If you’re going to absolutely insist on exploring the surface of Venus, there are two enormous problems that need to be dealt with. Problem number one is the enormous pressure, and problem number two is the enormous heat. At 90 atmospheres of pressure and just under 500 degrees Celsius at the surface, very little is going to survive down there for long. The best we’ve managed so far is about two hours in the case of Russia’s Venera 14.
For a Venus lander mission, active cooling of most of the electronics would be necessary, but it would also need sensors, actuators, and microcontrollers that can stand up to Venus’ surface conditions. Trying to keep this stuff from immediate “puddleificaion” isn’t easy, but NASA has just thrown a quarter of a million dollars at a University of Arkansas spinoff to develop Venus-resistant chips for a weird little rover.
Thanks to some earlier National Science Foundation funding, Ozark Integrated Circuits already has a chip that can tick along quite happily at temperatures of up to 350 degrees Celsius. To bump that up to the temperatures required for Venus operation, Ozark is using a silicon carbide substrate, with a secret sauce (literally a secret, for now) for the interconnects that’s something much more stable and reliable than either aluminum or copper. Besides the physical hardware, Ozark also has to come up with biasing circuits and reference models to help compensate for high temperature operation.
NASA, understandably, wants to minimize the amount of electronics that need to be actively cooled on any Venus lander, because keeping things cool on the surface of Venus is going to suck down a massive amount of power. Photovoltaics won’t really work under all those clouds. But one slightly counterintuitive option might be a cooling system powered by a Stirling engine, which depends on the rover generating as much heat as it possibly can. Stirling engines convert a heat differential into mechanical energy, so the idea is that you’d bottle up a bunch of plutonium-238, which would heat itself to 1,200 °C through radioactive decay. With one side of a Stirling engine acting as a heat sink for the plutonium and the other side exposed to the comparatively frigid Venutian atmosphere, a Stirling engine could generate several hundred watts of power—enough to keep the electronics of a well insulated rover under 300 °C.
As far as Ozark’s high-temperature chips go, if NASA’s happy with the process design kits that they’ve ordered, the agency will task other vendors with using Ozark’s technology to design mixed-signal sensors, actuators, microcontrollers and other chips for the apparently-not-just-a-concept Venus Landsailing Rover. This rover would roll along, powered by the very-low-velocity, but very-high-density surface winds on Venus. Based on its design, if it got stuck, it would inflate a little balloon to lift itself off the ground and fly around for a bit. The Landsailing Rover has existed as a concept for the last several years, and there’s nothing to suggest that it’s going to turn into a real mission anytime soon. Having said that, the fact that NASA is actually ordering parts for the thing makes us a little bit optimistic that it might make it to Venus at some point in the future.
This post was updated on 5 August 2015 to reflect correct Venus surface temperatures.