The plan to get humans to the moon four years earlier than expected is taking shape in NASA Administrator Jim Bridenstine's mind, and he's pretty sure it's doable.

First, the agency will launch two Orion spacecrafts -- one with human and one without -- around the moon on the back of the government's heavy-lift rocket by 2023. Then, the agency plans to enlist the help of a commercial company to rocket pieces of a space station into the moon's orbit by 2024. Finally, officials will shuffle the government's rocket manifest to use its last flight in 2024 to send humans to that moon station instead of a probe to Europa, Jupiter's moon.

And while all this is being done, NASA will be developing a human lunar lander to take astronauts from the moon station, called the Lunar Orbital-Platform Gateway, to the surface.

That's a lot to do in five years. But more than anything, the problem is money.

"We've had strong bipartisan support and we've had strong budget requests in the past," Bridenstine said in an interview with the Houston Chronicle on Saturday. "But this is another level of support, so we'll find out."

Bridenstine was at Rice University speaking at the Owls in Space Symposium on Saturday.

Under President Donald Trump's leadership, NASA's plan was to put humans back on the moon by 2028. But then last month, Vice President Mike Pence directed the agency to accelerate that timeline to 2024 using "any means necessary."

This announcement was met with cynicism, especially since the president's most recent budget request called for a $500 million cut to the agency in the coming year. And that, of course, would not be enough.

So, NASA is working up a budget that would allow for faster operations without sacrificing safety. Bridenstine said he will deliver that budget to Congress in late April or early May.

He's not sure how much more money will be needed, but hopes that the request will ask Congress for multi-year funding for the moon programs so that political whims and changing support do not jeopardize the 2024 plan by eliminating money needed.

"Year-by-year funding is risky," he said. 'This would reduce the risk."

Also at risk of jeopardizing the moon 2024 plan is the government's problem-plagued, heavy lift rocket. The Space Launch System rocket, being built by Boeing, was supposed to launch Orion in 2017.

It has continued to fall behind schedule, however, and Boeing most recently told NASA it couldn't make the June 2020 launch date, which was supposed to send Orion without a crew around the moon.

This wouldn't do, especially after Pence's directive. The agency examined whether it would be better to use a commercial rocket to launch Orion instead -- and it found a viable option -- but NASA decided that it still wouldn't meet the launch deadline.

Bridenstine said agency officials have found a way to speed up the first SLS launch so that it is only six months behind schedule. But the agency is developing a commercial backup plan just in case SLS continues to experience problems.

The agency needs another SLS -- or an equally powered machine -- to send the first crewed Orion around the moon by 2023 and a third to the Gateway by 2024. The Europa Clipper, which was supposed to hitch a ride to Jupiter's moon on the third SLS, would then be launched via a commercial rocket.

"This is something we're thinking about for a second or third effort should [the Space Launch System rocket] continue to be challenged," Bridenstine told the Houston Chronicle on Saturday. "When we think about 2023/2024, we have another option that we can start putting together the pieces of right now if we want to and we're going through that process."

Bridenstine said the agency already is working on a lunar lander to take humans to the surface. It still will need to find a commercial company to launch the elements of the Gateway into the moon's orbit by 2024.

Alex Stuckey writes about NASA and science for the Houston Chronicle. You can reach her at alex.stuckey@chron.com or Twitter.com/alexdstuckey.