Below is a short summary and detailed review of this video written by FutureFactual:
Why SpaceX Favors Methane: Mars ISRU, Sabatier, and the Future of Reusable Rockets
Real Engineering explains how rocket fuel choices shape the future of spaceflight. The video contrasts kerosene in early stages with hydrogen and, increasingly, methane for SpaceX’s Starship engines. It explains why methane is attractive: better performance than kerosene, easier storage than hydrogen, and the possibility of producing fuel on Mars using carbon dioxide and water. The discussion also covers the Sabatier process and reverse water-gas shift as pathways to generate methane on Mars, the oxygen balance for life support, and the broader drive toward reusable, affordable rockets in the context of climate-aware engineering.
Overview
The video discusses how rocket fuels influence design, cost, and reusability, tracing the evolution from kerosene in the Saturn V to methane for SpaceX's Starship. It explains the limits of liquid hydrogen, including density and tank mass, and why methane is rising as a practical compromise for deep-space missions and Mars habitation.
Fuel Chemistry and Efficiency
Hydrogen offers a higher specific impulse than kerosene, but its low density means larger tanks and more insulation and boil-off issues. The video notes the specific impulse advantage of hydrogen (about 390 seconds vs kerosene's 285), and contrasts this with methane, which sits between kerosene and hydrogen in performance but is easier to store and produces less soot due to its single-carbon chemistry.
"Hydrogen has a much higher specific impulse than kerosene, around 390 seconds against kerosene's 285 seconds." - Brian McManus, Real Engineering
Methane on Mars and In Situ Resource Utilization
The video explains how methane could be synthesized on Mars using carbon dioxide from the atmosphere and hydrogen, which could be produced via water electrolysis. The Sabatier reaction (CO2 + 4H2 -> CH4 + 2H2O) and the reverse water-gas shift (CO2 + H2 -> CO + H2O) can be combined in a single reactor to produce methane and water, enabling fuel production and life-support oxygen, with favorable 2:1 methane-to-oxygen stoichiometry for the Raptor engine’s needs.
"This combination of these two reactions, the Sabatier and reverse water gas shift, can be done in the same reactor, ... This leads to an overall reduction of 35% in heat generation, improving the efficiency of the whole process." - Pioneer Astronautics
Engineering Challenges and Climate Context
The discussion highlights hydrogen embrittlement and boil-off as barriers to hydrogen-based reuse, and shows how methane offers a practical path forward given Mars infrastructure constraints. It also connects the pursuit of advanced propulsion to climate-action themes, noting that carbon capture and storage research could support long-term methane production as a renewable energy store, a potential benefit for both Earth and space.
"Mars's atmosphere is almost entirely carbon dioxide, 95%." - Brian McManus, Real Engineering
Implications for the Future of Spaceflight
By balancing mass, efficiency, and reliability, methane-fueled systems may unlock more affordable, reusable spacecraft capable of lunar missions and Mars settlement, while offering cross-cutting insights for climate-friendly energy storage technologies.
"Hydrogen has a much higher specific impulse than kerosene, around 390 seconds ..." - Brian McManus, Real Engineering