We propose to develop Mg rockets for Martian ascent vehicle applications. The propellant can be acquired in-situ from MgO in the Martian regolith (5.1% Mg by mass) and combusted with H20 that exists at the poles and below the surface. The vacuum Isp of a Mg-H20 rocket would be ~300 s. Mg can also be combusted with CO2 condensed from the Martian atmosphere to yield Isp ~215 s. The technology can also be used on the Moon, where regolith is 5.5% Mg. Al-H20 rockets would also be enabled; like Mg, Al is present in Martian and Lunar regolith. In Phase I, we will prove the feasibility of Mg rockets. Chemical Equilibrium Analysis codes will be used to predict rocket performance at various operating conditions and O/F ratios. Combustion with CO2, H20, and pure O2 will be considered. Experiments will focus on developing and characterizing delivery, ignition and combustion systems, starting with ARL's existing Mg combustion system. Ways to achieve low temperature, electrolytic ignition and stable combustion will be studied. Drawing upon both experimental and theoretical results, we will then design a 5-10 N metal-water rocket system to be built and tested in Phase II.