Specific impulse is a measure of how efficiently a reaction mass engine, such as a rocket using propellant or a jet engine using fuel, generates thrust.
A liquid-propellant rocket or liquid rocket utilizes a rocket engine burning liquid propellants. (Alternate approaches use gaseous or solid propellants.) Liquids are desirable propellants because they have reasonably high density and their combustion products have high specific impulse (Isp). This allows the volume of the propellant tanks to be relatively low.
The J-2, commonly known as Rocketdyne J-2, was a liquid-fuel cryogenic rocket engine used on NASA's Saturn IB and Saturn V launch vehicles. Built in the United States by Rocketdyne, the J-2 burned cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) propellants, with each engine producing 1,033.1 kN (232,250 lbf) of thrust in vacuum. The engine's preliminary design dates back to recommendations of the 1959 Silverstein Committee. Rocketdyne won approval to develop the J-2 in June 1960 and the first flight, AS-201, occurred on 26 February 1966. The J-2 underwent several minor upgrades over its operational history to improve the engine's performance, with two major upgrade programs, the de Laval nozzle-type J-2S and aerospike-type J-2T, which were cancelled after the conclusion of the Apollo program.
The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to 110 kN (24,729 lbf) of thrust per engine in vacuum. Three RL10 versions are in production for the Centaur upper stage of the Atlas V and the DCSS of the Delta IV. Three more versions are in development for the Exploration Upper Stage of the Space Launch System and the Centaur V of the Vulcan rocket.
Merlin is a family of rocket engines developed by SpaceX for use on its Falcon 1, Falcon 9 and Falcon Heavy launch vehicles. Merlin engines use RP-1 and liquid oxygen as rocket propellants in a gas-generator power cycle. The Merlin engine was originally designed for sea recovery and reuse, but since 2016 the entire Falcon 9 booster is recovered for reuse by landing vertically on a landing pad using one of its nine Merlin engines.
The Reaction Motors LR99 engine was the first large, throttleable, restartable liquid-propellant rocket engine. Development began in the 1950s by the Reaction Motors Division of Thiokol Chemical Company to power the North American X-15 hypersonic research aircraft. It could deliver up to 57,000 lbf (250 kN) of thrust with a specific impulse of 279 s (2.74 km/s) or 239 s (2.34 km/s) at sea level. Thrust was variable from 50 to 100 percent, and the restart capability allowed it to be shut down and restarted during flight when necessary.
The RD-58 is 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 N-1 rocket. Derivatives of this stage are now used as upper stages on some Proton and Zenit rockets. An alternative version of the RD-58 chamber, featuring a shorter nozzle, was used as the N-1's roll-control engine.
Thor was a US space launch vehicle derived from the PGM-17 Thor intermediate-range ballistic missile. The Thor rocket was the first member of the Delta rocket family of space launch vehicles. The last launch of a direct derivative of the Thor missile occurred in 2018 as the first stage of the final Delta II.
The YF-73 was China's first successful cryogenic liquid hydrogen fuel and liquid oxygen oxidizer gimballed engine. It was used on the Long March 3 H8 third stage, running on the simple gas generator cycle and with a thrust of 44.15 kilonewtons (9,930 lbf). It had four hinge mounted nozzles that gimbaled each on one axis to supply thrust vector control and was restart capable. It used cavitating flow venturis to regulate propellant flows. The gas generator also incorporated dual heat exchangers that heated hydrogen gas, and supplied helium from separate systems to pressurize the hydrogen and oxygen tanks. The engine was relatively underpowered for its task and the start up and restart procedures were unreliable. Thus, it was quickly replaced by the YF-75.
The YF-75 is a liquid cryogenic rocket engine burning liquid hydrogen and liquid oxygen in a gas generator cycle. It is China's second generation of cryogenic propellant engine, after the YF-73, which it replaced. It is used in a dual engine mount in the H-18 third stage of the Long March 3A, Long March 3B and Long March 3C launch vehicles. Within the mount, each engine can gimbal individually to enable thrust vectoring control. The engine also heats hydrogen and helium to pressurize the stage tanks and can control the mixture ratio to optimize propellant consumption.
The YF-77 is China's first cryogenic rocket engine developed for booster applications. It burns liquid hydrogen fuel and liquid oxygen oxidizer using a gas generator cycle. A pair of these engines powers the LM-5 core stage. Each engine can independently gimbal in two planes. Although the YF-77 is ignited prior to liftoff, the LM-5's four strap-on boosters provide most of the initial thrust in an arrangement similar to the European Vulcain on the Ariane 5 or the Japanese LE-7 on the H-II.
The LE-7 and its succeeding upgrade model the LE-7A are staged combustion cycle LH2/LOX liquid rocket engines produced in Japan for the H-II series of launch vehicles. Design and production work was all done domestically in Japan, the first major (main/first-stage) liquid rocket engine with that claim, in a collaborative effort from the National Space Development Agency (NASDA), Aerospace Engineering Laboratory (NAL), Mitsubishi Heavy Industries, and Ishikawajima-Harima. NASDA and NAL have since been integrated into JAXA. However, a large part of the work was contracted to Mitsubishi, with Ishikawajima-Harima providing turbomachinery, and the engine is often referred to as the Mitsubishi LE-7(A).
The LR87 was an American liquid-propellant rocket engine used on the first stages of Titan intercontinental ballistic missiles and launch vehicles. Composed of twin motors with separate combustion chambers and turbopump machinery, it is considered a single unit and was never flown as a single combustion chamber engine or designed for this. The LR87 first flew in 1959.
Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines.
TM65 is a rocket engine developed by Copenhagen Suborbitals. TM65 uses Ethanol and liquid oxygen as propellants in a pressure-fed power cycle.
The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta rocket, referred to as Delta-P, from 1972 to 1988. The rocket engine uses Aerozine 50 as fuel, and N
2O
4 as oxidizer. It was developed in the early 1970s by TRW as a derivative of the lunar module descent engine (LMDE). This engine used a pintle injector first invented by Gerard W. Elverum Jr. and developed by TRW in the late 1950s and received US Patent in 1972. This injector technology and design is also used on SpaceX Merlin engines.
The ascent propulsion system (APS) or lunar module ascent engine (LMAE) is a fixed-thrust hypergolic rocket engine developed by Bell Aerosystems for use in the Apollo Lunar Module ascent stage. It used Aerozine 50 fuel, and N
2O
4 oxidizer. Rocketdyne provided the injector system, at the request of NASA, when Bell could not solve combustion instability problems.
The S1.5400 was a Soviet single-nozzle liquid-propellant rocket engine burning liquid oxygen and kerosene in an oxidizer-rich staged combustion cycle, being the first rocket engine to use this cycle in the world. It was designed by V. M. Melnikov, an alumnus of Isaev, within Korolev's Bureau, for the Molniya fourth stage, the Block-L. It was also the first Soviet engine designed for start and restart in vacuum and had the highest Isp at the time of its deployment.
The RD-0216 and RD-0217 are liquid rocket engines, burning N2O4 and UDMH in the oxidizer rich staged combustion cycle. The only difference between the RD-0216 and the RD-0217 is that the latter has not a heat exchanger to heat the pressuring gasses for the tanks. Three RD-0216 and one RD-0217 were used on the first stage of the UR-100 ICBM. The engines were manufactured until 1974 and stayed in operational use until 1991. More than 1100 engines were produced.
The KTDU-80 (Russian: Корректирующе-Тормозная Двигательная Установка, КТДУ) is the latest of a family of integrated propulsion system that KB KhIMMASH has implemented for the Soyuz since the Soyuz-T. It integrates main propulsion, RCS and attitude control in a single system pressure fed from a common dual string redundant pressurized propellant system. The common propellant is UDMH and N2O4 and the main propulsion unit is the S5.80 main engine. It generates 2.95 kN (660 lbf) of thrust with a chamber pressure of 880 kPa (128 psi) and a nozzle expansion of 153.8 that enables it to achieve a specific impulse of 302 s (2.96 km/s). It is rated for 30 starts with a total firing time of 890 seconds. The integrated system without the pressurization or tanks weighs 310 kg (680 lb); it is 1.2 m (47 in) long with a diameter of 2.1 m (83 in).
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