In the ages before convenient global positioning satellites to query for one’s current location military aircraft required dedicated navigators in order to not get lost. This changed with increasing automation, including the arrival of increasingly more sophisticated electromechanical computers, such as the angle computer in the B-52 bomber’s star tracker that [Ken Shirriff] recently had a poke at.
We covered star trackers before, with this devices enabling the automation of celestial navigation. In effect, as long as you have a map of the visible stars and an accurate time source you will never get lost on Earth, or a few kilometers above its surface as the case may be.
The B-52’s Angle Computer is part of the Astro Compass, which is the star tracker device that locks onto a star and outputs a heading that’s accurate to a tenth of a degree, while also allowing for position to be calculated from it. Inside the device a lot of calculations are being performed as explained in the article, though the full equations are quite complex.
Not burdening the navigator of a B-52 with having to ogle stars themselves with an instrument and scribbling down calculations on paper is a good idea, of course. Instead the Angle Computer solves the navigational triangle mechanically, essentially by modelling the celestial sphere with a metal half-sphere. The solving is thus done using this physical representation, involving numerous gears and other parts that are detailed in the article.
In addition to the mechanical components there are of course the motors driving it, feedback mechanisms and ways to interface with the instruments. For the 1950s this was definitely the way to design a computer like this, but of course as semiconductor transistors swept the computing landscape, this marvel of engineering would before long find itself too replaced with a fully digital version.
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