Build the Planetary Nuclear Electric Cruiser Now

We should build the planetary nuclear cruiser.  Put a nuclear electric drive with near massless propulsion into high Earth orbit. Then when planetary missions need to be accomplished we can do so by docking the appropriate payload section to the cruiser propulsion pod. Manned missions to Mars will then be practical.   Use as large as a reactor as possible. Make it modular so you we can replace the near massless drive section over the years as they improve.