Is it possible to build a rocket that uses several different types of fuel/fuel delivery methods at different times during flight?
For example, it may use nuclear fuel to travel to a different planet and then, using the hydrogen from the atmosphere, land successfully on its surface (or being able to harness a variety of liquid propellants in a similar manner).
The Questions
-Could such a rocket possibly be built and function accordingly?
-What methods might the engineers of such rocket use, so that it could use many fuel sources during flight?