comparitive propulsion technologies
Here is a comparison of rocket technologies. Look at VASIMR ISP vs NTR. No comparison. Yes, NTR is fine for crewed Mars missions because it offers high thrust at great ISP but the toipc was outer solar system propulsion. VASIMR is a fairly simple concept. Microwave heating of a plasma and let 'er rip. REAL flight ready HW will be flight tested in 2 years a la DS1 It is not a power point "future" technology.
-p