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Throughout history, when pioneers set out across uncharted territory to settle in distant lands, they carried with them only the essentials: tools, seeds and clothing. Anything else would have to come from their new environment.

So they built shelter from local timber, rocks and sod; foraged for food and cultivated the soil beneath their feet; and fabricated tools from whatever they could scrounge up. It was difficult, but ultimately the successful ones made everything they needed to survive.

Something similar will take place when humanity leaves Earth for destinations such as the moon and Mars—although astronauts will face even greater challenges than, for example, the Vikings did when they reached Greenland and Newfoundland. Not only will the astronauts have limited supplies and the need to live off the land; they won't even be able to breathe the air.

Instead of axes and plows, however, today's space pioneers will bring 3D printers. As who is developing technologies to extend the human presence beyond Earth, I focus my work and research on these remarkable machines.

3D printers will make the tools, structures and habitats space pioneers need to survive in a hostile alien environment. They will enable long-term human presence on the moon and Mars.

From hammers to habitats

On Earth, 3D printing can , from replacement hips to hammers to homes. These devices take raw materials, such as plastic, concrete or metal, and deposit it on a computerized programmed path to build a part. It's often called "," because you keep adding material to make the part, rather than removing material, as is done in conventional machining.

Already, 3D printing in space is underway. On the , astronauts use 3D printers , such as . Depending on the part, printing time can take from around 30 minutes to several hours.

For now, the print materials are mostly hauled up from Earth. But NASA has also begun recycling some of those materials, such as waste plastic, to make new parts with , an advanced 3D printer installed in 2019.

Manufacturing in space

You may be wondering why space explorers can't simply bring everything they need with them. After all, that's how the decades ago—by hauling tons of prefabricated components from Earth.

But that's impractical for building habitats on other worlds. Launching materials into space is incredibly expensive. Right now, every pound launched aboard a rocket just to get to low Earth orbit . To get materials to the moon, NASA estimates the initial cost at around .

Still, manufacturing things in space is a challenge. In the microgravity of space, or the reduced gravity of the moon or Mars, materials behave . Decrease or remove gravity, and materials cool and recrystallize differently. The moon has one-sixth the gravity of Earth; Mars, about two-fifths. Engineers and scientists are working now to adapt 3D printers to function in these conditions.

Using otherworldly soil

On alien worlds, rather than plastic or metal, 3D printers will use the . But finding the right raw materials is not easy. Habitats on the moon and Mars must protect astronauts from the lack of air, extreme temperatures, micrometeorite impacts and radiation.

, the fine, dusty, sandlike particles that cover both the lunar and Martian surfaces, could be a primary ingredient to make these dwellings. Think of the regolith on both worlds as alien dirt—unlike Earth soil, it contains few nutrients, and as far as we know, no living organisms. But it might be a good raw material for 3D printing.

My colleagues began researching this possibility by first examining how regular . I am now joining them to develop techniques for turning regolith into a printable material and to .

But obtaining otherworldly regolith is a problem. The regolith samples in the 1960s and 70s are precious, difficult if not impossible to access for research purposes. So scientists are using to test ideas. Actual regolith may react quite differently than our simulants. We just don't know.

What's more, the regolith on the moon is . Martian regolith contains iron oxide –that's what gives it a reddish color—but moon regolith is mostly ; it's much finer and more angular. Researchers will need to learn how to use both types in a 3D printer.

Applications on Earth

NASA's Moon-to-Mars Planetary Autonomous Construction Technology program, , is advancing the technology needed to print these habitats on alien worlds.

Among the approaches scientists are now exploring: a made in part from surface ice; at high temperatures, and then using molds to form it while it's a liquid; and , which means heating the regolith with concentrated sunlight, or to fuse particles together without the need for binders.

Along those lines, my colleagues and I developed a Martian concrete we call MarsCrete, a material we used to 3D-print a .

Then, in May 2019, using another type of special concrete, we 3D-printed a that could support everything astronauts would need for long-term survival, including living, sleeping, research and food-production modules.

That prototype showcased the potential, and the challenges, of building housing on the red planet. But many of these technologies will .

In the same way astronauts will make sustainable products from natural resources, homebuilders from binders and aggregates found locally, and maybe even . Engineers are already adapting the techniques that could print Martian habitats to address housing shortages here at home. Indeed, 3D-printed homes are .

Meanwhile, the move continues toward establishing a human presence outside the Earth. , now scheduled for liftoff in 2027, will be the first human landing since 1972. A NASA trip to Mars could happen .

But wherever people go, and whenever they get there, I'm certain that 3D printers will be one of the primary tools to let human beings live off alien land.

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