Rockets (and other things) made simple

Robert Krulwich describes xckd's rocket diagram (all explained in words within the most frequent 1,000 used in English) as 'Deep Simple' and wishes there were more accessible explanation around. I was surprised to see 'space' in the top 1,000 words (it's well in, according to the Corpus of Contemporary American English at 522), whereas moon is down at 2471 (and, yes, given that we're diurnal, sun comes in at 1239).