Matt Gialich knows the cosmic odds are against him, but he doesn’t seem to care. Gialich is the co-founder of a startup called AstroForge, which aims to mine platinum from asteroids, process the materials in space and then sell the refined commodities back on Earth. It’s a venture that has the potential to be wildly lucrative, but it’s also one that for decades has seen its share of attempts and failures — remaining a tantalizing but elusive prospect for innovators and investors alike. AstroForge wants to change that. The company is slated to launch its first test mission Tuesday to...