SETTLING OFF EARTH
- transitioning to an ever expanding settlement -

A large lunar and Martian settlement could happen a lot earlier than many would anticipate. The key technology that would make this happen would be SpaceX's BFR. Not only would it be large enough to support a rapid population growth but, more importantly, a fully-reusable launcher would mean that the ticket price would be low enough to allow a very large number of people to afford to move off Earth. This would certainly be the ideal situation and the Space Development Network estimates it more likely than not that the BFR will become reality. But the BFR is certainly technically challenging to develop and is not a for sure thing. Is there an alternate in case the BFR doesn't become reality?

SpaceX's Falcon Heavy has already flown -- it's available now. A full-scale lunar lander could be developed relatively quickly if NASA had the Lunar COTS funding program. An example of a quickly-developed lunar lander could be United Launch Alliance's XEUS lander. The per-seat cost for such a combination system could start for around $80 million per seat. This means that many countries could afford to purchase one or more seats. The large, International Lunar Exploration Phase, would result in an increasingly high flight rate and hence a reduced per-seat price thereby opening the way for private settlement.

Increasing the number of people who can move to the Moon involves three things:
    - Number of launch sites,
    - Frequency of launches,
    - Number of passengers per launch,

NUMBER OF LAUNCH SITES
Right now, SpaceX is using one east-west launch site in Florida and is building another one in Texas. With time, one could imagine multiple launch sites becoming active in Florida. If there was a great demand, one could imagine other launch sites developing around the world. Over a period of 18 years, one could envision 16 launch sites being developed.

FREQUENCY OF LAUNCHES
SpaceX has stated that it is their goal to get their partially-reusable Falcon 9 launching as frequently as every day (load and launch with minimal inspection). Right now it takes at least three months between launches of the same rocket. But the Falcon 9 Block 5 is designed for rapid turn-around. The Falcon Heavy is based upon the Falcon 9 Block 5. Over 18 years, one could envision launches starting at once a month, then once a week, then every other day, then once a day.

NUMBER OF PASSENGERS PER LAUNCH
Dr. Robert Zubrin of the Mars Society has proposed such a transportation system to the Moon that would involve the launch of a Dragon capsule to low Earth orbit (LEO). Crew would then transfer from that capsule to a craft traveling between the Earth and Moon. The Dragon can hold a crew of seven. If there was a lot of demand, a transportation system could be developed based upon the Falcon Heavy which is able to put as much as four times of mass to LEO compared to the Falcon 9. One could imagine a new type of crew vehicle eventually being developed for the Falcon Heavy which would take advantage of the full capability of the Falcon Heavy. As such, each launch could lift as much as 50 or even 100 passengers at a time.

Put together, notice the graph of how these three factors would lead to a total population of about 1,000,000 on the Moon in as little as 13 years.