For fact 1: Real aerospace engineers have the actual densities of liquid hydrogen available and will undoubtedly have calculated the volume needed. NASA's conclusion is that in-situ utilization is an effective way to make an affordable Mars mission. Your reply is nothing but obfuscation.

For fact 2: The point was it takes more energy to land on the Moon than Mars even though it takes slightly less to reach it because of the lack of aerobraking. Your ramblings have nothing to do with that.

NASA is not a space business subsidy fund so your buying water suggestion makes no sense in its own right. NASA's benefit to space business is far more likely to come from directly attempting to reduce launch costs and permanently reduce a real economic barrier than by providing an artifical boost over it.

For fact 3: Did you have a point?

For Fact 4: The difference between artificial gravity on a space station and that suggested by Zubrin is the radius of rotation. Rotating a space station would leave noticable differences in rotation speed over short distances and diziness. Zubrin's tether approach was meant to reduce this coriolis effect to a negligible quantity, but there has been no work done to quantify at what level the effect becomes negligible.

Regards,
Mark Eby