Electronics robust enough for Venus
physicstoday.scitation.org
physicstoday.scitation.org
As soon as you start heating electronics up to these sorts of temperatures the things we already take for granted become problematic. As highlighted already, solder joints become a huge pain, wire bonds pop off, even just building the test rigs to test these devices is usually a pretty interesting problem - I built a high-temperature photovoltaic characterization rig and a high-temperature vibration rig, which was involved enough but the true monster was the gas-sensor characterisation lab which had evolved over many years that could do gas, high pressure and temperature up to 700 degC (I think).
All good fun, if someone is looking at a PhD in electronics I would recommend this area if even vaguely interested as it's a good mix of practical and theory and when you can't even bank on your solder joints holding, let alone a dielectric surviving then it makes for some interesting problems away from the pure electronics.
Found it... actually the arm was to measure the compress-ability of the Venusian soil
Reading through the paper I have to admit those are some really impressive numbers. A typical soldering station might run at 343C (650F) while Venus is 460C (860F) hotter than a reflow oven to be sure.
Nope. 90 bar is way too little for that. You'll need to crank up pressure to ~70 kilobar to get solid tin a at 460'C (733'K). [1]
[1] https://commons.wikimedia.org/wiki/File:Phase_diagram_of_tin...
> ...while Venus is 460C (860F)--hotter than a reflow oven, to be sure.
https://www.researchgate.net/publication/272522839_Venus_hig...
http://www.bbc.com/future/story/20160705-the-toughest-spaces...
That's your theoretical maximum output. Assuming the probe doesn't heat up during entry.
Heat dissipation is actually a gigantic problem in space: you can only radiate heat away (and try to reflectively shield against the sun) since you're in hard vacuum which is a fantastic insulator.
An effective radiator is an equally effective absorber, so management of light and shadow is critical.
But it's still sort of moot when you consider atmospheric friction on the way down.
You're not going to get much power out of the gradient. Even if you cooled an object in space to near absolute zero, space probes must necessarily be low mass to get into orbit from Earth. The low mass of the whole object, and the low heat capacity of most space-grade building materials combines to make it a really awful cold sink. You would essentially need to harvest water and ammonia from somewhere outside of a gravity well, use your radiator to cool it off as much as possible, and then drop it in the heat well. That's an awful lot of trouble to go to for the amount of power you will then get out of it.
Power systems for a Venus lander have been studied by NASA.[2] Sodium-sulfur batteries, which need to be hot to work at all, were considered.
[1] http://www.maxonmotorusa.com/maxon/view/application/Brushles... [2] https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201400... [2] http://www.firstmarkaerospace.com/pdf/vhtmotors.pdf
Venus is twice that, and the atmosphere is highly corrosive, though I guess you get the benefit of lower pressure (~90 atm).
[0]http://www.techbriefs.com/component/content/article/ntb/tech...
> Winds at the surface are slow, moving at a few kilometres per hour, but because of the high density of the atmosphere at the surface, they exert a significant amount of force against obstructions, and transport dust and small stones across the surface †
So maybe we could send some probes that would hover above the surface. Disposable instruments could be shielded behind covers, and only exposed once a sample was ready to be collected and analyzed, and then discarded or written off.
Since the atmosphere is dense, maybe a nuclear-powered hover-rover would be plausible, since it would be almost more like swimming than floating. Maybe an anchor could be dragged behind it to ensure that it doesn't get flung around too badly.
Wind might be the best bet. Turn one of the dangers into a power source at least, designing one that would work for a long time in those conditions wouldn't be easy but maybe.
You're right though: this would be rather large. However, it might be possible to make it smaller, by eliminating shielding. Your smallest planned reactor surely uses a bunch of shielding, because it's intended for use on Earth, around humans. For an automated probe on Venus, that's not a concern so you don't need shielding, except whatever's necessary for safe handling before launch. This is also a place where it'd be a lot better if we had a Moon base where we could build things like this; it's a lot easier to launch mass from the Moon than from the Earth. Landing the probe should be easy: Venus's atmosphere is extremely dense so a parachute (resistant to the sulfuric acid, at least for a short time) should be fine, though the high windspeeds could be a problem.
As an example, you can visit an Antarctic research station, but people actually live in Arizona.
On Mars, you can do a lot of things. You can mine, you can build underground habitats, you can try to grow stuff in the soil, you can explore the place and learn about the geology, etc. And you can do these things a lot faster and easier in some ways than with remote-control rovers.
On Venus, what are you going to do there? Sit around in your giant dirigible city and enjoy the scenery? You can't send people to the surface, and you can't even send probes there for very long. You can't mine (the equipment won't last long enough to make any progress), you can't do too much geology (again, the probes won't last long), you certainly can't dig and build underground habitats, and you sure as hell can't grow anything on the surface. You're limited to whatever you can do in your floating habitat. And I fail to see how you're really going to get that much more done on-site in a floating habitat than just using using automated probes sent from Earth.
According to everything I've read, floating habitats are perfectly feasible on Venus, but getting them there would be a huge and expensive challenge, and what's the point when you can't go to the surface? Yeah, it'd be kinda cool to hang out there in a giant dirigible for a little while, and supposedly you could even go outside with just a breathing mask on for a little while, and it is nice that the gravity is almost the same as Earth's, but that's a huge investment for not much return. The Moon, Mars, and even Mercury and Ceres all make more sense for sending humans for long-term missions.
High temperature electronics are really what makes this possible
In the latter case, they're talking only a few hours of lifetime for ROV's going into the 500+ Sv/hr environment. I bet the military has a bunch of research on rad-hard equipment they're not keen to share.
http://www.smithsonianmag.com/smart-news/fukushima-reactor-s...
While never deployed, a seismometer and thermopile battery were developed and tested, capable of operating indefinitely on the surface of Venus.
https://what-if.xkcd.com/30/ (not quite a scientific source, so make what you want of it)
Maybe if your plants can deal with the acid you might be able to do it. (I am not a biologist, chemist or anything relevant to answer this question, this is just my best guess).
[1] "NASA Study Proposes Airships, Cloud Cities for Venus Exploration" http://spectrum.ieee.org/aerospace/space-flight/nasa-study-p...
http://selenianboondocks.com/2013/12/venus-isru-condenseable...
Putting it in space opens up some advantages, though that comes with its own whackload of disadvantages, too. Perhaps you could stick something in permanent shade on the moon to avoid 10,000 years of thermal stress, for instance, but you've got a decent chance of something hitting you hard enough to break something over that time span, too.