Metal bipropellant rockets for martian ascent vehicles

A Mg bipropellant rocket is being developed for Martian sample return missions. This game-changing technology could enable a near-term demonstration of Martian In Situ Resource Utilization. In the first phase of the research and development program, it was determined through analysis that Mg can be combusted with CO₂ condensed in-situ from the Martian atmosphere to yield a specific impulse of approximately 220 s at the Martian surface. It was also determined that the effective specific impulse, considering only the propellant carried from Earth, will be many times higher. Performance with other oxidizers was also analyzed. Sustained combustion of magnesium powder with carbon dioxide was then demonstrated in a linear combustor outfitted with a thrust nozzle, thrust load cell, and optical access ports. Minutes of continuous operation were demonstrated. The measured thrust was over 50 N and Earth sea level specific impulse was almost 120 s. The difference between predicted and measured performance was related to losses associated with the test geometry. Temperatures in the reaction were derived from spectral measurements and found to correspond well to numerical predictions.