It's been 50 years since the last moonwalk. NASA astronauts explain why it took so long.

• NASA's new Orion spaceship is returning from its first flight to the moon on Sunday.
• The 50th anniversary of the last Apollo astronaut moonwalk is Wednesday. Nobody has been to the moon since.

NASA is about to receive its new Orion spaceship, returning from its first trip around the moon, just days before the 50th anniversary of the last Apollo moonwalk.

Nobody has set foot on the moon since December 14, 1972, when astronauts Gene Cernan and Harrison Schmitt conducted the last moonwalk of the Apollo program. But NASA built Orion to send astronauts back into lunar orbit and, as early as 2025, link up with SpaceX's Starship to land astronauts on the moon.

First Orion has to prove it can safely fly there and back, which is why NASA is flying this first mission, called Artemis I, with no humans on board. The spacehip will undergo its biggest test on Sunday: the fiery plummet through Earth's atmosphere, to an ocean splashdown. If it succeeds, NASA plans to put astronauts on its next flight around the moon.

"It's important that this initiative now succeed. We've tried two other times — administrations have tried — and they've been stillborn," Schmitt told Insider in 2019, after the Trump administration accelerated the new moon-landing timeline to 2024. (The goal has since been pushed to 2025.)

As early as 2004, former President George Bush was setting goals to return astronauts to the moon. According to those plans, it should have happened by 2020, maybe as early as 2015. Some of the delays have been technical. SLS, the cornerstone of the new Artemis lunar program, is 12 years and more than $20 billion in the making — twice its original timeline and budget.

But according to astronauts and NASA administrators, the main reason it's taken so long to launch a new moon mission has nothing to do with science or technology. The biggest obstacles: lack of budget and political will.

Returning to the moon was a hard sell in Washington

In order to fund a new NASA moonshot, Congress and the president had to doll out funding.

"Spaceflight is inherently risky, and spaceflight is hard," Bill Nelson, NASA's administrator, told Insider in August, when asked why it's taken so long to return to the moon. Before assuming the head role at NASA, in 2021, Nelson was a senator from Florida and a longtime fixture in Congressional committees on space.

Nelson's predecessor was more direct.

"The program took too long and it costs too much money," Jim Bridenstine, NASA administrator under former President Donald Trump, told reporters in 2019.

"If it wasn't for the political risk, we would be on the moon right now," Bridenstine said, adding, "In fact, we would probably be on Mars."

As a result, politicians haven't generally allocated the funding NASA would need to get back to the moon in the near future.

Lack of public interest hasn't helped matters. In 2018, a Pew survey found that most Americans prioritize climate research, monitoring hazardous asteroids, and basic space science over sending astronauts to the moon or Mars. While 72% of respondents thought it was "essential" for the US to maintain its world-leader status in space exploration, only 13% said it should be a "top priority" to send astronauts to the moon. Last year, a Morning Consult survey got similar results.

"Manned exploration is the most expensive space venture and, consequently, the most difficult for which to obtain political support," Walter Cunningham, an Apollo 7 astronaut, said during congressional testimony in 2015.

New presidents can give NASA whiplash

It doesn't help that new presidents often change NASA's plans and goals. As a result, NASA can get administrative whiplash, being ordered to drop certain projects or refocus on others every four to eight years. That makes it harder to commit to expensive projects that will take longer than one administration.

"Why would you believe what any president said about a prediction of something that was going to happen two administrations in the future?" Chris Hadfield, a former astronaut, previously told Insider. "That's just talk."

In 2004, for example, the Bush administration tasked NASA with coming up with a way to replace the Space Shuttle, which was set to retire, and also return to the moon. The agency came up with the Constellation program to land astronauts on the moon using a rocket called Ares and a spaceship called Orion. NASA spent $9 billion over five years designing, building, and testing hardware for that human-spaceflight program.

Yet after President Barack Obama took office — and the Government Accountability Office released a report about NASA's inability to estimate Constellation's cost — Obama pushed to scrap the program and signed off on the SLS rocket instead.

"Accelerating something that ambitious is a real challenge, and it takes commitment and dollars, and that's what's going to be required," Rusty Schweickart, an Apollo 9 astronaut, told Insider in 2019.

Money, money, money comes from Congress

In the end, a lot of what NASA can and can't do boils down to money.

"NASA's portion of the federal budget peaked at 4% in 1965," Cunningham told Congress in 2015. "For the past 40 years it has remained below 1%, and for the last 15 years it has been driving toward 0.4% of the federal budget."

Referring to Mars missions and a return to the moon, Cunningham said at the time, "NASA's budget is way too low to do all the things that we've talked about."

This year, though, President Joe Biden requested that Congress grant a whopping $25.9 billion for NASA in 2023, including an increase from $6.8 billion to $7.5 billion for the Artemis program.

According to Ars Technica, that means the new moonshot could have enough money to meet its goals for the first time ever.

This story has been updated with new information. It was originally published on August 27, 2022.