Michael Turner wrote:

... A lunar cycler that
would have been developed solely for lunar missions would
not be of much use for going to Mars.


Not so sure about that. A lunar cycler might actually be the ideal
'module' for construction of a larger Mars cycler.

Solar storms in cis-lunar space will be a serious threat, no less dire
than such storms while in transit to and from Mars. The main
reduction in risk is in the much lower travel time. Nevertheless,
lunar cycler orbits would have a period of about 1 month

http://www.moonminer.com/lunarcycler-orbits.html

which leaves passengers exposed for about two weeks on any leg. If
lunar cyclers are staffed, they might be posted for periods comparable
to a leg of a Mars mission.

Indeed, if there's a very good argument for cyclers for both Moon and
Mars, it's that you'll want a lot of raw mass to shield against
radiation: solar storms, GCR, and passage through the van Allen belts.

A quick dash to/from the cycler on less shielded shuttle craft makes a
prediction of a solar storm a piece of useful information -- you might
return to safety in time, or perhaps blow the fuel you'd planned on
using later just to get rendez-vous with the shielded cycler sooner,
in the hope of getting rescued later by some other shuttle craft.
Compa if you're one week out on a lunar cycler, and get a
prediction that a solar storm is coming and will peak in 24 hours,
that's little more than timely notice of a death sentence. A quick
dash reduces GCR risk to below negligible even if it's done outside
the Earth's magnetic shield. And the trajectory of quick dashes might
be chosen so as to avoid the van Allen belts entirely.

You are probably right here. I didn't think that the voyagers on a lunar
cycler would be in the cycler for that long. What I had in mind was a
cycler going to the Moon in about 4 days, come back in another 4 days,
then do two spacer orbits before starting again. In such a scenario,
you protect yourself of solar storms mainly by not leaving if a solar
event is approaching, so you don't need so much shielding.

As for some approximation of closed-cycle life support, well ... it
depends on what you're planning to do with your lunar cycler. If it's
rough-and-ready astronautical missions, you might limit recycling to
air and water. Likewise if the goal is adventure-travel-class space
tourism. But for true space tourism, the ability to grow fresh food
on the lunar cycler might be well worth the ticket price, to your
average billionaut.

I agree.


Alain Fournier