Rocket engineering is not like ditch digging. With ditch digging you can get 100 people and dig a ditch, and you will dig it a hundred times as faster if you get 100 people versus one. With rockets, you have to solve the problem of a particular level of difficulty; one person who can solve the problem is worth an infinite number of people who can't.

Interview With Elon Musk Tesla Motors (2000s)