The Anonymous Widower

Rules for Success? – PACE 231R

Whenever I do a presentation, I always put in a plug for the PACE 231R analog computer, I used for the simulation of chemical processes at ICI in the 1970s. Here are a couple of pictures.

In my view, there are computers, good computers and the PACE 231R.

The 231R was built in the 1960s and it was all valve or vacuum tube, if you are from the United States.   It was a formidable beast for solving differential equations and I have a feeling that there isn’t one left even in a museum.  These pictures taken by a colleague at ICI seem to be two of the only ones of a 231R in a working environment. Hopefully the Internet will preserve them for ever!

The biggest claim to fame of the 231R was that two of them were used in tandem to solve all of the mathematics and differential equations of getting the Apollo spacecraft to the moon. They were actually linked to virtually a real spacecraft to test everything out.

So when Apollo 13 blew up and they had to use the Lunar Excursion Module to bring the astronauts home, it was these two computers that were reprogrammed to try to find out how to do it. They wouldn’t have stood a chance with a digital machine, but the engineers, programmers and astonauts were able to get the two 231R’s to find a strategy. I’ve never seen the Apollo 13 film, but I suspect that the role of the 231Rs is downplayed or ignored.

So when you ask me, what is the greatest computer ever made, there is only one answer.  The amazing PACE 231R.

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March 9, 2011 - Posted by | World | ,


  1. […] Previous     Next 52.245212 […]

    Pingback by Rules for Success? – About Me « The Anonymous Widower | March 10, 2011 | Reply

  2. […] code. When I was at ICI, we used to write and distribute flyers about the jobs we did with our computer. They were successful in getting new business and this was because they were read.  And why were […]

    Pingback by Responsible Lending « The Anonymous Widower | April 13, 2011 | Reply

  3. I have a picture of a twin console PACE 231R. If you’d like to see it please let me know.

    Comment by Graham | October 16, 2022 | Reply

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