The White House is asking the United States Congress for an additional US$1.6 billion (NZ$2.4b) for Nasa’s budget next year as the space agency attempts to return humans to the moon by 2024. The announcement comes about six weeks after US Vice President Mike Pence called for an accelerated program to return humans to the lunar surface for the first time since the last Apollo lunar landing in 1972. But since the White House issued that bold mandate, Nasa has released few details about how it would achieve it or what the programme would cost. In a tweet Monday evening, US President Donald Trump wrote: “Under my administration, we are restoring @Nasa to greatness and we are going back to the Moon, then Mars. I am updating budget to include an additional $1.6 billion so that we can return to Space in a BIG WAY!” READ MORE: * The Moon is cooling, shrinking and has moonquakes, Nasa finds * Mike Pence wants American astronauts on moon in 5 years * Heads up, earthlings: 5 reasons why you should pay attention to space this year * Once more, Trump explores the idea of a Space Force * Donald Trump tells Nasa to send astronauts to Mars It was unclear exactly where that money would come from or what the reaction in Congress would be. Democrats in the House have been particularly critical of the White House’s plan, calling it a political gambit, timed to align with the elections calendar.NASAUS President Donald Trump wants American astronauts back on the Moon within five years. “The lack of planning evident so far is no way to run our nation’s human space exploration programme,” Representative Kendra Horn, chair of a subcommittee that oversees Nasa, said at a recent hearing. “The 2024 missive left Nasa in a tizzy – scrambling to develop a plan and hastening to pull together a budget amendment that still have not been delivered to Congress; and upending groundwork with international partners on future exploration goals.” Pence’s announcement took many inside Nasa by surprise. The agency had been aiming to get humans to the lunar surface by the end of the decade. And in March, the White House submitted a budget request totaling just over US$21 billion for Nasa, a nearly US$500 million cut of what the agency received this year. Since the White House called for Nasa to speed up the timeline, the space agency has been scrambling to see how it could pull off such a complicated mission in a short amount of time. At the moment, Nasa currently does not have the ability to fly astronauts anywhere in space. Instead, it pays Russia more than US$80 million a seat to fly its astronauts to the International Space Station. As part of the amended budget request, the White House included US$1 billion to begin the development of a lander capable of getting astronauts to the surface of the moon. An additional US$651 million would also go to help speed development of Nasa’s massive Space Launch System rocket, built largely by Boeing, and the Orion spacecraft, built by Lockheed Martin. It would also boost technologies to help the agency explore the lunar poles with robots ahead of a human mission, using solar energy as a propulsion source and converting ice found under the moon’s crust into water. “Under my Administration, we are restoring NASA to greatness and we are going back to the Moon, then Mars,” Trump wrote. After Trump’s announcement Monday, Nasa Administrator Jim Bridenstine tweeted: “This is the boost Nasa needs to move forward with putting the next man and the first woman on the Moon.” But Nasa officials warned that it would need additional money in the future in order to meet the goal. “This additional investment is a down payment on Nasa’s effort to land humans on the moon by 2024,” Bridenstine said in a call with reporters Monday evening. “In the coming years, we will need additional funds. This is a good amount that gets us out of the gate in a very strong fashion and sets us up for the future.” Instead of going directly to the surface of the moon, as Nasa did during the Apollo missions of the late 1960s and early 70s, it is instead looking to build a more permanent presence by building an orbiting outpost known as the Gateway. While that is a more ambitious endeavour, Bridenstine has said the agency wants to go back to the moon – but this time in order to stay. Still, in order to meet the ambitious five-year goal, Nasa has said it would scale back the scope of the Gateway, at least initially. To accommodate getting humans to the surface quickly, the budget amendment proposes cutting US$321 million from that project and shift “potential Gateway capabilities into the future.” It was not immediately clear where all of the money would come from. Nasa said that no programmes, other than Gateway, were being cut. It is also not clear what the reaction in Congress would be. Bridenstine said he had been reaching out to key Congressional leaders but that it was “not easy to get a hold of everyone” on short notice. “We will see various reactions” from Congress, he said. “But I will tell you when we talk about what Nasa is trying to achieve, there is a lot of excitement.” Nasa plans to launch its massive SLS rocket for the first time by as early as next year without astronauts. That would be followed by another mission, with astronauts in the Orion crew capsule, for a trip around the moon. The third mission, to come in 2024, would send a pair of astronauts, one woman and one man, to the Gateway, and then to the lunar surface. Shortly after Pence’s announcement, in which he said astronauts would get to the lunar surface “by any means necessary,” there was talk that the White House would ask for a huge amount of additional funding, as much as US$8 billion a year. But at a recent Congressional hearing, Bridenstine disputed that. The White House’s amended budget request comes a week after Jeff Bezos unveiled a lunar lander that his space company, Blue Origin, has pitched Nasa to get cargo and eventually people to the lunar surface. Many other companies, such as Boeing, Lockheed Martin and the Sierra Nevada Corporation are also vying to build various parts of the Gateway.