SpaceX lists a full Starship stack at 5,250 tonnes of propellant: 1,600 tonnes in the upper ship and 3,650 tonnes in the Super Heavy booster. Every kilogram of it is liquid methane or liquid oxygen. The choice of methane was deliberate, and the reasons are a mix of chemistry, handling and Mars.
What Musk said about the fuel
Years before Starship flew, Elon Musk laid out the logic in a talk to the Royal Aeronautical Society in London, reported by Space.com. Raptor would burn liquid oxygen and methane, where the Falcon 9 burned liquid oxygen and kerosene. “The energy cost of methane is the lowest,” Musk said, “and it has a slight ISP advantage over kerosene and doesn’t have any of the bad aspects of hydrogen.” Space.com added the background on that last point: hydrogen is hard to store at cryogenic temperatures, makes metal brittle and is very flammable.
A return ticket on Mars
The bigger argument is Mars. Space Daily’s Mission Notes column says methane was picked partly because both propellants could, in theory, be made there from carbon dioxide in the air and water ice in the ground. A ship that lands on Mars needs fuel to come home, and hauling all of it from Earth would mean landing enormous extra mass and keeping it cold. Making it locally shifts the burden to power plants, excavators, reactors and tanks.
On paper the chemistry closes. Electrolysis splits water into hydrogen and oxygen. The hydrogen goes to a Sabatier reactor, where it combines with carbon dioxide to produce methane and water. Recycle the water and the net result is carbon dioxide and water becoming methane and oxygen, close to the reverse of what happens inside a Raptor engine.
Oxygen is the bigger product stream. NASA concept studies often assume an oxygen-to-methane mass ratio near 3.5 to one for Mars ascent propellant. The Martian atmosphere is about 95 per cent carbon dioxide, but surface pressure is less than one per cent of Earth’s at sea level, so a plant has to process a great volume of thin air.
Proof of principle, not a factory
Nothing like that plant exists. The closest hardware is MOXIE, the toaster-sized experiment on the Perseverance rover. According to NASA’s Jet Propulsion Laboratory, it operated 16 times, produced 122 grams of oxygen in total and peaked at 12 grams per hour. It made no methane, no hydrogen and no liquid propellant. Space Daily puts it bluntly: methane’s local manufacturability is a design factor, not evidence that a working Mars factory exists.
There is a cold-storage catch too. Liquid oxygen boils at about minus 183 degrees Celsius and methane near minus 162 degrees, so tanks have to stay extremely cold.
Methane on the ground in Florida
The fuel choice is now shaping infrastructure. Interesting Engineering, citing Reuters, reported in October 2026 that Coastal Connect Services, a SpaceX subsidiary, asked the Florida Public Service Commission to approve a tariff for a 32.4-mile, 16-inch natural gas pipeline through Brevard County. It would link SpaceX facilities with the Florida Gas Transmission interstate line. The company says trucks and local pipelines cannot meet growing needs at Cape Canaveral.
SpaceX has also sought approval for a pipeline of about 8 miles at Starbase near Boca Chica, Texas, and Bloomberg reported that it has started hiring natural gas traders. The Florida line is still a proposal. The filing does not mean construction has been authorized.
Sources
- Starship stands roughly as tall as a 40-storey building and carries more than 5,000 tonnes of liquid methane and oxygen (Space Daily, Mission Notes column)
- SpaceX Chief Eyes Huge Mars Colony (Space.com, Rob Coppinger; report of a Musk talk at the Royal Aeronautical Society in London)
- SpaceX wants 32-mile gas pipeline for Starship fuel in Florida (Interesting Engineering, citing Reuters and Bloomberg)
