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posted by martyb on Monday April 24 2017, @04:18AM   Printer-friendly
from the power-to-the-lander dept.

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.


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  • (Score: 3, Interesting) by DBCubix on Monday April 24 2017, @02:17PM (1 child)

    by DBCubix (553) Subscriber Badge on Monday April 24 2017, @02:17PM (#498846)

    Right, which a shady area under the lander would be able to provide this differential.

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  • (Score: 0) by Anonymous Coward on Monday April 24 2017, @06:40PM

    by Anonymous Coward on Monday April 24 2017, @06:40PM (#498989)

    With the permanent overcast on Venus, a shady area is only possible with low ground clearance, which is bad for mobility. But that's okay, maybe your lander has no rover component, or at least that's not what we're worrying about right now.

    Even then, you'll have to cool it down somehow (after all, it wasn't shaded till you showed up, so it's hot at t=0); it can't conduct heat away to nearby, non-shaded rocks, because they're hot; it can't radiate heat to anything but your lander, which will soon be hot; you can't convect heat away with Venus's super-dense, and therefore super-good at heat transfer, atmosphere, because that's hot, too.

    On Earth, you can shade something from the sun, and still radiate heat away into the rest of the sky (on a clear day, which Venus doesn't have). You can, at least in summer (Venus has no seasons), conduct heat into the ground, because the sub-surface temperature is basically time-averaged on a scale longer than a year. And convection sometimes helps, because you may have a cool wind blowing from somewhere (like a sea) that is, again, time-averaged in some way (again, no seasons), or at a different latitude (Venus's surface temperature doesn't vary substantially with latitude). And there's evaporative cooling, whether direct (which actually would work on Venus, but requires you to bring your own volatiles) or by way of convection with the actual evaporation happening somewhere else (Venus doesn't have a water cycle, or any good equivalent; sulfuric acid may rain at altitude, but evaporates before it reaches the surface). All you have to do is block out the sun and let one or more of these cooling methods work.