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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.
Delta-v is typically provided by the thrust of a rocket engine, but can be created by other engines. The time-rate of change of delta-v is the magnitude of the acceleration caused by the engines, i.e., the thrust per total vehicle mass. The actual acceleration vector would be found by adding thrust per mass on to the gravity vector and the ...
The specific impulse relates the delta-v capacity to the quantity of propellant consumed according to the Tsiolkovsky rocket equation: [5] = where: m 0 {\displaystyle m_{0}} is the initial total mass, including propellant, in kg (or lb)
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 ...
where is the specific impulse of the rocket, measured in seconds, and is the gravitational acceleration at sea level. For a high delta-v mission, the majority of the spacecraft's mass needs to be reaction mass.
The Tsiolkovsky rocket equation shows that the delta-v of a rocket (stage) is proportional to the logarithm of the fuelled-to-empty mass ratio of the vehicle, and to the specific impulse of the rocket engine. A key goal in designing space-mission trajectories is to minimize the required delta-v to reduce the size and expense of the rocket that ...
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.
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 ...