Fred J. McCall wrote:

:And what about age ? Would younger crews have lesser problems with
:calcium and in fact less problems with exercising sufficiently to
:maintain good shape ?

I doubt anyone has a definitive answer here, either, so once again the
answer is 'maybe'.




Of course the solution to all this is simple...we need a Mars ship with
a one G artificial gravity field, but that is going to be a pretty big
ship. Still, that might prove to be the only real solution to the
problem in the long run; since the ship will probably use a reactor to
generate its power anyway, a long cable or framework (say 1000 feet)
with the ship's crew quarters and lander at one end and the reactor at
the other would solve the radiation problem while allowing a radius of
rotation that would be big enough not to cause nausea as the crew moved
around. Once Mars was reached it would be de-spun for the deployment of
the lander (the crew could handle the zero G for a a one or two month
sojourn of the lander's crew on the surface, or it could be re-spun up
after the lander is released and stopped again for the surface crew's
return*) and then it could be re-spun up for the return voyage.
Entering and leaving Mars orbit? Either nuclear or conventional motors
mounted at the reactor end with there nozzles angled outwards and facing
towards the center of rotation of the vehicle; once its de-spun the
motors are fired for the delta V change. Because of their direction of
thrust the floor stays the floor in the crew quarters at the other end
of the ship while the motors fire.

*So who stays in orbit and who goes down to the surface? Two landers,
each capable of carrying half the crew...the first lander goes down with
half the crew, and on its return the other half of the crew takes their
lander down to a different landing site. This has the advantage that if
one of the landers develops a fault on the way to Mars, you can at least
get half the planned landing mission out of the trip with the other
lander. If something happens to the first lander on the surface that
would prevent it leaving Mars, the other lander could serve as a
lifeboat with a skeleton crew piloting it down to the surface to pick up
the marooned crew.

Pat