The Basics of Nuclear Rocketry
A nuclear reaction typically releases ten million times the energy of a chemical reaction. Thus, it would seem that the weight of the fuel necessary for a nuclear rocket to deliver a certain payload would be significantly less than the weight of the fuel a chemical rocket would need to heave the same weight the same distance. So, a larger fraction of a nuclear rocket's total weight—including the weights of the rocket engine(s), the airframe, the fuel, and the payload—could go into the payload weight.