Just a guess -
Why moon base is an advantage ?
One of the problems with nuclear powered space travel is that people are afraid of the fallout incase of accidents.
Send huge nuclear engines - fully manufactured - to moon base.
It can be put into huge lead boxes - which can withstand high impact etc...
Now from moon base join it to the rocket and send it across..
Easier said than done.. But if they are planning for a moon base, there are indeed other advantages than just having lower gravity.
He3 is another.