Methane propulsion in rockets: a clean and efficient way to launch satellites

Rockets are essential for launching satellites into orbit, but they also have a significant environmental impact. Rocket engines produce various emissions, such as carbon dioxide, water vapour, black carbon, and nitrogen oxides, that can affect the atmosphere, the climate, and the ozone layer. Moreover, some rockets use toxic propellants, such as hydrazine, that can contaminate the soil and water.

One way to reduce the environmental footprint of rocket launches is to use methane as a fuel. Methane, or CH4, is a natural gas that can be combined with liquid oxygen to form a propellant known as methalox. Methane has several advantages over other fuels, such as kerosene or hydrogen, for rocket propulsion.

First, methane is more efficient than kerosene, meaning that it can produce more thrust per unit of mass. Methane has a higher specific impulse, which is a measure of how much momentum a propellant can impart to a rocket. A higher specific impulse means that a rocket can carry more payload or reach higher velocities with less fuel.

Second, methane is cleaner than kerosene, meaning that it produces less harmful emissions. Methane combustion results in carbon dioxide and water vapour, which are less damaging to the atmosphere than the soot and nitrogen oxides produced by kerosene combustion. Methane also has a lower global warming potential than kerosene, meaning that it has less impact on the greenhouse effect.

Third, methane is more versatile than hydrogen, meaning that it can be used for a wider range of missions. Methane has a similar density to kerosene, which makes it easier to store and transport than hydrogen, which is very low-density and requires large tanks. Methane also has a lower boiling point than hydrogen, which means that it can be kept in a liquid state for longer periods of time without requiring active cooling systems.

Moreover, methane is a potential resource for future exploration of the solar system. Methane can be found or produced on other planets or moons, such as Mars, Titan, or Enceladus, using various methods, such as mining, electrolysis, or the Sabatier reaction. This means that methane rockets could be refuelled in situ, enabling longer and cheaper missions.

Several companies and agencies are developing or testing methane rockets for launching satellites or other payloads. For example, SpaceX is working on the Starship, a reusable rocket that uses 33 methane-fuelled Raptor engines and aims to eventually carry humans to Mars. Blue Origin is developing the New Glenn, a heavy-lift rocket that uses seven methane-fuelled BE-4 engines and plans to launch commercial and military satellites. NASA is testing the RS-25, a modified version of the Space Shuttle main engine that can run on methane as well as hydrogen, for its future Artemis program.

In July 2023, a Chinese company called LandSpace became the first in the world to launch satellites with a methane rocket, beating SpaceX to the technology. The Zhuque-2 rocket, which uses four TQ-12 engines in the first stage and one TQ-12 engine in the second stage, successfully delivered nine satellites into orbit from the Jiuquan Satellite Launch Center. This was a significant achievement for the Chinese private space industry, which is aiming to compete with global players in the growing market for satellite launch services.

In conclusion, methane propulsion is a promising technology for launching satellites in a more efficient and environmentally friendly way. Methane rockets have several benefits over other types of rockets, such as higher performance, lower emissions, and greater versatility. Methane rockets are also compatible with the vision of exploring and utilising the resources of the solar system. Therefore, methane propulsion is likely to play an important role in the future of spaceflight.