planetary habitation, (4) advanced extravehicular activity, and (5) cross-cutting capabilities.¹³

During the discussion period, Donna Shirley mentioned that the architecture studies presented here looked like the same types of studies that have been done for the last 20 years. She thought that the outcomes of the studies would all be the same if the technologies one is looking at are the same. Shirley asked if NASA was looking at architecture studies for a variety of scenarios, some—e.g., the space elevator—more transformational than others. Geffre said that the team had not yet looked at space elevators or other radically transforming capabilities, but there was a need to do so and to infuse new ideas into NASA.

Joseph Guerci asked how the team budgets for technologies that would one day succeed. Geffre said that the team does not wait until all technologies are available before using their predicted performance metrics in system studies. The new transformational space infrastructures would instead allow NASA to choose and carry out the most ambitious of the missions based on projections of when the enabling technologies are expected to be ready. If certain technologies are unavailable, mission designers can then fall back on more traditional technologies. An incremental set of capabilities is funded as more resources become available.