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posted by martyb on Thursday October 24 2019, @08:46AM   Printer-friendly
from the Say-Hi-to-Reinhardt-and-Maximillian dept.

Wired reports that NASA Wants to Send a Probe to the Hellish Surface of Venus and make it last.

For perspective, the longest a probe has survived on the surface of Venus is 127 Minutes. The Soviet made Venera 13 in 1981.

Since the first (crash) landing on Venus in 1966, by a Soviet probe, spacecraft have only survived a total of a few hours on the planet's surface. But NASA's new probe is being designed [to] last up to 60 days on the punishing Venusian surface. Known as the Long-Lived In-situ Solar System Explorer, or LLISSE, each of the probe's components is specially engineered to withstand the high temperature, high pressure, and reactive atmosphere that define that infernal planet.

Longevity of sixty days is being targeted for a reason,

[Tibor Kremic, chief of the space science project office at Glenn Research Center in Ohio] and his team want the probe to last that long so it can witness the transition between night and day. If they land late in a Venusian day, which lasts almost four Earth months, they think they can eke out enough battery life to make that happen. "We don't have any data on how the conditions change from day to night on Venus," says Kremic. "We're trying to capture as much of that as possible."

The probe is small and intended to hitch a ride on another spacecraft heading near Venus rather than being a separate launch. Currently the team is looking at the Venera-D mission, which is scheduled for 2026.

Related: Here's a Plan to Send a Spacecraft to Venus, and Make It Last


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  • (Score: 0) by Anonymous Coward on Thursday October 24 2019, @02:06PM (4 children)

    by Anonymous Coward on Thursday October 24 2019, @02:06PM (#911202)

    Shouldn't be hard to make a computer live under those conditions, the old IBM mainframes probably qualify already(grin).

  • (Score: 0) by Anonymous Coward on Thursday October 24 2019, @03:22PM (3 children)

    by Anonymous Coward on Thursday October 24 2019, @03:22PM (#911228)

    You raise an interesting point. The surface temperature of Venus is 462°C and active cooling isn't really an option. Getting transistors to run at that temperature for 60 days without self destructing is a major achievement.

    • (Score: 2) by maxwell demon on Thursday October 24 2019, @05:46PM

      by maxwell demon (1608) on Thursday October 24 2019, @05:46PM (#911297) Journal

      Maybe vacuum tubes would be a better choice for those conditions? You certainly get the heating for free. ;-)

      --
      The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 0) by Anonymous Coward on Thursday October 24 2019, @08:15PM (1 child)

      by Anonymous Coward on Thursday October 24 2019, @08:15PM (#911351)
      Cooling should be possible, just the heatsink of your refrigerator has to be hotter than the ambient. Cannot imagine the power source, though, that can power such a fridge for 60 days non-stop. A common freezer-refrigerator in a kitchen may draw about 500W on average, 12 kW*h per day, 720 kW*h for 60 days. That is about 12 Tesla M3 batteries just for storing groceries on Earth. You'd need a bit more when your lander floats in boiling lead and zinc. Nothing short of a nuclear source will do, but then you have even more things to cool.
      • (Score: 0) by Anonymous Coward on Thursday October 24 2019, @11:46PM

        by Anonymous Coward on Thursday October 24 2019, @11:46PM (#911426)

        Cooling should be possible, just the heatsink of your refrigerator has to be hotter than the ambient

        Cooling with a refrigerator is likely to be literally impossible. The key point to remember is that the efficiency of a refrigerator drops as the temperature difference between the two sides increases. Once the coefficient of performance gets near 1 you will no longer achieve any useful cooling effect because the refrigerator won't provide enough cooling to maintain its own operation.

        The Carnot cycle establishes upper bounds on the efficiency of refrigerators. Supposing we need to maintain a working temperature of about 400K and the ambient is about 800K, we find that an ideal carnot refrigerator has a coefficient of performance of exactly 1. So even a theoretically perfect refrigerator will not help at all at these temperatures!

        A swamp cooler type approach, where you exploit the latent heat of the working fluid and expel it into the environment, should be much more practical. Let's do some back of the envelope calculations because it's fun. For example, we could imagine the craft having a supply water ice on board then melting and vaporizing of that water ice would absorb about 2.5MJ of thermal energy per kg of ice (and it can then be expelled from the lander). Averaged over 60 days that represents about half a watt of cooling per kg of ice. Then supposing you know the rate of heat transfer into the craft it's a relatively simple calculation how much coolant you need to last 60 days.

        Using the 400K and 800K numbers again), supposing the craft is a 1m×1m×1m cube with an R-40 insulation value, its surface area is 6 m² and we will therefore need to remove 6 m² * (800K-400K) / (40 K m² / W) = 60W to maintain that temperature difference. So that would mean ~120kg of water ice will suffice (plus a bit more to cool the instruments), and might even fit inside the vessel to boot.