Read an article last week in theEngineer on “Designing a mechanical rover to explore … Venus“, on a group at JPL, led by Jonathon Sauder who are working on a mechanical rover to study Venus.
Venus has a temperature of ~470c, hot enough to melt lead, which will fry most electronics in seconds. Moreover, the Venusian surface is under a lot of pressure, roughly equivalent to a mile under water or ~160X the air pressure at Earth’s surface (from NASA Venus in depth). Extreme conditions for any rover.
Sauder and his team were brainstorming mechanical rovers, that operated similar to Theo Jansen’s StrandBeest which walks using wind energy alone. (Checkout the video of the BEEST walking).
Jansen had told Sauder’s team that his devices work much better on smooth surfaces and that uneven, beach like surfaces presented problems.
So, Sauder’s team started looking at using something with tracks instead of legs/feet, sort of like a World War 1 tank. That could operate upside down as well as rightside up.
Rather than sails (as the StrandBeest), they plan to use multiple vertical axis wind turbines, called Sarvonius rotors, located inside the tank to create energy and store that energy in springs for future use.
They’re not planning to ditch electronics all together but need to minimize the rovers reliance on electronics.
There are some electronics that can operate at 450C based on silicon carbide and gallium carbide which have a very low level of integration at this time, just a 100 transistors per chip. And they could use this to add electronic processing and control to their mechanical rover.
Solar panels can supply electricity to the high temperature electronics and can operate at 450C.
But to get information off the rover and back to the Earth, they plan to use a highly radio reflective spot on the rover and a mechanical shutter mechanism. The mechanism can be closed and opened and together with an orbiting satellite generating radio pulses and recording the rover’s reflectivity or not, send Morse code from rover to satellite. The orbiting satellite could record this information and then transmit it to Earth.
The rover will make use of simple chemical reactions to measure soil, rock and atmospheric chemistry. Soil and rocks suitable for analysis can be scooped up, drilled out and moved to the analysis chamber(s) via mechanical devices. Wind speed and direction can be sensed with simple mechanical devices.
In order to avoid obstacles wihile roving around the planet, they plan to use a mechanical probe out othe front (and back?) of the rover with control systems attached to this to avoid obstacles. This way the rover can move around more of the planets surface.
Such a mechanical rover with high temperature electronics might also be suitable for other worlds in the solar system, Mercury for sure but moons of the Jovian planets, also have extreme pressure environments.
And such a electrical-mechanical rover also might work great to probe volcano’s on earth, although the temperatures are 700 to 1200C, ~2 to 3X Venus. Maybe such a rover could be used in highly radioactive environments to record information and send this back to personnel outside the environment or even effect some preprogrammed repairs. Ocean vents could also be another potential place where such a rover might work well.
Mechanical probes would need to be moved vertically and swing horizontally to be effective and would necessarily have to poke outside the tanks envelope to read obstacles ahead.
Sonar could work better. Sounds or clicks could be produced mechanically and their reflections could be also received mechanically (a mic is just a mechanical transducer). At the pressures on Venus, sound should travel far.
Morse code was designed to efficiently send alpha-numerics and not much else. It would seem that another codec could be designed to send scientific information faster. And if one mechanical spot is good, multiple spots would be better assuming the satellite could detect multiple radio reflective spots located in close proximity to one another on the rover.
Radio works but why not use infrared. If there were some way to read an infrared signal from the probe, it could present more information per pass.
For instance, an infrared photo of the rover’s bottom or top, using with a flat surface, could encode information in cold and hot spots located across that surface.
This could work at whatever infrared resolution available from the satellite orbiting overhead and would send much more information per orbital pass.
In fact, such an infrared surface readout might allow the rover to send B&W pictures up to the satellite. Sonar could provide a mechanism to record a (sound) picture of the environment being scanned. The infrared information could be encoded across the surface via pipes of cool and hot liquids, sort of like core memory of old.
What about steam power. With 450C there ought to be more than enough heat to boil some liquid and have it cool via expansion. Having cool liquid could be used to cool electronics, chemical and solar devices. And as the high temperatures on Venus seem constant, steam power and liquid cooling would be available all the time and eliminating any need for springs to hold energy.
And the cooling liquid from steam engines could be used to support an infrared signaling mechanism.
Still not sure why we need any electronics. A suitably configured, shrunken, analytical engine could provide the rudimentary information processing necessary to work the shutter or other transmitter mechanisms, initiate, readout and store mechanical/chemical/sonar sensors and control the other items on the rover.
And with a suitably complex analytical engine there might be some way to mechanically program it with various modes using something like punched tape or cards. Such a device could be used to hold and load information for separate programs in minimal space and could also be used to store information for later transmission, supplying a 100% mechanical storage device.
Going 100% mechanical could also lead to a potentially longer lived rover than something using some electronics and mostly mechanical devices on a planet like Venus. Mechanical devices can fail, but their failure modes are normally less catastrophic, well understood. Perhaps with sufficient mechanical redundancy and concern for tribology, such a 100% mechanical rover could last an awful long time, without any maintenance, e.g., like swiss watches.
Photo Credit(s): World War One tank – mark 1 by Photos of the Past
Vintage Philmor morse code practice … by Joe Haupt
Accompanied by an instructor… by vy pham;
Core memory more detail by Kenneth Moore;
Model of the Analytical Engine By Bruno Barral (ByB), CC BY-SA 2.5;
Punched tape by Rositslav Lisovy