Curiosity's Wheels

[RuBisCO]

I think they'll just have to thicken the wheels a bit for the next one. Yes it will add some weight, but it's probably still not much compared to the whole rover, and can probably be saved elsewhere by using more modern lighter science equipment.

As for Curiosity, NASA just don't want to drive over any stones. Which is a bit of a problem on Mars.

That will add weight, I suspect a material change, some kind of carbon fiber with titanium treads.

[Camacha]

That will add weight, I suspect a material change, some kind of carbon fiber with titanium treads.

Adding weight is not a problem if you know it is added from the start. There are good reasons the wheels were aluminium in the first place.

[RuBisCO]

Adding weight is not a problem if you know it is added from the start. There are good reasons the wheels were aluminium in the first place.

Well how much weight can the design take? What reasons are you eluding to?

[mellojoe]

The wheels look pretty good. I remember some images made quite a while back and the holes that can be seen now were pretty much all there back then. It at least means the problem is not worsening very rapidly.

Agreed. The wheel issue surfaced back in like the end of 2013 or so. Testing afterward showed some problems and the team has basically chosen routes and driving habits to minimize damage. This photo from this week shows very little additional damage, so I'm guessing they've found ways to drive to lessen the impact on the wheels. Yes they look bad, but definitely not as bad as I thought.

[Alshain]

The Curiosity is already over a year past it's intended mission. You guys expected the wheels to last forever?

I don't think they need a redesign at all unless you plan on launching a rover intended to last even longer.

All good things...

Edited August 21, 2015 by Alshain

[Camacha]

Well how much weight can the design take? What reasons are you eluding to?

The material of the wheels is an engineering choice. Titanium and aluminium are very similar in some respects, but very different in others. I am not sure about the exact reason aluminium was chosen, but I imagine it has something to do with it being softer (meaning vibrations and other forces are absorbed more than just transferred to vulnerable bits). Remember that the wheels absorb a lot of forces that tires and a suspension normally would, which can be seen rather well in the MER rover wheels. The 'whirly spokes' provide less rigidity, but allow a slight flex, allowing for the wheels to cope with bumps a little bit better.

Galvanic corrosion might also play a role, since aluminium is on the opposite end of the anodic index when compared to titanium, meaning that other, more sensitive parts might corrode instead of the larger, passive wheels.

I cannot answer how much weight the design could take, but I can only assume even tripling the weight is just an engineering problem that can easily be solved. Looking at the complexity of all the other problems that had to be solved, adding a little weight is not really a big issue at all.

I don't think they need a redesign at all unless you plan on launching a rover intended to last even longer.

Curiosity's sister rover, Mars 2020, will feature most of Curiosity's design. NASA has already indicated it will change the wheels due to the problems with the current ones. Long story short, NASA definitely sees the wheel issues as a problem.

Edited August 22, 2015 by Camacha

[cantab]

The Curiosity is already over a year past it's intended mission. You guys expected the wheels to last forever?

I don't think they need a redesign at all unless you plan on launching a rover intended to last even longer.

All good things...

Well, the "intended mission" is deliberately conservative. If Curiosity doesn't have a similar service life to Spirit and Opportunity it would be disappointing. And if it a billion dollar rover is rendered useless because a cylinder of metal wasn't quite thick enough, well that's a bit rubbish really.

[Kryten]

And if it a billion dollar rover is rendered useless because a cylinder of metal wasn't quite thick enough, well that's a bit rubbish really.

EoM being rubbish isn't really preventable though, unless we start fitting these mission with self-destruct devices. Spirit got stuck in some sand, the battery on Pathfinder went through too many charge cycles and broke, Yutu had a small rock break a wire, Chandrayaan overheated, et.c.

[Camacha]

EoM being rubbish isn't really preventable though, unless we start fitting these mission with self-destruct devices. Spirit got stuck in some sand, the battery on Pathfinder went through too many charge cycles and broke, Yutu had a small rock break a wire, Chandrayaan overheated, et.c.

The difference is that those were just normal tear and wear, which is expected sooner or later. The wheels on Curiosity are more fragile than expected. So yes, the mission has been extended already, but no, it is not what would normally be expected.

[Hcube]

Wow, that is some pretty hardcore damage... i wonder what could rip through relatively thick aluminum that way... Even though the wheels are 3 years old, i wouldn't have expected gaping holes like that !

Since we are talking about mars rover wheel design, am i the only one bugged with the design of ESA's ExoMars rover that should launch in 2018 ?

Those look very, very small and are not wide at all... I remember this has been a problem on previous rovers. They are flexible wheels, but still made of metal. I can imagine problems like the rover being stuck in sand because of having its mass distributed on such a small surface.

[Kryten]

Exomars is designed more as a mobile drilling platform than the long-distance explorer curiosity is. It has a lower expected life expectancy, and is very unlikely to venture into properly difficult terrain like sandtraps.

[Hal]

https://upload.wikimedia.org/wikipedia/commons/b/b3/Rover-Exomars-2010.png

The rover's going to be 660 meters tall? Bravo, ESA, I had no clue we could land something like that on Mars.

On a more serious note, on top of the physical changes to the wheels, the rover drivers now know just how dangerous some kinds of terrain can be, and will probably be as careful as they are now of Curiosity from the beginning for Mars 2020, which should help too. Or at least the damage won't be a surprise.