Speaker
Description
The Martian atmosphere is one of the easiest resources to access on the red planet. This makes it a prime candidate for in-situ resource utilization (ISRU). As a result, a handful of proposed architectures for manned mission to Mars have included the following ISRU scheme: the CO2 rich air, in conjunction with ice deposits, is reacted into methane and oxygen using the Sabatier reaction. As a rocket propellant, the mixture of methane and oxygen, also called Methalox, is much easier to store and less corrosive than hydrogen-based alternatives. Most notably, Elon Musk, the CEO of SpaceX, unveiled in 2016 a manned mission architecture that included ISRU for Methalox production on Mars. In this plan, one of SpaceX’s rockets, the so-called Starship, would be refueled on Mars during a single synodic period.
To evaluate the feasibility of a Methalox production plant on Mars, our team devised a process flow simulation in DWSIM and used it to evaluate the size of the equipment necessary. The production target for the simulated plant was 325 kg/day of liquefied methane and 1385 kg/day of liquified oxygen, enough to refuel SpaceX’s Starship over the span of 26 months with a 3.66 fuel ratio. The design of the simulated plant drew its inspiration from the many proposals for Methalox production plant published in the literature, mainly those involving the Sabatier reaction. The choice of equipment was made in accordance with best practices in the chemical industry. The plant design included a cryogenic atmosphere capture unit, a polymer electrolyte membrane electrolyzer, a Sabatier reactor, two membrane separators, two consecutive gas cleaning units, and a cascading liquefaction unit. Ice refining operations, as well as electricity production and propellant storage, were outside of the scope of our analysis
According to our simulation, this Methalox plant would consume a continuous 573 kW of electricity and have a volume of 41 m3. Overall, the electrolyzer consumed the most electricity and the Sabatier reactor occupied the most space. The biggest source of uncertainty in our simulation comes from the gas treatment unit and cooling unit which were modeled using extrapolations of correlations. This is especially true for the gas unit destined to scrub water and CO2 from the oxygen stream.
In all cases, our designed Methalox plant would fit within the 1000 m3 cargo space of SpaceX’s Starship. This does not contradict other published estimations. The current design of the plant can however be improved, especially on the level of equipment choice. From a chemical engineering standpoint, this is a miniature chemical plant. At this scale, electrochemical reactors, thermoelectric cryocoolers, and molecular sieves could be more advantageous than the equipment we chose for our analysis.
