⚙️ Specific Impulse 計算機

Specific impulse (Isp) is the key performance measure of a rocket engine or jet propulsion system. It tells you how efficiently a propellant is converted into thrust — essentially how many seconds one unit weight of propellant can produce one unit of thrust. A higher Isp means more efficient use of propellant, which directly affects how much payload a rocket can carry and how far it can travel.

Enter three values: the thrust F in newtons, the propellant mass flow rate ṁ in kilograms per second, and the standard gravity g₀ (default 9.80665 m/s²). The calculator returns the specific impulse in seconds and the effective exhaust velocity in metres per second.

The governing equation is

Thrust divided by mass flow rate gives the effective exhaust velocity (v_e) in m/s. Dividing that by standard gravity converts it into the more commonly quoted Isp expressed in seconds. Engineers use seconds because it is independent of the unit system, making engine comparisons easy worldwide.

Suppose an engine produces 1,000 N of thrust while consuming propellant at 0.5 kg/s, with g₀ = 9.80665 m/s². Then

and This is typical of a modest chemical thruster.