It's easy to say "We're going to Mars." The next president will find it hard to do.

Given how far NASA lies down the food chain of White House priorities, it's always welcome when a president engages in a discussion of space policy. And that's what President Obama did on Tuesday when he authored an op-ed that appeared on CNN.com and called for America to take a "giant leap" by sending humans to Mars in the 2030s.

There wasn't much new in the president's call to action, as it wasn't all that different from a space policy speech he delivered in 2010. The president said then at Kennedy Space Center, "by the mid-2030s, I believe we can send humans to orbit Mars and return them safely to Earth. And a landing on Mars will follow." The similarity of his words, spoken six years apart, gives us a chance to judge his administration's space policy, and the verdict is pretty straightforward: Obama has set NASA and the United States on a course to Mars.

It is an easy thing to say "We are going to Mars," however, and a far more difficult thing to do it. In reality, Obama has put NASA on an unsustainable pathway to Mars given NASA's current resources and approach, and he is leaving the hard work of actually getting to Mars to his successors. In other words, right now, NASA is on a journey to Mars in name only.

Obama sought change early on

Back in 2009, before Obama first articulated a Mars plan, the president's space advisers recognized that NASA's human exploration programs were in trouble. These confidants included Lori Garver who, although she was installed as deputy administrator of NASA, in reality ran the show. Garver and her leadership team felt that NASA's Apollo-like approach toward human exploration, with big government rockets using chemical propulsion, was no longer affordable. So in early 2010 they rolled out a new kind of budget, one that called for the cancellation of the big-ticket programs to build the Ares I and V rockets, as well as the Orion space capsule.

Instead, Garver and others sought to make space exploration sustainable in the 21st century. NASA would eventually need more powerful rockets, Garver and her allies realized, but they didn't have them back in 2010 when NASA had no immediate plans to go beyond low-Earth orbit. Rather, they felt NASA needed reliable, lower-cost vehicles to replace the space shuttle and faster, more efficient propulsion systems. So they continued the commercial crew program initiated by President George W. Bush to replace the shuttle, and they called for investment into new propulsion technologies that would zip astronauts through the solar system at higher velocity, thereby reducing the risk of health problems due to microgravity. By the end of this decade, when NASA might begin to need big rockets, Obama's advisers believed the private sector—either United Launch Alliance, SpaceX, or someone else—would be ready to build them.

But Congress hated this plan. It would further diminish the roles of the ten NASA field centers and cede more power and money to upstart companies like SpaceX. Congress fought back and forced the president to accede to building the costly Space Launch System rocket as well as continuing development of the Orion space capsule. Congress got its big, Apollo-like space program back.

At this point, in 2010 and 2011, Obama largely retreated from space policy. His advisers battled for commercial crew and Earth science funding with some degree of efficacy, but they largely abandoned efforts at game-changing propulsion and other space technology investments. Congress, meanwhile, assumed control of the nation's human exploration program. By 2013, Garver had left the agency and, feeling more free to speak, characterized Congress' insistence on government-developed rockets as a "socialist" approach toward exploration.

Ars has delved deeply into the flaws with NASA's current approach to Mars exploration, including publication of this feature-length article, Make Mars Great Again. Given these problems and where the space program is today, there are arguably two paths forward to a human Mars exploration program that the next presidential administration could take. That is, if a president really wants humans to walk on Mars in the 2030s, here is how she or he might get there from here. Unfortunately neither path is politically easy, nor likely to be realized.

Hard choice no. 1: Double the budget

The first approach is simple: double NASA's exploration budget. The space agency presently spends a little more than $4 billion annually to develop the Space Launch System rocket, Orion spacecraft, and related ground systems. But if Washington was really serious about sending humans to Mars in the 2030s, it would spend double that to research habitation modules for the trip to Mars, landing systems, surface habitats, surface power systems, redundant life support systems in deep space, radiation mitigation, and so much more. Instead, NASA's costly rocket and spacecraft eat up so much of the budget there is precious little money left over for anything else. When pressed about this, NASA doesn't have good answers.

The next president could find those funds in several places. Most simply, she or he could double the space agency's exploration budget by adding $4 billion to NASA's bottom line. But this seems highly unlikely given that there is no national imperative to explore Mars. It is an aspirational goal, to be sure, but it doesn't advance the cause of beating ISIS or addressing rising health care costs. Another alternative would be to take this money from the International Space Station program, which receives about $4 billion from NASA's annual budget to support the station and deliver supplies and astronauts to the orbiting laboratory. However, NASA has firm commitments to its international partners to fly the station through 2024, and the organization wants to continue the program through 2029.

Absent an infusion of funds, NASA appears likely to plod along and try to make incremental steps toward Mars in the 2020s and 2030s. A blue-ribbon review panel in 2014, led by the National Academies, found in its "Pathways to Exploration" report that such an approach was both risky and unlikely to succeed for a number of reasons, particularly because it would be so hard to sustain such a long-range vision across multiple presidential administrations. Are the next two or three presidents really going to be excited about sending humans to cislunar space (near the Moon) while China is landing humans there?

In short, the only way to have a real Mars program using the SLS rocket and Orion spacecraft is to find $4 billion more or so annually for NASA. Good luck with that, President Clinton or Trump.

An even harder choice

There is another way, one that is similar to what Obama tried (and failed) to do in 2010. That is ending NASA's own programs to directly oversee design and construction of launch vehicles. Since the late 1950s, NASA has had an "in the knickers" approach toward managing the development of its rockets and spacecraft. It has done so through cost-plus contracts, which enables NASA deep oversight into every facet of vehicle development. This approach affords NASA and its very smart engineers total control over design, but it is also costly and time-consuming. (For example, the agency has spent more $10 billion over 16 years developing the Orion spacecraft, and this vehicle is still likely seven years from launching a human into space).

The alternative is a fixed-cost contract. This is the approach NASA has taken toward commercial crew and cargo supply missions to the space station. A vendor, such as SpaceX, Orbital ATK, or Boeing, agrees to provide a service for which NASA agrees to pay a fixed price and no more. Critics of NASA's SLS rocket have suggested that NASA could take a similar approach toward heavy lift rockets. Instead of spending an estimated $3 billion per launch of the SLS rocket, for example, it might buy a Falcon Heavy launch from SpaceX for less than $300 million. This argument has been bolstered by a recent entrant into the launch industry, Blue Origin. Jeff Bezos' company says its heavy lift rocket New Glenn should begin flying by the end of this decade. As a bonus, both private launch vehicles are potentially reusable (the SLS is not).

However the next president, if he or she would like to consider this option, must contend with Congress like Obama did (and retreated from) in 2010. For a lot of reasons outlined in this article on the Space Launch System, Congress supports the cost-plus approach when it comes to large, heavy lift rockets. And for many members of Congress it appears that building such hardware, rather than doing meaningful stuff in space, is the real goal. For example, there is little evidence Congress is really interested in the exploration of Mars as it cuts funding for critical technologies simply to pile more money into rocket building.

To that end Congress has repeatedly warned the next president not to mess with the SLS rocket or Orion spacecraft, holding these vehicles up as the crown jewels of America's future exploration program. Therefore, forcing NASA to wean itself off SLS would require an immense amount of political capital neither a President Clinton nor Trump would be likely to expend.

Nevertheless, the option will exist for the next president to buy a Mars exploration program off the shelf. In a much ballyhooed speech last month in Guadalajara, SpaceX CEO Elon Musk laid out his vision for colonizing Mars in the 2020s. For just $10 billion, Musk said, his company could develop the Interplanetary Transport System to send the first humans to Mars, not as visitors but as colonists. Even if Musk's cost estimate is far too low, consider the following: between now and 2023, when NASA may finally fly its first crewed mission of SLS and Orion, the agency will spend an additional $25 to $30 billion on SLS and Orion development.
On Tuesday, SpaceX seized upon President Obama's call in his op-ed for NASA to work closely with private partners on its Mars exploration program. "SpaceX was founded with the ultimate goal of helping make humans a multi-planetary species," a company spokesman, Phil Larson, told Ars. "As Elon said at his recent talk, it will take a combination of public and private efforts to build a self-sustaining city on Mars. It's exciting to see President Obama advocate for the next frontier in human space flight, and we look forward to participating in the journey."

Musk's plan for Mars might be a little crazy, but essentially his company could offer NASA a plan to send humans to Mars for roughly the same cost it is now taking the agency to repeat a lunar flyby mission from half a century ago. That is the allure of privatizing the US launch industry.

So what will happen?

A number of key members of Congress view Musk with a healthy amount of skepticism (some, like Alabama's Richard Shelby, have outright hostility toward Musk. The SpaceX founder's ambitions threaten the Marshall Space Flight Center in Huntsville, Alabama). It is hard to see Congress folding on SLS and Orion. It is equally hard to see a new administration trying to fight that battle.

What seems more likely is that the next president, especially if it is Hillary Clinton, re-calibrates NASA's expectations. Any independent review of NASA's journey to Mars, including that espoused by President Obama on Tuesday, will almost certainly find it to be under-funded and behind schedule. That may very well lead a president to conclude that while Mars represents a very worthy horizon goal, NASA should instead shoot for a more reasonable interim target—human outposts on the Moon in concert with Europe and other international partners.

It is, after all, no coincidence that every piece of hardware and most of the research that NASA has done so far with respect to its "Journey to Mars" is destination agnostic. That is, should the next president desire to go to the Moon first before Mars, few resources will have been wasted.

Take, for example, what the chief architect of NASA's human exploration program during the Obama presidency, Bill Gerstenmaier, had to say in March when asked about destinations. “We need to be careful that we’re not really destination driven,” he replied. “It’s called a Journey to Mars, and I really stress the journey aspect. The fact that Mars is hard is good for us. It’s forcing us to look at new ways of doing business that we haven’t done before. It’s forcing us to look at new technology. It’s exactly the right thing that this agency ought to be doing. But I think we should be careful that we don’t stress so much on the destination.”

Gerstenmaier stands ready if the next president wants to pivot toward the Moon. And as fine as Obama's words were in his op-ed in calling for humans to Mars in the 2030s, he will be out of office in two months. His successor will be free to fly elsewhere—as long as the dollars continue to fly into SLS and Orion.