You Americans have a habit of loving things that drink down fossil fuels faster than we Brits neck a cup of tea, and Starship is no exception to the rule. Thanks to its size, proposed gigantic payload capacity, and the need for its rockets to land both stages, Starship is one of the most fuel-hungry rockets ever devised, requiring thousands of tons of propellant per launch. For the occasional test launch, this fuel-guzzling nature isn’t a problem. But Starship needs to be entirely refuelled in LEO (Low Earth Orbit) by other Starships before it can make it to Mars or the Moon. So, for the Starship program to be used as intended, it needs to be launched roughly every other day (read more here). That is a much bigger challenge. So, where is SpaceX getting all this fuel from? And how can they ensure it flows to their launchpads fast enough? More importantly, is this even possible? Or will Starship suffer from a critical fuel bottleneck?
Let’s start at the beginning: how much fuel does Starship need?
Well, according to SpaceX, Starship takes 1,600 tons of propellant, and the Super Heavy Booster takes 3,650 tons, meaning it requires 5,250 tons of propellant to get a fully stacked Starship ready for launch. This propellant is made of two parts: the LOX (liquid oxygen) oxidiser and the methane fuel, in roughly a 4/5 ratio by mass. This means Starship needs significantly more liquid oxygen than methane per launch, approximately 4,500 tons of the stuff.
Ensuring the methane fuel reaches LEO, chilling it into cryogenic liquid form, and then loading it into Starship is relatively easy. After all, methane gas has been pumped into most houses in the Western world to power stoves and boilers for well over 150 years. There is ample production capacity, and setting up infrastructure, such as pipelines, to shuttle it to the Starship launchpad is a pretty simple task, given that we already do it. Methane also has a higher boiling point than oxygen and a much lower specific heat capacity, making it easier to cool down and easier to turn into the cryogenic liquid state Starship requires.
So unless someone at SpaceX’s logistics department royally messes up, Starship should never have a problem getting enough methane to launch.
The same cannot be said for LOX.
The pure oxygen production capacity of the world is far, far smaller than methane, and the supply chain for launch-grade LOX is even tinier. Handling LOX is also much more dangerous than methane. Non-flammable materials can burst into flames when exposed to pure oxygen, given that it is such a powerful oxidiser (hence the name). One tiny mistake or leak can cause a catastrophic failure. Transporting LOX is even harder, as its boiling point is -182.9°C, and if it reaches above that threshold, the pressure in its container or pipe can spike to dangerous levels. Let’s also not forget that this lower boiling point and oxygen’s higher specific heat capacity make turning pure oxygen into launch-grade LOX slow and energy-intensive. This means that unlike with methane, cryogenic chilling is conducted off-site at specialised plants. But, because very few people or industries require LOX, and most of the ones that do only need a little, we haven’t developed the same kind of transport infrastructure that we have with methane/natural gas, so almost all LOX is transported in insulated trucks via roads.
A US truck can carry roughly 18.1 tons of LOX (40,000 lbs), meaning that it takes around 250 truckloads of LOX to refuel a Starship.
Again, at Starship’s current launch rate, that isn’t a problem, as they have literal weeks to fill up the fuel tanks.
But if Starship intends to reach the Moon, like NASA wants it to in 2028, this is a problem.
