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posted by janrinok on Saturday November 25 2017, @07:48AM   Printer-friendly
from the forget-the-puncture-kit,-give-me-a-welding-torch dept.

Chainmail tires re-invent the wheel to get future NASA rovers rolling.

NASA has developed chainmail tires with a memory and thinks they'll do the trick for future rovers.

As readers of The Register's coverage of the Curiosity Rover may recall, the vehicle has experienced considerable wheel damage that has led to changes to its route in 2014 and a 2017 software update to preserve the wheels and provide better grip.

Throw in the fact that it's not yet possible to send a spare wheel to Mars and have it fitted, and NASA has a clear need for more robust tires.

Enter a technology called "spring tires" that use a tubular structure of steel mesh – think tire-shaped chainmail - to cushion rovers as they roll. Spring tires have many fine qualities as the mesh forms a pattern that provides good grip on many surfaces. Mesh is also light by nature and can survive some damage. But spring tires don't deform well: if one rolls over a sharp rock, it can acquire a dent - or "plastic deformation" as NASA boffins put it.

The tires use a nickel titanium alloy that can endure plastic deformation.


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  • (Score: 3, Interesting) by frojack on Saturday November 25 2017, @08:03AM (7 children)

    by frojack (1554) on Saturday November 25 2017, @08:03AM (#601307) Journal

    it's not yet possible to send a spare wheel to Mars and have it fitted,

    Why not?

    Maybe they should develop a Rover Service Rover. And maybe design new Rovers to be serviced.

    Especially if they are all going to out-live their design life. (Curiosity is 5 years into its planned 2 year mission.)

    How can we seriously be discussing sending people to mars if a little problem with a wheel can't be foreseen and fix sent.

    --
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    • (Score: 3, Interesting) by takyon on Saturday November 25 2017, @08:39AM (6 children)

      by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday November 25 2017, @08:39AM (#601319) Journal

      I'm thinking it will cost no less than $500 million to use a new rover flown to Mars for the purpose of changing the tires on Curiosity. Better just to build future rovers with these new tires. Starting with Mars 2020 [wikipedia.org] which is launching in July 2020. NASA should be hounded repeatedly on whether Mars 2020 will use the chainmail tires instead of the originally planned ones. They were the ones who touted their chainmail tire breakthrough after all.

      Where we should have serviceability is our space telescopes. The James Webb Space Telescope is not designed to be serviceable. It will eventually run out of fuel for station keeping [nasa.gov]. Can a small spacecraft be sent to refuel JWST towards the end of its life anyway? Let's hope so. Although better telescopes than JWST will eventually be sent into space, old [wikipedia.org] and partially-broken [wikipedia.org] telescopes still get used as much as possible. There's an essentially infinite number of stars, galaxies, and other objects to point your telescope at, and making repeated or continuous observations can reveal planets, flares, etc.

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      • (Score: 2) by Runaway1956 on Saturday November 25 2017, @09:31AM (5 children)

        by Runaway1956 (2926) Subscriber Badge on Saturday November 25 2017, @09:31AM (#601334) Journal

        Station keeping . . . I've wondered why they don't put something like that into a higher orbit, where it's much easier to maintain station. And, if it does wander a little, the consequences are negligible. In LEO, being ten miles off course can be catastrophic. Somewhere close to the earth/moon Lagrange point, being a thousand miles off course would be almost meaningless. Everyone on earth who wants to see the signal from the satellite simply adjusts his antenna toward the off-course satellite. What, a couple tenths of a second, for 1000 miles at that range? Even if it's a whole minute, point your antenna at it's assigned position, then focus to get the strongest signal.

        That would, however, make it more expensive to perform maintenance, since you have to get a lot further up the gravity well to work on it.

        • (Score: 5, Informative) by takyon on Saturday November 25 2017, @09:42AM (4 children)

          by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday November 25 2017, @09:42AM (#601336) Journal

          An L2 orbit is meta-stable so it requires orbital station-keeping or an object will drift away from this orbital configuration.

          [...] The JWST will be located near the second Lagrange point (L2) of the Earth-Sun system, which is 1,500,000 kilometers (930,000 mi) from Earth, directly opposite to the Sun. Normally an object circling the Sun farther out than Earth would take longer than one year to complete its orbit, but near the L2 point the combined gravitational pull of the Earth and the Sun allow a spacecraft to orbit the Sun in the same time it takes the Earth. The telescope will circle about the L2 point in a halo orbit, which will be inclined with respect to the ecliptic, have a radius of approximately 800,000 kilometers (500,000 mi), and take about half a year to complete.[14] Since L2 is just an equilibrium point with no gravitational pull, a halo orbit is not an orbit in the usual sense: the spacecraft is actually in orbit around the Sun, and the halo orbit can be thought of as controlled drifting to remain in the vicinity of the L2 point.[107] This requires some station-keeping: around 2–4 m/s per year[108] from the total budget of 150 m/s.[109] Two sets of thrusters constitute the observatory's propulsion system.

          Why is JWST at L2?

          https://space.stackexchange.com/questions/284/why-should-the-james-webb-space-telescope-stay-in-the-unstable-l2 [stackexchange.com]

          1. The distance from the L2 to Earth is only 1.5 million km away. The L4/L5 are 1 AU, or about 150 million km away. That leads to a reduction in link margin of 40 db, or 1/10000. That is quite significant. In order to compensate for that difference, you either need a bigger radio dish, more power, or a loss in data.
          2. As you mentioned, the fuel usage is quite low to maintain that position, only on t.order of 150 m/s delta v for the entire mission. That isn't a whole lot, and in fact, is less than what is required to keep a satellite in geostationary orbit.
          3. The satellite is much closer, reducing the time to command an object. Light only will take 5 seconds to reach James Webb, whereas it will take 9 minutes to reach L4/L5. This limits the ability to do real time commands, which occasionally are useful (Think Gamma Ray Bursts, Super Novas, etc)

          http://en.wikipedia.org/wiki/Lagrangian_point#L2 [wikipedia.org]

          The Sun–Earth L2 is a good spot for space-based observatories. Because an object around L2 will maintain the same relative position with respect to the Sun and Earth, shielding and calibration are much simpler.

          It's important to make sure these instruments never point towards the Sun.

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          • (Score: 2) by frojack on Saturday November 25 2017, @09:02PM (3 children)

            by frojack (1554) on Saturday November 25 2017, @09:02PM (#601494) Journal

            Exactly.

            Its not an easy place to get to either.
            But a simple refueling port on the platform would have been cheap. You could easily justify the cost on a hunch that automated vehicles could be designed in the interim. Its expected life was 5 to 10 years.

            Musk's first flight was in 2008. He's routinely landing rockets today 8 years later. Shit is moving very fast these days, and JWST isn't even scheduled to launch till 2019.

            --
            No, you are mistaken. I've always had this sig.
            • (Score: 2) by takyon on Saturday November 25 2017, @10:16PM (2 children)

              by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday November 25 2017, @10:16PM (#601522) Journal

              It's not an easy place for humans to get to, ala Hubble servicing missions. Or in other words, it would be further away than humans have ever traveled from Earth (although not that far, just ~four times the distance to the Moon). But robotic spacecraft? No problem.

              I hope that despite its lack of serivceable design, it could still be serviced anyway. Even if takes physically ripping into it or having the second spacecraft grab onto JWST and become the new thruster. Because if you are going to let the nearly $10 billion scope go to waste, you might as well try.

              If the scope ends up performing for a full 10 years, by the time we get to year 5 the science value of JWST should be clear in that it will be beating Hubble for many observations. It should be enough to pressure who needs to be pressured to try and make this happen.

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              • (Score: 1) by anubi on Sunday November 26 2017, @08:56AM (1 child)

                by anubi (2828) on Sunday November 26 2017, @08:56AM (#601671) Journal

                (although not that far, just ~four times the distance to the Moon).

                Nor do we get the benefit of the Moon's gravitational field to sling us back.

                So we are gonna spend either a helluva lot of fuel braking and resuming the trip velocity back, or take a helluva lotta time creeping up to it.

                --
                "Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
  • (Score: 3, Informative) by Anonymous Coward on Saturday November 25 2017, @01:01PM (3 children)

    by Anonymous Coward on Saturday November 25 2017, @01:01PM (#601364)

    Compare this new "chainmail" tire to the original General Motors designed Lunar Rover tire,
        https://en.wikipedia.org/wiki/Lunar_Roving_Vehicle#Wheels_and_power [wikipedia.org]
    Very similar woven mesh design. The Lunar Rover tire has Titanium "tread" elements attached and there are various other detail differences.

    Chainmail is a poor term, the new rover tire does not have little links looped together like actual chainmail (as used for the joints in medieval armor).

    Why not acknowledge that this new wheel is a development of the older design?

    • (Score: 2) by mhajicek on Saturday November 25 2017, @05:56PM (2 children)

      by mhajicek (51) on Saturday November 25 2017, @05:56PM (#601436)

      Indeed. Nothing to do with chainmail, these are just a material upgrade of the old lunar rover wheels. My question is how the nitinol will perform in the extreme temperature variations of extraterrestrial environments. My company makes nitinol medical implants, and liquid nitrogen is used to put the material into it's squishy state where it doesn't spring back until warmed. Then it's put on a forming mandrel and heated in molten salt to set the new shape. These critical temperatures can be controlled by the alloy mix, but I don't know how far. If the environment is too cold for the alloy the wheels would just squish and stay there

      --
      The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
      • (Score: 0) by Anonymous Coward on Saturday November 25 2017, @06:40PM (1 child)

        by Anonymous Coward on Saturday November 25 2017, @06:40PM (#601451)

        A friend who had recently retired from Goodyear R&D, was asked to work on a volunteer project about 10 years ago -- re-create the Lunar Rover wheels/tires. While they had a sample to look at, the original tooling was gone, along with the know-how of the original makers. They had a devil of a time, but eventually worked out how to weave the wire and so on.

        One possible reason for Nitinol would be to relatively easily form it to the correct curve(s), before weaving? Then it would hold its shape instead of trying to spring back to straight like the original galvanized music wire (spring wire). But I take your concern about extreme temps in space, one would hope that they have considered this!

        How is Nitinol for abrasion resistance? Music wire is pretty darn hard, but if (as noted in Wiki) it was galvanized, that is not a hard surface. Maybe the Zinc was just to prevent rusting/oxidation while on Earth, before launch?

        • (Score: 2) by mhajicek on Saturday November 25 2017, @10:13PM

          by mhajicek (51) on Saturday November 25 2017, @10:13PM (#601519)

          I think it's pretty good for wear resistance. I know it eats endmills like popcorn when you machine it unless you're running liquid nitrogen for coolant. It's also what's called "superelastic", look up the yield curves.

          --
          The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
  • (Score: 0) by Anonymous Coward on Saturday November 25 2017, @07:01PM (3 children)

    by Anonymous Coward on Saturday November 25 2017, @07:01PM (#601456)

    We can build a tire for low temperature. It would likely be liquid at Earth temperature, but this is a minor annoyance.

    The obvious way to deal with that is to keep the tires at Martian temperature as we prep for launch.

    An alternative is to have a thin other layer that is not liquid. After the underlying portion has solidified during the trip and been taken to Mars, we drive the lander around and don't worry about the thin outer layer flaking off. It's a sacrificial tire mold.

    Solid is fine, as is a tweel or gas-filled. All will work, and this is a separate consideration.

    • (Score: 2) by frojack on Saturday November 25 2017, @09:16PM (1 child)

      by frojack (1554) on Saturday November 25 2017, @09:16PM (#601500) Journal

      We can build a tire for low temperature. It would likely be liquid at Earth temperature,

      Seriously? Where would that be on the periodic table?

      Its not THAT cold on Mars. -107 °C

      --
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      • (Score: 0) by Anonymous Coward on Sunday November 26 2017, @08:01AM

        by Anonymous Coward on Sunday November 26 2017, @08:01AM (#601662)

        The freezing point for gasoline is somewhere between -40°C and -60°C, depending on the mix and how solid you want it to be. That sounds about right for a Martian tire.

        Normal tires would tend to crack at that temperature.

    • (Score: 0) by Anonymous Coward on Sunday November 26 2017, @04:08AM

      by Anonymous Coward on Sunday November 26 2017, @04:08AM (#601590)

      Have you cut open a radial tire recently? Under the tread rubber there are two layers of steel wires (at opposite angles), close packed and held in position by the surrounding rubber -- thus "steel belted" tires.

      By weaving the two layers in the Rover tires, the wires are no longer close packed, there is lots of open space in the mesh. Even allowing for the extra wire in the Rover tires for the "sidewalls", there is probably less metal in the Rover tire than in a normal passenger car tire. In other words, these Rover tires are very lightweight, no rubber at all to hold the carcass together.

      Given the cost to launch anything, I can't see the advantage in lugging heavy rubber tires up into space...until such time that high speed vehicles are being used and high traction on paved surfaces is required.

  • (Score: 1, Insightful) by Anonymous Coward on Saturday November 25 2017, @07:13PM (2 children)

    by Anonymous Coward on Saturday November 25 2017, @07:13PM (#601462)

    The wheel damage is because NASA ignored both of these well-studied problems:

    https://en.wikipedia.org/wiki/Fatigue_limit [wikipedia.org]
    https://en.wikipedia.org/wiki/Stress_corrosion_cracking [wikipedia.org]

    Aluminum is just going to fail. Titanium and spring steel are far better. Mars also has perchlorate salts, so that probably eliminates spring steel. There you go: titanium.

    A wheel design without the inside corners (high stress points) would also help. That zig-zag rib in the tread should have had the corners rounded.

    • (Score: 2) by frojack on Saturday November 25 2017, @09:27PM (1 child)

      by frojack (1554) on Saturday November 25 2017, @09:27PM (#601506) Journal

      Wheel damage has pretty much tapered off in the second half of the mission.
      The guy who wrote the hand-wringing wail of the wheels has pretty much admitted he was mistaken. [soylentnews.org]

      I've been concerned about the potential for wheel damage from the Naukluft crossing ever since I wrote my long explainer on wheel damage one Mars year ago, but that concern seems to have been misplaced. While the wheels are continuing to degrade, there was no acceleration in the rate of damage during the crossing; the wheels are holding up better than I expected.

      I'm also sure that if YOU yourself look at the wheels (with all your engineering credentials,) you will the damage shown is NOT from the things you seem to quote. Corrosion is almost nil at those temperatures. None of the wheel damage is occurring at the inside corners, and fatigue is not the source of these problems. (lots of recent pictures at the link posted above).

      The photos show damage, but since they started driving sensibly, (around instead of over things) it has dramatically tapered off. Like a teenager with a new hot rod, the first set of tires go quickly. Then sticker shock makes the next set last 4 times as long.

      --
      No, you are mistaken. I've always had this sig.
      • (Score: 0) by Anonymous Coward on Sunday November 26 2017, @09:23AM

        by Anonymous Coward on Sunday November 26 2017, @09:23AM (#601673)

        First of all, your link is broken.

        The pictures that would be needed are microscopic, preferably scanning electron microscope pictures of properly treated surfaces. Those pictures don't exist.

        Anyway, fatigue is obvious. Aluminum does not have a fatigue limit. This is a fatal flaw. Any repeated flexing, no matter how minor, will cause aluminum to fail. Titanium and spring steel have fatigue limits; flexing that is minor enough can be repeated forever without causing damage.

        Regular corrosion isn't the issue. This isn't about wheels being simply eaten through. It's about crack propagation that is promoted by corrosion that is invisible to the human eye. The temperature may be low, but this isn't friendly garden soil. Perchlorates are nasty.

        Mars has iron oxide and perchlorates to go with the rover's aluminum wheels. Can you remember where else NASA mixed those components? It was the fuel of the Space Shuttle's solid rocket boosters. The fuel was literally that, plus a rubbery binder holding it together. These chemicals are anything but peaceful when you put them together. Aluminum strongly takes oxygen and would spontaneously ignite in Earth atmosphere if not for the hard layer of aluminum oxide that forms on the surface. Chlorine tends to disrupt that layer; chlorine is found in the perchlorate ion. Without being silly (liquid mercury perhaps) it would be hard to come up with a worse chemical environment for aluminum wheels.

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