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123-491: The Centaur is a family of rocket propelled upper stages that has been in use since 1962. It is currently produced by U.S. launch service provider United Launch Alliance , with one main active version and one version under development. The 3.05 m (10.0 ft) diameter Common Centaur/Centaur III flies as the upper stage of the Atlas V launch vehicle, and the 5.4 m (18 ft) diameter Centaur V has been developed as

246-505: A NSSL certification flight, on 4 October 2024, which achieved a perfect orbital insertion, despite the nozzle on one of the GEM-63XL solid rocket boosters falling off which led to reduced, asymmetrical thrust. The Vulcan Centaur re-uses many technologies from ULA's Atlas V and Delta IV launch vehicles, with an aim to achieve better performance and lower production costs. The biggest change between Vulcan first stage and its predecessors

369-471: A Vulcan first stage, a Centaur upper stage with RL10CX engines with a nozzle extension and six SRBs. The payload capacity of Vulcan Centaur versions are: 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. Future launches are listed chronologically when firm plans are in place. The order of

492-417: A crane. This is generally not practical for larger space vehicles, which are assembled off the pad and moved into place on the launch site by various methods. NASA's Apollo / Saturn V crewed Moon landing vehicle, and Space Shuttle , were assembled vertically onto mobile launcher platforms with attached launch umbilical towers, in a Vehicle Assembly Building , and then a special crawler-transporter moved

615-510: A dragon's head with an open mouth. The British scientist and historian Joseph Needham points out that the written material and depicted illustration of this rocket come from the oldest stratum of the Huolongjing , which can be dated roughly 1300–1350 AD (from the book's part 1, chapter 3, page 23). Another example of an early multistaged rocket is the Juhwa (走火) of Korean development. It

738-562: 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. Centaur V is the upper stage of the new Vulcan launch vehicle developed by the United Launch Alliance to meet the needs of the National Security Space Launch (NSSL) program. Vulcan

861-615: A goal of halving the cost of the Atlas V rocket. 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

984-441: A half times more energy than the upper stage ULA currently flies. “But that’s just the tip of the iceberg,” Bruno elaborated. “I’m going to be pushing up to 450, 500, 600 times the endurance over just the next handful of years. That will enable a whole new set of missions that you cannot even imagine doing today.” Vulcan finally launched on 8 January 2024 and the stage performed flawlessly on its maiden flight. On 4 October 2024, in

1107-408: A higher cost for deployment. Hot-staging is a type of rocket staging in which the next stage fires its engines before separation instead of after. During hot-staging, the earlier stage throttles down its engines. Hot-staging may reduce the complexity of stage separation, and gives a small extra payload capacity to the booster. It also eliminates the need for ullage motors , as the acceleration from

1230-415: A higher specific impulse means a more efficient rocket engine, capable of burning for longer periods of time. In terms of staging, the initial rocket stages usually have a lower specific impulse rating, trading efficiency for superior thrust in order to quickly push the rocket into higher altitudes. Later stages of the rocket usually have a higher specific impulse rating because the vehicle is further outside

1353-531: A lengthed version of the GEM 63 SRBs developed for the Atlas. Vulcan Centaur offers heavy-lift capabilities in a smaller footprint than three-core vehicles. With a single core and six GEM boosters, the Vulcan Centaur can lift 27,200 kilograms (60,000 lb) to low Earth orbit (LEO). For comparison, the Atlas V could lift 18,850 kg (41,560 lb) to LEO with a single core and five GEM boosters, and

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1476-453: A limitation imposed by the laws of physics on the velocity change achievable by a rocket stage. The limit depends on the fueled-to-dry mass ratio and on the effective exhaust velocity of the engine. This relation is given by the classical rocket equation : where: The delta v required to reach low Earth orbit (or the required velocity of a sufficiently heavy suborbital payload) requires a wet to dry mass ratio larger than has been achieved in

1599-553: 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

1722-441: A mission is the burn time, which is the amount of time the rocket engine will last before it has exhausted all of its propellant. For most non-final stages, thrust and specific impulse can be assumed constant, which allows the equation for burn time to be written as: Where m 0 {\displaystyle m_{\mathrm {0} }} and m f {\displaystyle m_{\mathrm {f} }} are

1845-428: 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. 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

1968-472: A multistage rocket introduces additional risk into the success of the launch mission. Reducing the number of separation events results in a reduction in complexity . Separation events occur when stages or strap-on boosters separate after use, when the payload fairing separates prior to orbital insertion, or when used, a launch escape system which separates after the early phase of a launch. Pyrotechnic fasteners , or in some cases pneumatic systems like on

2091-464: A possible experimental resource for testing in-space cryogenic fluid management techniques. 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

2214-529: A pre-recorded message during the broadcast of the Vulcan Cert-2 mission, Upgrades Development Director Amanda Bacchetti had stated that ULA would be developing a "LEO Optimized Centaur" set to launch aboard a Vulcan launch vehicle sometime in 2025. She had stated that this variant of Centaur V would be shorter (and therefore more mass efficient for LEO orbits), however specifications for this variant were not given. The Centaur concept originated in 1956 when

2337-466: A rocket system will be when performing optimizations and comparing varying configurations for a mission. For initial sizing, the rocket equations can be used to derive the amount of propellant needed for the rocket based on the specific impulse of the engine and the total impulse required in N·s. The equation is: where g is the gravity constant of Earth. This also enables the volume of storage required for

2460-402: A single rocket stage. The multistage rocket overcomes this limit by splitting the delta-v into fractions. As each lower stage drops off and the succeeding stage fires, the rest of the rocket is still traveling near the burnout speed. Each lower stage's dry mass includes the propellant in the upper stages, and each succeeding upper stage has reduced its dry mass by discarding the useless dry mass of

2583-399: A technical algorithm that generates an analytical solution that can be implemented by a program, or simple trial and error. For the trial and error approach, it is best to begin with the final stage, calculating the initial mass which becomes the payload for the previous stage. From there it is easy to progress all the way down to the initial stage in the same manner, sizing all the stages of

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2706-483: Is a commonly used rocket system to attain Earth orbit. The spacecraft uses three distinct stages to provide propulsion consecutively in order to achieve orbital velocity. It is intermediate between a four-stage-to-orbit launcher and a two-stage-to-orbit launcher. Other designs (in fact, most modern medium- to heavy-lift designs) do not have all three stages inline on the main stack, instead having strap-on boosters for

2829-415: Is a safe and reasonable assumption to say that 91 to 94 percent of the total mass is fuel. It is also important to note there is a small percentage of "residual" propellant that will be left stuck and unusable inside the tank, and should also be taken into consideration when determining amount of fuel for the rocket. A common initial estimate for this residual propellant is five percent. With this ratio and

2952-414: Is capable of up to twelve restarts, limited by propellant, orbital lifetime, and mission requirements. Combined with the insulation of the propellant tanks, this allows Centaur to perform the multi-hour coasts and multiple engine burns required on complex orbital insertions. The reaction control system (RCS) also provides ullage and consists of twenty hydrazine monopropellant thrusters located around

3075-453: Is generally assembled at its manufacturing site and shipped to the launch site; the term vehicle assembly refers to the mating of all rocket stage(s) and the spacecraft payload into a single assembly known as a space vehicle . Single-stage vehicles ( suborbital ), and multistage vehicles on the smaller end of the size range, can usually be assembled directly on the launch pad by lifting the stage(s) and spacecraft vertically in place by means of

3198-577: Is impractical to directly compare the rocket's certain trait with the same trait of another because their individual attributes are often not independent of one another. For this reason, dimensionless ratios have been designed to enable a more meaningful comparison between rockets. The first is the initial to final mass ratio, which is the ratio between the rocket stage's full initial mass and the rocket stage's final mass once all of its fuel has been consumed. The equation for this ratio is: Where m E {\displaystyle m_{\mathrm {E} }}

3321-428: Is intermediate between a five-stage-to-orbit launcher and a three-stage-to-orbit launcher, most often used with solid-propellant launch systems. Other designs do not have all four stages inline on the main stack, instead having strap-on boosters for the "stage-0" with three core stages. In these designs, the boosters and first stage fire simultaneously instead of consecutively, providing extra initial thrust to lift

3444-486: Is principally designed for the National Security Space Launch (NSSL) program, which launches satellites for U.S. intelligence agencies and the Defense Department , but ULA believes it will also be able to price missions low enough to attract commercial launches. ULA began developing the Vulcan in 2014, largely to compete with SpaceX 's Falcon 9 and to comply with a Congressional requirement to stop using

3567-427: Is repeated until the desired final velocity is achieved. In some cases with serial staging, the upper stage ignites before the separation—the interstage ring is designed with this in mind, and the thrust is used to help positively separate the two vehicles. Only multistage rockets have reached orbital speed . Single-stage-to-orbit designs are sought, but have not yet been demonstrated. Multi-stage rockets overcome

3690-803: Is similar in size as the Delta family's Common Booster Core (Vulcan is about 0.3-meter (1 ft) larger in diameter) and is built in the same manufacturing facility in Decatur, Alabama using much of the same equipment. The second stage is the Centaur V , a larger and improved version of the Centaur III used on the Atlas V, 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 (SRBs) built by Northrop Grumman . These are

3813-658: Is that it uses liquid methane (liquefied natural gas) as its fuel along with liquid oxygen in two BE-4 engines built by Blue Origin . Compared to the cryogenic liquid hydrogen fuel used on Delta, methane is more dense with a much higher boiling point, allowing fuel tanks to be constructed smaller and lighter. Methane also burns cleaner than the kerosene fuel used on Atlas, which enables engines to be more easily reused as they are less likely to be contaminated and eventually clogged with hydrocarbon combustion byproducts. This characteristic will be important if ULA implements its proposed SMART reuse system. The Vulcan first stage

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3936-514: Is the empty mass of the stage, m p {\displaystyle m_{\mathrm {p} }} is the mass of the propellant, and m P L {\displaystyle m_{\mathrm {PL} }} is the mass of the payload. The second dimensionless performance quantity is the structural ratio, which is the ratio between the empty mass of the stage, and the combined empty mass and propellant mass as shown in this equation: The last major dimensionless performance quantity

4059-402: Is the mass of the oxidizer and m f u e l {\displaystyle m_{\mathrm {fuel} }} is the mass of the fuel. This mixture ratio not only governs the size of each tank, but also the specific impulse of the rocket. Determining the ideal mixture ratio is a balance of compromises between various aspects of the rocket being designed, and can vary depending on

4182-455: Is the payload ratio, which is the ratio between the payload mass and the combined mass of the empty rocket stage and the propellant: After comparing the three equations for the dimensionless quantities, it is easy to see that they are not independent of each other, and in fact, the initial to final mass ratio can be rewritten in terms of structural ratio and payload ratio: These performance ratios can also be used as references for how efficient

4305-720: Is the upper stage of the Atlas V rocket. 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. The Dual Engine Centaur (DEC) configuration will continue to use the smaller RL10-A-4-2 to accommodate two engines in the available space. The Atlas V can fly in multiple configurations, but only one affects

4428-435: 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

4551-730: The Magellan Venus probe. After the Space Shuttle Challenger accident , and 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. The probes were launched with the much less powerful solid-fueled IUS , with Galileo needing multiple gravitational assists from Venus and Earth to reach Jupiter. The capability gap left by

4674-439: 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. Centaur I

4797-517: 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. On 8 January 2024, Vulcan lifted off for

4920-620: 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

5043-480: The Falcon 9 Full Thrust , are typically used to separate rocket stages. A two-stage-to-orbit ( TSTO ) or two-stage rocket launch vehicle is a spacecraft in which two distinct stages provide propulsion consecutively in order to achieve orbital velocity. It is intermediate between a three-stage-to-orbit launcher and a hypothetical single-stage-to-orbit (SSTO) launcher. The three-stage-to-orbit launch system

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5166-624: The Integrated Vehicle Fluids (IVF) feature expected to allow the extension of upper stage on-orbit life from hours to weeks. Centaur V uses two different versions of the RL10-C engine with nozzle extensions to improve the fuel consumption for the heaviest payloads. This increased capability over Common Centaur was intended to permit ULA to meet NSSL requirements and retire both the Atlas V and Delta IV Heavy rocket families earlier than initially planned. The new rocket publicly became

5289-534: 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

5412-734: The RTV-G-4 Bumper rockets tested at the White Sands Proving Ground and later at Cape Canaveral from 1948 to 1950. These consisted of a V-2 rocket and a WAC Corporal sounding rocket. The greatest altitude ever reached was 393 km, attained on February 24, 1949, at White Sands. In 1947, the Soviet rocket engineer and scientist Mikhail Tikhonravov developed a theory of parallel stages, which he called "packet rockets". In his scheme, three parallel stages were fired from liftoff , but all three engines were fueled from

5535-509: The Singijeon , or 'magical machine arrows' in the 16th century. The earliest experiments with multistage rockets in Europe were made in 1551 by Austrian Conrad Haas (1509–1576), the arsenal master of the town of Hermannstadt , Transylvania (now Sibiu/Hermannstadt, Romania). This concept was developed independently by at least five individuals: The first high-speed multistage rockets were

5658-490: The Soviet and U.S. space programs, were not passivated after mission completion. During the initial attempts to characterize the space debris problem, it became evident that a good proportion of all debris was due to the breaking up of rocket upper stages, particularly unpassivated upper-stage propulsion units. An illustration and description in the 14th century Chinese Huolongjing by Jiao Yu and Liu Bowen shows

5781-608: The TRL of the Advanced Cryogenic Evolved Stage Centaur successor. Although Centaur has a long and successful flight history, it has experienced a number of mishaps: Upper stage By jettisoning stages when they run out of propellant, the mass of the remaining rocket is decreased. Each successive stage can also be optimized for its specific operating conditions, such as decreased atmospheric pressure at higher altitudes. This staging allows

5904-580: 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

6027-697: The Vulcan Centaur in March 2018. In May 2018, the Aerojet Rocketdyne RL10 was announced as Centaur V's engine following a competitive procurement process against the Blue Origin BE-3 . Each stage will mount two engines. In September 2020, ULA announced that ACES was no longer being developed, and that Centaur V would be used instead. Tory Bruno, ULA's CEO, stated that the Vulcan's Centaur 5 will have 40% more endurance and two and

6150-523: The "stage-0" with two core stages. In these designs, the boosters and first stage fire simultaneously instead of consecutively, providing extra initial thrust to lift the full launcher weight and overcome gravity losses and atmospheric drag. The boosters are jettisoned a few minutes into flight to reduce weight. The four-stage-to-orbit launch system is a rocket system used to attain Earth orbit. The spacecraft uses four distinct stages to provide propulsion consecutively in order to achieve orbital velocity. It

6273-409: The 1970s and 1980s. By the end of 1989, Centaur-D had been used as the upper stage for 63 Atlas rocket launches, 55 of which were successful. 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

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6396-548: 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. An updated version, called Centaur-D1A (powered by RL10A-3-3 engines), was used on the Atlas-SLV3D came into use during the 1970s. The Centaur-D1AR was used for the Atlas-SLV3D and Atlas G came into use during

6519-467: The Atlas booster and finesse of the upper stage. 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 LH 2 tank to overheat and rupture. This version was powered by two RL10A-1 engines. After extensive redesigns,

6642-457: 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 (51 ft)) or L for Long (21.3 m (70 ft)). 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

6765-594: 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 2018, ULA announced that it had picked the BE-4 engine from Blue Origin and fueled by liquid oxygen (LOX) and liquid methane (CH 4 ) to replace the RD-180 on a new first-stage booster. The engine

6888-593: The Russian-made RD-180 engine that powered 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 new BE-4 first-stage engine and the Centaur second-stage. The Vulcan Centaur had a near perfect first launch on 8 January 2024 carrying the Peregrine lunar lander , the first mission of NASA's Commercial Lunar Payload Services program. It made its second launch,

7011-486: 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

7134-520: The atmosphere behind an inflatable heat shield. Through the first several years, the ULA board of directors made quarterly funding commitments to Vulcan Centaur development. As of October 2018 , 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,

7257-462: The atmosphere and the exhaust gas does not need to expand against as much atmospheric pressure. When selecting the ideal rocket engine to use as an initial stage for a launch vehicle, a useful performance metric to examine is the thrust-to-weight ratio, and is calculated by the equation: The common thrust-to-weight ratio of a launch vehicle is within the range of 1.3 to 2.0. Another performance metric to keep in mind when designing each rocket stage in

7380-401: The breakup of a single upper stage while in orbit. After the 1990s, spent upper stages are generally passivated after their use as a launch vehicle is complete in order to minimize risks while the stage remains derelict in orbit . Passivation means removing any sources of stored energy remaining on the vehicle, as by dumping fuel or discharging batteries. Many early upper stages, in both

7503-419: The different stages of the rocket should be clearly defined. Continuing with the previous example, the end of the first stage which is sometimes referred to as 'stage 0', can be defined as when the side boosters separate from the main rocket. From there, the final mass of stage one can be considered the sum of the empty mass of stage one, the mass of stage two (the main rocket and the remaining unburned fuel) and

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7626-404: The drawbacks of a less efficient specific impulse rating. But suppose the defining constraint for the launch system is volume, and a low density fuel is required such as hydrogen. This example would be solved by using an oxidizer-rich mixture ratio, reducing efficiency and specific impulse rating, but will meet a smaller tank volume requirement. The ultimate goal of optimal staging is to maximize

7749-400: The end of the rocket stage's motion, as the vehicle will still have a velocity that will allow it to coast upward for a brief amount of time until the acceleration of the planet's gravity gradually changes it to a downward direction. The velocity and altitude of the rocket after burnout can be easily modeled using the basic physics equations of motion. When comparing one rocket with another, it

7872-468: The engine end of the stage. 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). 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

7995-598: The entire vehicle stack to the launch pad in an upright position. In contrast, vehicles such as the Russian Soyuz rocket and the SpaceX Falcon 9 are assembled horizontally in a processing hangar, transported horizontally, and then brought upright at the pad. Spent upper stages of launch vehicles are a significant source of space debris remaining in orbit in a non-operational state for many years after use, and occasionally, large debris fields created from

8118-411: The equations for determining the burnout velocities, burnout times, burnout altitudes, and mass of each stage. This would make for a better approach to a conceptual design in a situation where a basic understanding of the system behavior is preferential to a detailed, accurate design. One important concept to understand when undergoing restricted rocket staging, is how the burnout velocity is affected by

8241-511: 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

8364-486: The first stage of the American Atlas I and Atlas II launch vehicles, arranged in a row, used parallel staging in a similar way: the outer pair of booster engines existed as a jettisonable pair which would, after they shut down, drop away with the lowermost outer skirt structure, leaving the central sustainer engine to complete the first stage's engine burn towards apogee or orbit. Separation of each portion of

8487-607: 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

8610-420: 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. As of August 2020 , 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

8733-467: The fuel to be calculated if the density of the fuel is known, which is almost always the case when designing the rocket stage. The volume is yielded when dividing the mass of the propellant by its density. Asides from the fuel required, the mass of the rocket structure itself must also be determined, which requires taking into account the mass of the required thrusters, electronics, instruments, power equipment, etc. These are known quantities for typical off

8856-450: The full launcher weight and overcome gravity losses and atmospheric drag. The boosters are jettisoned a few minutes into flight to reduce weight. Vulcan (rocket) 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

8979-405: The initial and final masses of the rocket stage respectively. In conjunction with the burnout time, the burnout height and velocity are obtained using the same values, and are found by these two equations: When dealing with the problem of calculating the total burnout velocity or time for the entire rocket system, the general procedure for doing so is as follows: The burnout time does not define

9102-443: The largest rocket ever to do so, as well as the first reusable vehicle to utilize hot staging. A rocket system that implements tandem staging means that each individual stage runs in order one after the other. The rocket breaks free from the previous stage, then begins burning through the next stage in straight succession. On the other hand, a rocket that implements parallel staging has two or more different stages that are active at

9225-467: The later launches is much less certain. Launches are expected to take place "no earlier than" (NET) the listed date. 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

9348-529: 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 a mass simulator with some "experiments and demonstrations" to help develop future technology for the Centaur upper stage. Vulcan Centaur lifted off on

9471-403: The mass of the payload. High-altitude and space-bound upper stages are designed to operate with little or no atmospheric pressure. This allows the use of lower pressure combustion chambers and engine nozzles with optimal vacuum expansion ratios . Some upper stages, especially those using hypergolic propellants like Delta-K or Ariane 5 ES second stage, are pressure fed , which eliminates

9594-464: The mass of the propellant calculated, the mass of the empty rocket weight can be determined. Sizing rockets using a liquid bipropellant requires a slightly more involved approach because there are two separate tanks that are required: one for the fuel, and one for the oxidizer. The ratio of these two quantities is known as the mixture ratio, and is defined by the equation: Where m o x {\displaystyle m_{\mathrm {ox} }}

9717-486: The mass of the tanks, maximizing the stage's overall performance. A common bulkhead separates the LOX and LH 2 tanks, further reducing the tank mass. It is made of two stainless steel skins separated by a fiberglass honeycomb. The fiberglass honeycomb minimizes heat transfer between the extremely cold LH 2 and less cold LOX. The main propulsion system consists of one or two Aerojet Rocketdyne RL10 engines. The stage

9840-566: The most expensive components potentially reusable and second-stage improvements to allow the rocket to operate for months in Earth-orbit cislunar space . 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

9963-566: The nearly spent stage keeps the propellants settled at the bottom of the tanks. Hot-staging is used on Soviet-era Russian rockets such as Soyuz and Proton-M . The N1 rocket was designed to use hot staging, however none of the test flights lasted long enough for this to occur. Starting with the Titan II, the Titan family of rockets used hot staging. SpaceX retrofitted their Starship rocket to use hot staging after its first flight , making it

10086-654: The need for complex turbopumps . Other upper stages, such as the Centaur or DCSS , use liquid hydrogen expander cycle engines, or gas generator cycle engines like the Ariane 5 ECA's HM7B or the S-IVB 's J-2 . These stages are usually tasked with completing orbital injection and accelerating payloads into higher energy orbits such as GTO or to escape velocity . Upper stages, such as Fregat , used primarily to bring payloads from low Earth orbit to GTO or beyond are sometimes referred to as space tugs . Each individual stage

10209-419: The number of stages that split up the rocket system. Increasing the number of stages for a rocket while keeping the specific impulse, payload ratios and structural ratios constant will always yield a higher burnout velocity than the same systems that use fewer stages. However, the law of diminishing returns is evident in that each increment in number of stages gives less of an improvement in burnout velocity than

10332-454: The oldest known multistage rocket; this was the " fire-dragon issuing from the water " (火龙出水, huǒ lóng chū shuǐ), which was used mostly by the Chinese navy. It was a two-stage rocket that had booster rockets that would eventually burn out, yet, before they did so, automatically ignited a number of smaller rocket arrows that were shot out of the front end of the missile, which was shaped like

10455-416: The only Centaur-B flight on 26 November 1963 was successful. This version was powered by two RL10A-3 engines. Centaur-C flew three times between 1964 and 1965, with two failures and one launch declared successful although the Centaur failed to restart. This version was also powered by two RL10A-3 engines. Centaur-D was the first version to enter operational service in 1965 , with fifty-six launches. It

10578-525: The outer two stages, until they are empty and could be ejected. This is more efficient than sequential staging, because the second-stage engine is never just dead weight. In 1951, Soviet engineer and scientist Dmitry Okhotsimsky carried out a pioneering engineering study of general sequential and parallel staging, with and without the pumping of fuel between stages. The design of the R-7 Semyorka emerged from that study. The trio of rocket engines used in

10701-632: The overall payload ratio of the entire system. It is important to note that when computing payload ratio for individual stages, the payload includes the mass of all the stages after the current one. The overall payload ratio is: Where n is the number of stages the rocket system comprises. Similar stages yielding the same payload ratio simplify this equation, however that is seldom the ideal solution for maximizing payload ratio, and ΔV requirements may have to be partitioned unevenly as suggested in guideline tips 1 and 2 from above. Two common methods of determining this perfect ΔV partition between stages are either

10824-455: The oxygen tank. The next Titan-Centaurs launched Helios 1 , Viking 1 , Viking 2 , Helios 2 , 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. The Centaur D-1T had the following general specifications: Shuttle-Centaur

10947-532: 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 (4.8 km/h) on rail bogies, standing 183 ft (56 m) tall. In February 2021, ULA shipped the first completed Vulcan core booster to Florida for pathfinder tests ahead of

11070-723: 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. 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

11193-573: The payload ratio (see ratios under performance), meaning the largest amount of payload is carried up to the required burnout velocity using the least amount of non-payload mass, which comprises everything else. This goal assumes that the cost of a rocket launch is proportional to the total liftoff mass of the rocket, which is a rule of thumb in rocket engineering. Here are a few quick rules and guidelines to follow in order to reach optimal staging: The payload ratio can be calculated for each individual stage, and when multiplied together in sequence, will yield

11316-412: The pioneering nature of the effort and the use of liquid hydrogen. In 1994 General Dynamics sold their Space Systems division to Lockheed-Martin . 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

11439-402: The previous increment. The burnout velocity gradually converges towards an asymptotic value as the number of stages increases towards a very high number. In addition to diminishing returns in burnout velocity improvement, the main reason why real world rockets seldom use more than three stages is because of increase of weight and complexity in the system for each added stage, ultimately yielding

11562-427: The rocket system. Restricted rocket staging is based on the simplified assumption that each of the stages of the rocket system have the same specific impulse, structural ratio, and payload ratio, the only difference being the total mass of each increasing stage is less than that of the previous stage. Although this assumption may not be the ideal approach to yielding an efficient or optimal system, it greatly simplifies

11685-516: 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 a perfect orbital insertion. In a press release after the launch, the Space Force called the test flight a "certification milestone" and a significant achievement for both ULA and the nation's strategic space lift capability. The Space Force added that it

11808-518: The same time. For example, the Space Shuttle has two Solid Rocket Boosters that burn simultaneously. Upon launch, the boosters ignite, and at the end of the stage, the two boosters are discarded while the external fuel tank is kept for another stage. Most quantitative approaches to the design of the rocket system's performance are focused on tandem staging, but the approach can be easily modified to include parallel staging. To begin with,

11931-416: The savings are so great that every rocket ever used to deliver a payload into orbit has had staging of some sort. One of the most common measures of rocket efficiency is its specific impulse, which is defined as the thrust per flow rate (per second) of propellant consumption: When rearranging the equation such that thrust is calculated as a result of the other factors, we have: These equations show that

12054-451: The second of two flights needed to certify the rocket for future NSSL missions at 11:25 UTC on 4 October 2024. Approximately 37 seconds into the launch, the nozzle on one of the solid rocket boosters (SRB) fell off resulting in a shower of debris in the exhaust plume. Although the SRB continued to function for its full 90-second burn, the anomaly led to reduced, asymmetrical thrust. This caused

12177-518: The shelf hardware that should be considered in the mid to late stages of the design, but for preliminary and conceptual design, a simpler approach can be taken. Assuming one engine for a rocket stage provides all of the total impulse for that particular segment, a mass fraction can be used to determine the mass of the system. The mass of the stage transfer hardware such as initiators and safe-and-arm devices are very small by comparison and can be considered negligible. For modern day solid rocket motors, it

12300-414: The spent lower stages. A further advantage is that each stage can use a different type of rocket engine, each tuned for its particular operating conditions. Thus the lower-stage engines are designed for use at atmospheric pressure, while the upper stages can use engines suited to near vacuum conditions. Lower stages tend to require more structure than upper as they need to bear their own weight plus that of

12423-693: The stage in two 2-thruster pods and four 4-thruster pods. For propellant, 150 kg (340 lb) of Hydrazine is stored in a pair of bladder tanks and fed to the RCS thrusters with pressurized helium gas, which is also used to accomplish some main engine functions. As of 2024, two Centaur variants are in use: Centaur III on Atlas V, and Centaur V on Vulcan Centaur. All of the many other Centaur variants have been retired. 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. Common Centaur

12546-486: The stages above them. Optimizing the structure of each stage decreases the weight of the total vehicle and provides further advantage. The advantage of staging comes at the cost of the lower stages lifting engines which are not yet being used, as well as making the entire rocket more complex and harder to build than a single stage. In addition, each staging event is a possible point of launch failure, due to separation failure, ignition failure, or stage collision. Nevertheless,

12669-576: 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. The upper stage of

12792-760: The three-core Delta IV Heavy could lift 28,790 kg (63,470 lb) 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 . 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

12915-445: The thrust of the remaining stages to more easily accelerate the rocket to its final velocity and height. In serial or tandem staging schemes, the first stage is at the bottom and is usually the largest, the second stage and subsequent upper stages are above it, usually decreasing in size. In parallel staging schemes solid or liquid rocket boosters are used to assist with launch. These are sometimes referred to as "stage 0". In

13038-494: 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. 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,

13161-406: The type of fuel and oxidizer combination being used. For example, a mixture ratio of a bipropellant could be adjusted such that it may not have the optimal specific impulse, but will result in fuel tanks of equal size. This would yield simpler and cheaper manufacturing, packing, configuring, and integrating of the fuel systems with the rest of the rocket, and can become a benefit that could outweigh

13284-459: The typical case, the first-stage and booster engines fire to propel the entire rocket upwards. When the boosters run out of fuel, they are detached from the rest of the rocket (usually with some kind of small explosive charge or explosive bolts ) and fall away. The first stage then burns to completion and falls off. This leaves a smaller rocket, with the second stage on the bottom, which then fires. Known in rocketry circles as staging , this process

13407-488: The upper stage of ULA's new Vulcan rocket. Centaur was the first rocket stage to use liquid hydrogen (LH 2 ) and liquid oxygen (LOX) propellants , a high-energy combination that is ideal for upper stages but has significant handling difficulties. Common Centaur is built around stainless steel pressure stabilized balloon propellant tanks with 0.51 mm (0.020 in) thick walls. It can lift payloads of up to 19,000 kg (42,000 lb). The thin walls minimize

13530-493: 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

13653-646: 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,

13776-529: 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. The latest Common Centaurs can accommodate secondary payloads using an Aft Bulkhead Carrier attached to

13899-515: Was a low mass payload, with approximately 28% (5,400 kg (11,900 lb)) of LH 2 /LOX propellant remaining after separation. Several on-orbit demonstrations were conducted over 2.4 hours, concluding with a deorbit burn . 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, and will increase

14022-613: 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

14145-433: 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 2,400- kilonewton (550,000  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

14268-522: 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 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 (18 ft) diameter to support the use of the less dense methane fuel. In late 2017,

14391-614: 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

14514-494: 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. 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, with the first launch of the resulting Titan IIIE in 1974. The Titan IIIE more than tripled

14637-525: Was initially intended to enter service with an upgraded variant of the Common Centaur, with an upgrade to the Advanced Cryogenic Evolved Stage (ACES) planned after the first few years of flights. In late 2017, ULA decided to bring elements of the ACES upper stage forward and begin work on Centaur V. Centaur V will have ACES' 5.4 m (18 ft) diameter and advanced insulation, but does not include

14760-419: Was powered by two RL10A-3-1 or RL10A-3-3 engines. 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 LH 2 in space. By

14883-515: Was proposed by medieval Korean engineer, scientist and inventor Ch'oe Mu-sŏn and developed by the Firearms Bureau (火㷁道監) during the 14th century. The rocket had the length of 15 cm and 13 cm; the diameter was 2.2 cm. It was attached to an arrow 110 cm long; experimental records show that the first results were around 200m in range. There are records that show Korea kept developing this technology until it came to produce

15006-451: Was reviewing the launch data to determine Vulcan's suitability for future national security missions. Space Force Colonel James Horne later praised the launch and "the robustness of the total Vulcan system", with the USSF "knee deep in finalizing certification". ULA has four-character designations for the various Vulcan Centaur configurations. They start with VC for the Vulcan first stage and

15129-588: Was the last version of the stage to feature separating insulation panels. Centaur II was initially developed for use on the Atlas II series of rockets. Centaur II also flew on the initial Atlas IIIA launches. Atlas IIIB introduced the Common Centaur, a longer and initially dual engine Centaur II. Source: Atlas V551 specifications, as of 2015. 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

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