Re Fact 1: If you meant what you said in the latest reply you should have said it instead of writing something that seemed to imply in-situ utilization was not realistic. And yes it is a bit of hydrogen when compared to the mass of fuel that would need to be shipped as is for a return. It is this drastic reduction in fuel mass that directly relates to the drop in the cost to reach Mars. Is this obfuscation or do you just not get it?

Original Fact 2: "There is no aerobraking available on the Moon and so in energy terms it costs more to land there and pick up fuel. Perhaps it could be catapulted into orbit via a base but that's a VERY advanced base needed before we get to Mars."

You responded to the secondary comment as if that negated the primary point. Nough said or is this obfuscation in your view?

As for the rest you obviously still don't get the delta v arguments. It's not due to obfuscation on my part, its you having no clue about the subject. I suggest http://www.jpl.nasa.gov/basics/bsf-toc.htm

For Fact 4: It is that simple. Using the tether approach on the space station would be silly. The tether approach requires a balancing weight. Do you want to pay twice as much just to provide ballast? It is my understanding that the solid rotating cylinder approach for a space station is curently considered imparactical due to engineering complexity and/or sheer size required. To use a structure and avoid the coriolis effect you need a large diameter structure. Since the point of the ISS is supposedly 0 g research your whole comment regarding the ISS is rather silly regardless of the engineering details.

None of those limits applies to Zubrin's plan because the componants are primarily those needed anyway - The hab and the burnt out second stage as ballast. Larry J has pointed out (and I do trust his expertise on this matter if not on GW) that the tether approach is a complicated contol problem, but that is not the same as a complicated mechanical system which is likely to be high maintenance. There is a big difference between a design problem and a maintenance one when it comes to having a reliable system. Is this obfuscation or just too difficult for you to grasp?

Regards,
Mark