Lukyanov, a Soviet engineer, was trying to calculate heat transfer in concrete structures.
Hand calculation was cumbersome, so he developed an analog computer to physically model the math relationships.
It worked *really* well.
Known as the “Water Integrator”, it solved partial differentials with just gravity, with an error rate around 2-3%.
Because of the simplicity of “programming” with valves, it was successfully used for Geology, thermal physics, metallurgy, and even rocket engineering.
The insane part? Digital computers weren’t able to match the utility of the Water Integrator for DECADES.
In the mid-70s, they were still being used at over 115 Soviet research sites.
These “Lukyanov integrators” weren’t decommissioned until the late 1980s!