Nuclear is definitely the preferred power source for powering in-situ fuel generation for a manned mission in Zubrin's scenario due to the large volume of fuel needed. NASA may have skirted this by keeping a larger return vehicle in orbit and launching from Mars in a much smaller vehicle. I don't remember what their power source was, but this seems like a likely additional reason for that change in addition to making the return vehicle larger. Launching a nuclear reactor is a political issue not a technical one. Challenger failed on launch under abnormal conditions and the issue was corrected. Columbia failed on return which is not an issue for a reactor going to Mars. What these failures and Apollo 13 showed is that staying close to Earth is no garauntee of safety and furthermore that launch and return are by far the biggets risks in space travel no matter how far you go. You are most likely correct that there will be a Cassini style outcry against launching a small nuclear reactor, but it will be just as misguided if not more so as the reactor may be uranium rather than plutonium based and will not be launched in an high radiation generating active mode. Demonstrating the fuel technology on a small scale robotic mission will not need nuclear power.

The landing of large masses on Mars is an issue because of changing atmospheric conditions. We have never tried to develop the technology to do this. This is an issue Zubrin does not have a ready answer for. His mission design takes some of this uncertainty into account by launching the fuel generating return vehicle 2 years in advance. If our development of large mass landing technology proves defective, humans won't be at risk on the demonstrator mission. An expert in landing systems told me at a MS convention that landing large masses on Mars is really technically challenging, but there was no reason to believe we can't meet that challenge if we actually focus on it.

If another country wants to waste money on CAPs I'm fine with it. It's not my tax dollars being wasted and any effort in space is potentially synergistic with others. Let's just say however given your past accuracy record that I doubt you have correctly analyzed the situation. I read lots of space news and have not heard anything about this. Do you have any proof China is working on CAPS?

Regards,
Mark