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Specific impulse (usually abbreviated I sp) is a measure of how efficiently a reaction mass engine, such as a rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the impulse , i.e. change in momentum, per mass of propellant.
Engine Origin Designer Vehicle Status Use Propellant Power cycle Specific impulse (s) [a] Thrust (N) [a] Chamber pressure (bar) Mass (kg) Thrust: weight ratio [b] Oxidiser: fuel ratio AJ-10-190 USA: Aerojet: Space Shuttle, Orion, Apollo CSM: Active Upper N 2 O 4 /MMH: Pressure-fed: 316 [1] 26,689 [1] 8.62 [1] 118 [1] 23.08: Archimedes New ...
The designation for a specific motor looks like C6-3.In this example, the letter (C) represents the total impulse range of the motor, the number (6) before the dash represents the average thrust in newtons, and the number (3) after the dash represents the delay in seconds from propelling charge burnout to the firing of the ejection charge (a gas generator composition, usually black powder ...
The most important metric for the efficiency of a rocket engine is impulse per unit of propellant, this is called specific impulse (usually written ). This is either measured as a speed (the effective exhaust velocity 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 ...
In the 1960s, Rocketdyne test-fired an engine using a mixture of liquid lithium, gaseous hydrogen, and liquid fluorine to produce a specific impulse of 542 seconds, likely the highest measured such value for a chemical rocket motor. [2] Despite the high specific impulse, the technical difficulties of the combination and the hazardous nature of ...
The specific impulse (I sp) of a rocket engine is the most important metric of efficiency; a high specific impulse is normally desired. Cold gas thrusters have a significantly lower specific impulse than most other rocket engines because they do not take advantage of chemical energy stored in the propellant.
The RL10 was the first liquid hydrogen rocket engine to be built in the United States, ... and a specific impulse of 465.5 seconds (4.565 km/s). ...
The RS-68A is an updated version of the RS-68, with increased specific impulse and thrust (to over 700,000 pounds-force (3,100 kN) at sea level). [11] The first launch on 29 June 2012, from the Cape Canaveral Air Force Station used three RS-68A engines mounted in a Delta IV Heavy rocket. [12]