Propulsion Systems

Propulsion systems are required to do three things. First, they must provide lift for the launch vehicle and its payload, and take it from the launch pad up into space. They must then ensure the payload travels around the Earth, so that it can enter a low Earth orbit or a parking orbit, and not fall back down to Earth. The third task is to manoeuvre the payload into the desired height, position or trajectory.

The propulsion system on the launch vehicle is also often responsible for moving the payload straight into the parking orbit. Once in orbit, other propulsion systems are usually used to transfer the payload from the parking orbit into a higher orbit or into a trajectory for planetary encounters. As the movement of the spacecraft around its orbit already balances the force of gravity, and as it does not need to battle with air resistance, propulsion systems that produce a small force or thrust can be used for this third stage.

There are various methods of getting a propellant to produce thrust. The main three are a chemical reaction used in chemical propulsion systems, a nuclear reaction for nuclear propulsion systems and an electric propulsion system, which uses electricity.