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86-503: The NK-33 and NK-43 are rocket engines designed and built in the late 1960s and early 1970s by the Kuznetsov Design Bureau . The NK designation is derived from the initials of chief designer Nikolay Kuznetsov . The NK-33 was among the most powerful LOX / RP-1 rocket engines when it was built, with a high specific impulse and low structural mass. They were intended for the ill-fated Soviet N1F Moon rocket, which

172-433: A propelling nozzle . The fluid is usually a gas created by high pressure (150-to-4,350-pound-per-square-inch (10 to 300 bar)) combustion of solid or liquid propellants , consisting of fuel and oxidiser components, within a combustion chamber . As the gases expand through the nozzle, they are accelerated to very high ( supersonic ) speed, and the reaction to this pushes the engine in the opposite direction. Combustion

258-409: A vacuum to propel spacecraft and ballistic missiles . Compared to other types of jet engine, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest specific impulse ). The ideal exhaust is hydrogen , the lightest of all elements, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity. Here, "rocket"

344-542: A consultant to the American Institute of Aeronautics and Astronautics and Universities Space Research Association and a former professor of aerospace engineering at Princeton University , suggested using the RD-180 for a prospective NASA heavy-lift launch vehicle. For those who might be concerned about too much reliance on Russia, he pointed out that RD Amross was "very close to producing a U.S.-built version of

430-549: A default letter, warning that it would terminate the COTS agreement with Rocketplane Kistler in 30 days because RpK had not met several contract milestones. The initial version of the Orbital Sciences Antares light-to-medium-lift launcher had two modified NK-33 in the first stage, a solid Castor 30 -based second stage and an optional solid or hypergolic third stage. The NK-33s were imported from Russia to

516-637: A fully operational engine by 2020 or sooner, depending on partnership with the U.S. Defense Department. As a result of the geopolitical and US political considerations, United Launch Alliance considered a possible replacement for the Russian RD-180 engine used on the first-stage booster of the ULA Atlas V. Formal study contracts were issued in June 2014 to a number of US rocket-engine suppliers. In September 2014, ULA announced that it had entered into

602-519: A higher thrust and specific impulse, but makes it longer and heavier. It has a thrust-to-weight ratio of about 120:1. The predecessors of NK-33 and NK-43 are the earlier NK-15 and NK-15V engines respectively. The oxygen-rich technology lives on in the RD-170/-171 engines, their RD-180 , and recently developed RD-191 derivatives, but these engines have no direct connection to the NK-33 except for

688-470: A higher velocity compared to air. Expansion in the rocket nozzle then further multiplies the speed, typically between 1.5 and 2 times, giving a highly collimated hypersonic exhaust jet. The speed increase of a rocket nozzle is mostly determined by its area expansion ratio—the ratio of the area of the exit to the area of the throat, but detailed properties of the gas are also important. Larger ratio nozzles are more massive but are able to extract more heat from

774-439: A hot gas jet for propulsion. Alternatively, a chemically inert reaction mass can be heated by a high-energy power source through a heat exchanger in lieu of a combustion chamber. Solid rocket propellants are prepared in a mixture of fuel and oxidising components called grain , and the propellant storage casing effectively becomes the combustion chamber. Liquid-fuelled rockets force separate fuel and oxidiser components into

860-493: A maximum limit determined only by the mechanical strength of the engine. In practice, the degree to which rockets can be throttled varies greatly, but most rockets can be throttled by a factor of 2 without great difficulty; the typical limitation is combustion stability, as for example, injectors need a minimum pressure to avoid triggering damaging oscillations (chugging or combustion instabilities); but injectors can be optimised and tested for wider ranges. RD-180 Atlas V

946-444: A new engine by 2022. In June 2014, Aerojet Rocketdyne proposed that the federal government "fund an all-new, U.S.-sourced rocket propulsion system", the 2,200-kilonewton-class (500,000 lbf) thrust kerosene/ LOX AR-1 rocket engine . As of June 2014 , Aerojet's projection was that the cost of each engine would be under US$ 25 million per pair of engines—not including the up to US$ 1 billion development cost to be funded by

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1032-424: A number called L ∗ {\displaystyle L^{*}} , the characteristic length : where: L* is typically in the range of 64–152 centimetres (25–60 in). The temperatures and pressures typically reached in a rocket combustion chamber in order to achieve practical thermal efficiency are extreme compared to a non-afterburning airbreathing jet engine . No atmospheric nitrogen

1118-524: A partnership with Blue Origin to develop the BE-4 LOX / methane engine to replace the RD-180 on a new first-stage booster that would succeed the Atlas V . At the time, the engine was already in its third year of development by Blue Origin, and ULA expected the new stage and engine to start flying no earlier than 2019. Two of the 2,400- kilonewton (550,000  lbf )-thrust BE-4 engines would be used on

1204-432: A variety of design approaches including turbopumps or, in simpler engines, via sufficient tank pressure to advance fluid flow. Tank pressure may be maintained by several means, including a high-pressure helium pressurization system common to many large rocket engines or, in some newer rocket systems, by a bleed-off of high-pressure gas from the engine cycle to autogenously pressurize the propellant tanks For example,

1290-576: Is being phased out due to the national security implications of reliance on the Russian-built engine, which became a concern after the Russian annexation of Crimea . In 2021, Atlas manufacturer United Launch Alliance announced that it was retiring the Atlas V and that it had already taken delivery of the RD-180 engines for the remaining rockets. As of June 2024 , 16 launches remain. In 2022, Russian supplies and maintenance were discontinued as

1376-476: Is considering an acquisition strategy to stimulate the commercial development of booster propulsion systems and/or launch systems for Evolved Expendable Launch Vehicle (EELV)-class spacelift applications." The day before, the United Launch Alliance had taken delivery of two RD-180s, the first since the Russian annexation of Crimea . It was not clear when or if the RD-180 would be replaced, and

1462-400: Is designed for, but exhaust speeds as high as ten times the speed of sound in air at sea level are not uncommon. About half of the rocket engine's thrust comes from the unbalanced pressures inside the combustion chamber, and the rest comes from the pressures acting against the inside of the nozzle (see diagram). As the gas expands ( adiabatically ) the pressure against the nozzle's walls forces

1548-412: Is difficult to arrange in a lightweight fashion, although is routinely done with other forms of jet engines. In rocketry a lightweight compromise nozzle is generally used and some reduction in atmospheric performance occurs when used at other than the 'design altitude' or when throttled. To improve on this, various exotic nozzle designs such as the plug nozzle , stepped nozzles , the expanding nozzle and

1634-408: Is either measured as a speed (the effective exhaust velocity v e {\displaystyle v_{e}} in metres/second or ft/s) or as a time (seconds). For example, if an engine producing 100 pounds of thrust runs for 320 seconds and burns 100 pounds of propellant, then the specific impulse is 320 seconds. The higher the specific impulse, the less propellant is required to provide

1720-404: Is force divided by the rate of mass flow, this equation means that the specific impulse varies with altitude. Due to the specific impulse varying with pressure, a quantity that is easy to compare and calculate with is useful. Because rockets choke at the throat, and because the supersonic exhaust prevents external pressure influences travelling upstream, it turns out that the pressure at the exit

1806-554: Is ideally exactly proportional to the propellant flow m ˙ {\displaystyle {\dot {m}}} , provided the mixture ratios and combustion efficiencies are maintained. It is thus quite usual to rearrange the above equation slightly: and so define the vacuum Isp to be: where: And hence: Rockets can be throttled by controlling the propellant combustion rate m ˙ {\displaystyle {\dot {m}}} (usually measured in kg/s or lb/s). In liquid and hybrid rockets,

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1892-423: Is important that the maximum pressures possible be created on the walls of the chamber and nozzle by a specific amount of propellant; as this is the source of the thrust. This can be achieved by all of: Since all of these things minimise the mass of the propellant used, and since pressure is proportional to the mass of propellant present to be accelerated as it pushes on the engine, and since from Newton's third law

1978-508: Is most frequently used for practical rockets, as the laws of thermodynamics (specifically Carnot's theorem ) dictate that high temperatures and pressures are desirable for the best thermal efficiency . Nuclear thermal rockets are capable of higher efficiencies, but currently have environmental problems which preclude their routine use in the Earth's atmosphere and cislunar space . For model rocketry , an available alternative to combustion

2064-406: Is no 'ram drag' to deduct from the gross thrust. Consequently, the net thrust of a rocket motor is equal to the gross thrust (apart from static back pressure). The m ˙ v e − o p t {\displaystyle {\dot {m}}\;v_{e-opt}\,} term represents the momentum thrust, which remains constant at a given throttle setting, whereas

2150-409: Is permitted to escape through an opening (the "throat"), and then through a diverging expansion section. When sufficient pressure is provided to the nozzle (about 2.5–3 times ambient pressure), the nozzle chokes and a supersonic jet is formed, dramatically accelerating the gas, converting most of the thermal energy into kinetic energy. Exhaust speeds vary, depending on the expansion ratio the nozzle

2236-443: Is present to dilute and cool the combustion, so the propellant mixture can reach true stoichiometric ratios. This, in combination with the high pressures, means that the rate of heat conduction through the walls is very high. In order for fuel and oxidiser to flow into the chamber, the pressure of the propellants entering the combustion chamber must exceed the pressure inside the combustion chamber itself. This may be accomplished by

2322-427: Is termed exhaust velocity , and after allowance is made for factors that can reduce it, the effective exhaust velocity is one of the most important parameters of a rocket engine (although weight, cost, ease of manufacture etc. are usually also very important). For aerodynamic reasons the flow goes sonic (" chokes ") at the narrowest part of the nozzle, the 'throat'. Since the speed of sound in gases increases with

2408-443: Is the water rocket pressurized by compressed air, carbon dioxide , nitrogen , or any other readily available, inert gas. Rocket propellant is mass that is stored, usually in some form of tank, or within the combustion chamber itself, prior to being ejected from a rocket engine in the form of a fluid jet to produce thrust. Chemical rocket propellants are the most commonly used. These undergo exothermic chemical reactions producing

2494-423: Is used as an abbreviation for "rocket engine". Thermal rockets use an inert propellant, heated by electricity ( electrothermal propulsion ) or a nuclear reactor ( nuclear thermal rocket ). Chemical rockets are powered by exothermic reduction-oxidation chemical reactions of the propellant: Rocket engines produce thrust by the expulsion of an exhaust fluid that has been accelerated to high speed through

2580-402: The A e ( p e − p a m b ) {\displaystyle A_{e}(p_{e}-p_{amb})\,} term represents the pressure thrust term. At full throttle, the net thrust of a rocket motor improves slightly with increasing altitude, because as atmospheric pressure decreases with altitude, the pressure thrust term increases. At the surface of

2666-627: The Atlas V rocket. This company also acquired a license for the production of new engines. About 60 engines survived in the "Forest of Engines", as described by engineers on a trip to the warehouse. In the mid-1990s, Russia sold 36 engines to Aerojet General for $ 1.1 million each, shipping them to the company facility in Sacramento CA. During the engine test in Sacramento, the engine hit its specifications. Aerojet has modified and renamed

NK-33 - Misplaced Pages Continue

2752-926: The RD-181 for the first stage engines, which is a modified RD-191, but shares some properties like a single combustion chamber unlike the two combustion chambers used in the RD-180 of the Atlas V and the four combustion chambers used in the RD-170 of the Energia and Zenit rocket families, and the RD-107 , RD-108 , RD-117 , and RD-118 rocket engines used on all of the variants of the Soyuz rocket. The NK-33 series engines are high-pressure, regeneratively cooled oxygen-rich staged combustion cycle bipropellant rocket engines. The turbopumps require subcooled liquid oxygen (LOX) to cool

2838-404: The aerospike have been proposed, each providing some way to adapt to changing ambient air pressure and each allowing the gas to expand further against the nozzle, giving extra thrust at higher altitudes. When exhausting into a sufficiently low ambient pressure (vacuum) several issues arise. One is the sheer weight of the nozzle—beyond a certain point, for a particular vehicle, the extra weight of

2924-562: The first stage of the Antares 100-series. RSC Energia is proposing an "Aurora-L.SK" launch vehicle, which would use an NK-33 to power the first stage and a Blok DM-SL for the second stage. In the early 2010s the Soyuz launch vehicle family was retrofitted with the NK-33 engine – using the lower weight and greater efficiency to increase payload; the simpler design and use of surplus hardware might actually reduce cost. TsSKB-Progress uses

3010-654: The reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines , producing thrust by ejecting mass rearward, in accordance with Newton's third law . Most rocket engines use the combustion of reactive chemicals to supply the necessary energy, but non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. Vehicles propelled by rocket engines are commonly used by ballistic missiles (they normally use solid fuel ) and rockets . Rocket vehicles carry their own oxidiser , unlike most combustion engines, so rocket engines can be used in

3096-639: The Atlas III. The engine has design features similar to the NK-33 , which was developed by a different bureau ( Kuznetzov ) nearly a decade earlier. Doubts about the reliability of the supply chain for the RD-180 arose following the Russian military intervention in Ukraine in March 2014. For over 13 years since the engine was first used in the Atlas III launch vehicle in 2000, there was no serious jeopardy to

3182-516: The Atlas V launch vehicle, in addition to 29 engines that the company had ordered before US sanctions were imposed on Russia over Crimea, and just days after the US Congress lifted the ban on Russian engines for American rockets. There were several plans to manufacture the RD-180 in the US, but none of them came to fruition. Under RD AMROSS , Pratt & Whitney is licensed to produce the RD-180 in

3268-603: The Earth the pressure thrust may be reduced by up to 30%, depending on the engine design. This reduction drops roughly exponentially to zero with increasing altitude. Maximum efficiency for a rocket engine is achieved by maximising the momentum contribution of the equation without incurring penalties from over expanding the exhaust. This occurs when p e = p a m b {\displaystyle p_{e}=p_{amb}} . Since ambient pressure changes with altitude, most rocket engines spend very little time operating at peak efficiency. Since specific impulse

3354-451: The N-1 program was shut down, all work on the project was ordered destroyed. A bureaucrat instead took the engines, worth millions of dollars each, and stored them in a warehouse. Word of the engines eventually spread to the US. Nearly 30 years after they were built, rocket engineers were led to the warehouse. One of the engines was later taken to the US, and the precise specification of the engine

3440-559: The NK-33 as the first-stage engine of the lightweight version of the Soyuz rocket family , the Soyuz-2-1v . The NK-33A intended for the Soyuz-2-1v was successfully hot-fired on 15 January 2013, following a series of cold-fire and systems tests of the fully assembled Soyuz-1 in 2011–2012. The NK-33 powered rocket was finally designated Soyuz-2-1v , with its maiden flight having taken place on 28 December 2013. One NK-33 engine replaces

3526-659: The RD-170's combustion devices with half-size turbomachinery. After successful performance on a test stand and high-level agreements between the US government and the Russian government , the engines were imported to the US for use on the Lockheed Martin Atlas III , which flew from 2000 to 2005. The engine has been used since 2002 on the United Launch Alliance Atlas V , the successor to

NK-33 - Misplaced Pages Continue

3612-605: The RD-180 on the Atlas V. Even though the Russian government could cut off the supply to ULA of imported RD-180 engines, the US Congress , with emerging support from the Air Force , came to the view that it would not be advantageous to build a US production line for the RD-180, mainly because it would need a license from the Russian government. However, the US Congress in 2014 advocated a new US rocket engine program to field

3698-465: The RD-180, and with some infusion of NASA funding could be manufacturing that engine (and perhaps even a 1,700,000 lbf or 7.6 MN thrust equivalent of the RD-170) in a few years". On February 24, 2022, Russia began a large-scale military invasion of Ukraine . Six days later on March 2, 2022, as Russia continued the invasion, they announced an end of all sales and support of the RD-180 engines to

3784-703: The RFI asked for several options including similarity to the Russian engine, whether it would come in a new configuration and the use of "alternative launch vehicles" for the EELV mission. In 2014, RD-Amross were selling the RD-180s (to ULA) for $ 23.4m each. In January 2015, Orbital Sciences Corporation received all the necessary permissions from government bodies for the delivery of 60 engines from NPO Energomash. On 24 December 2015, United Launch Alliance announced that it had placed an order for more RD-180 engines to be used by

3870-480: The Soyuz's central RD-108 , with the four boosters of the first stage omitted. A version of the Soyuz rocket with four boosters powered by NK-33 engines (with one engine per booster) has not been built, which results in a reduced payload compared to the Soyuz-2 launch vehicle . During the years there have been many versions of this engine: Rocket engine A rocket engine uses stored rocket propellants as

3956-760: The US Government. Aerojet believed that the AR-1 could replace the RD-180 in the US Evolved Expendable Launch Vehicle fleet, and that it would be more affordable. On 21 August 2014, the U.S. Air Force released an official request for information (RFI) for a replacement for the RD-180. The RFI seeks information on "booster propulsion and/or launch system material options that could deliver cost-effective, commercially-viable solutions for current and future National Security Space (NSS) launch requirements. Air Force Space Command (AFSPC)

4042-715: The United States from using Russian-made rocket engines for military launches" —a frequent payload of the ULA Atlas V launch vehicle, which powers its first stage with a single RD-180 engine that is expended after each flight. In response, the US Air Force asked the Aerospace Corporation to evaluate alternatives for powering the Atlas 5 booster with non-RD-180 engines. Early estimates in 2014 were that it would require five or more years to replace

4128-459: The United States, modified, and re-designated as Aerojet AJ26s. This involved removing some electrical harnessing, adding U.S. electronics, qualifying it for U.S. propellants, and modifying the steering system. In 2010 stockpiled NK-33 engines were successfully tested for use by the Orbital Sciences Antares light-to-medium-lift launcher. The Antares rocket was successfully launched from NASA's Wallops Flight Facility on 21 April 2013. This marked

4214-691: The United States. According to a 2005 GAO Assessment of Selected Major Weapon Programs, Pratt & Whitney planned to start building the RD-180 in the United States in 2008 with a first military launch by 2012, but this did not occur. United Launch Alliance (ULA) announced in February 2015 that it was considering undertaking US production of the Russian RD-180 engine at the Decatur , Alabama, rocket stage manufacturing facility. The US-manufactured engines would be used only for government civil (NASA) and commercial launches, not for US military launches. This project

4300-465: The atmosphere, and while permitting the use of low pressure and hence lightweight tanks and structure. Rockets can be further optimised to even more extreme performance along one or more of these axes at the expense of the others. The most important metric for the efficiency of a rocket engine is impulse per unit of propellant , this is called specific impulse (usually written I s p {\displaystyle I_{sp}} ). This

4386-407: The axis of the engine, a side force may be imparted to the engine. This side force may change over time and result in control problems with the launch vehicle. Advanced altitude-compensating designs, such as the aerospike or plug nozzle , attempt to minimize performance losses by adjusting to varying expansion ratio caused by changing altitude. For a rocket engine to be propellant efficient, it

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4472-555: The bearings. The United States had not investigated oxygen-rich combustion technologies until the Integrated Powerhead Demonstrator project in the early 2000s. The Soviets, however, perfected this method. The problem is that hot high-pressure oxygen must flow throughout the engine. If the surfaces contacting this oxygen were bare metal, they would corrode too quickly. The problem was solved using an inert enamel coating on all metal surfaces in contact with

4558-424: The combustion chamber, where they mix and burn. Hybrid rocket engines use a combination of solid and liquid or gaseous propellants. Both liquid and hybrid rockets use injectors to introduce the propellant into the chamber. These are often an array of simple jets – holes through which the propellant escapes under pressure; but sometimes may be more complex spray nozzles. When two or more propellants are injected,

4644-462: The combustion gases, increasing the exhaust velocity. Vehicles typically require the overall thrust to change direction over the length of the burn. A number of different ways to achieve this have been flown: Rocket technology can combine very high thrust ( meganewtons ), very high exhaust speeds (around 10 times the speed of sound in air at sea level) and very high thrust/weight ratios (>100) simultaneously as well as being able to operate outside

4730-423: The cycle allow an oxygen-rich preburner to give a greater power-to-weight ratio , but with the drawback that high-pressure, high-temperature gaseous oxygen must be transported throughout the engine. If the surfaces contacting this oxygen were bare metal, they would corrode too quickly. The RD-180 solves this problem using an inert enamel coating on all metal surfaces in contact with the hot oxygen. The movements of

4816-452: The desired impulse. The specific impulse that can be achieved is primarily a function of the propellant mix (and ultimately would limit the specific impulse), but practical limits on chamber pressures and the nozzle expansion ratios reduce the performance that can be achieved. Below is an approximate equation for calculating the net thrust of a rocket engine: Since, unlike a jet engine, a conventional rocket motor lacks an air intake, there

4902-544: The engine nozzles are controlled by four hydraulic actuators . The engine can be throttled from 47% to 100% of nominal thrust. The roots of the RD-180 rocket engine extend to the Soviet Energia launch vehicle. The RD-170, a four-chamber engine, was developed for use in the strap-on boosters for this vehicle, which ultimately launched the Buran orbiter . This engine was scaled down to a two-chamber version by combining

4988-564: The engine supply, despite an uneven record of US–Russian relations since the Cold War . However, worsening relations between the West and Russia after March 2014 led to several self-imposed blockages, including a short-lived judicial injunction from the US courts that was unclear whether the scope of the US sanctions covered importing the Russian engine. On 13 May 2014, Russian Deputy Prime Minister Dmitry Rogozin announced that "Russia will ban

5074-678: The engine's liquid-oxygen turbopump and design flaws in the hydraulic balance assembly and thrust bearings were proposed as two possible causes of the 2014 Antares launch failure . As announced on 5 November 2014, Orbital decided to drop the AJ-26 first stage from the Antares and source an alternative engine. On 17 December 2014, Orbital Sciences announced that it would use the NPO Energomash RD-181 on second-generation Antares launch vehicles and had contracted directly with NPO Energomash for up to 60 RD-181 engines. Two engines are used on

5160-579: The first launch of the Atlas LV with RD-180), all 90 launches so far were recognized as successful. During the early 1990s, General Dynamics Space Systems Division (later purchased by Lockheed Martin ) acquired the rights to use the RD-180 in the Evolved Expendable Launch Vehicle (EELV) and the Atlas program . As these programs were conceived to support United States Government launches, as well as commercial launches, it

5246-652: The first successful launch of the NK-33 heritage engines built in early 1970s. Aerojet agreed to recondition sufficient NK-33s to serve Orbital's 16-flight NASA Commercial Resupply Services contract. Beyond that, it had a stockpile of 23 1960s- and 1970s-era engines. Kuznetsov no longer manufactures the engines, so Orbital sought to buy RD-180 engines. Because NPO Energomash 's contract with United Launch Alliance prevented this, Orbital sued ULA, alleging anti-trust violations. Aerojet offered to work with Kuznetsov to restart production of new NK-33 engines, to assure Orbital of an ongoing supply. However, manufacturing defects in

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5332-518: The hot oxygen. The NK-33 engine has among the highest thrust-to-weight ratio of any Earth-launchable rocket engine; only the NPO Energomash RD-253 , SpaceX Merlin 1D , and SpaceX Raptor engines achieve a higher ratio. The NK-43 is similar to the NK-33, but is designed for an upper stage, not a first stage. It has a longer nozzle, optimized for operation at altitude, where there is little to no ambient air pressure. This gives it

5418-411: The jet may be either below or above ambient, and equilibrium between the two is not reached at all altitudes (see diagram). For optimal performance, the pressure of the gas at the end of the nozzle should just equal the ambient pressure: if the exhaust's pressure is lower than the ambient pressure, then the vehicle will be slowed by the difference in pressure between the top of the engine and the exit; on

5504-536: The jets usually deliberately cause the propellants to collide as this breaks up the flow into smaller droplets that burn more easily. For chemical rockets the combustion chamber is typically cylindrical, and flame holders , used to hold a part of the combustion in a slower-flowing portion of the combustion chamber, are not needed. The dimensions of the cylinder are such that the propellant is able to combust thoroughly; different rocket propellants require different combustion chamber sizes for this to occur. This leads to

5590-740: The new launch vehicle booster. Dynetics and Aerojet Rocketdyne (AJR) also offered their AR1 hydrocarbon-fueled rocket engine as replacement of the RD-180. ULA CEO Tory Bruno said in early 2015 that both the AR-1 option and the US manufacture of the RD-180 by ULA under license were backup options to the primary option ULA was pursuing with the Blue Origin BE-4 engine. By March 2016, the US Air Force had signed development contracts with AJR and Blue Origin to fund development for both engines. The first Vulcan flight with new engines occurred in January 2024. As of May 25, 2020 (20 years since

5676-417: The nozzle outweighs any performance gained. Secondly, as the exhaust gases adiabatically expand within the nozzle they cool, and eventually some of the chemicals can freeze, producing 'snow' within the jet. This causes instabilities in the jet and must be avoided. On a de Laval nozzle , exhaust gas flow detachment will occur in a grossly over-expanded nozzle. As the detachment point will not be uniform around

5762-495: The nozzle. As exit pressure varies from the ambient (atmospheric) pressure, a choked nozzle is said to be In practice, perfect expansion is only achievable with a variable–exit-area nozzle (since ambient pressure decreases as altitude increases), and is not possible above a certain altitude as ambient pressure approaches zero. If the nozzle is not perfectly expanded, then loss of efficiency occurs. Grossly over-expanded nozzles lose less efficiency, but can cause mechanical problems with

5848-403: The nozzle. Fixed-area nozzles become progressively more under-expanded as they gain altitude. Almost all de Laval nozzles will be momentarily grossly over-expanded during startup in an atmosphere. Nozzle efficiency is affected by operation in the atmosphere because atmospheric pressure changes with altitude; but due to the supersonic speeds of the gas exiting from a rocket engine, the pressure of

5934-431: The other hand, if the exhaust's pressure is higher, then exhaust pressure that could have been converted into thrust is not converted, and energy is wasted. To maintain this ideal of equality between the exhaust's exit pressure and the ambient pressure, the diameter of the nozzle would need to increase with altitude, giving the pressure a longer nozzle to act on (and reducing the exit pressure and temperature). This increase

6020-598: The oxygen-rich staged combustion cycle technology, the kerosene/RP-1 fuel, and in case of the RD-191 and its variants like the RD-193 and the RD-181, the single combustion chamber instead of the multiple chambers in previous Russian rocket engines. The N-1 launcher originally used NK-15 engines for its first stage and a high-altitude modification (NK-15V) in its second stage. After four consecutive launch failures and no successes,

6106-407: The pressure that acts on the engine also reciprocally acts on the propellant, it turns out that for any given engine, the speed that the propellant leaves the chamber is unaffected by the chamber pressure (although the thrust is proportional). However, speed is significantly affected by all three of the above factors and the exhaust speed is an excellent measure of the engine propellant efficiency. This

6192-648: The previous main engine. This vehicle was later renamed the Atlas III . An additional development program was undertaken to certify the engine for use on the modular Common Core Booster primary stage of the Atlas V rocket . RD-180 was proposed to be used with a new family of Rus-M Russian space launch vehicles, proposed by Roskosmos contractors, but the program was canceled by the Russian Space Agency in October 2011. In March 2010, Jerry Grey,

6278-607: The project was cancelled. While other aspects of the vehicle were being modified or redesigned, Kuznetsov improved his contributions into the NK-33 and NK-43 respectively. The 2nd-generation vehicle was to be called the N-1F. By this point the Moon race was long lost, and the Soviet space program was looking to the Energia as its heavy launcher. No N-1F ever reached the launch pad. When

6364-409: The propellant flow entering the chamber is controlled using valves, in solid rockets it is controlled by changing the area of propellant that is burning and this can be designed into the propellant grain (and hence cannot be controlled in real-time). Rockets can usually be throttled down to an exit pressure of about one-third of ambient pressure (often limited by flow separation in nozzles) and up to

6450-424: The rest were sitting in a warehouse. “We took early delivery, if you will, with the RD-180, so I can end that relationship and not be dependent upon [Russia] because that’s what Congress asked us to do”, he said. The 122 RD-180 engines from Energomash generated billions in revenue for Russia's space program. Several options for replacing the RD-180 on Atlas V were investigated, but ULA ultimately decided to replace

6536-489: The result of trade sanctions imposed after the 2022 Russian invasion of Ukraine . The combustion chambers of the RD-180 share a single turbopump unit, much like in its predecessor, the four-chambered RD-170 . The RD-180 is fueled by an RP-1 / LOX mixture and uses an extremely efficient, high-pressure staged combustion cycle . The engine runs with an oxidizer-to-fuel ratio of 2.72 and employs an oxygen-rich preburner, unlike typical fuel-rich US designs. The thermodynamics of

6622-425: The rocket engine in one direction while accelerating the gas in the other. The most commonly used nozzle is the de Laval nozzle , a fixed geometry nozzle with a high expansion-ratio. The large bell- or cone-shaped nozzle extension beyond the throat gives the rocket engine its characteristic shape. The exit static pressure of the exhaust jet depends on the chamber pressure and the ratio of exit to throat area of

6708-408: The rocket with Vulcan Centaur instead. In February 2010, despite the availability of necessary documentation and legal rights for producing RD-180 in the United States, NASA was considering development of an indigenous core-stage engine that would be "capable of generating high levels of thrust approximately equal to or exceeding the performance of the Russian-built engine". NASA desired to produce

6794-520: The self-pressurization gas system of the SpaceX Starship is a critical part of SpaceX strategy to reduce launch vehicle fluids from five in their legacy Falcon 9 vehicle family to just two in Starship, eliminating not only the helium tank pressurant but all hypergolic propellants as well as nitrogen for cold-gas reaction-control thrusters . The hot gas produced in the combustion chamber

6880-412: The square root of temperature, the use of hot exhaust gas greatly improves performance. By comparison, at room temperature the speed of sound in air is about 340 m/s while the speed of sound in the hot gas of a rocket engine can be over 1700 m/s; much of this performance is due to the higher temperature, but additionally rocket propellants are chosen to be of low molecular mass, and this also gives

6966-620: The updated NK-33 to AJ26-58 , AJ-26-59 and AJ26-62 , and NK-43 to AJ26-60 . Kistler Aerospace, later called Rocketplane Kistler (RpK), designed their K-1 rocket around three NK-33s and an NK-43. On 18 August 2006, NASA announced that RpK had been chosen to develop Commercial Orbital Transportation Services for the International Space Station . The plan called for demonstration flights between 2008 and 2010. RpK would have received up to $ 207 million if they met all NASA milestones, but on 7 September 2007, NASA issued

7052-657: Was a backup plan to the new engine development work by ULA with Blue Origin on the BE-4 . In 2014, the Defense Department estimated that it would require approximately $ 1 billion and five years to begin US domestic manufacture of the RD-180 engine. Overall, by April 14, 2021 Energomash delivered 122 RD-180 rocket engines to the United States over more than 20 years. In an interview on August 26, 2021, ULA's CEO Tory Bruno said that three or four RD-180s were installed on Atlas V rockets for upcoming missions, and

7138-638: Was also arranged for the RD-180 to be co-produced by Pratt & Whitney . However, all production took place in Russia. The engine was sold by a joint venture between the Russian developer and producer of the engine NPO Energomash and Pratt & Whitney, called RD Amross . The RD-180 was first deployed on the Atlas IIA-R vehicle, which was the Atlas IIA vehicle with the Russian (hence the R) engine replacing

7224-514: Was an upgraded version of the N1. The NK-33A rocket engine is now used on the first stage of the Soyuz-2-1v launch vehicle. When the supply of the NK-33 engines are exhausted, Russia will supply the new RD-193 rocket engine. It used to be the first stage engines of the Antares 100 rocket series, although those engines are rebranded the AJ-26 and the newer Antares 200 and Antares 200+ rocket series uses

7310-483: Was demonstrated on a test stand. The NK-33 oxygen-rich closed-cycle technology works by sending the auxiliary engines' exhaust into the main combustion chamber. The fully heated liquid O 2 flows through the pre-burner and into the main chamber in this design. The extremely hot oxygen-rich mixture made the engine dangerous: it was known to melt 3-inch (76 mm) thick castings "like candle wax. Oxidizer-rich staged combustion had been considered by American engineers, but

7396-469: Was not considered a feasible direction because of resources they assumed the design would require to make work. One of the controversies in the Kremlin over supplying the engine to the US was that the design of the engine was similar to Russian ICBM engine design. The NK-33's design was used in the later RD-180 engine, which had twice the size of the NK-33. The RD-180 engines were used (as of 2016) to power

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