V used on United Launch Alliance's rocket and continuing in service on the as of 2025, the stage features upgraded RL10C engines with up to 24,000 pounds of thrust each, restart capability for multiple burns, and advanced guidance for complex orbits including geosynchronous, trans-lunar, and highly elliptical paths. This evolution ensures continued reliability, with nearly 400 flights and over 700 in-space firings as of 2025, supporting both commercial and scientific endeavors.

Design and Characteristics

Structural Features

The Centaur rocket stage employs a pressure-stabilized balloon tank design, utilizing thin-walled for the primary tanks to achieve a lightweight cryogenic structure capable of withstanding internal pressures up to 75 psi while minimizing structural mass. The cylindrical tanks maintain a standard diameter of 3.05 m (10 ft), with overall stage lengths varying by variant—for instance, early versions like the Centaur-A measured about 8.9 m in length, while stretched configurations in later models extended to 12.7 m or more to accommodate increased loads. This balloon tank approach, where the tanks themselves provide load-bearing rigidity without additional internal framework, enables high structural efficiency under cryogenic conditions, supporting axial loads from integration and dynamic flight stresses. Integrated into the forward equipment compartment are helium-pressurized bladder tanks for the (RCS), storing up to 340 lb (154 kg) of to feed clusters of low-thrust thrusters for attitude control and three-axis stabilization. These bladder tanks, typically two in number with pressure-regulated feed systems, prevent sloshing in zero gravity and ensure reliable expulsion, contributing to the stage's precise orbital maneuvering capabilities without compromising the main tank integrity. Over its development, the Centaur's thermal protection evolved from rigid foam insulation on the liquid hydrogen (LH2) tank in early variants to advanced (MLI) blankets in modern configurations, significantly reducing cryogenic boil-off rates from around 2% per day to below 1.1% per day for extended missions. This shift to MLI, often combined with purging and shields, enhances propellant retention during coast phases while maintaining the stage's low mass. Auxiliary structures, such as interstage and forward adapters, incorporate aluminum-lithium alloys for added strength-to-weight benefits in load-bearing interfaces. The design achieves a of approximately 90-91% in contemporary variants, reflecting the optimized balance between thin-wall tankage, minimal structural reinforcements, and efficient insulation that maximizes usable cryogenic propellants relative to total stage mass. This high fraction underscores the Centaur's role as a high-performance upper stage, where structural simplicity directly supports overall velocity increments.

Propulsion System

The Centaur rocket stage relies on the RL10 family of liquid-propellant engines as its primary propulsion, burning and in an configuration for efficient upper-stage performance. These engines are deployed in either single or dual configurations across , with the dual setup common on Atlas-derived Centaurs to deliver combined vacuum exceeding 198 kN while optimizing capacity to . The RL10's design emphasizes reliability and precision, supporting a wide range of mission profiles through its lightweight construction and high-efficiency turbomachinery. Early stages employed the RL10A-1 engine, which produced 65.6 kN of and a of 421 seconds, marking the debut of operational cryogenic upper-stage in 1963. Over time, evolutions addressed optimization needs, culminating in the RL10A-4 series with extended nozzles—increasing the to enhance exhaust velocity. The RL10A-4-2 variant, introduced in the 1990s for advanced Atlas missions, achieves 99.2 kN of and 451 seconds of , representing a significant performance leap from initial models through refined and technologies. A key feature of the RL10 engines is their restart capability, facilitated by reliable ignition systems that allow multiple firings in space without atmospheric interference. In Atlas V operations, the Centaur stage has demonstrated up to three burns per mission, enabling complex maneuvers such as initial orbit insertion followed by circularization and payload deployment. This flexibility has supported over 200 successful -powered flights, underscoring the engine's robustness in varying thermal and zero-gravity environments. For future enhancements, the RL10E-1 variant—featuring a 3D-printed thrust chamber and fixed extension— is slated for integration starting late 2025, offering a 5-10% increase to approximately 107 kN per while reducing manufacturing complexity with 98% fewer parts in the assembly. This upgrade builds on the RL10C-1 baseline used in initial Vulcan flights, prioritizing cost efficiency and sustained high above 450 seconds for deep-space missions.

Propellant Management

The Centaur rocket stage relies on cryogenic (LH₂) and (LOX) propellants to achieve its high , making it suitable for precise orbital insertions and deep space trajectories. These propellants are stored in separate, pressure-stabilized tanks with a common bulkhead design that minimizes structural mass while separating the fuels. For the Centaur III variant, the total usable propellant load is approximately 20,830 kg (with LOX about 17,230 kg and LH₂ about 3,600 kg at a mixture ratio of approximately 4.8:1), allowing for extended burn times of several hundred seconds depending on mission profile. Tank pressures are maintained during flight by a helium pressurization system, which supplies gaseous to both the LH₂ and tanks at approximately 21 psia (1.45 bar) for the LH₂ tank and 30 psia (2.07 bar) for the tank to ensure positive for the engines and prevent . The system uses high-pressure helium bottles, typically four in number, with regulators and bubblers for the tank and energy dissipators for the LH₂ tank to manage gas injection efficiently. This autogenous-assisted approach, supplemented by for initial pressurization, reduces overall system weight compared to purely autogenous methods. Innovations in management include the Computer-Controlled Vent and Pressurization System (CCVAPS), which automates venting of excess gas to sustain pressure limits in zero-gravity environments, achieving minimal boil-off—such as a single LH₂ vent over a 5.25-hour period. Real-time monitoring of temperature, pressure, and gas composition supports detection of boil-off rates and adjustments to venting and insulation performance, minimizing loss during phases. Vented propellant tanks incorporate and sidewall radiation shields to limit heat ingress, reducing LH₂ boil-off from baseline rates of over 11 kW to under 1 kW. Additionally, subcooled LOX techniques, involving pre-chilling the oxidizer below its via or in-flight heat exchange, increase density by up to 10%, thereby enhancing overall stage performance without increasing tank volume. These methods have been validated in Centaur-derived test beds for long-duration missions, ensuring reliable delivery to the engines.

Historical Development

Early Design and Testing (1950s-1960s)

The development of the Centaur upper stage rocket began in the mid-1950s as part of efforts to create high-performance for vehicles, with (a division of ) proposing the concept in 1956 to leverage for superior . In 1958, the and the U.S. awarded a to develop Centaur as a versatile cryogenic upper stage, initially intended for integration with the Atlas missile family to enable deep-space missions. German-American engineer Krafft A. Ehricke served as the chief designer, drawing on his experience with advanced concepts to emphasize a lightweight, pressure-stabilized structure using balloon tanks filled with (LH2) and (LOX). A primary technical challenge during early design was managing cryogenic boil-off in LH2, which evaporates rapidly due to its low of 20 K, potentially depleting propellants during coast phases of long-duration flights. Engineers addressed this through innovations in , including the application of rigid on tank exteriors and later (MLI) blankets to minimize heat ingress and maintain propellant usability for up to several hours in vacuum. These advancements were critical for Centaur's role as a restartable stage, distinguishing it from earlier or storable-liquid upper stages. Ground testing played a pivotal role in validating these designs, with prototypes subjected to rigorous simulations at the Arnold Engineering Development Center (AEDC) in . There, facilities like the Tullahoma Vacuum Test Facility conducted thermal-vacuum and vibration tests to replicate space environments, ensuring structural integrity under extreme conditions such as acoustic loads exceeding 140 dB and temperature cycles from cryogenic to near-absolute zero. The first flight test of occurred on May 8, 1962, atop an Atlas booster (designated AC-1) from Cape Canaveral's Launch Complex 36, marking the inaugural U.S. launch of a liquid-hydrogen-fueled . The mission aimed to demonstrate basic and separation but failed 54 seconds after liftoff when an insulation panel on the LH2 tank separated prematurely, causing a structural rupture and of the upper stage. This setback, attributed to inadequate of the foam insulation under dynamic loads, highlighted vulnerabilities in the cryogenic design but provided valuable data for refinements, including improved bonding techniques and structural reinforcements. Subsequent ground tests at AEDC and 's Lewis Research Center's Plum Brook Station refined these issues, paving the way for successful demonstrations in 1963.

Initial Integrations (Atlas A-D, Saturn S-V)

The A-D variants represented the initial operational adaptations of the upper stage for integration with the Atlas launch vehicle, designed to replace the less capable Agena upper stage for higher-energy missions. These early variants featured shortened propellant tanks to optimize compatibility with the Atlas booster's dimensions and performance envelope, enabling efficient deep-space trajectories and significant delta-V contributions for interplanetary missions. The first successful flight of a D variant occurred on November 27, 1963, during the AC-2 mission, which demonstrated the stage's / propulsion in a suborbital test. This success paved the way for precursor missions to the Surveyor lunar program, including the AC-4 launch on December 11, 1964, which carried a 2,090-pound mass model of the Surveyor to validate integration and orbital insertion capabilities. These integrations established Centaur as a critical asset for NASA's early planetary exploration efforts, with the A-D variants flying multiple test and operational missions through the mid-1960s. Early Mariners used Atlas-Agena due to Centaur delays, but Centaur enabled subsequent high-energy missions. Parallel to Atlas developments, Centaur was adapted as the S-V third stage for the proposed Saturn I Block II configuration to support upper-stage testing, though Block II was canceled. The S-V flew as an inert boilerplate on the Saturn I Block I launches (SA-1 to SA-4) from 1961 to 1963, verifying structural interfaces and vehicle stability for future cryogenic upper stages like the S-IVB. These flights contributed to the validation of orbital assembly techniques essential for lunar missions. The S-V boilerplate tests highlighted Centaur's potential as a high-performance hydrogen-fueled stage within the Saturn family, influencing subsequent Apollo launch vehicle designs.

Titan and Shuttle Programs (D-1T, G/G-Prime, T)

The Centaur D-1T upper stage was adapted for integration with the launch vehicle to support deep space missions requiring extended coast periods in . This variant featured enhanced thermal protection and an integrated system to accommodate the Titan's higher performance profile compared to earlier Atlas integrations. The D-1T debuted on December 10, 1974, with the launch of the Helios 1 solar probe from Cape Canaveral's Launch Complex 41. Over the next three years, it completed six successful flights, including Helios 1 and 2, and 2 to Mars in 1975–1976, and and 2 in 1977, demonstrating reliable cryogenic propellant management during multi-burn sequences. The D-1T's propulsion system utilized two RL10A-3-3 engines, delivering a combined vacuum thrust of approximately 133 kN and a of 444 seconds, enabling efficient transplanetary injections. Its tank had a usable capacity of roughly 20,400 kg, paired with about 4,000 kg of , stored in pressure-stabilized aluminum-lithium tanks separated by an insulated common bulkhead. These features allowed the stage to handle the Titan IIIE's dynamic environment, including longer park orbits up to several hours, while maintaining boil-off below 1% per hour through passive insulation and helium pressurization. The D-1T's Centaur-specific flights were limited to these six. In the mid-1980s, NASA pursued the Shuttle-Centaur program to leverage the Space Shuttle's payload capacity for ambitious planetary missions, leading to the development of the G and G-Prime variants. Designed in 1984, the Centaur G was a shortened version (about 6 m long) optimized for multiple Shuttle deployments, while the G-Prime extended to 9 m for greater propellant load to support high-energy trajectories. These stages were specifically tailored for the Galileo Jupiter orbiter and Ulysses solar polar probe (originally the International Solar Polar Mission), with the G-Prime providing the delta-V needed for direct injection to Jupiter using two RL10A-4-2 engines. The program involved significant modifications, including strengthened mounting interfaces for the Shuttle's payload bay and enhanced safety systems to mitigate hydrogen leak risks during ground operations. However, following the Challenger disaster on January 28, 1986, the initiative was canceled in June 1986 due to concerns over the volatile liquid hydrogen propellant's potential to exacerbate explosion hazards in the event of an orbiter anomaly, prompting NASA to redesign the missions for expendable Titan IV launches. The T variant emerged as a key evolution for the heavy-lift program, introduced in the early 1990s to handle classified military payloads and deep-space probes requiring substantial upper-stage performance. This design, with a 3.05 m and approximately 9 m , incorporated larger tanks for increased capacity, powered by two RL10A-3A engines producing a total vacuum thrust of 147 kN and a of 448 seconds. The first / T flight occurred on February 14, 1994, validating the configuration's ability to deliver over 5,000 kg to geosynchronous transfer orbit. It supported 26 missions through 2005, including high-profile efforts such as the Cassini-Huygens launch on October 15, 1997, which utilized the extended burn capability to send the 5,600 kg probe on a gravity-assist to Saturn. The T's design emphasized robustness for polar orbits from Vandenberg Air Force Base and equatorial launches from , with integral for autonomous guidance and fault-tolerant propulsion control.

Production Variants

Atlas-Specific Variants (I, II, III)

The Centaur I upper stage was tailored for the Atlas I launch vehicle, entering service in 1991 and operating through 1995. This variant utilized dual Pratt & Whitney RL10A-3-3 engines, providing reliable propulsion for medium-class payloads in commercial and scientific missions. Over its operational lifespan, Centaur I supported five launches from Cape Canaveral, demonstrating the stage's role in transitioning Atlas from military to commercial applications with enhanced payload fairing options. Its performance enabled delivery of up to 3,180 kg to geosynchronous transfer orbit (GTO), balancing efficiency with the Atlas boost stage's capabilities for low-Earth orbit insertions and beyond. Building on this foundation, the Centaur II variant was developed for the more powerful and early Atlas III rockets, with operations spanning to 2002. Equipped with dual RL10A-4 engines featuring extendible nozzles for improved vacuum performance, Centaur II incorporated upgraded , including an inertial navigation unit and systems for precise orbital insertions. This configuration achieved 25 successful missions, contributing to a high reliability rate for the Atlas family and enabling diverse payloads such as communications satellites. Notable among these was the TDRS-I mission in 1995, which leveraged the stage's cryogenic propulsion for insertion. The variant's emphasized modularity, allowing integration with stretched booster stages to meet varying mission demands. The introduction of Centaur III in 1999 marked a pivotal evolution in the Atlas-specific lineup, incorporating lightweight aluminum-lithium tanks to reduce mass while maintaining structural integrity under cryogenic conditions. Its first flight occurred aboard an Atlas III vehicle in 2000, serving as a transitional design that bridged to the standardized Common for broader use across launch systems. Centaur III retained the dual-engine architecture of its predecessor but offered optional stretched tanks for increased capacity, enhancing overall vehicle performance. For context, the Centaur II baseline delivered a delta-V of approximately 5.9 km/s, with Centaur III's modifications providing incremental gains in and payload margins for GTO and high-energy trajectories. These variants collectively solidified Centaur's legacy in Atlas evolutions, prioritizing cost-effective upgrades over radical redesigns.

Common Centaur and Derivatives (III, SEC, DEC)

The Common , introduced in 2002 as the upper stage for the launch vehicle, features a derived from the earlier Single Engine Centaur, with stretched propellant tanks to enhance capacity and performance. This standardization allows compatibility with both lighter and heavier payload requirements through configurable engine setups, utilizing pressure-stabilized tanks for (LH2) and (LOX) propellants. The stage measures 3.05 meters in diameter and approximately 12.7 meters in length, with a fueled mass of around 30,000 kg, supporting reliable cryogenic operations across diverse mission profiles. The Single Engine Centaur (SEC) variant employs a single RL10A-4-2 engine, delivering 99.2 kN of vacuum thrust and a of 444 seconds, optimized for missions with moderate masses. Integrated into the 300 and 400 series configurations, the SEC measures about 11.8 meters in length and provides efficient propulsion for insertions into (LEO) or geosynchronous transfer orbits, where single-burn or dual-burn profiles suffice without the added complexity of dual engines. This setup has proven versatile for scientific and commercial satellites, emphasizing the stage's heritage of restartable cryogenic performance. For demanding heavier-lift missions, the Dual Engine Centaur (DEC) configuration equips the Common Centaur with two RL10A-4-2 engines, yielding combined vacuum thrust of 198.4 kN while maintaining the same overall stage dimensions and propellant load. Primarily used in the 500 series, the DEC enables payload delivery of up to 18,850 kg to LEO, supporting multi-burn trajectories for precise orbital insertions, including those for and crewed vehicle demonstrations. The dual-engine arrangement enhances ascent efficiency for high-energy missions, with electromechanical actuators for thrust vector control in the SEC transitioning to hydraulic systems in the DEC for improved stability. Since its debut, the Common Centaur has underpinned 105 successful Atlas V flights as of November 2025, demonstrating exceptional reliability with a near-perfect mission success rate in cryogenic upper stage operations.

Advanced Variant (Centaur V)

The Centaur V variant emerged in the 2010s as the dedicated upper stage for United Launch Alliance's (ULA) launch vehicle, evolving from earlier Centaur designs to meet the demands of next-generation heavy-lift missions. Originally, ULA planned to pair Vulcan with the (ACES) starting around 2023, but following the program's cancellation in September 2020 due to shifting priorities and technological assessments, development shifted to enhancing the Centaur lineage into the Centaur V configuration. This transition incorporated select ACES-derived technologies, such as improved cryogenic fluid management concepts, while retaining the core hydrolox propulsion heritage to ensure reliability and cost efficiency. The variant's debut occurred on Vulcan's Certification Flight 1 (Cert-1) mission from on January 8, 2024, where it successfully demonstrated orbital insertion capabilities alongside primary and secondary payloads. Key features of the Centaur V include upgraded avionics from ULA's Common Avionics System, which provide enhanced guidance, navigation, and control for precise multi-burn trajectories and complex orbital insertions, building on proven heritage to reduce development risks. The stage boasts a larger 5.4-meter aluminum-lithium structure compared to the 3-meter III, enabling a propellant capacity of approximately 120,000 pounds (54,400 kg) of (LH2) and (LOX), an increase over prior variants that supports extended endurance for high-energy missions. It is powered by two RL10C-1 engines, each delivering 24,000 lbf (107 kN) of with a of 453.8 seconds in vacuum, with upgrades to RL10E engines planned for late 2025 to further improve performance; it maintains compatibility with Vulcan configurations featuring up to six (GEM 63) solid rocket boosters, including the four-booster setup for balanced performance in medium- to heavy-lift profiles. Future upgrades, such as potential RL10E engine integration, are under consideration to further boost and efficiency, though these remain in early planning stages tied to broader enhancements. In terms of performance, the Centaur V delivers a delta-V capability of approximately 6.2 km/s, enabling Vulcan to achieve payload capacities of up to 14,500 kg to geosynchronous transfer orbit (GTO) in its fully boosted configuration, with injection accuracies better than 100 meters. This was validated in operational use during the USSF-106 mission on , 2025, where the stage successfully deployed U.S. experimental payloads, including the NTS-3 navigation satellite, directly to , marking Vulcan's first national security launch. Integration with Vulcan's first stage presented challenges, particularly in redesigning structural and fluid interfaces to accommodate the /LOX-powered booster's larger diameter and different thermal environment, requiring modifications to mating adapters, umbilical connections, and cryogenic venting systems to ensure seamless stage separation and propellant transfer reliability. These adaptations, informed by extensive ground testing, have positioned the Centaur V as a versatile enabler for diverse orbits, from GTO to .

Operational History

Key Missions and Achievements

The Centaur upper stage has powered more than 300 launches since its operational debut, enabling the deployment of numerous scientific and commercial spacecraft with a success rate over 92% overall and exceeding 97% for missions since 2000. This reliability has made it a cornerstone for high-energy orbital insertions and interplanetary trajectories. One of Centaur's seminal achievements was its role in the 1977 launch of Voyager 2 aboard a Titan IIIE vehicle, which propelled the probe on a grand tour of the outer planets, including groundbreaking flybys of Jupiter, Saturn, Uranus, and Neptune—the only spacecraft to visit the latter two. In 1997, a Titan IVB/Centaur configuration set a record by lofting the Cassini-Huygens spacecraft, the heaviest single interplanetary payload at 5,712 kg, toward Saturn for a 13-year mission that revolutionized understanding of the ringed planet and its moons. The stage's precision performance was again demonstrated in 2006 with an Atlas V/Centaur launching New Horizons to Pluto, arriving in 2015 to capture the first close-up images of the dwarf planet and its largest moon, Charon. Centaur has also advanced commercial spaceflight, supporting launches of communications satellites for providers like and SES on [Atlas V](/page/Atlas V) rockets, including the dual deployment of SES-20 and SES-21 in to enhance global broadcasting coverage. Its evolution culminated in the successful 2024 debut of the , which carried the Peregrine lunar lander toward the , marking the stage's integration into next-generation heavy-lift capabilities.

Cryogenic Fluid Management Experiments

The Cryogenic Fluid Management (CFM) experiments on the upper stage have focused on demonstrating key technologies for in-orbit handling, leveraging residual propellants from missions to test advanced techniques for future long-duration space operations. These tests have primarily utilized the Cryogenic Orbital Testbed (CRYOTE) concept, which integrates with the to provide a low-risk platform for microgravity evaluations of LH2 and LO2 behaviors. One early demonstration involved no-vent fill techniques for LH2, aimed at filling tanks without atmospheric venting to minimize losses . This approach uses thermodynamic cooling from the incoming liquid to condense vapors, achieving high fill efficiencies in low-gravity conditions. Ground and conceptual flight tests showed potential for up to 97% fill efficiency by optimizing inlet conditions and tank geometry, reducing the need for vent systems that could expel usable . Such methods were explored as part of preparations for extended operations, informing designs for depots. Between 2014 and 2019, multiple CRYOTE configurations were proposed for flights to investigate and control, critical for stable acquisition during future depot transfers. Slosh tests examined motion under low-acceleration environments, using sensors to measure wave propagation and damping in partially filled tanks, while control experiments validated settling thruster sequences to position liquid at outlets without excessive mixing. These efforts highlighted the challenges of zero-gravity behavior, such as stratification and interface stability, using Centaur's existing for autonomous operation post-payload deployment. Data from these tests supported modeling for depots, emphasizing passive stabilization techniques to enable reliable transfers over hours to days. Projected CRYOTE demonstrations on flights in 2025 aim to further validate these CFM technologies in operational environments. Collectively, these experiments yielded valuable data that shaped the Centaur V variant, incorporating enhanced insulation and venting strategies to achieve boil-off rates below 0.1% per day for LH2, a significant improvement over baseline systems and essential for extended missions like in- refueling. This low boil-off performance, validated through thermodynamic modeling calibrated by flight data, supports scalability to depot architectures with minimal propellant waste.

Integration with Vulcan Centaur

The integration of the Centaur upper stage into the Vulcan rocket represents a significant evolution in United Launch Alliance's (ULA) launch capabilities, leveraging the stage's proven cryogenic propulsion for enhanced performance in the configuration. The Centaur V variant, with its dual RL10C-1-1 engines, provides precise orbital insertion for a range of missions, building on decades of reliability while adapting to Vulcan's methane-fueled first stage and reusable solid rocket boosters. Certification of for (NSSL) Phase 3 contracts required two demonstration flights. The first, designated Cert-1, launched successfully on January 8, 2024, from , carrying NASA's and demonstrating nominal Centaur performance in a lunar trajectory. The second flight, Cert-2 on October 4, 2024, achieved an acceptable orbital insertion despite a minor anomaly with one nozzle, validating the system's overall integrity. These successes enabled U.S. certification on March 26, 2025, clearing for operational missions under NSSL Phase 3. Vulcan Centaur's operational debut occurred with the USSF-106 mission on August 12, 2025, launching from Space Launch Complex 41 and delivering classified payloads directly to geosynchronous Earth orbit (GEO) using the Centaur V stage. This flight marked the first NSSL operational mission for the vehicle, showcasing its ability to handle multi-manifest payloads for the U.S. Space Force's . Planned commercial operations include Amazon's Project Kuiper constellation, with the first launch carrying Kuiper satellites targeted for the fourth quarter of 2025, deploying up to 45 satellites per mission to . Compared to the retiring , offers advantages in launch cadence and payload capacity, enabled by reusable first-stage boosters through ULA's SMART reuse program and the optimized Centaur V upper stage. While in its 551 configuration delivers approximately 18,800 kg to LEO, with six solid rocket boosters achieves up to 27,200 kg to LEO, supporting heavier and more frequent missions. Looking ahead, ULA has scheduled over 30 launches through 2030, including additional Kuiper deployments, GPS III satellites, and national security payloads, as completes its final missions and retires by the end of 2025. This manifest positions as ULA's primary vehicle, aiming for a sustained cadence of at least 20 launches annually starting in to meet growing demand in both commercial and government sectors.

Incidents and Legacy

Major Mishaps

The Centaur rocket stage has experienced a number of major mishaps over its operational history, though these represent a small fraction of its total flights, with failures occurring in roughly 4% of approximately 260 missions as of 2025. The program's first significant failure occurred on May 8, 1962, during the maiden suborbital test flight of the AC-1 vehicle from . At T+54 seconds, the Centaur upper stage underwent structural breakup when aerodynamic forces dislodged insulation panels from the tank, causing rapid boil-off, a pressure surge, and tank rupture. The spilled ignited upon contact with the hot exhaust, engulfing the vehicle in a fireball and leading to its destruction; however, the unmanned test resulted in no injuries. This incident, which delayed early lunar and planetary efforts, was attributed to inadequate margins for the pressure-stabilized tank under flight loads. A ground-based mishap highlighting the hazards of handling took place on July 13, 1987, during pre-launch preparations for the Centaur AC-68 mission at . A workstand support arm accidentally gouged a gash in the pressurized tank on the pad, causing the tank to rupture violently and release its contents in an explosive decompression. The incident caused minor injuries to two workers and extensive damage that required rebuilding the tank, delaying the launch until September 1989. This event, occurring amid growing concerns over cryogenic upper stages in the Shuttle program, exemplified the volatile risks of propellants and contributed to broader debates leading to the cancellation following the 1986 Challenger disaster. In-flight anomalies continued in later years, including a notable glitch during a 1999 Titan IVB mission. The software error in the 's inertial guidance set resulted in loss of attitude control and off-nominal burns, leading to mission termination by and loss of the classified . The root cause was identified as deficiencies in , testing, and processes.

Safety Improvements and Retirement Plans

Following early failures in the , upper stage underwent significant safety enhancements, including the integration of redundant systems in the D-1A and D-1T configurations during the to improve reliability and . These upgrades featured a digital computer unit that consolidated guidance, control, and sequencing functions, along with a coast-phase and computer-controlled vent/pressurization system using redundant valves and high-accuracy transducers. Additionally, the was made fully redundant, and energy dissipators were added to boost pump volute bleed systems to minimize propellant disturbances in low-gravity environments. The cancellation of the program after the 1986 Challenger disaster, due to heightened concerns over carrying cryogenic propellants in the orbiter's , shifted focus to hypergolic alternatives like the for certain missions. However, Centaur's extensive operational experience with and oxygen contributed to broader cryogenic standards, emphasizing redundant pressurization, venting, and thermal protection protocols that informed subsequent expendable designs. In the Centaur V variant for the rocket, modern enhancements include advanced avionics for multi-burn missions and a debris-free separation system with spring packs and frangible joints to enhance structural integrity during jettison. Post-separation, the stage performs automated collision and avoidance maneuvers to mitigate orbital risks, supporting Vulcan's planned ramp-up to 20-25 launches annually by 2026. The legacy of the Centaur includes over 280 flights across variants as of November 2025, with the configuration alone achieving approximately 90 successful launches before its retirement around 2030. Centaur V is expected to continue operations through the 2030s on Vulcan, with ULA developing future upper stages such as the Simple, Modular, Agile, Resilient, Trusted () stage, which incorporates integrated vehicle fluids for extended-duration missions.

References

  1. https://www.nasa.gov/history/centaur-americas-workhorse-in-space/
  2. https://www.ulalaunch.com/rockets/vulcan-centaur
  3. https://ntrs.nasa.gov/api/citations/20150007890/downloads/20150007890.pdf
  4. https://www1.grc.nasa.gov/wp-content/uploads/Centaur-D-1A-pamphlet-1973.pdf
  5. https://www.ulalaunch.com/docs/default-source/upper-stages/the-centaur-upper-stage-vehicle.pdf
  6. https://www.ulalaunch.com/docs/default-source/upper-stages/centaur-upperstage-applicability-for-several-day-mission-durations-with-minor-insulation-modifications-2007-5845.pdf
  7. https://www.ulalaunch.com/docs/default-source/upper-stages/history-of-the-titan-centaur-launch-vehicle.pdf
  8. https://www.ulalaunch.com/docs/default-source/extended-duration/atlas-centaur-extensibility-to-long-duration-in-space-applications.pdf
  9. https://www.l3harris.com/all-capabilities/rl10-engine
  10. https://engineering.purdue.edu/~propulsi/propulsion/rockets/liquids/rl10.html
  11. https://spaceflightnow.com/2022/06/30/atlas-5-ussf-12-live-coverage/
  12. https://www.l3harris.com/newsroom/editorial/2024/01/vulcan-rocket-set-debut-aerojet-rocketdyne-propulsion
  13. https://www.l3harris.com/newsroom/press-release/2024/11/l3harris-delivers-new-generation-rl10-rocket-engines
  14. https://spacenews.com/new-rl10-engine-to-be-introduced-on-vulcan-in-2025/
  15. https://ntrs.nasa.gov/api/citations/19730023886/downloads/19730023886.pdf
  16. https://ntrs.nasa.gov/api/citations/20080015891/downloads/20080015891.pdf
  17. https://ntrs.nasa.gov/api/citations/20180000059/downloads/20180000059.pdf
  18. https://www.nasa.gov/wp-content/uploads/2023/04/sp-4230.pdf
  19. https://www.thespacereview.com/article/4757/1
  20. https://ntrs.nasa.gov/api/citations/19710069676/downloads/19710069676.pdf
  21. https://ntrs.nasa.gov/api/citations/19750004937/downloads/19750004937.pdf
  22. http://www.astronautix.com/t/titaniiie.html
  23. https://www.nasa.gov/wp-content/uploads/2018/04/hq-0019-hq-rod-galileo_and_ulysses_missions-1989_0.pdf
  24. https://arstechnica.com/science/2015/10/dispatches-from-the-death-star-the-rise-and-fall-of-nasas-shuttle-centaur/
  25. https://science.nasa.gov/photojournal/cassini-orbiter-and-huygens-probe-aboard-the-titan-iv/
  26. https://space.physics.uiowa.edu/plasma-wave/crres/press-kit/atlas-i.html
  27. https://apps.dtic.mil/sti/tr/pdf/ADA258845.pdf
  28. https://www.ulalaunch.com/docs/default-source/rockets/atlasv-cutaway.pdf?sfvrsn=3bf92929_4
  29. https://www.ulalaunch.com/docs/default-source/rockets/atlas-v-and-delta-iv-technical-summary.pdf
  30. https://space.skyrocket.de/doc_stage/centaur.htm
  31. https://www.ulalaunch.com/rockets/atlas-v
  32. https://spacenews.com/ula-studying-long-term-upgrades-to-vulcan/
  33. https://www.ulalaunch.com/docs/default-source/rockets/2023_vulcan_user_guide.pdf?sfvrsn=e9cc773f_4
  34. https://www.ulalaunch.com/docs/default-source/rockets/vulcancentaur.pdf?sfvrsn=10d7f58f_2
  35. https://www.nasa.gov/wp-content/uploads/2024/01/national-aeronautics-and-space-administration-vulcan-fonsi-bg-word.pdf?emrc=1d8873
  36. https://www.ulalaunch.com/missions/next-launch/vulcan-ussf-106
  37. https://newspaceeconomy.ca/2024/08/26/why-the-centaur-upper-stage-is-an-unsung-hero-of-the-space-age/
  38. https://science.nasa.gov/mission/voyager/voyager-2/
  39. https://science.nasa.gov/mission/cassini/quick-facts/
  40. https://www.planetary.org/space-images/new-horizons-atlas-v-rocket
  41. https://www.ulalaunch.com/missions/archived-launched/atlas-v-ses-20-ses-21
  42. https://newsroom.ulalaunch.com/releases/united-launch-alliance-successfully-launches-first-next-generation-vulcan-rocket
  43. https://ntrs.nasa.gov/api/citations/20090037680/downloads/20090037680.pdf
  44. https://ntrs.nasa.gov/api/citations/20080023145/downloads/20080023145.pdf
  45. https://www.sciencedirect.com/science/article/abs/pii/S0011227512000124
  46. https://ntrs.nasa.gov/api/citations/20150022115/downloads/20150022115.pdf
  47. https://arstechnica.com/space/2024/10/ulas-second-vulcan-launch-will-pave-the-way-for-military-certification/
  48. https://www.ulalaunch.com/missions/archived-launched/vulcan-cert-1
  49. https://www.nasaspaceflight.com/2024/10/vulcan-cert2-launch/
  50. https://spacenews.com/space-force-certifies-vulcan-for-national-security-launches/
  51. https://spaceflightnow.com/2025/08/13/ula-launches-vulcan-rocket-on-first-space-force-mission/
  52. https://www.aboutamazon.com/news/innovation-at-amazon/project-kuiper-satellite-internet-first-launch
  53. https://www.space.com/vulcan-centaur-rocket
  54. https://aerospaceamerica.aiaa.org/ula-forecasts-launching-at-least-20-times-a-year-starting-in-2026/
  55. https://spacenews.com/ulas-vulcan-centaur-launches-first-national-security-mission/
  56. http://sunnyday.mit.edu/accidents/titan_1999_rpt.doc
  57. https://ntrs.nasa.gov/api/citations/19750013258/downloads/19750013258.pdf
  58. https://www.ulalaunch.com/docs/default-source/extended-duration/cryogenic-orbital-testbed-%28cryote%29-2009.pdf
  59. https://spacenews.com/ula-forecasts-nine-launches-in-2025-but-sharp-increase-for-2026/
  60. https://blog.ulalaunch.com/blog/atlas-v-starliner-oft-by-the-numbers
  61. https://spacenews.com/bruno-next-big-thing-ula-long-endurance-upper-stage/
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