ROVER WHEELS: Monitoring changes over time, NOTE: Read back through the thread to avoid repeating misconceptions Options

[jmknapp]

Ah, I should have looked back in this thread at some of your wheel maps. Looks like they've been doing this since about January?

As for what they did about it, does it refer to this item from February?: Curiosity Adds Reverse Driving for Wheel Protection

[elakdawalla]

Yes, I expect the public event to just be the story behind how they determined they should drive backwards, and drive in valleys instead of on high ground -- a nice story about how you solve an unexpected problem on a distant planet! This story is neat in that it's an engineering problem but understanding how to solve it required very close cooperation with the science team, which is kind of unusual for solving problems with spacecraft.

[Tom Tamlyn]

Any prospect of a video replay (official or bootleg) of the July 16 talk by Grotzinger and Heverley? It looks as though it might be particularly interesting to our crowd.

[bobik]

On June 9, the Washington Post featured an article on the MSL wheel issue.

"What was happening to the wheels was a really big surprise to the team, and not a good one," said Curiosity project manager James Erickson. “We had done extensive testing on those wheels, but we didn’t do testing on extremely sharp and pointy rocks embedded into the ground. But it turns out that Mars has many, many of them."

Project scientist John Grotzinger said the wheel issue "quickly became an epic-scale problem for the mission. . . . It’s a little like being told you’re critically ill. You don’t know how much longer you have, but you know it will be a rough road."

By the way, will the wheel design need to be changed for the Mars 2020 mission?

[jmknapp]

"Critically ill"? Nothing to see here but an "epic-scale problem." Glad they were able to pivot, literally.

[vikingmars]

Everything you want to know about Martian wheels but are too afraid to ask...
https://archive.org/details/nasa_techdoc_19930008925
A JPL/University of Texas study done in 1991... Enjoy !

[Gerald]

[Disclaimer: The images of this post are not actual images from Mars.]

This provides an idea of how far you can go until a wheel fails:

(Screenshots of this video.)

[mcaplinger]

This provides an idea of how far you can go until a wheel fails...

The video is very interesting, but it doesn't describe exactly what is meant by "test to failure". Usually this has a very specific definition for a subsystem test like this. It's not clear to me that the rover would be unable to move with one or more wheels broken even this badly.

[Gerald]

I'd also assume, that the principle of redundance on each subsystem level is applicable to the wheels, meaning one or two wheels should be redundant to some degree. But I've no link to a paper I could reference to, to underpin this assumption, just some extrapolation from the MER rovers.

... Here a Sol 679 image of a passenger on the right middle wheel:

[nprev]

Has there been any attempt made to determine the composition of the rocks that are doing the damage? All I've seen is a reference to an unexpected number of 'small, pointy' rocks in the soil, so I've been assuming that these are shards of basaltic rock that seem to be ubiquitous at every landing site to date save Meridiani.

[fredk]

They could only do that statistically, since I doubt anyone has identified a particular rock punching a hole in a wheel.

Also it sounded like part of the problem was an underlying surface that didn't "give" when driving over a rock. Perhaps under those circumstances there are enough sufficiently sharp garden-variety pieces of basalt to do the damage.

[nprev]

Ah, thanks, missed the part about the substrate. Wonder if perhaps the entire area has underlying hard-tack evaporites.

[Astro0]

That was really clingy soil on Sol 673. Right centre wheel.
Temporary patching on a few cracks

[jmknapp]

Ouch

[climber]

They intended to write a nice "JPL" at regular space on the soil. Well, the message will be a bit confused now...