Ahhh chainmail, mon amour
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 …
COMMENTS
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Monday 20th November 2017 17:14 GMT Anonymous Coward
"Have these types of wheels ever been implemented on any terrestrial form of transport?"
Hmm... I don't think you'd want to use them anywhere wet and muddy, and not on deep sand either; too much of what you're supposed to be driving on would end up inside the tyre instead of beneath it.
There's also the greater force of gravity on Earth, which would need a heavier build of tyre, with a more robust mesh, or 'weave' as it were, to prevent it from squashing under the greater 'weight'.
The trouble with a more robust mesh though, is that if you deform it to the same degree as a finer mesh it will be stressed to a greater degree and more likely to become fatigued and break; when you bend something you get different stresses on the inside and outside of the bend, and the thicker the thing you're bending, the greater the differences in stress.
It might be that the particular combination of dryness (but not deep sand) and lower gravity that you have on the Moon & Mars means that you can use a finer mesh that will still support the vehicle whilst also being more flexible and less susceptible to fatigue.
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Monday 20th November 2017 20:15 GMT cray74
Have these types of wheels ever been implemented on any terrestrial form of transport?
No, because they have very short lives. The original Apollo rover tires had, as I recall, a life of some tens of miles. It was an award-worthy breakthrough in 2009 to develop similar tires with a range of several thousand kilometers. Which is still rather short compared to the life of a modern car tire (on paved roads.)
These metal tires are handy in space because they work over a wider temperature range than rubber. While there are polymers with very wide usable temperature ranges (I work with silicones and fluorosilicones used from -60C to +250C), their mechanical properties shift significantly. Rubber at -60C has quite different behavior than the same at 150C, even if you formulate them to avoid a ductile-to-brittle transition at the low end. Metal wires don't experience that change. (Before anyone says it, vacuum is not an issue for rubber tires. It's just a difference of another 14.7psi. The shuttle tires were kept in unpressurized bays while in orbit. Compared to their ~300psi operating presure, vacuum was a rounding error.)
On the other hand, metal tires experience wear and damage that would just bounce off (har har) a rubber tire. If you CAN use rubber tires because you're in a narrower temperature band (like on Earth), they're a superior option for durability and - usually - traction and ride compared to metal tires. There's just not many reasons to use metal tires on Earth.
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Monday 20th November 2017 09:11 GMT Voland's right hand
So how do you heat it?
The "shape recovery" magic property of of titanium alloys needs heat. The alloy has two temperatures:
1. Recovery range - if you warm it up to that temperature it recovers its "remembered" shape
2. Memorize range - that is the temperature you beat it into shape at.
Most alloys recover ~ 100 degres or thereabouts. So how do you heat the tyre to that temperature on Mars? Bonus points for doing it evenly so it does not warm up too much and too fast ending up remembering its current shape.
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Monday 20th November 2017 11:26 GMT allthecoolshortnamesweretaken
Re: So how do you heat it?
"Or they could alloy the an appropriate ratio of nickel and titanium to ensure its attains superelasticity at the desired temperature range " (And what Dave126 posted.)
Thinking along similar lines here... Basically, it comes down to using an alloy that maintains elastic properties while in use. As in "that'll just pop back after the force doing the deforming is gone again"; IOW "that'll buff out by itself". Like, you know, a spring. Clever, but if that's what they're doing, the bit about plastic properties is a bit misleading. Time to test the elastic/plastic properties of (sub)editors?
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Monday 20th November 2017 20:24 GMT cray74
Re: So how do you heat it?
The "shape recovery" magic property of of titanium alloys needs heat. The alloy has two temperatures:
True, the *shape memory* effect of the Nitinol family happens with heating. However, the alloys have another useful property: a huge elastic range, called superelasticity or pseudoelasticity. Most normal metals can stretch 0.2% of its original length and snap back to their original shape ("elastic deformation"), and any greater stretching results in permanent shape change ("plastic deformation"). Nitinol and friends can exhibit elastic deformations of up to 6%, or 30x that of other metals. This has nothing to do with the shape memory effect.
Hence Nitinol is used in eyeglass frames, bra underwires, and (now) space tires.
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Monday 20th November 2017 11:13 GMT Dave 126
I guess we have a pretty good idea of the composition of Mars dirt by now... Plus there's naff all water to make the soil claggy and sticky. We can knock up some fake Marsian soil on here and do extensive testing. I suspect that the flexible wheels would soon shed off any bits of grit that might stick in the holes.
Lunar dust, due to the lack of atmosphere allowing micro meteorite impacts abrading and fusing, is an absolute pain the arse though. It's like tiny fractals of razor sharp glass.
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Monday 20th November 2017 13:00 GMT Anonymous Coward
"I suspect that the flexible wheels would soon shed off any bits of grit that might stick in the holes."
My thoughts were that a mesh hole will expand as it distorts*** Then a piece of rock of appropriate size/shape could be forced inside - and be unlikely to escape.
Just shape alone could be critical if the rock's length is greater than its width.
Barring Sod's Law such rocks could be uncommon - but over the years they could build up like monks' sandals wearing away steps in old monasteries.
*** The old party trick of dropping a coin through a smaller hole in a flexible surface
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Monday 20th November 2017 11:59 GMT Velv
"Throw in the fact that it's not yet possible to send a spare wheel to Mars and have it fitted"
You can. You just call out The AA or the RAC. But I believe you need to be with your vehicle with your membership card to hand when they arrive. (adapted from Sheldon Cooper, The Big Bank Theory)
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Monday 20th November 2017 13:25 GMT Steve the Cynic
"You just call out The AA or the RAC. But I believe you need to be with your vehicle with your membership card to hand when they arrive"
Not necessarily. I called out the AA on a "Will Join" basis on one occasion. (Specifically, a failed alternator(1).) They arrive, and you end up paying a bit extra compared to a normal join followed by a normal call-out.
(1) On another occasion, I had the voltage regulator fail "hot"(2) - that's not good, but the car will still run. But the "will join" was for the alternator failing "off". Eventually the car stops because there's no electricity for the ignition, neither from the alternator nor from the now-flat battery.
(2) That is, not forcing the voltage down to the appropriate range.
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Monday 20th November 2017 13:09 GMT Anonymous Coward
As it is about something in the USA then one should expect their variant spellings - even if only due to cut&paste from original sources.
There are so many - and really no different from the change in the English spelling of "coud" to "could" in the 15th century so that it matched "would" and "should".
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Monday 20th November 2017 12:12 GMT Anonymous Coward
hello nasa
I was that uncurious that I forgot the curiosity rover existed.
Maybe if they had plonked it down next to the mountains in total recall or that matt damon film I might have been interested in looking at the pictures.
Im glad the nasa boffins invented something. Probably in the hrs of extreme boredom monitoring this mission.
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Monday 20th November 2017 12:59 GMT Nimby
My old glasses
The frames of my old glasses were a titanium alloy, super light, super bendy. 3D print a frame, powder coat, cinter up a wheel of titanium (alloy) foam, and there you go. Replaces bones. Replaces tyres. (On Mars rovers.) An expensive modern solution. (Kind of obvious if you ask me, and probably better all around than a memory-metal chain-mail tyre.)
Or do what an old Mennonite friend did, weld a bunch of rebar to reinforce and add traction to old tractor rims, sans-tyre. It may or may not climb a rocky hill, but it'll last forever. If it rides too bumpy, soften the suspension or drive slowly. Should be fine for a Mars rover. (Except maybe for the whole weight thing.)
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Monday 20th November 2017 13:23 GMT JimmyPage
Terrestrial uses ?
A shame it takes a mission to another planet to kickstart innovation which would enhance the lives of tens of thousands of earthly wheelchair users ?
In fact if NASA had bothered to scour the less able community, they would have probably found a solution all ready to roll (pun intended).
I wait the Russian trollbot downvotes.
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Thursday 14th December 2017 14:52 GMT Spudley
Re: Terrestrial uses ?
A shame it takes a mission to another planet to kickstart innovation which would enhance the lives of tens of thousands of earthly wheelchair users ?
Without commenting on the merits or otherwise of your specific suggestion re this tech, you're missing a major point of trickle-down invention.
In fact, kickstarting innovation is probably one of the major benefits to humanity of the space industry. There are a significant number of inventions that were first developed in the space industry which have gone on to become mainstream products.
Far from being a shame that it happened this way, you should be applauding the fact that the space industry is innovating, because some of those innovations will eventually make their way into your hands.
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Monday 20th November 2017 16:00 GMT W4YBO
Driving through mining country...
in southwest Virginia, you'll see dump trucks with rubber tires covered with a heavy, chain-like mesh. The tires on some of these these trucks are 10 - 12 feet diameter, and cost $20,000 plus.
Several mining companies in the area have only female dump truck drivers because they are so much easier on the equipment.