NASA’s administrator Jim Bridenstine has finally revealed the total cost estimate for the space agency’s plan to put astronauts back on the Moon: $20 to 30 billion. That’s the extra money that NASA will need on top of the agency’s average annual budget to pull off this ambitious program, Bridenstine told CNN in an interview.

“It would be $20 to $30 billion on top of the normal NASA budget, but of course that would be spread over five years,” Bridenstine said in the interview.

This is the first time that anyone at NASA has revealed the full cost for the plan to put people on the lunar surface again — a program the agency has recently dubbed Artemis. NASA is aiming to put a crew on the Moon by 2024, after being challenged by Vice President Mike Pence to expedite the mission. During that initial landing, the agency plans to make history by having the first woman set foot on the lunar surface.

This is the first time that anyone at NASA has revealed the full cost for the plan

To jump-start the Artemis program, the White House has requested an additional $1.6 billion during fiscal year 2020, on top of the $21 billion budget that the president requested for the rest of NASA next year. However, Bridenstine has been clear that this initial budget is just a “down payment” for the program. NASA officials, including Bridenstine, have repeatedly dodged questions about what the full five-year program is going to cost. And representatives from Congress have expressed frustration over not having the entire price tag up front.

Based on this estimate given to CNN, NASA is going to need an additional $5 to $6 billion each year for the next five years to make this Moon landing a possibility. Bridenstine didn’t go into details about how that money would be spent exactly, but NASA has been clear about the architecture it wants to build for Artemis. NASA is finishing up the development of a massive new rocket, called the Space Launch System, as well as a new crew capsule called Orion, both of which will carry people to the vicinity of the Moon. Additionally, the agency wants to create a new space station around the Moon called the Gateway, where astronauts can live for short periods of time and then travel down to the lunar surface. NASA has already awarded a contract to an aerospace company called Maxar to build the first module for the Gateway.

And of course, NASA is going to need a very crucial piece of hardware: a landing system that can safely transport people away from the Gateway, touch down on the surface, and then take people back to the station. Over the next few months, NASA plans to put out a final call for lunar lander designs and then pick companies to create the system over the next couple of years.

Artemis’ success hinges on Congress approving the extra funding for the program, and it’s unclear if that will happen. The White House called on taking the initial $1.6 billion investment for NASA from the Pell Grant fund, which provides scholarships for low-income students, and that didn’t sit well with many lawmakers. Meanwhile, the most recent budget proposed by the House Appropriations Committee for 2020 gives NASA a boost in funding, but did not address any extra funding for Artemis.

Without a budget increase, it’s possible NASA will resort to cutting money from other programs to achieve their goal. When the White House asked for extra money for Artemis in a budget amendment, the request also included language that would allow the administrator to move funds from other projects within NASA to fund the Moon program. NASA officials are already bracing themselves for tough cuts ahead.

“I don’t think we’re going to be able to get the entire budget as new money.”

“I don’t think we’re going to be able to get the entire budget as new money,” Bill Gerstenmaier, NASA’s associate administrator for human exploration, said during a recent meeting of the NASA Advisory Council. “We’re going to have to look for some efficiencies and make some cuts internally to the agency, and that’s where it’s gonna be hard.” Lawmakers like Rep. Eddie Bernice Johnson (D-TX), chair of the House Science Committee, expressed concern over this sentiment and worried that science programs might suffer as a result.

Bridenstine claims that he will not “cannibalize” other programs in NASA to get people to the Moon. Still, getting an extra $20 to $30 billion from Congress over the next five years may be a big feat. NASA’s budget got a big boost during the Apollo program in the 1960s, but that was during the height of the Cold War, and the political climate has changed significantly since then.

NASA will have a better idea of where Congress stands as the budget for next year is finalized. But if the agency doesn’t even get the extra $1.6 billion it requested for Artemis for 2020, NASA’s dreams of landing people on the Moon in the next five years may not come true.