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54-545: Initial versions of the Blok DM-03 are powered by a single RD-58M engine, burning RG-1 and liquid oxygen . The last evolution is powered by the improved RD-58MF , a less powerful but more efficient evolution of the venerable engine. It can carry 25% more propellant than the Blok DM-2, which it replaced as a Proton upper stage for some government launches. However most government launches and all commercial missions use

108-433: 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

162-565: A rocket engine , developed in the 1960s by OKB-1 , now RKK Energia . The project was managed by Mikhail Melnikov , and it was based on the previous S1.5400 which was the first staged combustion engine in the world. The engine was initially created to power the Block D stage of the Soviet Union 's abortive N1 rocket . Derivatives of this stage are now used as upper stages on some Proton and Zenit rockets. An alternative version of

216-409: 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"

270-623: A November 2014 interview, Vladimir Kolmykov, the Deputy General Director of the Chemical Division of Krasnoyarsk Machine-Building Plant, stated that the production of Block-DM was suspended during that year, but work on the stage and development of the RD-58MF will resume during 2015. This engine has had many versions through the years: Rocket engine A rocket engine uses stored rocket propellants as

324-470: 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

378-439: 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

432-424: 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

486-432: 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,

540-400: 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

594-412: 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

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648-408: 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

702-404: 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

756-554: 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,

810-423: 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

864-508: 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

918-406: 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

972-409: 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

1026-443: 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

1080-427: 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

1134-443: 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

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1188-618: Is under development and is known as the RD-58MF (manufacturer designation 11D58MF). It will reduce thrust to 49.03 kilonewtons (11,020 lbf) to keep the same length but increase expansion ratio to 500:1. This will enable it to gain 20s of isp (to an expected 372s). It will eventually fly on the Blok DM-03 . This new version of the engine will be built in the Krasnoyarsk Machine-Building Plant . During

1242-423: 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

1296-402: 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

1350-559: The Briz-M instead. The payloads for the first two Blok DM-03 launches were groups of three Uragan-M satellites for the GLONASS programme, with further missions slated to carry three more Uragan-M satellites, and two Ekspress satellites on separate launches. The Blok DM can inject payloads into orbit more accurately than the Briz-M, making it better suited for launching satellites such as

1404-678: The RD-58M , called 17D12 , as its main orbital correction engines. Instead of RG-1 , it burned Syntin , and could be ignited 15 times. It is assumed that it was the base for the RD-58S , which had practically the same specifications and powered the Blok DM-2M . But the manufacturer states that the engine is compatible with both propellants. The current version of the engine is the RD-58M (manufacturer designation 11D58M), which has slightly reduced thrust, but increased isp. An even newer version

1458-404: 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

1512-654: 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

1566-467: The 14S49 will apply the new-generation 11D58MF engine. As of September 2015, 3 Proton-M/Blok DM-03 have been launched, of which 2 have failed. In the 2010 failure, the rocket was too heavy to reach orbit and reentered the atmosphere during a coast phase between the end of third stage flight and the beginning of the Blok DM-03's first burn, whilst the 2013 flight failed after the rocket went out of control seconds after liftoff. The first launch to use

1620-643: The Blok DM-03 was conducted on 5 December 2010, from Site 81/24 at the Baikonur Cosmodrome . The rocket was expected to deploy three Uragan-M satellites for the GLONASS constellation, with the first three stages of the Proton placing the Blok DM and payload into low Earth orbit , and the Blok DM then propelling the satellites into their operational medium Earth orbits . During preparations for launch,

1674-507: The Blok DM-03 was fuelled using instructions intended for the Blok DM-2, which included an instruction to fill the tanks to 90% capacity. Owing to the DM-03's larger tanks, this was more propellant than needed for the mission, and left the rocket too heavy to achieve orbit. The Blok DM, with payload still attached, reentered over the Pacific before the start of its scheduled first burn. Following

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1728-499: The Deputy General Director of the Chemical Division of Krasnoyarsk Machine-Building Plant, stated that the production of Block-DM was suspended during that year, but work on the stage and development of the RD-58MF resumed during 2015. The development for the 11S861-03 stage is covered under the Dvina-DM ( Russian : Двина-ДМ ) program. The specifications of this program ( Technical requirements on development work «Modernization of

1782-603: 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

1836-586: The RD-58 chamber, featuring a shorter nozzle, was used as the N1's roll-control engine. The RD-58 uses LOX as the oxidizer and RG-1 as fuel in an oxidizer rich staged combustion cycle. It features a single gimbaled chamber, radial centrifugal pumps with auxiliary booster pumps, and an oxygen-rich preburner . Recent modifications include a lightweight carbon-composite nozzle extender developed by NPO Iskra. The Buran spacecraft used two of an evolution of

1890-470: The Uragan-M which lack apogee motors. When production ended in 2012, five Blok DM-03 stages had been produced by RKK Energia , for use on Proton and potentially Zenit rockets. A new version of the upper stage is expected to be introduced once the five launches are complete; all five DM-03s have been slated for Proton launches between 2010 and 2015. During a November 2014 interview, Vladimir Kolmykov,

1944-465: 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

1998-407: 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

2052-424: 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,

2106-462: 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

2160-452: 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

2214-473: The failure, the Blok DM-03 was grounded for further tests, with a Proton-M/Briz-M and several smaller Soyuz-2 rockets being used for GLONASS launches over the next 30 months. The July 2013 flight, which marked the Blok DM-03's return to flight was another GLONASS launch, also conducted from Site 81/24, with liftoff occurring on time at 02:38:22 UTC. The rocket went off course almost immediately, before disintegrating. The payload fairing and upper stage were among

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2268-399: The first parts of the rocket to detach. Debris fell around 1,000 metres (3,300 ft) from the launch pad, with the parts of the rocket still intact exploding upon impact. An investigation determined that three first stage yaw sensors had been installed backwards, resulting in the failure of the vehicle's guidance system. RD-58M The RD-58 (manufacturer designation 11D58 ) is

2322-411: 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

2376-536: 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

2430-417: 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

2484-495: 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

2538-403: 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

2592-431: 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

2646-407: 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

2700-409: 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

2754-425: 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

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2808-520: 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

2862-412: 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

2916-429: The upper stage «DM» for the carrier rocket heavy class» ) defines three different evolutions of the 11S861-03 stage: In 2014 RSC Energia designated two versions: 14S48 Persei (Perseus) and 14S49 , which incorporated most features of the proposed 11S861-03 Phase II , including the use of nontoxic propellants in auxiliary propulsion systems and new compact flight control system. The 14S48 will use an 11D58M engine, while

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