The speed power coefficient (Cs) is a dimensionless parameter used in the analysis of propellers and rotors, similar to the thrust coefficient and the power coefficient discussed earlier. It represents the efficiency of converting power into thrust by the propeller or rotor.
Cs = Speed power coefficient V = Forward speed of the aircraft or vehicle relative to the air (in m/s) ρ = Air density (in kg/m^3) P = Power produced by the propeller or rotor (in Watts) n = Rotational speed of the propeller or rotor (in revolutions per second, RPS)