It's never just point and shoot.
So the current SpaceX estimates are going to be for the most efficient and cheapest trajectories.
If you want to ignore the synodic cycle and run missions every day for years, the costs are going to be much higher.
For example, Musk repeatedly mentions a six-month trip. No, it is 9 months, at best.
He talks about transporting 100 colonists for those 9 months, 6500 hours, in a ship with the room that an airliner uses taking that many with their baggage across the Atlantic Ocean, up to 9 hours.
Might they not need food, water and, maybe, air for 9 months? The airliner pumps air through on the way. It collects its sewage, to deliver there. Maybe a pressure suit for when they get there? Change of underwear?
By NASA standards, Starship has room for at most 17 crew for such a trip. That is if you know they all get along, or don't care how many kill one another on the way. More practically, 8 is probably the limit.
Probably you need to send ships in pairs, so they can be swung on a cable between ships' noses for centrifugal gravity. That way their bones don't dissolve on the way. Will 1/3g be enough? Nobody knows. But it had better be.
It is a good plan to send uncrewed cargo ships ahead of time with what they will need there. You probably need at least five of those per colonist ship. With on-orbit fueling, that amounts to ~80 Superheavy launches, 10 for each colonist.
Will Starship be rated for launching crew? Maybe you need a couple of Falcon/Dragon launches, besides, for each Starship-load of 8 colonists.
So for a million colonists, you need ten million Superheavy launches. At 10 launches/day, every day, that is 3000 years. Maybe breeding colonists in situ would be faster? Because over 3000 years, some will die. (Hopefully not all at once.) How many do you need to launch just to keep numbers from falling? Maybe later ones can move into dead colonists' pressure cans, so need less cargo?
But a million colonists is very far from enough to be self-sufficient. No microchip manufacturing, no biochemicals, no Cybertruck. So you still need all the cargo launches, 10 every day, century in and century out. Hopefully the colony produces enough (movies?) to pay for that, because you can't bring them back.
So, no, there will be no SpaceX Mars colony. But promoting it keeps Tesla stock price inflated.
Probably the most valuable things they could send back would be the vacuum Raptor engines they got there on, probably with their bells cut off.
If you can figure a way to get a million-person Mars colony together in under, say, a thousand years, with SpaceX hardware, go wild.
Freeze and stack colonists like cordwood? Nobody said they have to be alive, right? They'd keep. Maybe somebody will figure out how to revive them, someday.
I have some questions about this bit!
1.) Why would their bones dissolve? If bones aren’t used do they really just collapse? My hands don’t really experience gravity (I think!) and they are fine.
2.) Couldn’t you make some sort of exercise thingy that could simulate gravity?
Thanks!
"One of the major obstacles to long-term space missions in the threat of severe bone loss in astronauts. In the microgravity environment of space, astronauts lose on average 1% to 2% of their bone mineral density every month. For a short-duration flight, bone loss is a fairly minor consequence.
On a long-duration space flight, such as those planned for missions to Mars and beyond, bone loss can be a serious impediment. This loss may not hinder astronauts while they are in orbit, but upon return to Earth, their weakened bones will be fragile and at an increased risk of fractures. At this time, it is unknown whether this bone loss will eventually reach a plateau, or whether it will continue indefinitely." [1]
2) ISS astronauts spend a couple of hours every day exercising to keep the worst of the space-related medical issues at bay... but it's simply no substitute for real gravity.
Space has all sorts of weird effects on the human body: [2]
[1] https://www.asc-csa.gc.ca/eng/astronauts/space-medicine/bone...
[2] https://www.smithsonianmag.com/science-nature/nasas-twins-st...
Autopilot has been "6 months away" since what, 2015?
There is no need for a million colonists to achieve self-sufficiency. Even one hundred thousand is much more than enough. The only reason for which a large number of colonists could matter would be to ensure enough genetic diversity for a colony that would lose contact with Earth.
For manufacturing all that is needed, the number of colonists is much less important and the main obstacle is not technical. The most important obstacle is that you cannot go e.g. to a library and learn how to make everything that must be made in a self-sufficient colony, because there is a huge amount of know-how details that is hidden in the trade secrets of thousands of companies scattered around the globe.
None of this secret know-how is something that could not be rediscovered by a good engineer, but rediscovering how to make everything that is made on Earth now is indeed a job for at least one million of engineers.
So for a self-sufficient Mars colony it matters very little how many colonists would be sent there, but it matters if it would be possible for the colonists to license all the technologies that are required for making everything. Most companies existing today might not want to license their technologies at all, or they would request a very large amount of money for that and a Mars colony could not produce anything valuable enough to pay such licenses.
So besides financing the transportation by SpaceX, the creation of a Mars colony would need a many times larger financing for licensing manufacturing technologies, supposing that there would be any willing providers.
Many of the existing manufacturing technologies would need a lot of research to be adapted to Mars conditions, mainly to make them less wasteful and to improve recycling, but in general the Mars ambient conditions, i.e. the lack of an oxidizing and humid atmosphere, can make most manufacturing processes simpler, not more difficult, except for the fact that it may make cooling more difficult, as the Martian atmosphere is useless for that, so the use of other cooling fluids is mandatory.
A clear majority of colonists would necessarily be wholly occupied with just keeping the colony alive, breathing, and eating. So an extra population to do electronics, another for chemical engineering, another for mining, another for medicines, more for plumbing and electrical wiring, construction, pilots, drivers, agronomists, programmers, economic planners, dieticians, physical therapists, optometrists, lens grinders, glassmakers ...
There are reasons why exactly zero societies under a million sustain any of these industries domestically.
The expertise of "millions" would be needed only when none of them has the practical experience about all the details of how something is made and they have to design all the technological processes from scratch, instead of just improving and adapting a set of known technological processes.
While indeed I am not aware of any society with under 1 million people that was able to sustain all these industries domestically, some decades ago there were a few countries in Western Europe and many of the countries from the Eastern Europe enslaved by the Russian Communists, which could have been entirely self sustained for all the industries, while having a population of only a few millions.
Moreover, the population actually involved in the industries was no more than a few hundred thousands in each country.
Already after 1980, and especially after 1990, the globalization has destroyed the local industries and none of those countries could be self sufficient now.
However the reasons why that has happened have nothing to do with technology or with the human potential of those populations.
Had those countries been kept insulated from external influences, they would have remained self sufficient until now. There is no doubt that technological evolution would have been slower inside a smaller society, but nonetheless they would not look too different from what we have today, e.g. many such countries could manufacture a personal computer with domestic components at that old times, so they certainly would have been able to make better computers 30 years later, even if not so fast and small as we have today in a globalized world.
A smaller society has increased risks of failure, but those risks have nothing to do with technology or with the human potential of its engineers and technicians, but to factors like a parasitic political class which grabs all the power and which also prevents the other people to do properly their jobs, like it happened in the Communist countries.
I thought maybe the experience of supply chain disruptions in the past couple of years would remind people of their dependence, but apparently memories are short.
Why would the bones dissolve, astronauts spends many months at a time on the ISS with relatively minor consequences.
And, it takes rather more launches of tankers to fuel up each starship before it blasts off again for Mars. I might have undercounted.
Maybe read up a bit on space medicine? Bone mass loss is not a controversial topic.
The potential upsides of this approach would be better living conditions while in journey, with potentially larger accommodations and artificial gravity from spinning the craft. If these cruise-ships are designed in a modular fashion they can be added to every time they make a return orbit around Earth and will end up having a sizable population of people permanently living on them making their money providing services to the guests travelling between worlds.
Voyager 1 launched after Voyager 2 and overtook it; both overtook earlier probes to leave the solar system.