Metallized Propellants for the Human Exploration of Mars

Advanced chemical propulsion using metallized propetlants can enable significant launch mass reductions for piloted Mars missions. Metallized propellants allow the density and/or the specific impulse (7sp) of the propulsion system to increase. These density and /sp increases can reduce the propellant mass and the propulsion system dry mass. Both of these effects are discussed and analyzed in the paper. Detailed mass scaling equations and estimates of the 7sp for the metallized propellant combinations are presented. The most significant savings with metallized propellants are derived from increasing the payload delivered to Mars. For the same mass in low Earth orbit (LEO), a metallized Mars vehicle can deliver 20-22% additional payload to the surface. Using metallized propulsion can accelerate the delivery and construction of a Mars base or outpost. This 20% payload increase reduces the total number of Mars flights and, therefore, significantly reduces the number of space transportation system-cargo (STS-C) launches for the entire Mars architecture. Using metallized propellants to reduce the mass in LEO per flight is not as effective as increasing the payload delivery capacity. While over 20% more payload can be delivered to Mars per mission, the mass savings per flight (while delivering the same payload with a higher /sp system) is much smaller. Using metallized propellants in all of the Mars propulsion systems, a modest 3.3% LEO mass savings is possible. This translates into a savings of 38,000 kg over that required with O2/H2 propulsion. The Mars excursion vehicle (MEV) using Earth- or space-storable propellants for the ascent can be an alternative to storing cryogenic H2 on Mars. There will be a mass penalty for using these alternatives because of the lower Isp of these systems. A space-storable system using oxygen/monomethyl hydrazine/aluminum (O 2/MMH/A1) delivered the lowest mass penalty over O2/H2. For the expedition case missions, the LEO mass penalty for using metallized O2/MMH/A1 is only 3-5%. A-D E g sp =