A key attribute of Space Settlement Design Competition scenarios is that the first settlement is built very quickly–in about a dozen years. The real reason for this is that the Competition organizers want to offer a chronology of widely varying scenarios that participating students could see during their working careers, or at least during their natural lifetimes. It would be less interesting for students to work on a space settlement design planned to operate a half-century after they expect to retire.
The Competition organizers do believe that once the first settlement is built in space, and a mining, refining, manufacturing, and transportation infrastructure is established, economics and ingenuity will enable large settlements to be built in fewer than 15 years. This is akin to a “Southern California freeway phenomenon”, wherein a new freeway is built into a remote area with very little population, and in just a few years the freeway is clogged with traffic because the access it provides enables communities and businesses to be established on its flanks. Having infrastructure in place makes it easier to get more infrastructure in place.