The throat exhaust air velocity in a rocket engine refers to the speed of the exhaust gases at the throat of the rocket nozzle. The throat is the narrowest section of the nozzle where the flow reaches its maximum speed. The velocity at the throat is a critical parameter in determining the overall performance of the rocket. The relationship between the throat and exit velocities, along with the areas at these points, is described by the rocket equation:
The continuity equation is based on the principle of mass conservation, and Bernoulli’s equation expresses the conservation of energy.
The continuity equation is given by:
where:
-  and  are the cross-sectional areas at the nozzle entrance and exit, respectively,
-  and  are the velocities at the nozzle entrance and exit, respectively.
which gives
where,
- A1 is the Cross-sectional area at the throat of the nozzle in m2Â
- A2 is the Cross-sectional area at the exit of the nozzle in m2
- V1 is the Velocity of the exhaust gases at the throat in m/s
- V2 is the Velocity of the exhaust gases at the nozzle exit in m/s