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Breaks Observed in Rover Wheel Treads
- redcalx 10y agoI assume they're titanium. I wonder though if they use titanium crystals as per jet engine turbine blades?
- jamespetercook 10y agoThe article states they're milled out of solid aluminum
- jordanb 10y agoTurbine blades are made from inconel. And all solid metal is crystalline.
- mtreis86 10y agoSome axial turbines have ceramic blades
- mtreis86 10y agoSome axial turbines have ceramic blades
- andy_ppp 10y agoYou can grow a turbine blade out of one crystal of titanium rather than many which improves the strength. Here's an amazing video about other parts of the structure and construction of Rolls Royce titanium turbine blades. It's awesome. I've no idea about inconel... https://www.youtube.com/watch?v=aFRdp1Js9Kc https://www.youtube.com/watch?v=aFRdp1Js9Kc
- comicjk 10y agoYou're mistaken about all solid metal being crystalline - look up amorphous metal. I've held a ribbon of it, it's quite impressive how it flexes. https://en.m.wikipedia.org/wiki/Amorphous_metal https://en.m.wikipedia.org/wiki/Amorphous_metal
- the8472 10y ago> And all solid metal is crystalline. https://en.wikipedia.org/wiki/Amorphous_metal https://en.wikipedia.org/wiki/Amorphous_metal
- SEJeff 10y agoSpaceX "3D Prints" their merlin engine chambers from the same alloy, inconel. http://www.spacex.com/news/2014/07/31/spacex-launches-3d-printed-part-space-creates-printed-engine-chamber-crewed http://www.spacex.com/news/2014/07/31/spacex-launches-3d-pri...
- greglindahl 10y agoSpaceX's entire Super Draco rocket engine is 3d printed, too.
- redcalx 10y agoSee https://en.wikipedia.org/wiki/Superalloy https://en.wikipedia.org/wiki/Superalloy
- mabbo 10y ago"A routine check of the aluminum wheels" - first sentence of the article.
- averagewall 10y agoTitanium is heavier than Aluminium and only a little bit stiffer, so it's not necessarily a good choice for a weight-sensitive load bearing part even with unlimited budget.
- 6DM 10y agoBreaking after a mere 10 miles, to me sounded really awful, but apparently they planned on this. The construction must have been to save on weight, making the wheels no more reliable than the exact distance they wanted to travel: "...milled out of solid aluminum. The wheels contact ground with a skin that's about half as thick as a U.S. dime, except at thicker treads."
- arethuza 10y agoI wonder if stresses build up from the day night cycles on Mars - which I suspect would be pretty harsh on finely machined bits of metal.
- ceejayoz 10y agoSort of. The early wear was much faster than anticipated, so they've since been using softer ground (sand instead of rock) as much as possible. You don't want to carry around any unnecessary grams on a rover, but I suspect the next one will have sturdier wheels.
- jakobegger 10y agoI thought NASA used metric units; would be nice if their press releases did too. I have no clue what "half as thick as a U.S. dime" means.
- pc86 10y agoIt's easily Google-able. A little more than half a millimeter.
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- overcast 10y agoThe wear patterns on these wheels always seemed so strange to me, considering the extremely slow pace at which this thing moves. The wheels look like they've been hit by shrapnel. Obviously I have no context as to what conditions are like on Mars, but it just seems strange that driving over rock, slowly produces wear like that. Seems like they were never strong enough to support the weight, over something sharp.
- Klathmon 10y agoI used to think the same thing, it looks pretty intense for just rolling over some rocks! But then I learned that in between the "treads" the aluminum is "half the thickness of a dime" (as the article puts it). So if you think of it like the lid of a can of soup or something, it's easy to see how it could deform and break like that when rolled up against sharp rocks with a ton of weight on top of it.
- overcast 10y agoI understand that, which is why I said it never seemed strong enough to begin with. I get you need to conserve weight, but doing so on the wheels, seems, crazy? The most important thing of an entire car is the tires. Without good tires, a race car can't do anything, no matter how well engineered the rest of it is.
- Klathmon 10y agoI think it's a gamble. If they made them thick enough to never break, they could have blown the whole weight budget. But if they make them too thin, the whole project is a waste. I mean the wheels are probably among the heaviest single "things" on the rover, so adding even a small amount of thickness will really increase the weight, and that would mean cutting other things. It's a tough call, and I'm sure as hell glad I wasn't the one that had to make it, but I think all things consitered they did a good job! It's been running for 5 years and even though these look bad, apparently it still has a lot of life left in it!
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- JetDogRush 10y agoThis seems dramatic, but there is a ton of life left in the wheels. Some of my colleagues performed life testing on the wheels after we first discovered the cracks and found the rover is capable of driving around on the titanium support struts even after the aluminum wheels have completely disintegrated. We've got a long way to go yet!
- kahnpro 10y agoIf Kerbal Space Program taught be anything about space, it's that most problems can be solved with struts.
- JetDogRush 10y agoIf only Curiosity were as fast as the KSP rovers... top speed is somewhere around 100 meters/hour, and usually more like 40!
- TeMPOraL 10y agoShould have strapped an SRB on the rover. Reminds me; I wonder just how much ion engines are overpowered in KSP compared to their real-life equivalents. Or, put differently, if one could replicate a hovering Minmus rover I made in KSP (which used ion engines to stay afloat for a long time).
- jerf 10y agoMinmus surface gravity is 0.491 m/s^2; current ion drives thrust with a couple hundred millinewtons, so I don't think a drive could even support itself against that level of gravity let alone with power and a ship attached. However, we currently design our ion drives for power-to-thrust efficiency and long-term effectiveness. I'm not sure what we could get if we designed them for maximal thrust. Especially since in real life, right now the answer to "Do you want a 'maximal thrust' ion drive?" is pretty much "Well, have you considered using... not an ion drive?", so I'm not sure I've ever seen a treatment of that question based on current tech.
- dayjah 10y agoThis appears to be a brilliant case of reliability engineering. I'm always super impressed with these sorts of tales; given how NASAs budget always seems to be concern seeing them deliver solutions which have just enough wiggle room in them to deliver the intended results without going too far into gold plating their solutions really leaves the software infrastructure engineer in me in awe. Even more so when you consider the time spans involved in this; I personally believe we've a ton to learn in the software space from practices like this.
- jeremiep 10y agoI think we also have a ton to learn in the software project management space. Agile for example would be quickly laughed off and dismissed. Our field is currently full of cargo-cult practices, studies and best practices without any empirical research, java schools, a strong focus on "awesome" and easy to get started instead of useful and simple; we're still a pop culture for the most part.
- mayukh 10y agoSolution dictates the construction process. No point in over engineering a consumer facing app when flexibility dictates who wins in the market place. Not endorsing agile or any other practice in particular.
- saiya-jin 10y agoagile has its place, in some form, in some places. problem is people treat it like panacea. completely agree about the pop culture analogy especially with devs with say < 5-7 years experience, a good one :)
- SomeStupidPoint 10y agoWhat's wrong with Agile? I mean, I wouldn't design a rocket, bridge, or certain kinds of software that way... But talking about most web front-ends or feature services?
- KaiP 10y agoUse the right tool for the job. Risk profiles between web app software and rover software are totally different.
- DanBC 10y agoThis comment from a while ago links to a really good blog about the wheels: https://news.ycombinator.com/item?id=8206378 https://news.ycombinator.com/item?id=8206378 Here's a direct link to the 2014 blog talking about damage to the wheels: http://www.planetary.org/blogs/emily-lakdawalla/2014/08190630-curiosity-wheel-damage.html http://www.planetary.org/blogs/emily-lakdawalla/2014/0819063...
- pfortuny 10y agoSo ir broke after how many years of life longer than the expected utility? Like forever, iirc...
- krallja 10y agoYou're probably thinking of Spirit and Opportunity, the smaller rovers which landed in the early 2000s and long outlived their primary scientific missions. This is Curiosity, the SUV-sized rover which landed in 2012, and is still in its primary mission.
- JetDogRush 10y agoNot quite - primary mission was two years (one Martian year). We are in Extended Mission #2.
- krallja 10y agoOops, you're right! Thanks.
- tetraodonpuffer 10y agothis picture definitely helps with comparing the relative scales of the rovers https://marsmobile.jpl.nasa.gov/images/Evans_Mars_Yard.jpg https://marsmobile.jpl.nasa.gov/images/Evans_Mars_Yard.jpg
- kirykl 10y agoNASA is funded by Americans, and this is a press release not a scientific paper. US customary units and dimes is intentional for the audience.
- JackFr 10y agoAlso very descriptive, since dimes are also noticeably thinner than our other coins.
- wintom 10y agoMartians popping our tires? In all seriousness its unclear to me how this could happen so quickly? The article does not really explain why they didn't think through this.
- JoeAltmaier 10y agoThe tires are exactly as strong as needed to perform the primary mission, and no stronger. They are doing that easily. This was successful engineering, not some mistake.
- AnkhMorporkian 10y agoThey did think through it, but the rover has already exceeded its planned mission time by over 2.5 years! Wheels can't last indefinitely, and more than doubling the time of a 2 year mission before they see any wear is pretty incredible.
- reneherse 10y agoThere are a combination of factors not mentioned in the article: One, encountering terrain with unexpectedly sharp, immovable rocks. Two, a suspension arm design that happens to put increased force on certain wheels when they encounter immovable rocks. Three, the wheels have a tread pattern with a sharp, angular geometry, causing stress risers at the points of the pattern, where the thin metal meets the thicker raised treads. The thinner metal thus tends to crack more readily at these points. (BTW, it is only this last point that I consider to be a legitimate design flaw, given the innumerable constraints the engineers had to work within. The rover is a marvel of engineering on every level.) An article for reference.[1] [1] http://www.planetary.org/blogs/emily-lakdawalla/2014/08190630-curiosity-wheel-damage.html http://www.planetary.org/blogs/emily-lakdawalla/2014/0819063...
- typetypetype 10y agoTangential, but the quality and resolution of that image is incredible.
- mrfusion 10y agoHow's it possible to get all that wear in ten miles? That's just a trip to church. My car tires don't even register that.
- Cthulhu_ 10y agoYour car tires aren't made out of <1mm thick aluminium driving over rocks either.
- deleted 10y ago[deleted]
- olex 10y agoYour car tires are rubber, and designed to last for a long time at speed. Curiosity's tires are aluminum, and are designed for much less and much slower driving. That seems weird, but the important point is their mass: they only weigh 3 lbs (~1,4kg) per wheel, compared to over 20 lbs for the tire alone (without the rim) on a normal car. Mass budgets are extremely tight on space missions, every pound saved can either go towards more scientific payload or significantly decrease launch costs.
- ianai 10y agoCar tires also have the benefit of a nearby support system. They were looking for wheels that would do the job with 100% certainty of never being able to be replaced.
- valuearb 10y agoAlso rubber would disintegrate given hot/cold cycles and radiation.
- ufmace 10y agoAnd they probably do like 99.9% of their distance over roads in effectively perfect condition.
- pjc50 10y agoYour trip is presumably not over some extremely sharp rocks.
- yread 10y agoApparently the new rover - Mars 2020 - will have narrower, thicker wheels with more growsers with a different shape https://mars.nasa.gov/mars2020/mission/rover/wheels/ https://mars.nasa.gov/mars2020/mission/rover/wheels/
- mentos 10y agoAlways loved the name of the Curiosity rover, was just reading the wikipedia article, apparently it was crowd sourced from 9,000 proposals and the selected name was from a 12 year old student. Very cool "A NASA panel selected the name Curiosity following a nationwide student contest that attracted more than 9,000 proposals via the Internet and mail. A sixth-grade student from Kansas, twelve-year-old Clara Ma from Sunflower Elementary School in Lenexa, Kansas, submitted the winning entry. As her prize, Ma won a trip to NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, where she signed her name directly onto the rover as it was being assembled. Ma wrote in her winning essay: Curiosity is an everlasting flame that burns in everyone's mind. It makes me get out of bed in the morning and wonder what surprises life will throw at me that day. Curiosity is such a powerful force. Without it, we wouldn't be who we are today. Curiosity is the passion that drives us through our everyday lives. We have become explorers and scientists with our need to ask questions and to wonder." https://en.wikipedia.org/wiki/Curiosity_(rover) https://en.wikipedia.org/wiki/Curiosity_(rover)
- abandonliberty 10y agoI'm very happy that we're involving students and helping increase passion for space. Is it crowd-sourcing when the result is selected? If infinite monkeys give us Shakespeare, 9000 students should generate a pretty dense set of data given student vocabulary. Cynicism: 1. Know what you want to call it 2. Canvass 9000 people 3. Pick the best one that agrees with you (because there must have been collisions)
- BurningFrog 10y agoSounds like the work of Kristen Wiig in The Martian.
- vkou 10y agoIf you know what result you want, why not just have a patsy write your suggestion in, so that you can select it?
- beached_whale 10y agoThis poetry really speaks to me. It could have gone the other way and been named Marszi McMars Rover or something else. It would have been funny, but very uninspiring.
- ianai 10y agoAm I the only one that thought they meant the tracks left on the ground?
- postit 10y agoWhat surprises me is that the wheels aren't covered with a honeycomb-like texture instead of these longitudinals M's
- Splendor 10y agoI would love to see a write-up of everything we've learned about wheel engineering from the Mars rovers. What would the team(s) responsible for Curiousity's wheels do different now? (I don't mean to imply that their design is not successful -- just that I'm sure they've learned from this iteration)
- nanodano 10y agoDoes anyone else think it's odd that the treads are wearing like that after TEN miles? They probably could have done better by sticking a Goodyear on it.
- JoeAltmaier 10y agoWould be less confusion in this thread, if the title added "as predicted and on schedule for successful mission completion"
- anotheryou 10y agoas predicted after more tests. they where surprised about the ammount of damage initially.
- theandrewbailey 10y agoMeanwhile, Opportunity keeps going after 13 years. https://mars.nasa.gov/mer/mission/status.html https://mars.nasa.gov/mer/mission/status.html
- jcoffland 10y agoThe spin machine is always on at NASA. It's not that the wheel is failing it's "nearing a wheel-wear milestone." Still it's impressive what they have achieved.
- gregcohn 10y agoDid you know the wheels have morse code embedded in their tread? https://www.jpl.nasa.gov/news/news.php?feature=3497 https://www.jpl.nasa.gov/news/news.php?feature=3497
- JKCalhoun 10y agoAre the materials used in the rover wheels too exotic? I'm metallurgist, but I know that steel, though heavy, is malleable and, if correctly tempered, unlikely to break like the rover's wheels. At what cost ultralight, exotic metals? Edit: Are they really made of aluminum? If so, while hardly exotic, definitely more brittle than steel. I know steel is heavy as hell, but of course you can use a thinner steel for an equivalent strength (still heavier I suppose).
- MadManE 10y agoOne of the first things that I got told in my materials class was that for the strength and weight, carbon steel and aluminum are essentially the same. Steel is about 3x as dense, but also 3x as strong, and does not fatigue like aluminum. I'm assuming that NASA knows this, and chose aluminum for another reason that I'm not aware of.
- danaliv 10y agoFun little bit of trivia: those slots in the wheels are Morse code, and they spell out "JPL." The original design had the letters JPL emblazoned on the wheels but they felt this was a little too tooting-your-own-horn, so they made them Morse code instead.[0] 0. Personal communication from MSL engineer
- awinter-py 10y agoeven blizzak coatings last more than 10 miles this doesn't bode well for their JD Power rating I guess if you start the odometer at launch their numbers look a little better
- gene-h 10y agoIt's a shame that the trend in increasing rover size probably won't continue. If scaling does continue, we might expect to have rovers the size of monster trucks on Mars by 2030.