What is a Bipropellant Thruster?
A bipropellant thruster is a thruster that uses two propellants (very often liquid propellants) which are kept separately before reacting to form a hot gas to be used for propulsion.

Bipropellant systems require the combustion of two (Bi) propellants. First one is a fuel and the second is an oxidizer. These propellants are kept in separate tanks are then injected separately into the bipropellant thruster combustion chamber where they react spontaneously to perform high-temperature combustion products which are expelled through a nozzle.