Lunar ISRU Explained: Making Oxygen and Fuel From Moon Dirt

Every kilogram not launched from Earth is a kilogram you don't pay launch costs on — and propellant is most of the mass. In-situ resource utilization (ISRU) is the discipline of making it locally. On the Moon that means two feedstocks: oxygen locked in regolith minerals, and water ice in permanently shadowed polar craters. The free Lunar ISRU Optimizer lets you compare the process chains quantitatively.

Oxygen is everywhere; hydrogen is not

Lunar regolith is roughly 40–45% oxygen by mass, bound in silicates and oxides. Processes like molten regolith electrolysis or hydrogen reduction of ilmenite can liberate it — at a price of roughly 20–40 kWh per kilogram of O₂ depending on the process. Hydrogen, though, is scarce outside the polar ice deposits, which is why "water at the poles" reshaped lunar strategy: water gives you both propellant components at far lower process energy.

The mass payback question

An ISRU plant only makes sense if it produces more than its own delivered mass reasonably fast. A useful figure of merit is annual production divided by plant mass: published concepts range from ~2 to ~10 kg of product per kg of plant per year. The optimizer computes payback time directly from your assumptions — plant mass, power, process energy, duty cycle — so the viability question gets a number instead of a vibe.

Power drives everything

Extraction is energy-intensive, and the lunar night is 354 hours long. Polar sites offer near-continuous sunlight on crater rims adjacent to the ice — the reason every serious ISRU concept clusters at the south pole. The tool couples production to available power so you can see how a solar+storage or nuclear option changes annual output.

FAQ

What's the most mature process?

Hydrogen reduction of ilmenite is the most studied; molten regolith electrolysis promises higher yield per kg of feedstock but at higher temperatures and materials challenges. Water extraction from icy regolith is conceptually simplest but depends on ice concentration, which remains uncertain until we drill.

Why not just bring propellant from Earth?

For early missions you will. ISRU wins when demand is recurring — a base, a fleet, a depot — and the payback math in the optimizer shows exactly where that crossover sits.

Is anything uploaded?

No — the model runs entirely in your browser.

Try it: Lunar ISRU Optimizer. Pairs well with the Lunar Regolith Processing Hub and Lunar Launch Economics Calculator.