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On Wednesday, April 19th, in a seminar titled "An Air-Breathing Metal-Combustion Power Plant for Venus in situ Exploration", NASA engineer Michael Paul presented a novel idea where existing technology could be used to make longer-duration missions to Venus.
To recap the history of Venus exploration, very few probes have ever been able to explore its atmosphere or surface for long. Not surprising, considering that the atmospheric pressure on Venus is 92 times what it is here on Earth at sea level. Not to mention the fact that Venus is also the hottest planet in the solar system – with average surface temperatures of 737 K (462 °C; 863.6 °F).
Hence why those few probes that actually explored the atmosphere and surface in detail – like the Soviet-era Venera probes and landers and NASA's Pioneer Venus multiprobe – were only able to return data for a matter of hours. All other missions to Venus have either taken the form of orbiters or consisted of spacecraft conducting flybys while en route to other destinations.
[...] "What can you do with other power systems in places where the Sun just doesn't shine? Okay, so you want to get to the surface of Venus and last more than a couple of hours. And I think that in the last 10 or 15 years, all the missions that [were proposed] to the surface of Venus pretty much had a two-hour timeline. And those were all proposed, none of those missions were actually flown. And that's in line with the 2 hours that the Russian landers survived when they got there, to the surface of Venus."
The solution to this problem, as Paul sees it, is to employ a Stored-Chemical Energy and Power System (SCEPS), also known as a Sterling[sic] engine. This proven technology relies on stored chemical energy to generate electricity, and is typically used in underwater systems. But repurposed for Venus, it could provide a lander mission with a considerable amount of time (compared to previous Venus missions) with which to conduct surface studies.
For the power system Paul and his colleagues are envisioning, the Sterling[sic] engine would take solid-metal lithium (or possibly solid iodine), and then liquefy it with a pyrotechnic charge. This resulting liquid would then be fed into another chamber where it would combined with an oxidant. This would produce heat and combustion, which would then be used to boil water, spin turbines, and generate electricity.
Such a system is typically closed and produces no exhaust, which makes it very useful for underwater systems that cannot compromise their buoyancy. On Venus, such a system would allow for electrical production without short-lived batteries, an expensive nuclear fuel cell, and could function in a low solar-energy environment.
Stirling engines could extend the mission durations.
(Score: 2) by VLM on Monday April 24 2017, @02:10PM
Its interesting that the space age is so old that Venus surface conditions were once upon a time recent cutting edge in a chemical plant or refinery. But that was the old days and its just not as cutting edge anymore.
Lets say you build a fluid catalytic cracker (kind of like a thermal hydrocracker on steroids) in a refinery just getting spun up to very large industrial scale in 1950 at what was then considered insane temps and pressures. And 15 years later while you're feeling barely comfy with FCC technology depending on your local level of arrogance, the commies land the first probe on the surface of Venus and damn if the surface of Venus isn't roughly as awful of a place to visit as the inside of your FCC while its in operation. Well, the propeller beanie people are going to have a rough time of it given the joy of operating a large early FCC down here on earth using 1960's technology. If there's a leak its not like the space guys can shut off the atmosphere for a bit while a guy with a wrench tightens the bolts to spec again. Yeah yeah don't hassle me about the temps in a FCC being about 10% lower and pressure being 10% higher than Venus, that detail doesn't matter, the inside of an operating FCC was merely the first thing I thought of that's reasonably similar to Venus surface environment.
I'm not saying it'll be easy today, but I am saying it hasn't been 1960 for a long time now and there's a lot of academic and institutional knowledge gathered since 1960.
The really hard part is turning something like an electrical feed-thru that works fine in those conditions and is completely roughneck-proof, and safety-of-man-life reliable against leaks, blowouts, fireproof, and corrosion proof, unfortunately probably weighs as much as your entire lander electrical system budget, given how cheap the rocket guys tend to be. If using nuclear rockets you could land something as big and heavy as a refinery on Venus, then hanging out on Venus wouldn't be fun, but scientifically and engineering wise really wouldn't be much of a challenge.
Another point of comparison is building the SSME engine was almost impossible in the 70s, but given a lot of dev work in the 80s it turned into a decently reliable engine and actually got uprated for thrust after some decades of experience. Another example the V-22 wasn't that the one where the airforce thought it would be funny to double hydraulic pressures and it took decades to get it to work?
I'd say as an engineering rule of thumb given standard industry experience you can double internal pressures and things will be touch and go for about a decade, but in a decade it'll be the new standard industry experience and institutional knowledge of how to do it safely etc. You really can't rush it and it doesn't seem to matter if its hydraulics or rocket fuel or chemical plant process equipment and I'm sure you can have people argue its 5 years or 20, but to an order of magnitude thats about how long it takes.