specific impulse

ranges of thrust and specific impulse for different propulsion systems

The ranges of specific impulse and thrust for different types of propulsion system.

Specific impulse is the ratio of a rocket engine's thrust to the weight of fuel burned in one second. Measured in seconds, specific impulse is an important gauge of the efficiency of a rocket propulsion system and, in particular, of a rocket propellant. It is similar to the idea of miles per gallon with cars. The higher its value, the better the performance of the rocket.