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Mars Space Science

Mars Winds Clean Spirit's Solar Panels Again 269

Titoxd writes "In a blast from the past, NASA reports that Spirit's solar panels have received a much-needed cleaning courtesy of the Red Planet. The report states, 'The cleaning boosts Spirit's daily energy supply by about 30 watt-hours, to about 240 watt-hours from 210 watt-hours. The rover uses about 180 watt-hours per day for basic survival and communications, so this increase roughly doubles the amount of discretionary power for activities such as driving and using instruments.'"
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Mars Winds Clean Spirit's Solar Panels Again

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  • by jellomizer ( 103300 ) on Wednesday February 18, 2009 @04:24PM (#26906485)

    Rule 1 of engineering: Underestimate your estimates.
    The thing was designed to run for years. However they gave it a 90 Day limit to save their butts if it breaks in 85 days. as well the mission spec was for 90 days, so they made sure it would last that 90 days as much as possible. It is not like you going to put up a million dollar probe and skimp on parts. You are going to make it as robust as possible as estimating 90 days of operation in the unknown is quite hard.

  • by dlevitan ( 132062 ) on Wednesday February 18, 2009 @04:48PM (#26906899)

    NASA probably has a good idea. Published estimates were likely wrong on purpose from the start to give them the opportunity for more media coverage and subsequently budget opportunities.

    Not exactly. Estimates are based on worst case scenarios. What would have been the public's reaction if NASA had said that the rovers would last 1 year but they only lasted 6 months? NASA guidelines require that when something is supposed to last x months/years, then it's engineered such that it will last that long, no matter what. Specifying mission requirements is actually a tricky problem for the scientists on a mission because you want the most possible science that fits within a budget and that will last for as long as you say it will last. And usually the only way to convince NASA that something will last is if you add in backup systems. With new, expensive technology this becomes even harder.

    So yes, the rovers were conservatively estimated to last 3 months. I'm sure the scientists on the mission expected that they would last longer, but 3 months was a good benchmark that provided a good amount of science for a reasonable cost. Everything else has just been icing on the cake (and in this case, a lot of icing). Personally, I think they did a great job and cannot fault them at all.

    (I am a grad student working on a NASA mission and have seen a bit of how this process works)

  • Re:Next time . . . (Score:4, Insightful)

    by sremick ( 91371 ) on Wednesday February 18, 2009 @04:50PM (#26906937)

    I don't see how the benefits are minor, considering how much press and excitement is triggered each time the winds clean the dust off. Also considering the massive longevity to the mission that more runtime creates. More life = more science, and since the whole point of these missions is "science", that's more bang for your buck.

    It's not easy to get stuff to Mars, and there are only occasional windows of opportunity. Best to get as much as you can out of the missions you DO send.

    I don't see how there can be much "static cling" if just wind can dust them off.

  • Re:Next time . . . (Score:4, Insightful)

    by Tubal-Cain ( 1289912 ) on Wednesday February 18, 2009 @04:55PM (#26907021) Journal
    The wind is (somewhat tongue-in-cheek) taking the level of dust from "almost thick enough to grow weeds in" to merely "heavy".
  • Re:Next time . . . (Score:2, Insightful)

    by Taibhsear ( 1286214 ) on Wednesday February 18, 2009 @04:59PM (#26907069)

    Just reverse the polarity. In start trek it fixes everything.

  • by Capt.DrumkenBum ( 1173011 ) on Wednesday February 18, 2009 @06:42PM (#26908879)
    How about we all stop thinking that we have better ideas than the guys who built these incredible pieces of machinery?
    I mean the designers built two rovers that had to survive a launch from earth, months in deep space, a bouncy landing on another world, and then operate correctly with a 10 minute (Or longer) radio delay.
    That is an incredible accomplishment! Then for it to continue to operate for YEARS! I am in awe of the designers.
    Now here on /. we have a bunch of armchair engineers believing they could do better?
    Do you honestly believe that the same people who built these incredible machines didn't think of a solar panel wiper? A can of compressed air? A fan? A compressor?

    To the designers: If any of you are reading this. My hat is off to you. Well done!
  • by Anonymous Coward on Wednesday February 18, 2009 @07:01PM (#26909151)

    Only on Slashdot can a post that confuses power (watt) and energy (watt-hour) be modded +3 Interesting.

    You're right, everywhere else it would be +5 informative.

  • by iNaya ( 1049686 ) on Wednesday February 18, 2009 @08:47PM (#26910617)
    Reading some of the comments here shows, that some people, when all the math is done for them, still don't get it.
  • Re:Next time . . . (Score:3, Insightful)

    by SilverJets ( 131916 ) on Wednesday February 18, 2009 @09:04PM (#26910845) Homepage

    So you think a tiny air nozzle would sandblast the panels compared to the dust storms on Mars?

  • Re:Next time . . . (Score:3, Insightful)

    by UnknowingFool ( 672806 ) on Thursday February 19, 2009 @01:39AM (#26913015)

    First of all the dust is not only super clingy, it may also be abrasive. Physically removing the dust via brush may scratch surfaces.

    Second, if the dust isn't abrasive what materials would the brushes and plastic film be made of. Remember they have to be softer the the panels or they'll scratch them. Typically on earth they are made of a synthetic like nylon and HDPE. Would such materials survive the harsh environment of Mars? The extreme shift of cold and hot of Mars days would make most soft material brittle after a short time period. For the plastic film the transparency would also be affected by the extreme conditions.

    Third you are using a motor. Motors will fail after certain amount of time. For example 2 wheels on each rover have failed. If the motor fails, the rover is no better off than it is now. Such a device would cost weight and space on the rover.

    Fourth are you planning to cover all the solar panels or just a few? The rover was packed with as many panels at it would allow. Such a system would necessitate fewer panels just to implement for weight and space considerations. That would reduce the amount of power the rover can gather in a day.

Always leave room to add an explanation if it doesn't work out.