What happens when you send a robot probe to another planet — or asteroid or comet — and it breaks? Space agencies have been pondering this problem for years, and one idea is obviously to fabricate a new part on site.
Since a lot of the celestial bodies we're exploring these days are freezing cold, a group of scientists recently had idea that is — pun very much intended — pretty cool: Why not make the probe out of ice? That way, if any part breaks, you could make a replacement part out of ice in the ambient environment!
They wrote up a paper about it here, with some fascinating findings. One is that when it come to making parts, it was easiest to drill or cut the ice, then plop the electrical components — like motors or actuators — into the holes, where they'd freeze into place. They also tried to use flame (a blowtorch) to shape the ice, but the runoff water goes places you don't want.
Another finding: Robot wheels made of ice tend to melt during the friction that inheres when wheels do work. When they tested the robot on a rubbery surface in freezing cold room, they got some slippage, so they had to add more weight to compensate. Ultimately, though, IceBot was able to roll up an incline of 2.5 degrees, and could nudge light obstacles out of its way.
I am thoroughly charmed by this concept! It also has some potential ecological benefits, too, I'd imagine. If a big chunk of your bot is made from frozen water gathered on its ice planet, when you're done with the bot you can let the water return to its natural state, hopefully minimizing the ecological impact of a probe.
The possibilities for self-repair also enticing, as one of the project's leaders notes in this Q&A at IEEE Spectrum:
When I think of an arctic (or planetary) exploration robot that incorporates self-modification or repair capabilities I envision a system with two types of robots—the first explores the environment and collects materials needed to perform self-augmentation or repair, and the second is some sort of manipulator/manufacturing system. We can envision the exploration class of robot returning to a centralized location with a request for a plow or some other augmentation and the manufacturing system will be able to attach the augmentation directly to the robot. Similarly with repair—if, for example, a robot recognizes a crack, the manipulator would be able to patch the crack using an ice band-aid of sorts, sealing the crack and preventing it from propagating further.