Hybrid rocket engines combine features of both liquid and solid rocket engines. In a hybrid rocket engine, one component is typically in a liquid state (such as a liquid oxidizer), while the other component is in a solid state (such as a solid fuel).
For a hybrid rocket, the mass flow rate of exhaust gases is influenced by both the liquid oxidizer and the solid fuel, and the exhaust velocity is influenced by the combustion characteristics of the solid fuel and the expansion of the combustion gases in the nozzle.
The thrust equation for a turbojet engine using control volume analysis is expressed as:
where,
- is the thrust force,
- ṁe is the mass flow rate of exhaust gases in kilograms per second (kg/s).
- is the Exhaust velocity at the nozzle exit in meters per second (m/s).
- ṁ0 is the mass flow rate of inlet gases in kilograms per second (kg/s).
- is the Exhaust velocity at the nozzle Inlet in meters per second (m/s).
- is the Pressure at the nozzle exit in pascals (Pa).
- is the Pressure at the nozzle inlet in pascals (Pa).
- is the Area of the nozzle exit in square meters (m²).