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#1 Yesterday 21:30:06
- kbd512
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- Registered: 2015-01-02
- Posts: 8,572
Fluidics-Based Computing
I've asked myself what kind of computer can withstand intense radiation in the Van Allen Belts or in deep space for many years, and many tens of thousands of thermal cycles, long enough to travel to another star. The answer is that vanishingly few solutions exist if the timetable is measured in decades or centuries. However, one kind of compute core is remarkably durable over these time spans.
To be clear, fluidics are not like-for-like replacements for modern electronics in terms of achievable clock speeds or data throughput rates. Realistic clock speeds range from single-digit Hertz to 5 kiloHertz. They won't hold a candle to any smartphone in terms of computing power, even the original models from 20 years ago. However, most navigation, life support, and vehicle control functions require tiny amounts of processing power and bandwidth, which is why the Orion space capsule uses chips that were "state-of-the-art" about 20 years ago. It doesn't need or meaningfully benefit from more power.
The Apollo Guidance Computer (AGC), an early mostly solid-state electronic device from the 1960s, featured clock speeds near 2 MegaHertz, which sounds blazing fast compared to 1-5kHz fluidics-based devices, except that the systems and peripherals it communicated with were all ponderously slower than it was, and largely still are. Moreover, its serial bus communication would not be any faster in practice than a modern parallelized-logic fluidics-based computer operating at 1-5kHz.
A fluidics computer could replicate the AGC's logic using a machined block of many layers of diffusion-bonded Silicon (high-purity Silicon, but nowhere near as pure as a microchip or photovoltaic cell, therefore less costly) about the size of a playing card deck. It would be powered by Supercritical Nitrogen at 350bar and a tiny pump delivering acoustic pressure waves. Logic gate feature sizes would be 50-100nm, though thankfully RAM and ROM "bits" can be much smaller than that. The device would be just as fast as the AGC in practice through parallelization, but would use only 1 to 2 Watts of pumping power compared to the AGC's 55 Watts, and it'd weigh 1lb or less compared to the AGC's 70lbs, but likely 15lbs for a complete AGC as we know it with robust protection, mounting hardware, and the user interfaces to enter and execute commands. It would still function at temperatures and radiation flux values that would completely destroy the AGC, not over a year, but over a century or several centuries.
Using Orbital Angular Momentum (OAM) and 5kHz clock speeds for monitoring critical life support functions, such as detecting pressure hull breaches (compartment pressure drops or detection of an interruption to the flow of sN2 through fluid channels carved into the hull) for sending signals back to a central compute core aboard a large interstellar spaceship, uncompressed plain digital data could be sent from per-compartment compute nodes at a rate of 32,000 bits per second. Latency would be limited to sN2's speed of sound at 350bar, about 510m/s, but that is fast enough for the in-compartment compute node or for a response from centralized voting computers to seal off any affected compartment(s).
We've been discussing fusion reactors and fusion rocket engines lately, and one interesting conclusion I've come to is that fluidics-based devices operating at 5kHz, physically mounted to the walls of a Tokamak, may actually be several times faster than a network of fiber optics and a supercomputer located hundreds of meters away to avoid the intense radiation fields created by the superconducting electromagnets, for controlling plasma instability, simply due to network latency and all the overhead of modern digital electronic computers with operating systems. It may actually be fast enough to respond to micro-tears in the plasma because it's integrated into and powered by the walls of the tokamak. These devices would still need to communicate with each other using fiber optics vs pressure waves, but close proximity to the reactor, enabled by the ability to withstand temperatures and magnetic fields that would instantly destroy any electronics-based control system, makes a world of difference.
So... as unimpressive as their low clock speeds and data throughput rates are, not dying because a power cable was cut, network latency killed throughput, or a battery backup failed is a lot more impressive.
Repost of an old Scientific American article on the topic:
Scientific American, December 1964, pages 80-88
From the article:
How reliable are fluid amplifiers compared with their electronic counterparts? A number of comparative tests have been made under various conditions. In the range of what may be called ordinary temperatures -- between 150 degrees and minus 50 degrees centigrade -- electronic amplifiers give a more reliable performance. But at higher or lower temperatures the fluid device is more reliable; for example, at 250 degrees C. or minus 150 degrees C. Its reliability is five times greater than that of an electronic device. When they are compared in various environments of ionizing radiation, the story is much the same: the electronic systems are more reliable at ordinary radiation levels but the fluid systems surpass them under exposure to high radiation levels, such as in or near a nuclear reactor. The fluid systems also stand up much better under vibration -- an important factor in a rocket, where the guidance system is subjected to the severe vibration accompanying the rocket's takeoff and acceleration. Strong vibration tends to weaken the solder joints and other connections' of an electrical system; it has little or no effect on a fluid ampliHer. One test model has come through 3,500 million cycles of high-speed vibration at 260 cycles per second without any detectable impairment of its performance.
Fluidics and Electronic Circuit Logic Equivalents
FLUID CIRCUIT performs the operation of dividing by 10 in an all-fluid digital computer: for every 10 input pulses circuit delivers one output pulse. Input pulses enter from above the plane of circuit through circular, bumplike hole attached to straight channel running from top to bottom just to right of center. The 10 identical logic elements, or modules, are arranged in a series of five pairs, three at left and two at right. Each pair contains two steady input streams (small sausage shapes), two outputs (small circular shapes attached to short straight channels), eight control jets (small teardrop shapes) and eight open vents (large circular shapes). Shallow channels were chemically etched in Dycril plastic by a special process, called Optiform, developed by Bowles Engineering Corporation. For this photograph the channels were filled with white paint to increase the contrast. Normally the working fluid is air.
Another small tech write-up from "obsolete.studio" an organization specializing in the "intersection between art and science":
Form for Fluid Computer
Univac FLODAC explanation PDF:
FLODAC-A PURE FLUID DIGITAL COMPUTER
A very nice write-up showing more logic gates and how they're used:
Fluidic Computation Kit: Towards Electronic-free Shape-changing Interfaces
A collection of PDF presentations from 2007:
Coding and Computation in Microfluidics
If you've worked on cars with automatic transmissions, you may be familiar with the complex valve body that wholly or partially governs the transmission's operation. This is a very primitive fluidics-based computing application that uses hydraulic pressure from the transmission fluid to manipulate the path the fluid takes through the valve body. It looks a lot like a circuit board, except carved into metal, because that's exactly what it is.
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#2 Yesterday 21:50:31
- tahanson43206
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- Registered: 2018-04-27
- Posts: 26,327
Re: Fluidics-Based Computing
This post is reserved for an index to posts that may be contributed by NewMars members.
This new topic appears to me to have significant upside potential, and I'm not talking about some distant future. Vehicles being designed by GW Johnson right now would seem to me to be strong candidates for computing hardware as robust as the opening post suggests they might be. Johnson's designs are intended to last for many years in space transit operations. It seems to me they won't require ultra-high-speed computers to manage the onboard systems. Modern communications systems operate at high data rates, but a vehicle that takes Earth years to complete an operations cycle (such as some of GW's space tugs would do) may not require such high data rates to maintain contact with it's owners.
What GW's designs most certainly ** will ** require is computing hardware that can be counted upon to remain functional despite the great variety of assaults the Universe we live in will throw at it over decades or longer.
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#3 Yesterday 22:01:45
- kbd512
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- Registered: 2015-01-02
- Posts: 8,572
Re: Fluidics-Based Computing
To the best of my knowledge, the only major modern-day application of fluidics is "computer-on-a-chip" (a literal piece of plastic that a human or automated machine injects fluids to test for a very specific interaction) biomedical lab testing, where it is used extensively. I guess hydraulics and transmissions are also major applications, but nowhere near as sophisticated as biomedical fluidics. Regardless, think of this as SCADA using supercritical fluids instead of electronics. Most of the same basic concepts used in electronics still apply to fluidics, but you're using an actual fluid instead of a stream of electrons. If you're more worried about end-of-the-world reliability than data throughput rates for systems that don't require high data rates, then I think there's something here worth pursuing.
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