A Home Away from Home

Someday, many people hope, humans will travel to Mars. The U.S. National Aeronautics & Space Administration (NASA) has plans for a mission to the planet in the 2030s, and entrepreneur Elon Musk says his SpaceX company can do it by 2024. If people succeed in setting up an outpost on Mars, they’ll need to build someplace for astronauts to live, sleep, and work. But hauling building materials across 225 million km of spacethe average distance between Earth and Mars would be a nightmare. It costs about $4,000 to launch a kilogram of material to low Earth orbit, and many times that amount to send it to Mars, so trying to ship tons of concrete would be financially ruinous and logistically very difficult, says Robert P. Mueller, senior technologist for advanced products development at the Swamp Works, an innovation laboratory he cofounded at NASA’s Kennedy Space Center. Any new inhabitants of the red planet will have to do what colonists have always done: Use the materials they have at hand to build shelters. On Mars, that material is regolith, a dusty, pulverized rock layer deposited throughout the solar system over billions of years by asteroid collisions. “It’s a ready-made construction materialcrushed rock sitting on the surface of the planet,” Mueller says. “All we have to do is develop the technology to use that aggregate that already exists and somehow bind that aggregate together.” That’s the goal of teams trying a variety of approaches to turn the stuff into a substance suitable for three-dimensional (3-D) printing. This manufacturing technique, which creates objects by depositing material layer upon layer, would allow NASA to send robots ahead of any colonists to prebuild habitats. Three-dimensional printing can also create structures with shapes and thinness that might not be possible with standard concrete pouring techniques. Part of the challenge is developing a building material that is amenable to 3-D printingin terms of consistency and hardening timeand creates stable structures. A handful of researchers have already shown that they can probably turn the red dirt of Mars into sturdy construction materials. Some have been spurred by NASA’s 3D-Printed Habitat Challenge, which Mueller helped to launch. The challenge offers $2.5 million in prizes to encourage industry and academic scientists to explore ways to build on Mars. The first phase sought new architectural concepts that take advantage of 3-D printing, and the second phase delivered prizes in August to five teams who printed beams and other shapes out of a regolith simulant. A third phase just began.