Liquefied Natural Gas (LNG) is increasingly used in modern rocket engines as a high-performance fuel source. LNG is primarily composed of methane (CH₄), which typically makes up 85–98% of natural gas, depending on processing and origin. In aerospace applications, LNG provides liquid methane for advanced methalox (methane + liquid oxygen) propulsion systems.
How LNG Is Used in Rocket Propulsion
1. Liquefaction and Cryogenic Storage
Natural gas is cooled to approximately −162°C (−260°F) to become LNG. In this liquid state, methane is far denser than its gaseous form, allowing rockets to store large amounts of fuel in compact tanks. Many launch vehicles use subcooled LNG, stored slightly below its boiling point, to increase density and improve engine performance.
2. Methalox Propellant System
LNG (or refined liquid methane derived from it) is paired with liquid oxygen (LOX) as the oxidizer. The fuel and oxidizer are stored in separate cryogenic tanks and delivered under high pressure into the rocket engine’s combustion chamber.
3. Combustion and Thrust Generation
Inside the engine, liquid methane and LOX mix and ignite in a precisely controlled combustion process. Methane burns cleanly with oxygen, producing water vapor (H₂O) and carbon dioxide (CO₂) as exhaust. Compared to kerosene-based fuels, methane combustion creates significantly less soot and coking, improving engine reliability and reusability.
Combustion reaction:
CH₄ + 2O₂ → CO₂ + 2H₂O + energy
The resulting high-temperature, high-pressure gases expand through the engine nozzle at extreme velocity, generating thrust according to Newton’s Third Law of Motion.
4. Advanced Engine Cycles
Modern LNG-fueled rocket engines use high-efficiency cycles such as full-flow staged combustion or oxygen-rich staged combustion. These systems burn small amounts of propellant in pre-burners to power turbopumps, then route the gases into the main chamber for complete combustion. This design delivers exceptional efficiency, power, and engine longevity.
Advantages of LNG and Methane Rocket Fuel
- Clean burning fuel – Minimal carbon buildup enables rapid engine reuse and reduced maintenance
- High performance – Specific impulse falls between kerosene/LOX and hydrogen/LOX systems
- High density – Similar to kerosene, allowing compact fuel tanks and high thrust output
Cost-effective and abundant – Widely available and inexpensive, particularly in the United States - Easier handling – Less extreme cryogenic requirements than liquid hydrogen
- Mars compatibility – Methane can be produced on Mars using the Sabatier process, supporting in-situ resource utilization (ISRU) for return missions
Why LNG Is Shaping the Future of Spaceflight
Unlike household natural gas, LNG used in rockets is a highly refined, cryogenic propellant engineered for extreme performance. By delivering methane in liquid form, LNG enables powerful, efficient, and reusable rocket engines. As space agencies and private launch providers focus on sustainability, reusability, and deep-space missions, methalox propulsion using LNG has become one of the most promising fuel technologies for the next generation of spaceflight.