Cold gas propulsion systems use pressurized gases (usually inert gases like nitrogen or helium) for thrust generation. Unlike traditional rocket engines that involve combustion, cold gas propulsion relies on the rapid expulsion of pressurized gas to produce thrust.
In a cold gas propulsion system, the mass flow rate of expelled gas is determined by the rate at which the gas is released, and the exhaust velocity is influenced by the nozzle design. The pressure of the expelled gas is dependent on the initial pressure of the gas source.
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).