A Shire on Mars

As the clock wound down on NASA’s 3D-Printed Habitat Challenge last May, the fate of AI SpaceFactory, a leading firm for multi-planetary architecture, fell in the hands of a lanky industrial robot. After four years and a few elimination rounds, the New York-based team was head-to-head with researchers from Pennsylvania State University, vying for a top prize of $500,000 and a chance to inspire future Martian settlements.

Nearly ten hours into the last day of competition, hundreds watched as AI Spacefactory’s robotic arm dangled a circular skylight over a mud-colored, vase-like structure, lowering it slowly as if placing the roof on a house of cards. For a few seconds, the skylight seemed secure. Observers began to cheer. Then, with little warning, the skylight slipped and fell through an opening in the roof, crashing to the floor with a hollow thud.

Such a mishap would be devastating for a mission on Mars. But AI SpaceFactory’s 3D-printed structure, Marsha, still impressed the NASA judges enough to earn the top prize. The firm now hopes Marsha will serve as a prototype for the first human habitats on the Red Planet.

Designed like an egg, Marsha’s form is both aesthetically svelte and extraterrestrially efficient. “On Mars the exterior air is very thin, just one percent of the Earth’s atmosphere,” explains David Malott, CEO and co-founder of AI SpaceFactory, who oversaw the building’s design. As a result, Marsha would have to be pressurized on the inside to match Earth’s atmosphere; this pressure difference would cause the structure to want to pop like a balloon. The egg shape, says Malott, is meant to help keep the building from exploding.

Inside, Marsha’s amenities wouldn’t be much different from those inside a small townhouse, with a few sciencey exceptions. The habitat features four floors, including a kitchen, exercise room, sleep pods and a garden where astronauts might grow herbs and leafy greens. A wet and dry lab offers space for experimentation, while a docking port on the ground floor provides easy access to a rover. The structure’s outer layer of basalt fiber, to be sourced from Martian regolith or bioplastic recycled from astronaut trash, would be designed to protect inhabitants from cosmic rays and micrometeoroids. Save a rusty dust storm, astronauts may actually forget they’re on the Red Planet.

But not all proposed Martian habitats share Marsha’s sleek design. Some resemble ant hills more than eggs and employ cruder methods than 3D printing to make use of Martian materials.

“Many of the concepts I’ve seen look like mounds of regolith piled on top of habitats,” says Metzger, our planetary science expert from before. For example, inflatable modules would be used as the habitat’s inner core, connected by a series of tubes that would serve as tunnels between main chambers. From above, the product would “look like curvy structures,” says Metzger, “like something out of The Hobbit.”

Source: NASA/JPL-Caltech/University of Guelph

Each design method — printing and piling — has its own list of merits and setbacks. While piling regolith may be quicker and less prone to printer error, it would still require humans to ship the inflatable inner habitats, which would come at a cost. Piled regolith would also have to be secured in some way, perhaps through microwaving, compacting, or the addition of polymers. For Edmundson, piling is a temporary solution. “Once we get into the sustainability portion of exploration, we’re going to need to start building our own habitats,” she says.

3D printing offers more of the in-situ experience, but it can be resource intensive. What’s more, 3D printing requires a precise mixture of specific elements, which will have to be as close as possible in composition to the simulated regolith used in experiments on Earth. There’s little margin for error when you’re millions of miles away, and regolith minerality varies depending on its source.

Research with regolith simulants is vital for the safety of future missions, says Edmundson. “That’s part of the reason why I think I have job security. People are going to have to know what the differences are between the planet’s surface itself and the simulants they’re using [on Earth].” Today there are about 10 Martian regolith simulants and a few dozen simulants for the Moon. “But that number is probably going to change pretty quickly,” she adds, “now that we’re planning to go back.”

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