The impulse produced by a rocket divided by the mass \(mp\) of propellant consumed. Specific impulse \({I_{sp}}\) is a widely used measure of performance for chemical, nuclear, and electric rockets. It is usually given in seconds for both U.S. Customary and International System (SI) units. The impulse produced by a rocket is the thrust force \(F\) times its duration \(t\) in seconds. \(I_{sp}\) is the thrust per unit mass flowrate, but with \(g_o\), is the thrust per weight flowrate. The specific impulse is given by the equation: \(I_{sp} = \frac{F}{\dot{m}g_o}\).