Elon Musk comes up with design ideas in the shower. That may be his only free time. In 2010, Tesla successfully IPO'd, and SpaceX became the first commercial company to recover a spacecraft from the Earth's orbit. As a designer, Musk says, he tries "to imagine, from a physics standpoint, what an ideal solution would look like and how practical it is." He rarely draws them out; he is in the shower, after all.
I rarely draw out ideas. I usually just think about it and then tell people what I'm thinking and see if it makes sense.
Was there a book that changed how you see?
Reading fiction can be helpful particularly for rockets. Sci-fi fiction can--even though what you see on the TV or movie screen is impossible because of physics, you can still sometimes generate ideas. I like the Foundation Series by Isaac Asimov. Star Trek, Star Wars, all the classic sci-fi fantasy stuff. I like The Lord of the Rings, though I can't say I've had many designs come from that.