Space travel is always expensive - especially having to build satellites on the ground and then drag them up into orbit. Why not use 3D printers to build those satellites in orbit?
That's the idea being put forward by a company called Made in Space, which believes a much more cost-effective way to put satellites and craft in space is to actually build them in orbit. To do that, they propose to put huge 3D printers in space, which can remotely build just about anything by being fed thin layers of various feedstock, which includes metal, plastic, or pretty much anything else.
Currently, satellites and space stations are built to withstand forces that they only experience for the first tiny fractions of their operational lives: the extreme g-forces and vibrational effects of launch. Once a satellite is past that phase, it spends the rest of its tour of duty in zero gravity, which doesn't require nearly as much shielding and support. In fact, satellites could lose as much as 30% of their mass if they were built and operated exclusively in zero gravity.
This is because the feedstock itself wouldn't need the same sort of special craftsmanship. Instead, it could be launched as a sort of gray goo, an amorphous substance that could fill any spare space on the rocket carrying it up. That means the payload is cheaper and lighter than it is now. That last bit is also good for the rocket - a cheaper payload means less fuel is required, which again saves money for all involved.
It wouldn't just be new satellites that would benefit either. The 3D printers could be installed in places like the International Space Station and then used to quickly replace any broken components. That would greatly cut down on the amount of time spent waiting for repairs, which could well save the lives of the astronauts on board if the fault is serious enough.
Any repair work would have a dual function as well - not only would the 3D printers build a new part, they could take the raw materials of the broken part and recycle it as new feedstock. Along the same lines, this could also offer at least a partial solution to our space junk crisis. Old, useless junk up in orbit could be scooped up and recycled as feedstock for the 3D printers.
But why contain ourselves to just the Earth's orbit? The designers think the 3D printers would be perfect for colonizers on the Moon or Mars. Settlers could bring along metal and plastic feedstock to help build simple shelter or, even better, worker robots to assist in construction. In fact, soil from either world should be a compatible feedstock for the printers, meaning the rocks of these worlds could be substituted and reduce colonists' dependence on Earth for supplies. Once mining operations could be set up, the printers could also use metals extracted from the lunar or Martian interior.
All of this is just speculative for now, but the company is already taking baby steps towards their lofty goals. They're currently figuring out the best printers to use for the job, and they've already printed out space-ready plastics. Now they are preparing for trials in zero gravity and, if that works, a potential trial run on board the International Space Station in the relatively near future.