# What sort of analysis was performed before “modern” computing and the invention of finite element analysis and computational fluid dynamics?

I am not sure if this question is appropriate for this SE - Ideally this should be posted in Engineering SE but as far as I'm aware it does not exist! (I can only assume that the scope of engineering is far too broad for one sub-domain.)

Anyway,

In the 1960s and 70s computers such as the CDC-6600, and its successor the CRAY-1, were considered the pinnacle of computing power. Now, in my understanding of computers and FEA/CFD etc., the power of these computers (60-80MHz-ish) would be nowhere near powerful enough to perform FEA/CFD calculations within realistic time frames and to a reasonable degree of accuracy.

So what tools did NASA, and other entities with similar requirements (be it in construction, automotive, aerospace industries), use to perform their stress analysis, aerodynamics, engine fluid flows, pressures etc. before constructing and indeed launching their vehicles (, implementing their designs in general)?

As an engineer I can appreciate the importance of these steps in a design process so I'm truly stumped.

• They used slide rules. – GdD Jan 16 '15 at 14:57
• Can you elaborate? – Phizzy Jan 16 '15 at 15:29
• At a guess, I'd imagine they'd do similar kinds of analysis "by hand" (i.e. with electronic calculators or early computers) over a much smaller number of elements ("assume a spherical cow of uniform density...") and look at flows in an analog simulator (i.e. a scale model in a wind tunnel). – Russell Borogove Jan 16 '15 at 15:39
• amazon.com/Roarks-Formulas-Stress-Strain-Edition/dp/0071742476/… – Erik Jan 16 '15 at 17:41
• FEA is doable, and practical results can be obtained, using nothing but paper and pencil. If you ever take a finite elements course, you'll probably be solving out some problems by hand on the exams. I did, at least, and it was in this millenium :) – Reinstate Monica Jan 13 '16 at 20:00

As an engineer who has used slide rules, logarithmic tables, calculators, computers and done designs on paper and using computers, in the paper design era engineers concentrated on the critical areas of designs.

These days, computers and mathematical techniques such as FEA & boundary element analysis, etc. allow engineers to consider a larger number of options and to consider a larger number of "what if" scenarios. These days, engineers can be bogged down in data, detail and decimal point accuracy.

In the pre computerized era engineers also used graphs that others had developed such as psychrometric charts and where they didn't know they did laboratory and larger scale testing, such as wind tunnels with smoke and streamer and hydraulic channels and dye for hydraulics and streamlining.

To test the streamlining of high performance cars, small streamers were placed all over the body to be able to view how the air flowed over the car.

One method used to envisage stresses and stress flow was to cut shapes into perspex sheets and to view the prismatic light patterns in the perspex when it was placed under different stress regimes (it was a bit like stress contours). It didn't give any numerical values but people could get a better idea of where adverse stress concentrations could occur and then alter the design accordingly.

Prior to the mid 1970s engineers had to know mathematics and hand calculation shortcuts, i.e. to approximate $\pi$ to 2 or 3 decimal places using 22/7; particularly for junior engineers.

Neil Armstrong & Buzz Aldrin took slide rules to the Moon as part of NASA standard issue.

http://www.worthpoint.com/worthopedia/apollo-11-slide-rule-neil-armstrong-77275561

Buzz Aldrin's slide rule from Apollo 11 (courtesy of sliderulemuseum.com)

During the early part of the Cold War scientists and engineers in the West had access to powerful computers. In the Soviet Bloc countries scientists and engineers didn't have such access, they developed mathematical techniques to be able to get answers quickly.

• +1. I have that very same Pickett slide rule, complete with black leather slide rule case! But somewhere along the way I lost my much better bamboo slide rule. – David Hammen Jan 17 '15 at 13:02

What sort of analysis was performed before “modern” computing and the invention of finite element analysis and computational fluid dynamics?

Techniques such as computational fluid dynamics (CFD) and finite element method (FEM) are older than you think and were used early on in the space age. Although CFD is very computationally demanding, CFD predates digital computers. The development of the finite element method post-dates the development of digital computers, but not by much. M. Jon Turner at Boeing is generally credited with being one of the key inventors of the FEM during the 1950s. Precursors to FEM also pre-date digital computing.

Below is a picture of a roomful of highly parallel computer processors from the pre-digital age. This image also depicts an old-style data storage system, the box full of nicely filed paper at the bottom right.

http://s7.computerhistory.org/is/image/CHM/500004225-03-01?$re-medium$

Prior to the widespread use of digital computers, analog computation provided an alternative to hand calculation computation. Analog computers were heavily used to simulate a number of physical processes, including engines and rockets. The next two images show Vannevar Bush's differential analyzer, a mechanical analog computer that could solve up to sixth order differential equations, and the Beckman Instruments EASE analog computer, which the Allison division of General Motors used to design jet engines. Until the 1960s, many saw analog computers as being superior to digital computers.

http://s7.computerhistory.org/is/image/CHM/102618648-03-01?$re-zoomed$

http://s7.computerhistory.org/is/image/CHM/500003053-03-01?$re-zoomed$

• Fantastic pictures. I recall my boss and mentor for thermal analysis recounting that in earlier times (I'm not sure, the '60s or '70s perhaps) the organisation had a maths department who ran a room full of people whose job was to invert matrices as a service to other technical departments. – Puffin Jan 13 '16 at 20:32

You also had reference books like Formulas for Stress and Strain by Roark (and Young) and Stress Concentration Factors by Peterson. Prediction might not have been as strong as it is today but often enough comparison was possible.