Read: The moon is open for business

“We have amazing capability that exists right now that we can use off the shelf in order to accomplish this objective,” Bridenstine said.

A return to the moon has been a top priority for NASA since President Trump was elected, and the Space Launch System is key to the effort. The Trump administration wants to use the rocket to help build a floating lunar outpost, the equivalent of a little International Space Station around the moon, and it wants construction completed by 2024.

But the SLS program, established during Barack Obama’s administration, is running behind schedule and over budget. The office of NASA’s inspector general has criticized NASA and Boeing, the rocket’s main contractor, over their management and performance, predicted more delays, and even questioned whether the entire effort is sustainable.

NASA has a long history of being late, including on some of its most high-profile missions, such as the Hubble Space Telescope and the Mars Curiosity rover. According to government auditors, the agency’s major projects experienced average launch delays of 12 months in 2018, the worst in a decade. Some degree of delay is certainly expected, considering the nature of the work; when your job is to try something no one else has ever done before, in outer space, it’s difficult to estimate how long it will take.

But engineering challenges are only part of the equation. NASA tends to set overly ambitious deadlines, a habit forged in the days of the Apollo era, when budgets and schedules were secondary concerns to success. When the payoff was beating the Soviets to the moon, lawmakers ultimately accepted these pitfalls.

This kind of culture might have been sustainable if NASA’s budget continued to grow, or even remained steady, in the years since the Apollo program, but it has shrunk instead. (The president’s budget proposal for NASA, released days ago, included a 17 percent cut in funding for SLS.) Add the effects of rotating casts in Washington throughout the years, featuring players with their own ideas about what NASA should do, and you’ve got a recipe for not getting much done on time.

Bridenstine said the moon mission would require a heavy-lift vehicle, a type of powerful rocket capable of lifting something into orbit above Earth. The administrator didn’t say which rockets the agency would consider, but he has options. There’s the Delta IV Heavy, built by the United Launch Alliance, a joint venture of Boeing and Lockheed Martin, the contractor for the capsule. This mammoth rocket launched the Orion capsule into orbit for a quick, four-hour test in 2014. And then there’s the Falcon Heavy, even more powerful, from Elon Musk’s SpaceX, which flew for the first time last year.

SpaceX seems like a natural fit for this endeavor. The company is currently building a rocket-and-capsule combo designed to reach the moon in 2023, and a Japanese billionaire has already bought a ticket for as many as eight passengers. Musk has spent years saying that someone should have built a base on the moon by now. He said it again less than two weeks ago, and Bridenstine was literally sitting next to him. “I hope we go back to the moon soon,” Musk said. “We should have a base on the moon, like a permanently occupied human base on the moon.”