Space X and the prospects of Mars colonization.
The goal of 1 million inhabitants on Mars is unfeasible. With the Mars Colonial Transporter, at 100 passengers per flight, this would require 10,000 flights only to transport the people.
But the material support is about 10 times more demanding. So, as Elon Musk recognizes, the system would require 110,000 flights (see
https://aeon.co/essays/elon-musk-puts-his-case-for-a-multi-planet-civilisation; see his recent presentation
https://www.youtube.com/watch?v=10gECHeMSds).
Even at one flight a day, it would take 301 years. And to be able to make a flight a day, taking in account that the voyage to go and return would take much more than 1 year (during times when Mars is more far away, it would be much longer), he would need 425 reusable spacecrafts. That is beyond the normal resources of any company or country.
To finance the passengers flights, he would need to find 1 million people willing to pay 200,000 USDs to go live permanently on hell. Only the poor would be ready to try their luck, looking for well paid jobs on hell. But they won't have 200,000 USDs.
Musk might find 1 million people willing to go and work there for very good jobs, but someone else would have to pay for the trip.
Selling tourism trips won't pay the voyages either. I doubt he will be able to find 20 people willing to pay 1 million bucks to pay the ticket of the other 80 for at least 14 months to go and return to hell, especially after the trip became more common.
It wouldn't be like a month on the Moon or on a tourist space station. With time to wait for the shortest return, it would be about spending more than two years on a living hell.
I don’t see many people eager to go live on Antarctica, the most similar place on Earth.
Therefore, unless there are on Mars very rich minerals, or other very valuable resources, that would pay for the trips (people and resources going to Mars and minerals coming back to Earth), with current technology of space flight, Mars will be dependent on Earth, with a few thousand or, probably, hundreds, of inhabitants.
We'll be a two planets species, but the second planet will end badly if the first planet ends badly too. Only with new technology on flight and energy, Mars will be able to be independent.
Even at 24 flights a year, 110,000 flights would take 4583 years.
The goal of making humankind a dual planet species is very worthy from the perspective of ensuring that we can endure millions of years more.
But normal people, who care first about how to pay their bills, just do what is practical to this goal and hope for the best. They won't ruin their life to go to Mars and ensure some of us will survive on the remote case that a catastrophe strikes Earth.
If massive colonization of Mars isn't economically feasible, it won't happen.
It will be fantastic to humankind in terms of pride and self-esteem to go to Mars and build a permanent station there for investigation and some scarce tourism, but we won't have more than that until we find economic reason to do more.
If Space X is able to send humans to Mars sooner than NASA, even if with NASA cooperation (if NASA figures out that Musk is really going to make it, they will jump on board), Musk will have his deserved place in History, side by side with Von Braun and Korolev (forget about Armstrong, beside courage, he had little merit).