For a man known for grandiose ambitions, perhaps President Donald Trump’s most lofty is his pledge, formalized in a December order, to land a human being on the surface of Mars.

It would be easy to doubt Trump’s seriousness, given that he’s equally known for inconsistent follow-through. But Trump has raised the idea repeatedly since that order, most recently last month before the National Space Council, the advisory group Trump revived last year and tasked Vice President Mike Pence with running.

Trump seems serious about getting to Mars. He’s even picked a fight with the Republicans in the House and Senate over where to spend NASA’s resources, proposing this year to phase out funding for the International Space Station, or ISS, by 2025 and redirect it toward a return trip to the moon and to deep space exploration. On the moon, Trump told the space council last month, “We will establish a long-term presence, expand our economy and build the foundation for the eventual mission to Mars, which is actually going to happen very quickly.”

In a Republican Party increasingly united around Trump, that idea has raised eyebrows. At a June hearing of his Senate Commerce Subcommittee on Space, Science, and Competitiveness, for example, Chairman Ted Cruz blasted the proposal.

“As long as Article I of the Constitution remains intact, it will be Congress that is the final arbiter of how long the ISS receives federal funding,” he said, referencing the section of the founding document that gives Congress the power of the purse. Cruz’s state, Texas, is home to the Johnson Space Center, which manages its more than $3 billion annual budget.

Cruz’s dispute with Trump underscores the essential problem that’s held up a Mars mission since President George Bush first promised one in 1989: money. There is no easy source of the resources needed, roughly estimated in the hundreds of billions, making a human mission to Mars little more than sci-fi fantasy.

In a Congress deeply divided on so many issues, support for NASA is bipartisan. Members of both parties are effusive about the agency and its space mission. They say they want a Mars mission by 2033, the year a NASA working group said was realistic six years ago and has since become a rallying cry.

But in authorizing hearings, the Republicans who oversee the agency, led by Texas Rep. Lamar Smith, are frustrated with the agency’s progress. For seven years, since NASA shuttered the Space Shuttle program, it has relied on Russia to transport astronauts to the International Space Station. A program to develop a new vehicle is years behind schedule. A telescope to replace the 28-year-old Hubble is also delayed and billions over budget. Smith, whenever he gets the chance, presses NASA officials: “The taxpayers and Congress have neither infinite budgets, nor infinite patience,” he said.

20th century approach

Smith is not naive about the challenges. For NASA to get to Mars by 2033, it will take a revving of technological advancement akin to the 20th century’s advancements in flight, which saw the Wright brothers first launch a rickety plane in 1903 and a man on the moon just 66 years later. “It will take focus and a dedication of a significant amount of funds. It’s very, very ambitious,” he said.

In Smith’s view, to get to the moon, and to earn some more leeway from appropriators, NASA will have to start hitting some deadlines.

It will also have to hope that its shift toward greater reliance on the private sector yields dividends in greater efficiency, better operations and lower costs. If it doesn’t, don’t expect a Mars mission anytime soon.

[Trump Taps Senate’s Deputy Sergeant-at-Arms for NASA Post]

In May, at George Washington University in Washington, space enthusiasts gathered for a “Humans to Mars Summit.” They waved placards proclaiming “We can do this” beneath the goal, 2033, and a picture of the red planet.

What they heard from the politicians who came to speak, among them Cruz and NASA’s new administrator, Jim Bridenstine, is that NASA’s hopes of getting there rely on private companies seeing profit in going to space.

Cruz drew loud applause when he made a “clear and unequivocal commitment that we are going to Mars.” But, he added, “if we are going to go to Mars … nobody thinks that is going to be driven solely by public funds by the taxpayer. That endeavor is far too enormous given the constraints of modern budget reality.”

Bridenstine told the crowd that NASA needed to use “public funds to support private equity and private funds.”

In an interview, Bridenstine said private firms have incentive to help, given the profits they are reaping from space-based global positioning services, satellite TV and internet, and lucrative potential industries, such as mining. “The technologies that are coming from commercial industry, whether it’s reusable rockets, the miniaturization of electronics, these capabilities are getting us more access to space at a lesser cost than ever before,” he said.

NASA’s outlay, of approximately $20 billion a year, is equivalent to one-half of 1 percent of the federal budget. That contrasts with the 5 percent of the budget dedicated to it during the 1960s space race. No one expects a similar dedication of public funds in the future.

In his previous job, as the Republican representative from Tulsa, Oklahoma, Bridenstine had taken an interest in refocusing NASA on deep space exploration and incentivizing more private sector involvement. He proposed a sweeping “American Space Renaissance Act” that had sought to strengthen the involvement of other agencies — and other funding streams — in space, like the Federal Aviation Administration, and especially the Defense Department. He’d pushed for government agencies to fill more of their needs related to space by contracting with private companies, and for NASA to focus on Mars.

His confirmation, by a 50-49 vote, was controversial not so much because of this, but because Democrats worry that NASA will now forgo its efforts to track climatic changes on Earth, a shift many Republicans support.

Bridenstine said Trump is committed to NASA’s climate research and Bridenstine supported it as a congressman because of its importance in predicting the tornadoes that afflict Oklahoma.

[Q&A: NASA Administrator Jim Bridenstine]

When the House Science, Space and Technology Committee voted on a new authorization bill for NASA by its space subcommittee chairman, Brian Babin of Texas, in April, it adopted an amendment by Colorado Democrat Ed Perlmutter keeping Earth science funding steady. The full committee then approved the bill on a bipartisan basis. In keeping with the views of Cruz and Bridenstine, it directs NASA “to the greatest extent practicable” to “prioritize the acquisition and use of space products provided by a United States commercial provider or through a public-private partnership.”

That same month the House passed Smith’s bill, the American Space Commerce Free Enterprise Act, to clear hurdles to commercial space activity by adopting a “presumption of approval” and by tasking the Commerce Department’s Office of Space Commerce with all regulatory authority. The bill says that if regulatory decisions aren’t made in a timely way, companies will be able to move ahead with their plans. It wasn’t controversial, passing on a voice vote.

And it follows enactment, three years ago, of the U.S. Commercial Space Launch Competitiveness Act, which also aimed to make it easier for private businesses to pursue opportunities in space. That law bars regulators from adopting new rules until 2023 and offers commercial space launch companies like Northrop Grumman Innovation Systems, SpaceX and United Launch Alliance help for another seven years in insuring themselves for any damage they cause to third parties.

It most famously permits U.S. companies to mine asteroids, despite language in the 1967 Outer Space Treaty that bars “national appropriation” of space resources “by claim of sovereignty, by means of use or occupation, or by any other means.” Firms like Redmond, Washington-based Planetary Resources envision mining precious metals in space.

NASA is, of course, relying heavily on private firms. Orbital ATK, now part of Northrop Grumman, and SpaceX built the vehicles that transport cargo to the International Space Station. Lockheed Martin is the primary contractor on Orion, NASA’s eventual deep space vehicle. Northrop Grumman is building the James Webb telescope, which will replace the Hubble and give astronomers a better view of planets beyond our solar system.

Musk’s mission

But what remains to be seen is if private firms can find business models that go beyond government contracting.

Elon Musk, the founder of SpaceX, is the most enthusiastic. Two years ago, he said he’d put a person on Mars by 2024. At the Humans to Mars Summit, Joshua Brost, the company’s senior director of government business development, said Musk was sticking with the goal, even as it was merely “aspirational.”

“We’re trying to get it to the point where humanity can be an interplanetary species,” he said, adding that Musk didn’t plan to send just one or two people to Mars’ surface but “hundreds, then thousands, and eventually millions of people living and working in space, on Mars.”

This is clearly part of a strategy to motivate engineers to find the sort of breakthroughs that Smith sees as essential. “If you tell someone that something is going to happen in 20 years, 20 years is never,” Brost said. “Fifteen years is far enough away that it’s hard to even imagine that as an individual and be really motivated about it.”

But where exactly Musk sees a profit is a mystery.

And making money in space, absent the government as a client, seems a long way off, judging from the results of a 2017 study by the Institute for Defense Analyses Science and Technology Policy Institute, a government-sponsored group.

It examined whether private companies could make use of a commercial space station without government subsidies, highlighting a range of potential businesses, from space tourism to satellite support to manufacturing and research and development. It found that they could not. In fact, researchers found that under the most optimistic scenarios a private space station could bring in only about half of the more than $2 billion a year it would cost to operate.

That conclusion buttresses Cruz’s case that the government cannot cut funding for the space station, in which it has already invested close to $100 billion, and hope the private sector will take over.

Even looking at a station significantly smaller than the International Space Station, which is about the size of a football field, the researchers found that a profitable enterprise was a long way off. Venture capitalists they interviewed said they’d be reluctant to front money for a commercial station given how far away profitability would likely be.

Putting a human being on Mars presents equally mind-boggling financial challenges. A 2014 National Academy of Sciences study, requested by Congress, found that absent a significant increase in NASA’s budget, a Mars landing was folly. “To continue on the present course … is to invite failure, disillusionment and the loss of the long-standing international perception that human spaceflight is something the United States does best,” the researchers found.

Even Babin, chairman of the House space subcommittee, said while he supports a Mars mission, he doesn’t like the idea of setting a specific date. “I think that ignores the truism that there is a lot of stuff that we have to get under our belt first,” he said. “There’s a considerable amount of technology and advanced research and development that is going to have to happen before such a mission is going to be possible.”

For his part, Bridenstine called 2033 “an objective,” but he added a caveat: “It’s visionary.”

Outside groups that support space exploration are pessimistic. Casey Dreier, direct of space policy at the Planetary Society, the nonprofit group headed by Bill Nye, said he’d take the idea of a Mars mission seriously if “NASA and the broader space community were aligned around a clear goal with clear ways to evaluate progress toward that goal.” Instead, he said, “We have none of that right now. We’re spinning our wheels. This is not a serious effort.”

Moon launch pad

At the Humans to Mars summit, experts took heart that the NASA budget has grown more rapidly than the National Academy of Sciences expected in 2014. Torrey Radcliffe, who worked on the academy report and is the chief technologist for civil space systems at the Aerospace Corporation, a California firm that conducts research for NASA and other agencies, said that if Congress were to boost NASA’s budget at twice the rate of inflation, a mission to Mars might be possible in the late 2030s or early 2040s, provided it used the moon as a launching pad.

This approach, rejected by the Obama administration, is back in vogue. Trump has embraced it, the idea being that astronauts could land on the moon and use it as a staging area for a Mars mission. They’d test new technologies, build a base and, most important, mine the water to create rocket fuel to propel them further into space. Not having to carry all the fuel they need from Earth greatly enhances the prospects of a successful Mars mission.

Smith and Babin are proponents of the idea, but also see huge risks to the taxpayer in NASA’s plans.

“The bottom line is that NASA has had significant challenges managing several of its programs,” said Babin. “NASA has to be held accountable. We in Congress are responsible to the taxpayer.”

The authorization bill the House Science Committee passed in April would put contractors who don’t deliver what they promise on a watch list, underscoring the difficulty Congress has had in holding them accountable. It’s almost impossible to pull the plug on projects in which billions have already been invested. President Barack Obama’s decision to kill off the Constellation program, an ambitious plan to get back to the moon, in 2010 after spending $10 billion on it, remains controversial.

Among current projects, the James Webb telescope, initially projected to cost as little as $1 billion and to launch as early as 2007, is way over budget and behind schedule. NASA in March said it would not launch until 2020 and that it would likely bust its budget, which was revised upward in 2011 to $8.8 billion.

In tests, the telescope’s sun shield, necessary to keep it cool, is taking too long to deploy and the cables that hold it in place aren’t working properly, raising concern that the shield could rip. Once the telescope launches, it will be very difficult, if not impossible, to repair any damage that occurs to it.

The commercial crew program, which began in 2010 to develop a vehicle to replace the Space Shuttle, is on a fixed budget but it too has faced long delays. NASA contracted with two firms, SpaceX and Boeing, to build separate vehicles as a way of hedging its bets and inspiring competition. By all accounts, both firms are making progress but the initial projection of 2017 launches has now slipped to the end of 2019 or even 2020.

In the meantime, NASA is paying Russia, a partner in the space station, more than $80 million every time it transports a U.S. astronaut there. The current contract with Russia ends at the end of next year, putting more pressure on the contractors to deliver. NASA is considering keeping astronauts at the station for longer than the typical six months as a way of reducing the need for flights to and from.

Bridenstine is repentant but also defends his agency: “We do development. We don’t do production. When you think about what the Defense Department does — they make one fighter aircraft and they replicate it over and over and over again — most of what we do is first-time capability and I think that’s an important distinction.”

A big reason for the delays is NASA’s insistence that vehicles carrying crew be very safe. The agency has set a standard for safety that is three times tougher than that for the Space Shuttle. At the end of the shuttle program, NASA estimated a risk to the crew’s lives at 1 in 90 missions. It wants the risk to the crew in the Boeing and SpaceX vehicles to be 1 in 270.

The risk to the crew is also the main technological challenge holding up a Mars mission. It would require astronauts to travel for as long as three years, an unprecedented amount of time to remain in space. By contrast, a trip to the space station takes a day, the moon less than a week.

Neither trip exposes astronauts to the sort of radiation they’d experience on a Mars voyage. Without protection, cosmic rays would damage their organs, threaten their brain function and put them at much greater risk of cancer.

The confinement in a small ship would lead to bone and muscle loss. That and the absence of the comforts of home — family, friends, fresh food and fresh air — could cause psychological problems. The lack of gravity causes fluid to shift in the body, accumulating in the brain, threatening hearing and vision loss.

NASA can manage these threats within Earth’s orbit, or in the spacious environment of the International Space Station, but as yet no solutions exist for astronauts traveling in a small ship in deep space.

“We don’t have the technology to send astronauts and not kill them,” said Clive R. Neal, a professor in the Department of Civil and Environmental Engineering and Earth Sciences at the University of Notre Dame.

That’s not to say NASA isn’t looking at them. “We know what we need to know but we don’t have all the answers,” said Mark Kelly, an astronaut who visited the International Space Station four times. Success or failure, he said, is a political issue. “We have to decide if it’s what we want to do and give NASA the resources to do it.”