There was a time, now forgotten, where the expectations was that computers would run on fluid currents rather than electric currents.

Basic building blocks of a Fluidics based system.

Logical gates can be made in almost any fashion. Today we build logical gates such as AND, OR, NAND and XOR using combinations of transistors. However they are not the only way to do it. Earlier computers vacuum tubes instead of transistors. Before that relays where used. One of the first programmable computers the Z1, made by Konrad Zuse during WWII used mechanical logical gates.

Read more: Implementation of Konrad Zuse’s Logical Gates in Lego.

If you go really far back into computer history to the age of steam you will find the mechanical monsters dreamt up by computer pioneers such as Charles Babbage, who made steam powered mechanical computers performing their computations using and elaborate system of gears. These where however decimal based computers and not built on logical gates which is what is common for digital computer working with binary numbers.

A small part of the Analytical Engine, a mechanical computer using a decimal system rather binary numbers to perform calculations. This was designed and built by computer pioneer Charles Babbage.

The Advantage of Binary Digital Computers

Realizing that computers could be more easily built if one adopted a binary number system was a revolution. Konrad Zuse essentially did like Charles Babbage in that he create what was mostly a mechanical computer. But because he used a binary system, he could employ boolean logic based on logical gates such as AND, OR, NAND etc. This profoundly simplified the computer and allowed him to build a far more capable computer than Charles Babbage which could fit inside Konrad Zuse’s modest living room. Zuse was also able to fund this largely himself on his engineering salary.

Charles Babbage in contrast was trying to build a mechanical computer which would fill factory halls and which required the funding of what was the an empire spanning one forth of the globe. This shows the profound impact of getting the fundamental ideas right.

That means something like the Z1 could have been built with 1800s technology. Someone simply had to have realized that boolean logic was the way to go.

But if you are in a mood to imagine some alternative history, what could have happened in the 1800s does not stop there. In fact the manufacturing technology of the 1800s was in fact sophisticated enough to support a far more powerful technology which could have given the people of the 1800s relatively compact computers.

Fluidics Based Logical Gates

Chances are that you have never heard of this technology called Fluidics. It is based on using fluids such as liquids or gasses to perform computations. No it is not based on moving pistons and valves. In fact Fluidics systems are not mechanical at all. Rather they are based on how a jet of fluid can modify the direction of another jet of fluid.

How fluidics logical gates use control jets to affect output.

This principle was discovered quite late when researchers worked on airplanes. However engineers in the 1800s had everything they needed to build logical gates on this principle.

The benefit of fluidics is much like regular electronics. Without mechanical parts subject to wear and tear they are reliable and robust. You can also build fluidics devices at fairly high density.

Maker novelchip has a project which demonstrates creating an integrated circuit using fluidics, which can be placed on the equivalent of a printed circuit board (PCB).

An integrated circuit running on compressed air rather than electric current.

What Happened to Fluidics?

Logical circuits based on fluidics was in fact gaining ground in the 1960s and there was numerous companies with large catalogs of fluidics devices and circuits which you could order parts from.

In fact for a period this looked more promising than electronics. So how come so few have heard about it? Well you might not know either that whole cities send messages through pneumatic tubes? That instead of an electric network European cities had compressed air networks driving clocks, motors and even cooling systems in factories and stores.

Pneumatic tubes using compressed air to send messages. This was used historically all over Paris.

Yet a lot of these systems have since been forgotten because they tended to have been only been used for short periods of time. Often a competing technology comes along too quickly. E.g. the vacuum tube never got that widely used before it was replaced by transistors. Thus vacuum tube based computers only existed for a relative short time period.

Likewise compressed air system to deliver messages and power only existed for a short time before electricity replaced them. Fluidics suffered the same faith. It came into prominence over a relative short time period before electronic quickly got good enough to entirely replace it. Although fluids systems have been used to control trust vectoring system on airplanes.

Fluidics systems have found a niche in areas where operating temperatures are much higher than what electrical components can handle. In fact one the the reasons I have had an interest in Fluidics over several years is due to a certain fascination with colonizing the planet Venus.

Read more: Why Colonize Venus Instead of Mars?

If you read that story you will learn that the huge problem with Venus is the crazy temperatures on the surface. It gets to 460° Celsius. At that temperature it is game over for pretty much any kind of digital electronics, but not for fluidics based devices. This led me to explore what technologies could one use to build an entirely non-electric rover to explore the Venus surface. It would need some kind of computer, communication system and motors which are not electric based.

It turns out that, if you dig enough around the internet, you can find solutions to all these things: Making a Non-Electric Rover For the Venus Planetary Surface.

Have Fluidics Computers Been Built?

Sadly fluidics got abandoned before it could get too far but some researchers did manage to build a prototype for a very simple fluidics based computer called FLODAC. It was built in 1964 and was made up of 250 fluid NOR gates. . It had 4 bit word sizes and a memory of 4 words as well as 4 different instructions:

This was to demonstrate that a program made with the 4 most fundamental instructions for any computer. FLODAC ran at 10 cycles per second. It has however been theorized that clock rates of 10 to 100 kHz is possible. That sounds extremely low compared to an electronic computer which operates at arond 3 GHz today (2019). However that isn’t necessarily as limiting as it sounds. The human brain operates at a measly 30 Hz. Still the human brain outperforms almost every computer. It has been calculated that the human brain has a processing power of 6 peta flops. That is six million billion calculations per second. Which compares favorably to the worlds fastest super computer:

the world’s fastest supercomputer is actually about 30 petaflops. Of course, it cost half a month of China’s GDP to build, and requires 24 megawatts to run and cool, which is about the output of a mid-sized solar power station.

The human does roughly the same with just 20 watts.

How does the human brain achieve this while operating at such low frequency? Due to massive parallelism. Fluidics systems could likewise gain processing power from parallelism. Since you can build them in 3D using simple plastics, you can build quite a lot of channels in small area.

So as a rule of thumb we could say a fluidics system should be able to run at 300–3000 times faster clock cycle than the human brain.

Further Reading for the Curious

If you think this topic is interesting, you might want to read some of my older articles where I did into various aspects of air powered systems. One idea I was curious about was whether you could build a non-electrical industrial economy on another planet. Now why would I be curious about that? You might want to read my Venus colonization story to understand that better.

Read more: Building a Non-Electrical Economy on Other Planets.

If you are interested in Maker stuff, then surely you know about 3D printers. These are extremely versatile in letting somebody easily make almost any kind of part at home. Surely it is something colonizers on other planets would want to have. Or maybe Amish people as they avoid electricity but are okay with compressed air based systems. In fact Amish kitchens and workshops typically have their tools and equipment running on compressed air. So the question is: Could you build a 3D printer only running on air?

If you are interested in more of this space stuff, I have an overview page over the various articles I have written about rockets and space colonization.

Read more: Space Exploration and Colonization.