can block radiation. well, you have actually the powder in a layer, and then you spray with a nozzle the binder material. the binder material here was an inorganic salt water, and then it comes to a chemical reaction like concrete, if you like, and you build more or less a solid structure, layer by layer. this substance isn't quite perfect, though. so at some point, testing on the real, precious moondust needs to happen. but 3d printing on the moon could go beyond putting a roof over astronauts' heads. we can print polymers, metals, ceramic materials. and you could print food. you can print stem cells for medical applications. there's almost no limit of what you could not print. and even more important, what you can do is you can recycle. so you could actually then have a very sustainable operation by reusing stuff we have used