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Venus surface temperature is around 460 °C which makes conventional semiconductors useless. So nasa proposed a clockwork rover, drawing power from wind and using springs and gears to navigate the surface,- without any electronics whatsoever (https://www.nasa.gov/feature/jpl/a-clockwork-rover-for-venus). They even held a design competition for it (https://www.nasa.gov/feature/jpl/nasas-venus-rover-challenge-winners-announced).

But mechanism of communication with such a rover is an open design problem. It would have been so much easier to just make the electronics heat resistant.

I recently came across concept of semiconductorless microelectronics https://www.sciencealert.com/vintage-vacuum-tube-tech-could-take-electronics-and-solar-panels-to-the-next-level . Come to think of it, cramming thousands of triodes into a single evacuated tube using modern microlithography manufacturing processes is not that difficult to do. That would get us robust microprocessor based platform. I mean technically vacuum tubes can be made to work at 460 °C. Electric motors can be made to function in that that temperature range too. Energy harvesting and storage can be achieved with turbine and capacitors.

What are drawbacks of this approach? I don't think NASA went with clockwork concept without considering this technology.

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  • $\begingroup$ Soviet microcircuits based on semiconductor diamonds. And molten salt batteries. $\endgroup$
    – A. Rumlin
    Commented Oct 25, 2020 at 18:07
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    $\begingroup$ yes, I edited in my question shortly after ikrase comment. A.Rumlin suggested that diamond-based semiconductors can also be made to withstand extreme temperatures. I never knew this technology existed 0_o but it does. Both technologies seem vastly more capable than what can be achieved with purely mechanical design. $\endgroup$
    – Andrew Butenko
    Commented Oct 26, 2020 at 3:02
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    $\begingroup$ I wonder (without any knowledge of research in this area) whether any materials which are not conductors ( or perhaps semimetals) in fact become semiconducting at very high temperatures and pressures. Anyone know? $\endgroup$
    – Carl Witthoft
    Commented Oct 26, 2020 at 13:54
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    $\begingroup$ @CarlWitthoft I'm no expert but you can look up the band gaps of dielectric crystals like quartz and diamond. They show absorption edges in the UV near these points and they will show semiconducting properties when sufficiently hot to elevate some carriers high enough or are sufficiently doped, which is a lot easier if you grow them rather than dig them out of the ground: Diamond as an electronic material $\endgroup$
    – uhoh
    Commented Oct 27, 2020 at 1:37
  • $\begingroup$ See @MarkAdler's answer to What would be the (most difficult) challenge to make a “10,000 year satellite”? and all the comments below it. Also see this comment linking to Nanoscale vacuum-channel transistor $\endgroup$
    – uhoh
    Commented Oct 27, 2020 at 1:41

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As this article says, the silicon carbide integrated circuits were demonstrated to work stably in the range of 1000 °C and for more than 100 hours under 800 °C temperature without changing the signal or supply voltage. While diffusion in the material happened and affected the characteristics of the device, it stabilized after this initial burn-in.

The main challenge as of now is reducing the physical dimensions of the device, with current NASA Gen-10 technology including around 200 transistors per integrated circuit.

So, it looks like the vacuum tubes will be unnecessary for Venus.

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Interesting idea, and I don't see why it won't work. It'll probably even take less energy as you wouldn't need a heater filament. This also relates to something I've wondered recently about the use of SSTV to transmit images from the surface of Venus. SSTV, once demodulated is a relatively simple analog signal using three audible frequencies (representing RGB), with amplitude dictating the brightness. This technology can be combined with a facismile camera (mirror scanning camera, used on Viking Mars landers), to produce an extraordinary simple imaging system. Essentially, vacuum tubes could be used to generate frequencies and the amplitudes to form an sstv signal. Moving of motors for image scanning (tilt and pan) can be by controlled simple circuits continuously scanning the camera to create a panorama.

Alternatively but a bit more complicated, you can maybe use a vidicon tube (vacuum tube for imaging, used on most 60s/70s/80s spacecraft including Voyagers 1,2 and Apollo TV cameras). However, I'm not sure if electrons (electrons form the image on a plate) will stick to the store plate of a vidicon tube at high temperatures.

EDIT: A Nasa paper mentions the use of vacuum tubes for communications on Venus. https://ntrs.nasa.gov/api/citations/20050205652/downloads/20050205652.pdf

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