Nuclear fusion of light elements like hydrogen or helium would permit approaching the speed of light. It seems very attractive to refuel your space ships where the fuel is.
Our present nuclear fusion reactors are classified by the methods used to support the nuclear fusion reaction, which takes place at a temperature much hotter than the surface of the Sun.
Nearly all of our existing power sources are generators which use a heat cycle. This includes our coal, oil, and gas fired utilities, our automobiles, trucks, and trains, and even our nuclear fission utility power plants.
France generates a significant part of its energy requirements from fission reactors and these have achieved a perfect safety record. We build ours all differently.
We need the kind of leadership exemplified by President Kennedy to just do it! But we must do it as good stewards, aggressively exerting control over the moon. We can best do this by going there.
Rocket scientists agree that we have about reached the limit of our ability to travel in space using chemical rockets. To achieve anything near the speed of light we will need a new energy source and a new propellant. Nuclear fission is not an option.
