There are many building materials on Earth, but the moon offers only fine-grained lunar soil. However, that might be perfect for a 3-D printing process to build lunar habitats. Enrico Dini, inventor of the large-format 3-D printer D-Shape, is working with the European Space Agency and Foster + Partners using a simulated lunar soil to test the concept. "Our current printer builds at a rate of around two meters per hour. Our next-generation design should attain 3.5 meters per hour, completing an entire building in a week," Dini said.