The Artemis program to return humans to the Moon has an aura of inevitability now, with broad political support, robust international participation, and a successful first mission—Artemis I—under its belt.

Perhaps most critically, for Artemis, is that in a rare show of bipartisanship, both Republicans and Democrats support NASA’s plan to send humans to the Moon later this decade, at least once a year, reaching a point at which astronauts stay for 30 days at a time. Crafted during the Trump administration, the Biden White House reaffirmed these Artemis plans within days of taking office. Biden diplomats have also continued to add nations to the “Artemis Accords,” with two dozen countries now participating.

For all of this support, however, there is one worrying sign. The Artemis program’s budget is ballooning, and it is not at all clear when humans will start flying to the Moon. These concerns were highlighted this week at a meeting of NASA’s Advisory Committee for Human Spaceflight.