Dual mode propulsion systems combine the high efficiency of bipropellant rockets with the reliability and simplicity of monopropellant rockets. Dual mode systems are either hydrazine/nitrogen tetroxide, or monomethylhydrazine/hydrogen peroxide (the former is much more common). Typically, this system works as follows: During the initial high-impulse orbit-raising maneuvers, the system operates in a bipropellant fashion, providing high thrust at higher specific impulse; when it arrives on orbit, it closes off either the fuel or oxidizer, and conducts the remainder of its mission in a simple, predictable monopropellant fashion.
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This article is an automated import of the Wikipedia article "Dual mode propulsion rocket", available at https://en.wikipedia.org/wiki/Dual_mode_propulsion_rocket . Text is licensed under CC BY-SA 4.0.