NASA Safety Panel Says Starship Needs 22 Flights for Moon Landing

NASA's Aerospace Safety Advisory Panel now estimates that 22 Starship launches will be needed to fuel SpaceX's lunar lander for a single Artemis Moon mission, according to panel member Charlie Precourt, a former NASA astronaut, speaking at the panel's quarterly meeting Thursday and reported by Ars Technica.

How Many Starship Launches Does NASA Now Say Are Needed?

"We need to keep our eyes on numerous required fuelings for the lander. I think the last estimate is around 22 flights," Precourt said, according to Ars Technica's account of the meeting. Precourt did not name Starship directly, but the vehicle he referenced can only be SpaceX's rocket, since NASA's other human lunar lander, Blue Origin's Blue Moon, does not rely on orbital refueling for its initial mission design, Ars Technica reported.

The figure has climbed from earlier NASA statements. In 2023, then-director of NASA's Human Landing System program Lisa Watson-Morgan told Ars Technica the agency had "a general idea" but was "reluctant to say exactly what that is," later placing the number in the "high single digits to the low double digits." Other NASA officials have cited "high teens," per the same report.

What Do "Tanker" and "Depot" Flights Mean?

Under the architecture described by Ars Technica, SpaceX must first launch a "depot" Starship into low-Earth orbit. It then launches a series of "tanker" Starships that dock with the depot and transfer liquid oxygen and methane, the propellant combination Starship uses. Once the depot is full, it fuels the lander Starship, which then flies to the Moon, lands, and returns astronauts to lunar orbit. At the lower end of past estimates — about a dozen flights — that meant one depot plus 11 tankers, Ars Technica reported.

What Did SpaceX's Elon Musk Say in Response?

After Ars Technica reporter Eric Berger posted Precourt's 22-flight estimate on the social platform X, SpaceX founder Elon Musk disputed the number directly. "That's way too high," Musk wrote, according to Ars Technica. "Actual number will be more like 6 to 8." The gap between NASA's safety-panel figure and Musk's public estimate — roughly three times apart — has not been reconciled in public statements from either side, Ars Technica noted.

Why Has the Number Changed Over Time?

Ars Technica's reporting points to unresolved engineering variables: how much cryogenic methane and oxygen boils off during orbital storage, and how efficiently propellant transfers between two Starships in orbit. Those variables directly multiply the number of tanker flights required, which is why NASA's own public figure has moved from "high single digits" to "high teens" to 22 over roughly three years, per the Ars Technica account.

What's at Stake for Artemis IV?

Precourt's broader comment to the safety panel was that Artemis IV carries "a large number of firsts that reduce the likelihood of mission success," Ars Technica reported, with the refueling-flight count singled out as a specific risk to track. NASA officials, according to the report, have grown concerned that SpaceX's hoped-for gains in Starship's lift capacity — which would cut the number of tanker flights needed — may not materialize soon enough to support a Moon landing under Artemis this decade.

Neither NASA nor SpaceX has published a reconciled, official figure, leaving Precourt's 22 and Musk's 6-to-8 as the two public data points on record, per Ars Technica's report.