You're ignoring the prime reason humans aren't going to travel to Mars anytime soon: radiation. Good luck getting there without accumulating a huge dose of hard radiation that gives you cancer. This is why we should be worrying about building human settlements on the Moon first: we can put them underground (for radiation shielding, plus other benefits like avoiding meteorites), and the travel time is so short that the cumulative radiation exposure is very low. 3 days of exposure to cosmic rays is very low compared to a year or so, or at best 6 months.
Once we have manufacturing capability on the Moon, we can build much larger ships that have some decent radiation shielding.
Of course, the low gravity causes a bunch more problems. But here again, with significant space- and Moon-based industry, we could build much larger ships with spin gravity. This doesn't help the people working on the Moon though, but at least here we could cycle them on and off the Moon every 6 months or so, since the trip is only 3 days, so they could come back to Earth and re-acclimate to 1g periodically.
Once we have manufacturing capability on the Moon, we can build much larger ships that have some decent radiation shielding.
Of course, the low gravity causes a bunch more problems. But here again, with significant space- and Moon-based industry, we could build much larger ships with spin gravity. This doesn't help the people working on the Moon though, but at least here we could cycle them on and off the Moon every 6 months or so, since the trip is only 3 days, so they could come back to Earth and re-acclimate to 1g periodically.
https://www.smithsonianmag.com/smart-news/explorers-will-fac...