"After his girlfriend ran off with [L. Ron] Hubbard, he decided to create his own girlfriend and summon an elemental."This WIRED article features a brief history of rocket engineer Jack Whiteside Parsons, a founder of Jet Propulsion Laboratory who "developed the first castable solid propellant used to power aircraft." Parsons came at a time when space exploration via rocketry was still considered science fiction (and science fiction was considered extremely silly).
According to the article, Parsons' interest in rockets was inspired by SF literature. Unfortunately, the article doesn't mention his inspiration for his bat-shit insanity.
from NASA's website
From Parsons' Wikipedia page:
"There was a widely used astronomy textbook published in the early 1930s which said that rocket flight was impossible. It was something that was really not even on the fringes, even beyond the fringes of respectable science."