SpaceX could send humans to the surface of the moon in just five years’ time, founder Elon Musk declared Tuesday. The company’s upcoming Starship, under development at the firm’s Boca Chica test facility in Texas, is designed to send the first humans to the surface of Mars. Musk believes it’s possible the same ship could host a return to Earth’s nearest neighbor.

“I think so,” Musk wrote on Twitter in response to a question from an account called “Everyday Astronaut.” “For sure worth giving it our best shot! Would be great to have a competitive, commercial program to build a moon base that is outcome-oriented (not cost-plus), so you only get paid for safe delivery of cargo.”

The question came during a thread about Mike Pence’s declaration that the United States would send humans to the moon in five years. On Tuesday, at the fifth National Space Council meeting at the US Space and Rocket Center in Huntsville, Alabama, Pence stated that “America will once again astonish the world with the heights we reach, the wonders we achieve & we will lead the world in human space exploration once again.”

“It would be so inspiring for humanity to see humanity return to the moon!” Musk wrote.

The last time a human set foot on the moon was 1972. A return trip has been a big goal for President Donald Trump, who signed a directive in December 2017 calling for a return to the moon and eventually Mars. NASA’s Space Launch System, first started in 2010 as a project intended for both returning to the moon and more ambitious missions like Mars, has suffered from delays but is currently scheduled for its first launch in June 2020. The initial “Block 1” configuration stands 322 feet tall and weighs 5.75 million pounds, delivering 26 metric tons to places beyond the moon. The planned “Block 2” configuration will send 45 metric tons to deep space with 11.9 million pounds of thrust.

NASA's SLS NASA

Similar to the SLS, SpaceX’s Starship is designed to cover a multitude of missions. Its initial design, the BFR, unveiled in September 2017, stood 348 feet tall and weighs 9.7 million pounds. It also produces 11.9 million pounds, sending 100 tons of payload to low-Earth orbit. Musk has since tweaked the design to a Tintin-inspired stainless steel version.

The company has built a miniature “hopper” version in Texas, set to fly any time soon, ahead of an orbital prototype scheduled for 2020. From there, the plan is to send Japanese billionaire Yusaku Maezawa and a team of six to eight artists on a trip around the moon in 2023. The first flights to Mars could take place as early as 2024.

Cost-plus contracting, which Musk dismissed in his tweet, has received criticism from proponents of the private spaceflight industry. Rick Tumlinson, founder of the SpaceFund venture capital firm, derided the practice in an interview with Inverse as it enables government contractors to extract more profits.

“If you, the government, want me, the contractor, to build you a flashlight, I get to charge you 10 percent of whatever it cost me to develop. Why would I sell it to you for $10 and keep $1 when I can charge you $1 million and keep $100,000?” Tumlinson said.

Pence’s declaration to return to the moon was met with reassurance from NASA administrator Jim Bridenstine, who stated the team will do everything it can to meet that goal. Experts are slightly more skeptical that the delayed SLS can meet the challenge.

“I will be astonished if this happens,” Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, told Time. McDowell cited political budget infighting at NASA as a stumbling block, but that even without these disputes, it would be a tight deadline.

Of course, the next team to visit the moon may be neither NASA nor SpaceX. At a Morgan Stanley event in New York City in December 2018, 10 of the 12 representatives from the space industry predicted that China would be the next country to visit the moon.