> It's like that in other fields of engineering too, when they are making something they haven't built before.

Exactly this. I like to use an analogy of building bridges :)

  - OK, we have this valley and we want to drive cars over it. What do we 
    do?
  
  - Hmm, we could just make the road along the bottom of the valley
  
  - Wouldn't that cause the cars to fall because of the steep angle?
  
  - Good point. Maybe if we built the road with a lot of twist and turns
  
  - Then it's a slow and long drive.
  
  - Maybe we could build some sort of catapult setup to throw the cars
    across the valley
  
  - That would make safety a concern though. Is there a way we could use
    helicopter rotors to suspend a road in mid air over the valley?
  
  - Or what if we attach the road to each side of the valley and make a 
    road that's strong enough to not crack in the middle under its own weight?
  
  - Yeah, that sounds like a good idea. How do we make sure it can hold its
    own weight, though?
  
  - .....etc