For astronauts on long-duration space flights, the nearest supply depot would be millions of miles away. On such journeys, in-space manufacturing (ISM) could be a time- and cost-efficient way to manufacture tools, components, and infrastructure, as well as repair defective components or large structures. ISM could be conducted in transit, in orbit, and on the surface of extraterrestrial bodies.  

Metal additive manufacturing (AM) is likely the best method for creating these parts in space. Compared to packing metal parts and materials into the spacecraft, making them on board would be a huge logistical benefit. However, many conventional gravity-dominated methods cannot be carried out in space, including AM methods. For example, powder-based selective laser melting (SLM) exhibits the same problem—neither the feed materials, or printed parts, can be held in place by gravity.