The amount of radiation received on a Earth-Mars trip gives a cancer risk roughly that of being a smoker. Not awesome, but certainly survivable. Plus, a hundred people's worth of water stored in the walls should make a pretty nice shield (not to mention the propellant tanks, which they plan to aim at the Sun to absorb the brunt of radiation).

People already stay on the ISS two to four times as long as Musk's proposed travel time to Mars, and they'll be landing somewhere with a third of Earth's gravity. They might all need to hang out for a day or two to get their Mars legs, but I don't see an issue here either.

Micrometeorite impacts haven't done the ISS any appreciable damage in its nearly 20 year service history. Again, doesn't seem like a problem.

It's not really the trip that worries me, it's living on Mars. You need to live under five meters of soil in order to get the same radiation protection as Earth's atmosphere provides. You're basically mole people. Which means the difference between living on Mars and living in windowless apartment complex on Earth is that you can do a couple space suit jaunts through the Martian deserts each week.

People can definitely survive living almost entirely indoors. I expect VR will be big on Mars. But I think the lack of natural light will really limit the comfort level.

If someone can invent an invisible electromagnetic radiation shield that would change the game.

Artificial light isn't the best, but it can be made to resemble daylight; I don't see that as a show-stopper.

If we can find some nice lava tubes that can be sealed and pressurized, it might make for some rather spacious dwellings. But yes, I expect the first Martians to effectively be mole people.

I imagine living on Mars would be a lot like living in a place like Whittier Alaska [1] (a town where everyone lives in the same building). Not for everyone, but some people might like it.

[1] http://www.npr.org/2015/01/18/378162264/welcome-to-whittier-...

Sounds like a recipe for madness, suicide, and homicide to me, especially given the lack of escape.

Is EM radiation that can't be blocked by sheets of metal really an important problem? It looks like we can use magnetic fields to block charged particles and apparently that's good enough for space travel - but perhaps not for a person's whole life.

http://www.sr2s.eu/project-news/19-eu-space-project-will-all...

Sheets of metal have a lot of issues, unless you bring hugely THICK sheets of dense metals. All you do with thinner shielding is turn your alpha/beta risk into a re-radiated gamma risk. Plus, dense shielding is heavy... and therefore expensive in terms of its Delta-v.

Going outside routinely is dangerous on Mars. It takes a penny sized hole in your suit and you're dead.

I doubt that's the case. Suits will be tough, and undoubtedly come with patch kits, and folks will use the buddy system.

A penny-sized hole would give time to patch, and suits would likely be designed to compartmentalize in a leak. In a true worst-case scenario, chimp studies in the 1970s showed they could survive several minutes of total vacuum.

https://www.scientificamerican.com/article/survival-in-space...

How long a human would survive is one thing. How much medical care they'd need is another. They'd be on Mars, not Earth, and I imagine being a quadruple amputee on Mars would effectively be a death sentence.

Musk's plan is to have ships going back and forth every launch window. I'd expect anyone disabled like that to be offered a trip home.

I'll believe that when I see it.

And as missions become routine, costs drop, and dangers become well-known all of these things will only improve. The biggest obstacle to making space travel more human-friendly is that practically no humans are traveling through space. Change that part of the equation and the rest is downhill.

It's easy to talk about sacrificing people for the sake of progress, but it's still barbaric.

People have lived in zero g for a year at a time, without significant health impact. The SpaceX proposed transit of three months is a quarter of that.

These year long stays were on the space station, which has similar or less shielding. The Earth's magnetic field helps, but really, by the time you get to your Mars habitat with unlimited shielding mass available, your total dose is not that high.

There's all sorts of concerns after a year in space.

http://www.theverge.com/2016/3/1/11138102/scott-kelly-year-i...

I guess they aren't well characterized yet.

Risks are relative.

Early travelers will face very significant risks. Radiation and zero g are indeed risks, but a minor compared to the other risks.

Risks are relative. is a very different calculation than People have lived in zero g for a year at a time, without significant health impact.

Different, but both true.

If you have a 5% of dying in transit or at Mars due to equipment failure, as well as a 2% increased chance of getting cancer at some time in the future, the first obviously is the one to worry about.

It's going to be dangerous enough on Mars, without adding those factors in. Worse, it's going to be difficult if the person who dies is in a critical position. You would have some redundancy in personnel, but that's costly in terms of Delta-v too, for them, and for everything it takes to keep them alive.

The effects are really pretty bad after a year and significant even after 6 months with exercise. That's why it was so important to get the transit time down to 3 months.

I've always wondered why there haven't been any efforts to generate artificial gravity via spinning spacecraft ala 2001.

Have there ever been any serious plans or proposals to do that?

Nautilus-X was pretty serious.

You really want a pretty large diameter so that you don't have a huge gravity gradient causing your astronauts discomfort. Tethers might be more practical than the classical doughnut designs for the near future.

JAXA recently brought up a small wheel into the ISS that can be used to simulate varying levels of spin on mice. Research into .4G gravity is particularly important if we're going to be sending people to Mars, but in general if lower levels of gravity keep mice and people happy those'll be easier to generate on future spacecraft.

Would make a great TV series, a la Terra Nova. You might have a society where the average lifespan is cut in half, predominant diseases are space-related and accidents are a daily or weekly part of life. It wouldn't be like living on Earth, but it would be something.

You might enjoy The Expanse book series! There are several world-building tangents that delve into exactly this area.

I'm thinking (no spoilers) specifically of how Ceres, having been spun up to provide artificial gravity, becomes a destination for expecting mothers trying to avoid complications associated with low-G.

I also like how the only sci-fi conceit the book asks for (besides the antagonist aliens obviously) are the engines which are right on the edge of the theoretical maximum.

Surely Ceres would just fling itself apart?

It sure would. Not that you could spin up something so large.

That TV show is great.

see my response to marze:

https://news.ycombinator.com/item?id=12766618