It’s no secret that NASA’s Space Launch System is struggling to meet its schedule. The multibillion-dollar launcher is expected to ferry humans and cargo into deep space. The problem is, the agency has vocally committed to sending an American craft to the moon next year. NASA’s new lunar taxi, called Orion, is almost ready to go. But its ride—the big and bloated SLS—is still years from completion.

On Wednesday morning, NASA administrator Jim Bridenstine appeared before the US Senate Committee on Commerce, Science, and Transportation to discuss America’s leadership in space. During his testimony, he revealed an unexpected twist. For the first time, Bridenstine said that the agency would consider commercial rockets to get its crew capsule off the ground. For NASA, travel to deep space would no longer be SLS or bust.

"We are now understanding better how difficult this project is,” he explained. Before the retirement of NASA’s storied space shuttle program, the agency began laying out its vision for its next-generation rocket. In 2011, development began on SLS, which it hoped would become the biggest rocket in the world. But year after year, as it missed its targets and blew through its budgets, the agency faced criticism for the project’s shortcomings. Dubbed the rocket to nowhere by its critics, SLS was at times derided as more of an agencywide jobs program than a real ride to space. That is until 2017, when the rocket received a new goal: ferry astronauts to the moon.

Its inaugural launch was originally set for 2018, but that date soon slipped to 2019, then 2020, and now officials aren’t even sure that timeframe is feasible. But Bridenstine told Congress that he wants NASA to hit its deadlines going forward. “I want to be really clear,” he said. “I think we as an agency need to stick to our commitment. If we tell you, and others, that we’re going to launch in June of 2020 around the moon, I think we should launch around the moon in June of 2020.”

To meet those deadlines, the administrator acknowledged that all options—including commercial rockets—should be considered. Bridenstine’s comments were unexpected; for nearly a decade now NASA has supported an SLS-only approach to sending its astronauts into deep space. (The agency had originally limited its commercial partners to sending crews no farther than low earth orbit and back.) But with an extremely tight timeline and multiple technical [delays],(https://oig.nasa.gov/docs/IG-19-001.pdf) it’s now abundantly clear that SLS will almost certainly not be ready to fly in 2020.

Over the years, Orion’s destination changed from Mars to the moon, and even to the surface of an asteroid. But one thing was certain: On Orion’s first foray beyond Earth, a crewless capsule would complete a six-day circuit of the moon; that’s the mission Bridenstine now says could launch atop a commercial rocket. Dubbed Exploration Mission 1 (or EM-1), it had also been intended as SLS’s maiden voyage.

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The hitch is that Orion is too heavy for any commercial vehicle now in use to deposit it in lunar orbit. Bridenstine acknowledged this in his testimony: “The challenge is we don’t have a rocket right now that can launch Orion and the European Service Module around the moon.” (Built by the European Space Agency, the service module will provide power to Orion during flight.)

“That’s what the SLS is all about,” he added.

Instead, Bridenstine proposed that the mission could be done in phases. First, one rocket would send Orion and the European Service Module into orbit around Earth; a second rocket would launch an upper stage separately. That upper-stage rocket would have to meet up with the duo in orbit and boost them to the moon. But this, too, is easier said than done, as the docking technology required to pull it off doesn’t exist yet.