Do we know how many Starship launches SpaceX will need to get NASA astronauts to the moon? No. Will its refuelling plan be simple? Also no.

NASA’s Artemis IV mission, the program’s first crewed lunar landing, faces significant logistical complexities, particularly regarding the refueling requirements for SpaceX’s Starship if it serves as the lunar lander. Estimates for the number of refueling flights have varied widely; a 2021 Government Accountability Office audit suggested up to 16 launches might be necessary. More recently, a member of the Aerospace Safety Advisory Panel estimated the number could be as high as 22, a figure SpaceX CEO Elon Musk refuted on social media, stating the requirement would likely be closer to six or eight.

The specific mechanics of the refueling process remain a subject of scrutiny. According to a graphic released by NASA during a recent Artemis update, the operation involves a staggered orbital staging strategy. SpaceX will first launch a depot ship to low Earth orbit (LEO) to serve as a fuel repository. The graphic indicates that multiple tanker Starships will dock with this depot to fill it, though the exact number of these initial flights is not specified.

Following the depot’s initial fill, the Starship lunar lander will launch to LEO to dock with the depot for its first fuel transfer. After undocking, the lander will raise its altitude to a designated "final tanking orbit" (FTO). At this stage, SpaceX will launch another round of multiple tanker ships to replenish the depot with additional propellant. The depot will then travel to the FTO to dock with the lander for a final fuel transfer before the lander ascends to high Earth orbit.

In high Earth orbit, the Starship lander will rendezvous and dock with NASA’s Orion capsule, which carries four astronauts launched aboard a Space Launch System (SLS) rocket. The combined spacecraft will burn their engines to travel toward the moon, separating upon arrival in low lunar orbit. Two astronauts will remain in Orion while the other two descend to the lunar surface in Starship. After their surface mission, the two astronauts will return to Starship, launch back to lunar orbit, and dock with Orion for the journey home.

NASA states that this complex sequence serves a specific purpose by creating flexibility in the launch schedule for the SLS rocket, which launches Orion before Starship completes its final fueling. The agency notes that this approach reduces the total fuel required compared to previous plans, primarily because Starship will take Orion directly to low lunar orbit rather than a much higher orbit.

Despite these detailed plans, the mission architecture is not finalized. NASA retains the option to select Blue Origin’s Blue Moon lander for Artemis IV if SpaceX fails to demonstrate its orbital refueling strategy or does not complete an uncrewed lunar landing mission by the end of next year. As the launch date approaches, further details regarding the specific number of refueling flights and the exact execution of the orbital maneuvers are expected to become clearer.