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Mars NASA Transportation

Rough Roving: Curiosity's Wheels Show Damage 78

Posted by Soulskill
from the pit-stop-unlikely dept.
astroengine writes "In a recent batch of images beamed back to Earth from Mars rover Curiosity's MAHLI camera, obvious signs of wear and tear could be seen in the 'skin' of the robot's wheels. Considering Curiosity is only 281 sols (Mars days) into its mission and roved less than a kilometer after landing, surely this doesn't bode well? Fortunately, there's good news. 'The wear in the wheels is expected,' Matt Heverly, lead rover driver for the MSL mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News. 'We will continue to characterize the wheels both on Mars and in the Marsyard, but we don't expect the wear to impact our ability to get to Mt. Sharp.'"
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Rough Roving: Curiosity's Wheels Show Damage

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  • Fun fact (Score:5, Interesting)

    by funky49 (182835) on Wednesday May 22, 2013 @07:11PM (#43798565) Homepage

    There's a fun fact about the wheels of Curiosity. They spell out "JPL" in Morse Code in the sand of Mars. :)

    • by EETech1 (1179269)

      I wonder if this impacts the strength of the wheel any with all those dashes, perhaps just saying hi would make them more durable.

      • by aliquis (678370)

        "I WAS HERE!"

      • by Anonymous Coward

        Should have gone with Michelin. Because so much (money) is riding on your tires.

      • These guys are NASA engineers. I'm sure they've considered that. If there were any structural benefits to be gained from removing the pattern then they would have done so. That said, the design of the wheels is quite interesting. The "JPL" Morse code sections have holes through the wheels whereas the rest of the wheel is simply a solid tread pattern. The addition of holes is very interesting and I'd be interested to hear the rational for incorporating such sections into the wheels.
    • by Taco Cowboy (5327)

      I learn something new today. Thanks !

      BTW, looking at the picture ( @ http://upload.wikimedia.org/wikipedia/commons/3/37/Curiosity_wheel_pattern_morse_code.png [wikimedia.org] ) I am totally surprised at the sheer thinness of Curiosity's wheel !

      How can they expect Curiosity to last long with such thin wheel ??

      • Re:Fun fact (Score:4, Insightful)

        by Charliemopps (1157495) on Wednesday May 22, 2013 @11:26PM (#43800015)

        Because the project managers were given criteria. 1. it had to last for X months... 2. it had to be under X kilos. Which do you think was a harder goal? I think it's pretty obvious. Making things that last forever is easy. Making things that are light is easy. Making things that are both? Little bit more difficult.

      • Really look at the wheels; they are actually a very well designed machine component. The main design strengths are graceful degradation (inherently long working life), and an excellent balance of material conservation/functionality . A breakdown follows:

        1. The center ribs of the wheel are the first structural element, transmitting the forces exerted on the wheel to the hub.

        2. The treads are thicker material that provide several functions: provide traction, transmit the forces from the wheels' skin to the c

    • The engineered holes spelling out JPL may sound like a great idea, but it is not. Those holes will be a detriment if MSL finds itself in a soft powdery dust dune, i.e. the same stuff that trapped Spirit and Opportunity. Spirit never got out. The wheels are the one major design flaw in all these rovers. Here on Earth, when you drive through soft sand, you want large soft, and smooth tires-- the exact opposite of what is used on these rovers.
  • If they find a Les Schwab center to fix the tires, we'll know there's no intelligent life on mars.

    • by game kid (805301)

      Out there in Mars, that rover's more likely to find a Charles Schwab center and end up owing a consultant money.

      • >Out there in Mars, that rover's more likely to find a Charles Schwab center and end up owing a consultant money.

        $7.95 per turn of the wheel, in either direction.

        • by EETech1 (1179269)

          Quick someone figure out the cost per revolution of a wheel if the rover only completes the primary mission...

          Please

  • Wheel wearing (Score:5, Informative)

    by girlintraining (1395911) on Wednesday May 22, 2013 @07:20PM (#43798643)

    These wheels aren't like your normal car wheels. The very thin atmosphere means that the soil is more like lunar soil than Earth soil. Atmospheric erosion tends to smooth out sand particulate so it has a rounder shape -- it is less sharp. Lunar soil is incredibly corrosive. Think of all the problems our troops had operating in Iraq with their equipment, now multiply that by a hundred. It's like walking on microscopic needles. Martian soil isn't quite as bad, thanks to having had an atmosphere at one point, and retains a minimal one now, but it's still inhospitable.

    The rover was designed with multiple wheel-sets to operate independently, and the wheels themselves designed to wear somewhat more gracefully in the face of these obstacles. But yes, they're going to look ugly fast.

    • by Anonymous Coward

      Despite its thin atmosphere, Mars regularly experiences massive sandstorms, so there should be plenty of erosion going on.

    • Re:Wheel wearing (Score:4, Insightful)

      by Anonymous Coward on Wednesday May 22, 2013 @08:30PM (#43799061)

      I think you are confusing abrasive with corrosive.

    • by Max_W (812974)
      Add to this radiation. There is no magnetic field around Mars.
  • false freak out alert. I fail to see similar level of damage anywhere else on the wheels so maybe its just one area on the wheel that got dented during the landing.
    • Re:Rough Landing (Score:5, Insightful)

      by camperdave (969942) on Wednesday May 22, 2013 @07:47PM (#43798813) Journal
      If it was from the landing, it would have been noticed long before now. Curiosity went through a rigorous self check before it started on its primary mission of exploring the planet.
      • by illestov (945762)
        i was there and saw it happen
      • by kuhnto (1904624)
        But if you look at the pictures more closely, it looks like the dents were formed from the interior side of the wheel. I am not sure how terrain could cause that to happen.
        • But if you look at the pictures more closely, it looks like the dents were formed from the interior side of the wheel. I am not sure how terrain could cause that to happen.

          Me either. I just hope it's not some innate metallurgical or manufacturing flaw that would cut the mission short.

  • by Anonymous Coward on Wednesday May 22, 2013 @07:33PM (#43798731)

    Since those 2 rovers outlasted their expected mission life by a factor of 20ish, everyone now expects every science mission to do similar. When they last for the amount of time they were engineered for people are disappointed. That's the danger in overachieving and the reason people feel compelled to use their full budget each year - if they're frugal for a year people expect that they'll be able to do the same every year and cut the budget. Some aspects of human nature stink.

    • Really? I think its more a testament to just how well NASA over-engineers and builds everything for the absolute worst case scenario that we get so much extra use out of these things. I mean look at how long Voyager has lasted way the hell out in the cold depths, that's a tough built ship right there.

      But this is why I've always supported the robotics space exploration programs, with our current tech "meatbags in spaaace!" really doesn't make much sense. I mean when you figure in what it would take to get a crew of five to mars and back its just insanity, I remember seeing a video where they did the math and for a 3 month stay on the ground and round trip from here to there you'd have needed a ship bigger than the empire state building just to carry all the consumables and fuel needed, I don't even want to know how much it would cost for a stay as long as these rovers have had there. At the end of the day we can just get more done with the machine than we can with the man, our tech just isn't good enough right now to make "meatbags in spaace!" viable.

      • by SuperKendall (25149) on Thursday May 23, 2013 @12:30AM (#43800281)

        I remember seeing a video where they did the math and for a 3 month stay on the ground and round trip from here to there you'd have needed a ship bigger than the empire state building

        Your "math" is incredibly bad. Read any book on Mars from Zubrin and become educated.

        What you are overlooking is that one human in one day could day about 100x the total research done so far by all of the rovers combined. What doesn't make sense is to continue to send very expensive robots to learn less and less... we've reached the point where we simply need to send humans to really study the place.

        • But for the same cost as sending a human on a round trip to Mars you could build a fleet of rovers. Design and testing is a significant part of the cost so building extra rovers lowers the average cost dramatically.

          A human can do 100x more in a day? For the same cost I'd bet you could send may more than 100 rovers and explore a much larger area of Mars.

      • by cusco (717999)
        It's taken nine years for the Opportunity rover to equal the distance traveled by the astronauts on the final Apollo mission in under a week. A human can turn over a rock, dig more than four inches deep, climb on top of a boulder, recognize when something looks unusual and should be investigated, or cobble together an experiment from duct tape and cleaning materials.

        Perhaps the most important reason for humans to go exploring is because the only way to learn how to live in space is to do it.
        • by Bongo (13261)

          So robot bodies are durable but slow, human bodies versatile but fragile...

          can't we send zombies?

      • by skegg (666571) on Thursday May 23, 2013 @08:23AM (#43801717)

        I mean look at how long Voyager has lasted way the hell out in the cold depths, that's a tough built ship right there.

        Dude, relax, it's just science fiction. There was no caretaker, and no one was pulled into the Delta quadrant.

      • Yes but robots don't inspire the public nearly as much as sending a "Joe" or "Jane". That's how an agency survives - by being relevant to all those people who pay taxes and will write their Congressmen to keep funding NASA.
  • by sconeu (64226) on Wednesday May 22, 2013 @07:54PM (#43798855) Homepage Journal

    Otherwise, it's a hell of a long wait for the AAA. And who's going to to stand there next to the rover with their card?

  • by Excelcia (906188) <kfitzner@excelcia.ca> on Wednesday May 22, 2013 @08:11PM (#43798947) Homepage Journal

    From the article:

    “We have the same wheels on our Scarecrow test rover, which weighs the same on Earth as Curiosity weighs on Mars,” Heverly added. “We have driven Scarecrow about 12 kilometers (7.5 miles) in the Marsyard over rocks and slopes much harsher than we expect for Curiosity. There are some dents and holes in these wheels, but the rover is still performing well.”

    This sounds an idea from the same people that brought us the Mars Climate Orbiter crater.

    The problem with this is that Curiosity weighs 342kg but masses 900kg. Scarecrow weighs and masses 342kg. Whatever Curiosity weighs, it hitting a rock at 1m/s is still 900 newtons of force. Scarecrow hitting a rock at 1m/s is 342 newtons. The fact it drove 12km and has serviceable wheels does not make me feel better.

    • by Anonymous Coward

      The same force from gravity is exerted on Curiosity's/Scarecrow's wheels. I would think that, rather than impacts, would be the bulk of the wear and tear on the wheels.

    • by TrekkieGod (627867) on Wednesday May 22, 2013 @08:46PM (#43799195) Homepage Journal

      Whatever Curiosity weighs, it hitting a rock at 1m/s is still 900 newtons of force. Scarecrow hitting a rock at 1m/s is 342 newtons.

      Stop accusing NASA scientists of not understanding their job when you don't remember basic physics.

      F = m * a, not F = m * v. In this case a is the acceleration due to gravity. In addition, mass is measured in kg, weight is measured in Newtons, because weight is a force. The newtons are exactly the same between those two rovers.

      • by complete loony (663508) <[moc.liamg] [ta] [namekaL.ymereJ]> on Wednesday May 22, 2013 @09:25PM (#43799437)

        F = m * a

        Look it's right there, force equals *mass* times acceleration. On earth, Scarecrow is 342kg * 1g when stationary. On mars Curiosity is 900kg * 1mars-g *when stationary*. Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?. In this case, with the same initial velocity, the acceleration would be the same but the force experienced by Curiosity's tires would be ~3x larger (ignoring any shock absorption).

        • Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?

          Who says the rover is stopping when it encounters a rock? Either the 342 kg one or the 900 kg one? The same amount of force will stop both, but the force will need to be applied for longer in the 900 kg rover. The term you're looking for is momentum, not force. The 900kg, assuming it's moving at the same speed as the 342 kg one, has more momentum.

          Mass would certainly matter if they crashed the rover and transferred all that momentum, assuming they were moving at the same speed as the equivalent one is h

        • by hankwang (413283)

          force equals *mass* times acceleration. ... the acceleration would be the same but the force experienced by Curiosity's tires would be ~3x larger (ignoring any shock absorption).

          You do have a point -- I don't agree with some of the other responders who talk about traction forces being smaller as well. Just to make it clear: what you say applies to a cart on wheels, having constant horizontal velocity and approaching a bump in an otherwise flat surface. A larger mass of the cart will result in a larger force

        • Scarecrow is 342kg * 1g

          Ow, my units!

        • by necro81 (917438)

          Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?

          That's what's referred to as dynamic acceleration. Rolling along at 1 m/s and then coming to a sudden stop by running into a rock would indeed produce some big accelerations, and the difference in mass between Curiosity and Scarecrow would be pretty significant.

          However, the scenario that you and an earlier comment are talking a

        • Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?.

          1 m/s? Are you kidding? Curiosity has a top speed of less than 0.04 m/s on flat ground, it literally crawls along. Force due to gravity will be by far the dominant force on the rover's wheels.

      • by hazeii (5702)

        The force due to gravity is the same, however on impact the forces will be different (or would you argue the force would be zero in space, since a=0?).

        If I was the bump in the way, I would far sooner be hit by a 342kg mass than a 900kg one - and similarly the damage I'd inflict on the mass would be less.

    • by Anonymous Coward

      except that Curiosity goes nowhere near 1 m/s... more like a few cm/sec so gravity loads far exceed acceleration loads.

    • by necro81 (917438)

      The problem with this is that Curiosity weighs 342kg but masses 900kg. Scarecrow weighs and masses 342kg. Whatever Curiosity weighs, it hitting a rock at 1m/s is still 900 newtons of force. Scarecrow hitting a rock at 1m/s is 342 newtons. The fact it drove 12km and has serviceable wheels does not make me feel better.

      That distinction is really only revelant in the case of dynamic loading: hitting things at speed, rapid straightline accerelation, or quick turning. Whether Curiosity on Mars or Scarecrow on

  • It must have been rougher than normal driving. Can a comparison be made with images taken right after landing?

  • My tire-skin brings all the rovers to the marsyard
    And they're like,
    Its worse than yours,
    Damn right, much worse than yours
    I can teach you,
    But I'll eat your sols

  • They have a marsyard? Where can we get one?
  • the wheels wear as expected...

    In other news: Car tire worn out. "To be expected" claims manufacturer.
  • Doesn't anybody find it curious that it looks in one of the shots that the holes go from the inside to out? How is that even possible? I mean, dents on the outside are reasonable but how did the ones (and there are several deep ones) on the inside happen?

    • by ledow (319597)

      Not really. Work in a garage for a month, you see all kinds of weird damage come in.

      And this wheel is basically a cut-open barrel. Punch it on the outside and it makes a dent on the inside. It's rolling across a rocky landscape, after being basically dropped onto the planet. It probably bumps down a lot more rocks than you realise and even more than NASA ever plan, the chances of finding a level surface to wander over that doesn't have a hidden 10cm drop onto rock for at least one of the wheels hidden b

    • Could be an optical illusion, all the dents I can see on the images go from the outside in.

    • This was my first through.

      I mean, the thing does not travel fast enough to warrant getting a stone to punch through from the outside in,

      However, look at the "Speed Holes" on the wheel surface, I am sure stones caught caught up IN the wheel and then tumbled down to dent the wheel from the inside out.

      I mean, come on, you got big open wheels on a rocky surface, this ain't rocket science.

  • Don't worry, it's all according to the plan.

    Considering the continued cost of maintaining Opportunity (and until not so long ago, Spirit) still running strong many years past expected "expiration date", all new mars rovers have "planned obsolescence" features built in; they are designed to break soon after their planned mission time is past. /tinfoilhat

  • The rover loses 30% of its value as soon as you drive it off the lot. And if NASA tries to trade it in I bet a lot of "damage" will be discovered to drive down the price.

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