In discussing the really early days of computing, Jack Crenshaw explains what it meant to move into the Space Age:
After college, I went to work for the space agency, NASA. I was going to help put men on the moon (which I did). My first day, I received the two tools of my trade: an 18-inch government-issue slide rule and a book of five-place trig tables.See, NASA figured that the three-digit accuracy of the standard 10-inch slide rule just wouldn’t cut it for space travel. In general, to get one more digit of accuracy you need a slide rule 10 times longer. But it just happened that the 10″ rule could almost get four digits (it could, over part of its range), so that increasing the length to 18″ was just enough to get that precious extra digit.
Even more exciting, NASA had real desktop calculators! Electro-mechanical ones, which were sort of adding machines on steroids.
There were a number of brands around. Ours were Fridens. The Friden was a huge machine by today’s standards — as big as an old standard typewriter and much, much heavier. Inside were hundreds of little gears and levers that would drive a Swiss watchmaker into paroxysms of ecstasy.
The Friden worked much like the adding machines used for businesses, except it would multiply and divide, as well as add and subtract. There was a keyboard having 10 columns of 10 digit keys, and a carriage like a typewriter. On the carriage were numbered wheels that spun. You typed a number in by punching (that’s the right word — no electronics or power-assist here) one key in each column, and then punched the “go” key. To the accompaniment of the noise of a threshing machine, the carriage slewed, the wheels spun, and in a matter of decaseconds, there was your answer. Division was quite a sight to behold, and on those few machines that could do square roots, the noise level rose alarmingly as more and more wheels got into the act.
But most of us didn’t have access to the square root machines, and a measure of your proficiency with a Friden was how quickly you could find a square root on a non-square-root Friden. There was a neat algorithm for it that I’ve never forgotten (no, it’s not Newton’s method, it’s an exact, noniterative algorithm). I also learned the famous “Friden March,” a calculation that caused the carriage to chunk along in a neat, “rah, rah, rah-rah-rah” rhythm.
Despite the horrible noises emitted by the Fridens — sounds reminiscent of the clashing of a nonsynchromesh truck transmission — it always gave reliable answers. Over a period of five or six years, I never once saw a Friden give a wrong answer.
The big advantage of the Friden, other than its tendency to get the correct answer, was that we could calculate to as many as 10 digits of accuracy — unheard of until then. But most of our calculations were done to only five digits or so, because that’s as many as were in the trig tables. Later I managed to get a book of six-place tables. It was a big book.
Looking back upon the space race and all the high-tech things that were involved in it, helps to remember that, at least through projects Mercury and Gemini, the work was mostly done with slide rules and Fridens.