MIT’s newest 3D printer isn’t the sort you’d keep on your desk. With a long robotic arm and caterpillar treads, it’s designed to work in the construction sites of the future. To prove its mettle, it recently printed the biggest robot-built structure ever — in just over 13 hours. The robot is still at the proof-of-concept stage, but the MIT team that created it hopes that automating construction will cut costs and boost worker safety, according to a paper published this week in the journal Science Robotics. One day, it might even help humans colonize space, autonomously building houses on other planets before human settlers arrive.

This isn’t the first time engineers have attempted to automate construction. Nearly 100 years ago, Thomas Edison patented a system that would create concrete structures in a single pour. It didn’t work. Since then, we’ve tried tiny aerial drones and giant robotic arms, a brick-laying robot, and one that 3D-prints concrete. But so far, construction bots have mostly been used in labs and demonstrations. They haven’t broken into mainstream construction because people are still figuring out out how to make an automated construction robot that’s actually useful in the real world.

So to create their ideal construction robot, the authors came up with a number of criteria. The robot had to be able to use materials found on the construction site — and possibly scavenged from the environment, like ice or dirt. This would make it useful in remote areas, and even on other planets, like Mars. The robot should also be able to move on its own. Otherwise, people would have to move it, which could be dangerous. But it probably shouldn’t fly. Flying robots are too likely to be buffeted by wind or rain, and if they suddenly stop working, they wouldn’t just stall — they’d plummet to the ground. The robot would need a nice long arm to lift heavy things, stretch across big distances, and perform finely detailed tasks. And, it had to be able to integrate into existing construction practices and use existing materials.

No existing construction robots offered all this, so the MIT team decided to make their own. Called the Digital Construction Platform, their robot is basically a giant hydraulic arm that moves around on caterpillar treads. On the end of the arm is a one-fingered hand attached, which can move more freely and is responsible for fine-motor tasks. It can be fitted with a range of different tools, including a foam insulation gun, a welding attachment, a “thermoplastic extruder” that squirts out melted plastic, a glorified squirt gun, and even a simple bucket.

The original robot chassis they were using came with a diesel engine. But to make the bot more self-sufficient, the team equipped it with solar panels and battery packs to power an electrical drive system. Weighing in at more than 8,100 pounds, the entire setup costs about a quarter million dollars.

Next, they had to make sure it worked. The MIT team stuck a foam insulation gun in the robot’s “hand” and drove the whole thing out to an empty lot in Mountain View, California. Over the next two days, the robot built a sort of open-topped igloo using expanding foam that sets in just 30 seconds. The final structure was 12 feet high with a diameter of nearly 50 feet. It’s not the most polished of dwellings, but it’d be better than nothing for humans exploring another planet.

If this had been an actual construction project, that foam would have been used as a mold for concrete. But, the research team didn’t actually pour the concrete — presumably because the lot owners didn’t want a semi-permanent, giant concrete circle on their land. Experts say there’s still a lot of room for improvement with the platform, but others are more excited about putting the new robot to work. “The team has already been getting calls from NASA, the US military, Google, and one guy who saw the dome and made a special request for a famous client: an underground basketball court,” writes Matthew Hutson for Science.

There are some big challenges for the team, though. Given how quickly construction sites and environmental conditions can change, the robot will need to be able to navigate better than it does now, and understand and react to where it is in space, and what’s around it. This will mean equipping the robot with proximity sensors, to look out for other machinery or — most importantly — humans. After all, humans will still need to be around — robots aren’t smart enough yet to fully take over yet.

Eventually, the MIT researchers hope that automating construction and 3D-printing buildings will keep construction workers safer, cut costs, and make the timing of construction projects more predictable. There’s a lot to do before that happens, though. Even MIT’s new construction bot faced delays when dew settled on a layer of foam, and warped it. Looks like construction jobs are safe — for now.

Update April 27th, 11:45AM ET: The story has been updated with additional context and quotes.