Why refueling a rocket in orbit is so hard
NASA's plan to land people on the Moon depends on moving fuel between rockets in space. Here is why it is hard, and what is still unknown.
Reviewed by Jackson on Nov 8, 2026. How we work
Quick answer
NASA's current Artemis III plan depends on refueling a lander in Earth orbit: reusable tankers would deliver fuel to a storage depot, which would then fill the lander's tanks before it heads to the Moon. Moving super-cold fuel in weightlessness is the hard part.[1][2]
Key points
- NASA's Artemis III plan includes a storage depot in Earth orbit, filled by reusable tankers.[1]
- The lander's tanks must be filled in orbit before its trip toward the Moon.[1]
- The fuel is cryogenic, meaning it is kept extremely cold, and engineers must control how it behaves in space.[2]
- SpaceX attempted an in-space fuel transfer between Starship tanks in March 2024, according to Space.com. We could not confirm the results or any later test.[2]
Why it matters
Without orbital refueling, a Moon lander would need a much larger rocket. The method, if it works, would make crewed missions cheaper and more flexible.[1][2]
Why it is hard
Fuel in space floats, and cryogenic fuel boils when it warms. Engineers have to move liquid that is very cold, keep the tanks stable, and control how the fluid flows without gravity holding it down.[2]
What NASA plans
For Artemis III, NASA describes reusable tankers carrying propellant to a storage depot in orbit. The lander then docks, fills its tanks, and performs a burn toward the Moon.[1]
What we don't know yet
- Whether the in-space transfer has since been fully demonstrated. Our most recent source on the SpaceX test is from March 2024.
- When the Artemis III plan will be carried out, and whether its schedule will change.
- How much fuel a lander would need, and how many tanker flights that would take. NASA's plan describes the method, not the final numbers.
What changed
- Nov 8, 2026: First version. Uses a 2024 report for the SpaceX test, and NASA's current Artemis III plan.
Sources
- NASA: Artemis III (accessed Nov 8, 2026)
- Space.com: NASA celebrates SpaceX Starship's 3rd test flight, but more work needed ahead of Artemis moon missions (March 2024) (accessed Nov 8, 2026)