Dual mode propulsion rocket

Dual mode propulsion systems combine the high efficiency of bipropellant rockets with the reliability and simplicity of monopropellant rockets.{{cite book|author=L. G. Napolitano|title=Applications of Space Developments: Selected Papers from the XXXI International Astronautical Congress, Tokyo, 21 — 28 September 1980|url=https://books.google.com/books?id=qdogBQAAQBAJ&pg=PA134|date=22 October 2013|publisher=Elsevier Science|isbn=978-1-4831-5976-8|pages=134–}}

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.