What is a Monopropellant Thruster?

A monopropellant thruster is a thruster that uses a single chemical as its propellant. Monopropellants are propellants that consist of chemicals that release energy through exothermic chemical decomposition. This release of energy is usually accomplished with the help of a catalyst. A monopropellant does not require a separate oxidizer.

A Monopropellant thruster generates thrust by allowing liquid propellant to flow through an open valve into a catalytic decomposition chamber. This propellant supply to the thruster happens with one or more than one stage of flow control valves. The thrusters are equipped with an internal catalyst bed heater. A thrust is generated when the control valve is commanded to open causing propellant to be fed to the thrust chamber. When the propellant comes in contact with the catalyst a decomposition reaction takes place within the catalyst bed and the hot decomposition gases are then accelerated through a converging-diverging nozzle.

A monopropellant fuel burns without the need for an oxidizer since the oxidizer is already bound into the molecule. This makes the thruster or engine lighter, less expensive, and more reliable.