How did engineers manage to do calculations and modelling pre GUI PCs?

Hi! I was just watching the SR 71 speed check video and it reminded me of an episode in “The Americans” in which soviet scientists want to get a hand on the design (The cross-section, I think it was called?) of a plane the US is designing.

My question is: How did scientists and engineers at said time (Late 70’s, early 80’s) model air/turbulences/pressure without the GUI we have today?

I know from a friend who is studying mech.eng that software like MathLab allows you to simulate, via FEM, said situations. I saw one of his homeworks and it was a steel beam with different colors showing different pressure points and where it would break/bend.

However, without this visualization, how do you *read* the results? Is it like a partial derivative? Ie: You have numbers for each “slice” in the digital mock-up?

I have tried to find an answer for this before writing the question but either there is none or I missed the right keywords. If you already know a link explaining this, I would be more than glad to read it.


  1. It helps if you know what FEM actually *does*, behind the Scenes.

    When you prepare a model for FEM calculations, the Computer will break it down into small elements. Each of These elements is of a relatively simple shape, and calculations are performed on each of These elements. Connecting functions Transfer the results of one element to its neighbouring elements. This process is repeated for finer and more precise results until a certain lower treshold of Deviation is reached (for example, if the greatest Change in displacement within the model space is less than 0.1µm, but of course ,this depends on the specific modelling Task).

    Before Computers, or before proper Simulation Software, These calculations had to be done manually, on similarly Chosen sub-elements.

    Of course, the whole method is a tradeoff between accuracy and Speed.

    As or interpreting the results, it depends on what you are looking for. Each element of the resulting solution will contain a set of values like Tension, displacement, temperature, velocity (depending on the type of Simulation performed).

    You can then either look for the Point of highest Tension, and do something about it, if necessary (reinforce a steel beam, or add another one, for example), or look for the highest total displacement to see if you will remain within tolerances…

    These simulations are generally performed with a specific Goal in mind, not just because it Looks cool, so at the start of a Simulation, you’d usually know what you are looking for in the results. I know that this might not be a satisfying answer. In mechanical Engineering, it’s often failure Points or cooling Performance.

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