This NRA will solicit multiple studies, each of which will investigate an architecture, mission, or system concept with the potential to enable a great leap in space or aeronautics. NIAC is part of the Space Technology Mission Directorate. Aerospace architecture, mission, or system concepts proposed for NIAC Phase II studies must be exciting, unexplored, far-term, and credible. Proposals for narrow technology or subsystem development, or incremental or near-term advancement, are explicitly out of scope for this program. Finally, while NIAC encourages daring vision and accepts the accompanying risk, proposals must be technically credible and plausibly implementable.