LINK: How the Lockheed SR-71 Blackbird Works
The whole video is astonishingly well done and entertaining to boot, but the link above takes you to a specific point in the video where they discuss the flight controls, particularly...they go through all the major sub-systems, and in this example of engineering below, largely done with the human mind and slide rulers, they discuss "The Mixer":
"The Mixer"
The "Mixer" is, to me, a ridiculously elegant device to handle flight control in a new way that had never been done before that time (that I know of). All the movable flight surfaces at the tailing edge of the body had to move in a coordinated way to provide pitch, roll, and blends of both when a combination of pitch and roll are needed.
Nowadays, it wouldn't be very complicated, right? You have a computer that would provide input to the controls to make an unflyable plane...flyable by electronically adjusting the flight controls to . But back then, they did it mechanically, linked with...cables to hydraulic boosters. It is brilliant. And development was begun in 1958!!!!
It isn't that I don't think engineers can do this kind of thing today, they obviously could, I believe. But I think it would be harder for them to conceive of.
By the way, for you Gear Heads, there is a great section on how they started up the plane using two unmuffled, high-power V-8 engines!