How has Project Orion affected todays space engine designs?

Answer 1

Actually, it hasn't at all.

The Orion design works by using exploding nuclear bombs for propulsion.

The problem is that international treaty (The Partial Test Ban Treaty of 1963) prevents any of the nations of the Earth from exploding nuclear weapons in space. So the development of the Orion design into a real spaceship would be a violation of international law.

As a result, no space agency has ever even considered trying it in real life.

Answer 2

although this will tell you practically all there is to know, http://en.wikipedia.org/wiki/Project_Orion

i would say that project orion is just another step that we take on our continuing quest for the stars