Fascinating to think how much was accomplished by these engineers, designers, physicists, and other intellectuals with the most rudimentary of rudimentary computers. Machine shops, calipers, and the beloved slide-rule (I have one made of ivory purely for the novelty of it). What was done is nothing short of miraculous as well as impressive. Seat of your pants flying, every stitch of everything hand calculated, hand drawn, and so on. No cad machines. Test pilots truly were made of the Right Stuff...and plenty of it.