NASA is adding a fourth crewed spacecraft for ISS transportation with Sierra Space's Dream Chaser. Why? It’s part of a long-range NASA goal to increase competition in the commercial space industry and to provide redundancy to ensure uninterrupted station resupply and operations. * * * Want to watch this podcast as a video? This Week in Engineering is available on engineering.com TV along with all of our other shows such as End of the Line, Designing the Future, Manufacturing the Future, and the Engineering Roundtable.