Before there was an N73 system there was an N57 system, Like the N73, it was a strapdown system. In the simplest of terms, a strapdown system is one without gimbals. Too simple! In an ordinary Inertial Navigation System (INS), the stable platform, or instrument cluster, is kept at local level by torquing the gyros to keep the sensitive axis of one of the accelerometers pointing towards the center of the Earth. Since it is impossible to keep the  vehicle carrying the INS level at all times, a means of allowing the INS to stay level and at the same time allow the vehicle to maneuver is required. The motion of the vehicle is decoupled from the INS stable platform by a set of gimbals. A strapdown INS is one in which the entire INS is fixed to the vehicle and rotates with it. Now you know. The decoupling is done mathematically in the computer. This was the new world I was to work in until I retired. The input/output device for the N57 computer was an IBM selectronic typewriter. I never learned to type and I am very slow. That, plus the fact that instructions to the computer must Be 100 % correct every time. Bad things tend to happen otherwise. I had barely started in my new job when I was asked to input a set of instructions to a computer in order to initiate a test sequence. The instructions were typed out on a sheet of paper and I slowly and methodically typed them into the IBM typewriter. I pressed “enter” to start the process. It was the end of the workday and we left. It was expected the test would run that night and be completed when we came the following day.

I came in the next morning and found out the test had not even started. It was my fault, I was told, because I had  misspelled a word in the instruction sequence. Not good! I went and made my apology to the engineer who ordered the test and who had given me the typed instructions. He was a little miffed because he had lost a day of testing because of my mistake. I went back to my other work knowing I had not made a friend of the engineer. Later that day , I was approached by the engineer whose test I had screwed up and he began to apologize to me for incorrectly accusing me of screwing up his test. I was confused by the turn of events until he got the part where he admitted that he had misspelled the instructions he had given me for entry into the computer. I felt sorry for him as he turned himself inside out playing a part that was clearly unfamiliar to him. It was a long time before our relationship became normal. I do not know what was worse for my feelings, being the goat or the vindicated goat. Both ways, I felt bad.



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