At the International Space Station broken parts or tools can be a big deal. It isn't easy or cheap to launch cargo if something goes wrong and a replacement is needed. A 3D printer would allow astronauts to custom build parts as needed without outside help from ground crews and instead of launching individual parts to the ISS, spools of plastic could be sent instead. This would save space and minimize waste.
However, 3D printing in space faces a few unique challenges. Printers designed for use on Earth do not need to account for zero gravity, vibrations, overall size, pressure and temperature fluctuations, and the limited power supply like a printer aboard the ISS would. This posed a unique set of challenges when NASA chose a designer and manufacturer.
Ultimately, a startup called Made In Space was awarded the contract and tasked with a 3D printer that would revolutionize how repairs aboard the ISS are handled. Made In Space provided solutions to all of the problems and they have created a 3D printer about the size of a toaster that can handle the rigors of space.
This current model will purely be experimental to determine if it is possible for the ISS to remain self sufficient with spare parts. The pieces will be test for durability and accuracy. If successful, the implications would be incredible.
When describing the practicality of a 3D printer in space, the Apollo 13 mission is a fantastic example. On the mission to the moon in 1970, an oxygen tank ruptured onboard their spacecraft. The mission was aborted, but the crew was still faced with a dire situation as they had no way to remove the accumulating carbon dioxide. Using duct tape, a manual, and plastic, the crew managed to improvise a solution. While their harrowing tale had a happy ending, a 3D printer could have produced a suitable replacement in a matter of minutes.
The printers that are used in space, in addition to all of the other requirements, will need to minimize fumes produced by the plastic, manufacture parts for their own repair, and recycled the plastic for secondary use.
Some proponents of 3D printers in space note that it might highly beneficial and may even assist in living in space, as even 3D printers for food are gaining more traction.
The first item crafted in space will be a momentous occasion, and there is no word yet about what the astronauts will make first, though the CEO of Made In Space joked about manufacturing a Death Star.
The printer is set to be tested in space in 2014.