Yesterday President Trump signed Space Policy Directive 1 (SPD1), an executive order that will shape NASAs priorities going forward. Essentially the directive states that NASA’s primary mission is human space exploration, with a specific goal of returning to the moon.

The Directive is the result of recommendations made by the National Space Council (NSC) – a council of experts that advises the executive branch on all matters dealing with space. According to NASA, in June of this year:

President Trump has signed an executive order reestablishing the National Space Council. The council existed previously from 1989-1993, and a version of it also existed as the National Aeronautics and Space Council from 1958-1973. As such, the council has guided NASA from our earliest days and can help us achieve the many ambitious milestones we are striving for today.

The NSC recommended to the White House that NASA’s priority should be the Moon, and SPD1 is the result of that recommendation.

I think the core vision for SPD1 is solid, and something I have supported for years. Specifically, our human exploration priority should be establishing an Earth-to-Moon infrastructure, including a permanent presence on the moon. We should only set our sights on Mars after we have a stable moon base. There are several reasons for this.

First, colonizing the moon is much easier than Mars. The moon is three days away from Earth, while Mars is 9 or more months. We don’t even have the technology at this point to protect martian astronauts from the radiation they would be exposed to on the trip. Going to Mars is a logistical and technological problem perhaps an order of magnitude more difficult than going to the Moon.

Being close to Earth also means that resupply and rescue missions would be much more feasible. If something goes awry on Mars, good luck to you. Don’t expect help anytime soon. For a moon base, however, we could theoretically have a rocket on standby, something that could launch within a week, and be on the moon in another three days.

All of the main issues we would confront on a Mars colony would also exist on a moon colony, and so once we developed the knowledge and technology to have a self-sustaining base on the moon, we could use that knowledge to then build bases and colonies on Mars. A moon base would need proper shielding, an energy source, and sources of food, water, and oxygen.

We are currently eyeing possible lava tubes as locations for permanent bases on the moon. These are caves carved out by ancient lava. They could be geologically stable locations under ground, which would provide natural shielding from radiation and micrometeors. The same is true on Mars.

So walk before you run. It is likely hubris and folly to set our sights on Mars when the moon is much closer and more feasible.

But further – the moon could be a stepping stone to Mars. A trip to Mars could have two stages. The first is getting to a way station on the moon. This will get you largely out of the gravity well of Earth. You can also optimize ships and other infrastructure for getting from the Earth to the moon, and then have a separate infrastructure for getting from the moon to Mars or elsewhere.

SPD1 mentions a Deep Space Gateway – this is a station that would be in lunar orbit. The Gateway would be the transfer point to Mars and other distant destination in the solar system. NASA describes how this might work:

“This spacecraft would be a reusable vehicle that uses electric and chemical propulsion and would be specifically designed for crewed missions to destinations such as Mars,” agency officials said. “The transport would take crew out to their destination [and] return them back to the gateway, where it can be serviced and sent out again.”

One advantage to this kind of system is that you don’t have to lift all the fuel it takes to get to Mars with you out of Earth’s gravity. You just need the fuel to get to the Moon, and then take a separate ship to Mars. This all comes from the rocket equation – you need enough fuel to carry the fuel to carry the fuel, etc. So making one big trip with all the fuel is inherently inefficient. Any way we can break it up into stages, or refuel along the way, is highly useful.

Ideally we would produce the fuel on the moon, which is entirely possible. NASA is already working on ways to extract oxygen, water, and volatiles from the lunar regolith.

The new directive also has a loser, however. It ends NASA’s goal of sending a mission to an asteroid – the Asteroid Redirect Mission (ARM). This is unfortunate. Asteroids are also a potentially very useful resource. Developing the technology to mine asteroids could have a massive economic impact on our planet. Asteroids could be a source of fuel, water, oxygen, and enough metals to dwarf existing supplies of gold, platinum, and other precious metals.

While I know we can’t do everything, and we need to have priorities, I do lament the missions we must forgo. Of course, I would much rather see just a net increase in our investments in space. I think these are likely to be worthwhile investments which will pay for themselves many times over in the long run.

But there is another aspect to SPD1 that is encouraging – in addition to establishing NASA’s goals, the directive discusses optimizing how NASA will collaborate with the growing private space industry. I am perhaps even more encouraged by the development of private space companies in the last decade than by any NASA directive. Once we cross the line where going to space can be profitable, then space exploration will really take off.

There is, for example, a company called Planetary Resources, Inc. Their goal is to mine the solar system. If they manage to get their hands on one asteroid with platinum group metals, they will potentially net trillions of dollars. That is a big risk, but also a huge potential payoff. We may see a future with space mining corporations more wealthy and powerful than most nations.

I did not see any mention in the coverage of SPD1 of robotic exploration. I presume that NASA will continue this core mission as well. Robots are still the most efficient way to explore space. While I support human exploration and colonization, I recognize that humans are fragile. We are not built for space. Keeping people alive and healthy in space is a major part of the expense of human space travel. I still think it is a worthy endeavor for our species.

But we should ride on the backs of our robotic servants. Robots don’t need food, water, oxygen, or atmospheric pressure, and are much more tolerant of a wide range of temperature and exposure to radiation. If we just want to send a pair of eyes to a location to explore, robots are the way to go. Robots can even pave the way for our travel to new locations, like Mars. Let them do all the hard and dangerous work, and create an infrastructure for us to inhabit.

Overall I think the SPD1 is a good thing. I like that it shifts the focus away from Mars and towards the moon. That puts things in its proper order. I would much rather have a successful moon mission, that establishes a long term lunar presence, then a one-off or failed Mars mission.