In order to develop thrust, you have to eject some sort of mass out the back, that's Newton's Law.
Does this nuclear engine eject mass at twice the velocity?
What sort of mass?
How is it accelerated?
Not sure, but Newton’s Law might well have some flaws in it that we’re not aware of.
Didn’t scientists recently discover that mass (relativity) cannot be broken down beyond a certain point - meaning there is a finite point for mass and that means the universe is finite as well?