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1. have a rotating spaceship (would need a pretty big radius to feel right.)


I doubt the rotating wheel needs to "feel right" (which would require a radius of hundreds of feet, maybe more) to be biologically useful. A tenth G might be enough. And if the astronauts need to adjust to an environment that doesn't "feel right" so what?

The Russians already have enough data on long-duration stays in zero-G for human beings. There may be lingering questions about what happens at the cellular level in terms of orientation but those won't be answered this way. And I'm not convinced such affects are real since humans do just fine lying down and getting up whenever they want; i.e., the cell can't depend on a particular gravitational orientation for any period of time anyway.

It's possible that after a long Mars mission there will be enough bone mass loss to require extensive rehabilitation. Some people will go nuts I suppose if astronauts have to spend a year in the hospital upon return. I say big deal - there will be no shortage of qualified volunteers for a mission as long as full recovery is likely, even if it requires a year or two in the hospital, as long as they can write their papers and deliver lectures while recovering (and there would be plenty of qualified volunteers for much riskier missions).

You can't simulate every parameter and shouldn't waste effort on experiments whose results won't tell you anything new about the planned mission (a Mars mission is not like spending a year in a hospital bed with your head at a funny angle). Once you've gathered all the data possible just do it to the limit of reasonably expected safety, which is the only way to learn where the actual dangers lie. The only ways to improve on the Russian long-duration MIR experiment results are to either do more of them on ISS, which poses political problems, or to do a Mars mission (which is certainly risky but zero-G seems reasonably likely not to kill the astronauts).

Maintaining 1G in transit isn't realistic, but would a tenth G be hopeless if you had a nuclear reactor for power, a really big ion engine (lots of thrusters), and really, really big fuel tanks? I have no idea.

PS. CME = Coronal Mass Ejection. Think of it as a solar fart.
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