Velocity of Exhaust Gases At The Nozzle For a Liquid Propellant Rocket Engine Using Specific Impulse Calculator

The velocity of the exhaust gases at the nozzle exit for a liquid propellant rocket engine is determined by the rocket equation, which is based on the conservation of momentum and mass. The rocket equation is universally applicable to different types of rocket engines, including liquid propellant engines. Liquid propellant engines use liquid fuels and oxidizers stored in separate tanks and are mixed and burned in the combustion chamber.

The formula for calculating the nozzle exhaust air velocity using the rocket equation is:

Where:

• V_exit is the change in velocity of the rocket (in meters per second, m/s).
• I_sp​ is the specific impulse of the rocket engine (in seconds, s).
• g₀ ​ is the acceleration due to gravity at the Earth’s surface (approximately 9.81 m/s²).
• m₀​ is the initial mass of the rocket (including propellant, air and structure, in kilograms, kg).
• m_f ​ is the final mass of the rocket (after propellant burnout, in kilograms, kg).