The Integrated Mars In-Situ Propellant Production System (IMISPPS) is an end-to-end system that will produce rocket propellant on Mars from CO2 in the Martian atmosphere. The IMISPPS conducts both the Reverse Water Gas Shift (RWGS) and Sabatier (S/RWGS) reactions in a single reactor to produce a useful high-specific impulse fuel (methane plus carbon monoxide) and water, which is condensed and electrolyzed to produce oxygen and hydrogen. The hydrogen is recycled back to the S/RWGS reactor to react with fresh Martian CO2 to produce more fuel, while the oxygen is stored to provide oxidizer. Some of the carbon monoxide is removed by cryogenic separation to increase propellant specific impulse. The IMISPPS system produces the correct amount of oxygen to burn the methane produced, almost doubling the leverage of a Sabatier/Electrolysis system alone.