Honestly? how have we not seen this before!? a full feruchemest and mistborn (hemalurgy or natural) could totally travel through space.
Back story: I was sitting in my AP Psychology class and we were talking about memory. I started to daydream about being a feruchemest who could simply store memories. this led to me fantasizing about real world applications for feruchemests and mistborn. then i mentally played out a story in which i, a full mistborn/ feruchemest, travels the world being epic, then traveling to other worlds and.... then my mind exploded and i was forced to wait a nearly unendurable 8 1/2 minuets till the next bell rang so i could share my insights with Finallity.
so here it is: why cant we survive in space? there is no air and it is freezing (or roasting). however, if we didn't need to breathe and we could magically maintain body heat... however, through the power of compounding Feruchemical powers, we could totes travel through space!
wa-bwam!
so basically after launching ourselves out of the atmosphere, by pushing on the metals in the earth, one could fly through the cosmos traveling to other worlds at ridiculous speeds while staying warm and not needing to breathe. EDIT: also one could use the Feruchemical power of storing nutrition to stay... nutrient-full...uh... not hungry.
this also caused me to wonder if marsh has already traveled to other worlds...