With the Donald Trump administration infrastructure building has become all the rage again. Trump has promised to spend a lot of money fixing roads and bridges, upgrading air ports as well as canals and sea ports. The project will enhance America’s ability to move people and goods across the country and around the world. Not coincidentally the building program would employ tens of thousands of people.

Donald Trump might want to pay attention to Space infrastructure while he is in the mood to spend some money. What is space infrastructure, and why is it important?

Space infrastructure ensures the smooth and inexpensive movement of people and goods in space, for the purpose of this discussion between Earth, low-Earth orbit, cis-lunar space, and the lunar surface.

Currently, space infrastructure consists of expendable rockets that propel spacecraft to destinations in space, such as the International Space Station, geosynchronous orbit, or various destinations throughout the solar system. Currently space infrastructure is expensive to use, limiting what humans can do in space.

Clearly, if people on Earth propose to fully realize the economic potential of space, from lunar and asteroid mining to space tourism and manufacturing, space travel has to get a lot cheaper.

Just as building roads and railroads on Earth sparked economic activity, building the road to space would do the same beyond the home planet.

Two keys exist for creating an Earth-moon infrastructure.

The first key is reusable rockets. Since the beginning of the space age, space engineers have realized that throwing away a rocket every time it is used will keep space travel expensive.

The space shuttle was an early attempt to address the reusability problem, but it required too long a turn-around time between flights to be cost effective. SpaceX, Blue Origin, and United Launch Alliance are working on reusable rockets. NASA’s super-heavy-lift rocket, the Space Launch System, has high capacity but will be expensive to operate, as it is not reusable.

The second key is lunar water. Scientists have known for decades that deposits of water ice reside in shadowed craters at the lunar poles. Since water consists of hydrogen and oxygen, the components of rocket fuel, the moon has become a giant fueling station in the sky. The ice can also be used to support a lunar settlement.

How would President Trump develop a space infrastructure?

A few years ago, Paul Spudis of the Lunar and Planetary Institute and Tony Lavoie at NASA;s Marshall Spaceflight Center developed a a plan for what they call an “affordable lunar base” but would tie the Earth and moon together in a transportation infrastructure. The idea is to send out robots to prospect for lunar ice and refine it into rocket fuel.

The fuel would be transported to fuel depots, either in lunar orbit or at one of the Lagrangian points, where the gravities of the Earth And Moon cancel each other out. Other robots would create a lunar base with inflatable modules and use local materials and 3D printing technology.

Currently, spacecraft must take all of the fuel they require to conduct a voyage to low Earth orbit, the moon, or some destination beyond, such as Mars. With a refueling stop, spacecraft will only need to take enough fuel to reach the depot. They will top off and then continue on to their destination.

With the cost of space travel becoming cheaper, entrepreneurs who dream of doing business beyond the confines of Earth will be more likely to do so.

Even space agencies such as NASA will be able to do more with less. An MIT study suggested that refueling with lunar rocket fuel would reduce the cost and complexity of the Journey to Mars.

Donald Trump likes to boast about being a builder. A space infrastructure would be something to build that would change the world and make Trump’s presidency one of the most consequential in history.