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posted by hubie on Wednesday May 11, @02:01AM   Printer-friendly [Skip to comment(s)]
from the could-this-be-the-end-of-our-plucky-hero?-Tune-in-next-week! dept.

Mars is only going to get colder and darker for the next 10 weeks as winter deepens:

The Ingenuity helicopter has made 28 flights traveling about 7 km across the surface of Mars. Lately it has been accumulating dust on its solar panels making it hard to recharge its batteries. Recently they lost contact with the vehicle and they figured that its battery had run out, but after sunrise the batteries would charge enough that it would boot up and try to contact the rover, Perseverance.

So, the engineering team commanded Perseverance to halt all of its ongoing science activities for a full day to essentially sit there and listen intently for Ingenuity's call. The significance of this is that the helicopter was initially viewed as an add-on technology demonstration. Some of the rover's leadership team did not even want the added risk of bringing Ingenuity along. The helicopter was supposed to make five experimental flights in 30 days and then be set aside. Now, the entire Mars mission was being put on hold, nearly 13 months after Ingenuity's first flight, in the hopes of saving the small vehicle.

Well, happily, Ingenuity did call home after about 24 hours. According to NASA, the link was stable, and the solar array managed to charge its batteries to 41 percent. The engineers say they hope to resume Ingenuity's flight campaign within the next several days, after bringing the helicopter's batteries to a full charge.

This may be the beginning of the end, however. They've dropped the set point for the keep-alive heaters from -15C to -40C to conserve energy, and it isn't clear how long the commercial-off-the-shelf components in the system will last at these temperatures as it enters into the Martian winter.


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  • (Score: -1, Offtopic) by Anonymous Coward on Wednesday May 11, @03:03AM

    by Anonymous Coward on Wednesday May 11, @03:03AM (#1243989)

    for our mars choppers.

    Yaah.

  • (Score: -1, Troll) by Anonymous Coward on Wednesday May 11, @07:40AM

    by Anonymous Coward on Wednesday May 11, @07:40AM (#1244006)

    I blame Runaway for this, as I do for most things. We ought to abort him from SoylentNews, before he causes Ingenuity to be aborted.

  • (Score: 1, Interesting) by Anonymous Coward on Wednesday May 11, @10:47AM (4 children)

    by Anonymous Coward on Wednesday May 11, @10:47AM (#1244014)

    They've dropped the set point for the keep-alive heaters from -15C to -40C to conserve energy, and it isn't clear how long the commercial-off-the-shelf components in the system will last at these temperatures as it enters into the Martian winter.

    Non-materials engineer here...
    Can someone explain in really simple terms how just plain cold would reduce the lifetime of these components(*)? Isn't cold just 'less movement of the molecules'? How does that affect lifetime? Is this related to later getting the device back up to operating temperature (and thus something about stresses it will experience due to the now larger delta(temp))?

    (*) I'm somewhat surprised by the claim that that chopper contains COTS components, is that really true?

    • (Score: 0) by Anonymous Coward on Wednesday May 11, @11:34AM

      by Anonymous Coward on Wednesday May 11, @11:34AM (#1244020)

      The chopper contains COTS components, I believe, because it is only a demonstration project and was budgeted as such, so care went into selection of the components, but at least some of them weren't "space qual" level. I'm sure JPL had plenty of electronic components, but there are the mechanical parts of the motors and the processors. I can guarantee you there is a conference paper written up on part selection somewhere.

      The other question I only have limited insight into. COTS parts are typically only rated down to around -40C and that is often their survivability temperature, with their operating temperatures higher than that. Depending upon the part you can have differential expansion/contraction depending upon whether there are layers of different materials next to each other. We've had to deal with being careful about the parts you pick when putting electronics into a thermal vacuum chamber. Keep in mind that the -40C rating is not a breaking point, but a point where the part is rated to operate down, so you can operate it at much colder temperatures, but you'll get more and more failures the lower you go (same as if you push the upper end, but that temperature is usually close enough to burning the part that there's not a lot of room to play with up there). Batteries are a whole different beast for me and I can't say I know what goes on with them from a physics standpoint other than some batteries really don't like the cold.

    • (Score: 1, Interesting) by Anonymous Coward on Wednesday May 11, @12:22PM

      by Anonymous Coward on Wednesday May 11, @12:22PM (#1244023)

      Armchair Non-materials engineer here...

      From my limited knowledge of the matter,
      Degradation happens from thermal contraction and expansion of materials and connectors.
      Also, using a battery at low temps is equivalent to sucking air from a SCUBA tank 100m down.
      The battery looses efficiency and each draw for electrical output at cold temps uses more power than at optimum.

    • (Score: 3, Interesting) by FatPhil on Wednesday May 11, @04:25PM

      Another armchair non-engineer input.

      I'd have thought the batteries were issue #1. I presume the electrolyte is a solution, and you don't want crystalisation poking sharp corners anywhere in typical Li Ion batteries. Worse than that, lower temperatures can encourage dentrites on metals, I guess the lower energy levels encourage the more ordered growth, and again, you don't want spikes anywhere. That also applies to solder on boards too. There's also a thing called "cold welding", which has known to cause mechanical problems in space historically.

      Crossing fingers.

      Does Perseverence have a grabzorizer (very advanced technical term) - can it pick up Ingenuity and shake the dust off its panels?
      --
      I know I'm God, because every time I pray to him, I find I'm talking to myself.
    • (Score: 2) by Immerman on Wednesday May 11, @05:20PM

      by Immerman (3985) on Wednesday May 11, @05:20PM (#1244108)

      As a schooled but not certified engineer, I suspect the most systemic problem to offline survival is repeated thermal contraction.

      Materials expand when heated and shrink when cooled, and no two materials change size by quite the same amount. Fasten two materials together with glue, solder, bolts, or the lamination of a silicon CPU to its protective casing, and as the temperature changes the two materials will try to rip themselves apart as the parts that were the same size when connected become increasingly different sizes.

      That's actually the principle behind non-digital thermostsats, which typically relay on two thin strips of different metals laminated together - as the temperature changes one strip becomes longer than the other, causing the laminate to bend towards the shorter strip. In something that's not designed to flex though, the results can be a lot more destructive - it can take a LOT of force to stretch or compress many common materials even a tiny amount, which is what has to happen to keep things from coming apart. The mechanical components can probably handle it, they'll just warp a little, but it will also be happening to every soldering joint, cpu, resistor, even the layers within each circuit board itself. The damage from each cooling cycle probably isn't too bad, but it can add up quickly.

      A second potential problem is related to phase transitions between liquid and solid. Water tends to be the most destructive since it has the fairly unique property of expanding significantly when frozen (e.g. jars shattering in the freezer, small cracks in the road being torn open to form potholes, etc.), but contracting when frozen isn't necessarily a cakewalk. Probably not a major problem for any lubricants (and they likely use solid lubricants anyway), but batteries tend to use liquid electrolytes since ions can move through those much more quickly than solids (= greater power available), and if that electrolyte solidifies not only does the battery stop working until thawed, but the solidifying and contracting electrolyte may bond to the electrodes and tear off pieces of the surface.

      Note that I have no idea what kind of batteries are used, nor the corresponding freezing points. But it was only designed to survive a few days as a proof of concept that would have no trouble keeping itself warm, so there might be some concerns there.

  • (Score: 0) by Anonymous Coward on Wednesday May 11, @12:32PM (1 child)

    by Anonymous Coward on Wednesday May 11, @12:32PM (#1244025)

    maybe have some kind of mechanical, (wiper, vibrator or air stream) to clear the solar glass.
    Surprised they are not already using some kind of electrical repulsive field or chemical coating to keep things clean.
    How about a service station at the rover for future devices?
    Something that cleans the panels with a compressed air shot that can also be used for science studies to clean drill sites or help in clearing debris.
    Sure they have thought of this and future missions will address the issue of keeping things "cleaner".

    • (Score: 0) by Anonymous Coward on Wednesday May 11, @01:15PM

      by Anonymous Coward on Wednesday May 11, @01:15PM (#1244030)

      yeah, like a minirover that detaches from the main rover and crawles over the solar panels with a dust-brush.
      when the project fails, the orbital telescope remanouvered to take a look will see "chooper was here" drawn into the dusty panels with tracks leading away towards the north-east direction...

  • (Score: 2) by kazzie on Wednesday May 11, @01:22PM

    by kazzie (5309) Subscriber Badge on Wednesday May 11, @01:22PM (#1244033)

    A sequel to One of Our Aircraft is Missing [wikipedia.org]?

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