Nick,

Converting CO2 and H2 to CH4 and H2O is simple compared to most industrial chemistry today. Its a straight forward reaction with high conversion. It is an old old process as well. You are correct though that ice alone is sufficient.

The landing requirements by teh way for Mars Direct are less than those acheived by Apollo. The Martian atmosphere may make that tougher though. Again the accuracy of our landing technology will be tested by the fuel depot before human's ever leave Earth. There will be a difference in geometry though.

I assumed in my comparison that you would have the same stay period whether you went to a Moon or Mars. I believe the transfer times would apply under those circumstances. I see no justification for a trip to a moon being shorter than one to Mars. It's stupid anyway to spend far more time in transit than at the target, but I don't see how you can justify it other than on the basis of limiting total trip time.

There is no church of Zubrin and you should know that Nick having actually been to MS conferences. I don't need to run detailed numbers when people are throwing out stuff that is way off base and comparing apples to oranges as you just did.

The point about squabbling is a good one and I addressed it elsewhere.

I'm not mad in the least by the way, just frustrated because I have discussed this issue over and over in many different ways.

Regards,
Mark