This story is part of To the Moon, a series exploring humanity's first journey to the lunar surface and our future living and working on the moon.
It's been half a century since the space race between the Soviet Union and the US peaked with Apollo 11 and the first steps on the moon. But now the 21st century sequel is heating up courtesy of -- who else -- Elon Musk.
The SpaceX founder said in an interview published Thursday that he believes his company's Starship spacecraft could return humans to the surface of the moon just a few years from now.
"Well, this is gonna sound pretty crazy, but I think we could land on the moon in less than two years," Musk told Time. "Certainly with an uncrewed vehicle I believe we could land on the moon in two years. So then maybe within a year or two of that we could be sending crew. I would say four years at the outside."
In other words, Musk is saying his conservative estimate for sending people back to the moon aboard a SpaceX vehicle is 2023, the year before NASA hopes to send a crew -- including the first female astronaut to visit the moon -- as part of its new Artemis program.
Elon Musk shows off the shiny SpaceX StarshipSee all photos
Earlier this year, NASA Administrator Jim Bridenstine said the space agency would consider using a third-party rocket like the SpaceX Falcon Heavy for its return to the moon, but later said that Artemis will definitely use NASA's new Space Launch System.
Musk added that the quickest way back to the moon may be to go it alone.
"If it were to take longer to convince NASA and the authorities that we can do it versus just doing it, then we might just do it. It may literally be easier to just land Starship on the moon than try to convince NASA that we can."
The process of qualifying a new spacecraft to fly NASA missions, especially involving crew, can take many months or even years.
Musk, who is known for his bold predictions and aggressive timelines, seems to be upping the ante in this latest space race just as a few key SpaceX projects are working through minor setbacks.
Time conducted the interview with Musk on July 12. On Tuesday, a hold-down test firing of a single-engine Starship prototype ended with an unexpected fireball. While the prototype didn't appear to be seriously damaged, this week's plans for the so-called "Starhopper" to lift off the ground for the first time and hover before landing were subsequently delayed.
And earlier this year, a SpaceX Crew Dragon spacecraft was destroyed during a test firing. Crew Dragon, along with Boeing's Starliner craft, have been tapped by NASA to begin shuttling astronauts to the International Space Station from American soil for the first time since the end of the space shuttle program.
On Monday, SpaceX and NASA announced that the Dragon explosion was traced back to a leak in the craft's pressurization system. While Crew Dragon was initially set to carry its first crew this month, Musk now says that mission looks to be about six months away.
What makes the idea of SpaceX landing humans on the moon by 2023 even more interesting is that Musk previously set a goal of launching Starship around the moon -- without landing on the surface -- in 2023 at the earliest.
Beyond Apollo: See NASA aim for the moon with Artemis 2024See all photos
Meanwhile, Bridenstine told a Senate committee on Wednesday that NASA won't even have an estimate of the cost for its 2024 Artemis mission ready until next year.
The NASA head also recently shook up the staff overseeing the moon mission, re-assigning the agency's longtime head of human exploration.
And then there's the Space Launch System, which has been eight years in the making, plagued by delays and is yet to get off the ground.
So while goals for returning to the moon are getting more aggressive, the schedules to actually launch the vehicles that could take people there are slipping.
Bluster and bold talk were a key part of the first space race and NASA managed to do the seemingly impossible a little bit ahead of schedule in July 1969. Perhaps the same will be true for the 21st century sequel, but 2023 is coming up quick.