Back in March, the Trump administration declared that it was directing NASA to send humans back to the Moon no later than 2024. That’s an incredibly tight deadline for an agency with a budget that is nowhere near what it was (in adjusted dollars, anyway) when the Apollo missions made history, but Trump-appointed NASA administrator Jim Bridenstine bent over backward and promised it could be done.

Lots of people, myself included, were (and still are) highly skeptical that NASA can pull it off. Now, a new budget amendment proposal just surfaced that reveals how much more money NASA is going to need to even have a chance of fulfilling the Moon 2024 promise: $1.6 billion.

When Trump sent Mike Pence to tell NASA it had to get a manned mission on the Moon by 2024, the messaging was very clear: Make it happen with the resources NASA already has available to it. There was no mention of increased funding or resources to make the mission possible, and no promise from the Trump administration that it would do its part to grease the wheels of Congress and secure additional funding.

NASA is already spread rather thin when it comes to money. The agency received $21 billion in funding for the 2020 fiscal year. That might seem like an incredible amount of cash, but with several missions in the works at any given time, that money is used up rapidly. For context, the U.S. Defense budget for the 2019 fiscal year was over $686 billion.

Missions to explore the Solar System, keep the International Space Station going, and make new breakthroughs in countless research fields take time and funding. Heading to the Moon within five years was not something NASA was prepared to do. Now, scrambling to meet an unrealistic demand, the agency is asking for a budgetary increase of less than 10 percent, but even that modest request is not a guarantee of approval.

We’ll have to wait and see how lawmakers react to the request. This won’t be the only budget increase NASA proposes in the years ahead, as it only addresses the immediate need for new cash in 2020, but if Trump wants to go to the Moon he should know that it’s going to cost taxpayers a pretty penny.