Magnesium and carbon dioxide - A rocket propellant for Mars missions

Metal-CO2 Propulsion for Mars Missions: Current Status and Opportunities

“…It was shown that such particles ignite in air at 950-1060 K [69], as well as exhibit higher combustion rates and more complete oxidation than equilibrium alloy particles [71]. Qualitatively similar effects were reported for Al-Ti (10-25 at.% Ti) mechanical alloy particles in air [73], but Ti provides worse performance than Mg for metal-CO 2 propulsion [21]. Thus, it would be interesting to conduct experiments with metastable Al-Mg mechanical alloy particles in a CO 2 atmosphere.…”

“…This is not critical in solid rocket motors, where combustion of Al occurs at temperatures of 2700-3000 K [25], but is important for metal-CO 2 engines. Because their chamber temperatures for Al=CO 2 mixtures with high CO 2 fraction (which may be useful for Mars propulsion) are expected to be 2000-2500 K [21], stable ignition will likely need a permanent igniter which adds weight and power consumption. Thus, to use Al particles in metal-CO 2 propulsion, their ignition must be improved.…”

“…Lithium aluminum hydride may deserve further consideration, but the relatively low melting point of Li 2 O (1726 K) also indicates potential problems with oxide deposition. As for MgAl 2 H 8 , this compound looks promising in terms of specific impulse and oxide deposition but, as compared with Mg and Al, will exhibit a much lower combustion temperature (see data in [21] for MgH 2 ), which may became critical for engine operation.…”

“…On the other hand, the low atmospheric pressure of Mars (7-9 mbar), being a major problem for jet engines, is perfect for rockets (no need for pressure higher than 10 bar in the combustion chamber to obtain high nozzle expansion ratio). These favorable circumstances were noted by Shafirovich et al [21], who first conducted thermodynamic calculations of performance characteristics for rocket engines using metal-CO 2 propellants and made ballistic estimates.…”

“…Thermodynamic calculations of the CO 2 -using rocket engine performance characteristics for Li, Be, B, Mg, Al, Si, Ca, Ti, Zr, BeH 2 , MgH 2 , and mixtures of Be and Mg with N 2 H 4 , were reported by Shafirovich et al [21]. The calculations were made for a wide range of CO 2 =fuel mass ratios.…”