No substitute for gravity........
Look at how many Bowflex's are for sale on Craig's List.........
Kelly's problems were due to a year of negative gravity and that's the major factor to overcome in extended space flight that would take us to the stars...........
Mars' gravity is only 38% that of earth so the human body could handle that for an extended period of time.......but there would be muscle degeneration that would have to be regained upon return to earth. And the older the astronaut, the harder for that to happen........
“Kelly’s problems were due to a year of negative gravity and that’s the major factor to overcome in extended space flight that would take us to the stars.”
Any such extended trip would take many years of travel (under our current knowledge of physics). Presumably it would be desirable to accelerate the spacecraft at a constant rate which would be indistinguishable from actual gravity. If, at the midpoint of such a trip, the spacecraft is rotated 180 degrees and begins to decelerate at the same rate, there would be constant gravity for nearly the entire trip. So, the real challenge is supplying the power to create a constant acceleration and deceleration over such a long distance.
“Mars’ gravity is only 38% that of earth so the human body could handle that for an extended period of time.......but there would be muscle degeneration that would have to be regained upon return to earth.”
Living and work spaces could be designed to create artificial gravity to avoid this problem. This would be no small undertaking though.
The future Martians aren’t coming back. We’ll be divergent species.