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Gorn
2014-Jul-16, 01:24 AM
Hello. I have seen recently and only 'now...' noticed how 'thin' the rover's wheels are. Somehow it really does not compute.

How were the builders of this rover able to get away with making rover wheels that thin? They seem crazy thin to me.

Thanks for any and all responses
Bye
SC

John Mendenhall
2014-Jul-16, 01:38 AM
Hello. I have seen recently and only 'now...' noticed how 'thin' the rover's wheels are. Somehow it really does not compute.

How were the builders of this rover able to get away with making rover wheels that thin? They seem crazy thin to me.

Thanks for any and all responses
Bye
SC

They are. This has been beaten to death, as have the wheels, in several previous threads. Search for 'rover wheels' in CQ.

grapes
2014-Jul-16, 09:51 AM
They are. This has been beaten to death, as have the wheels, in several previous threads. Search for 'rover wheels' in CQ.
From
http://cosmoquest.org/forum/showthread.php?149845-Shurely-shome-mishtake

We get:
http://cosmoquest.org/forum/showthread.php?137216-Curiosity-Surface-Operations&p=2178717#post2178717

And
http://cosmoquest.org/forum/showthread.php?149189-Mars-Curiosity-Rover

And from "Fraser":
http://cosmoquest.org/forum/showthread.php?149461-Martian-Dune-Buggy-Curiosity-Adopts-New-Driving-Mode-to-Save-Wheels-from-Rough-Rocks

Squink
2014-Aug-20, 09:56 PM
This looks to be the latest in the chain, so:
Curiosity wheel damage: The problem and solutions (http://www.planetary.org/blogs/emily-lakdawalla/2014/08190630-curiosity-wheel-damage.html) Emily Lakdawalla 2014/08/19

It turns out that there are mechanical aspects of the mobility system that actively shove the wheels into pointy rocks. A wheel can resist the force of one-sixth of the rover's weight pressing down on a pointy rock, but it can't resist the rover's weight plus the force imparted by five other wheels shoving the sixth wheel into a pointy rock. The forces are worse for the middle and front wheels than they are for the rear wheels.

Van Rijn
2014-Aug-21, 12:14 AM
This looks to be the latest in the chain, so:
Curiosity wheel damage: The problem and solutions (http://www.planetary.org/blogs/emily-lakdawalla/2014/08190630-curiosity-wheel-damage.html) Emily Lakdawalla 2014/08/19

Fantastic - they understand what has been causing the damage now. Great article.

dethfire
2014-Aug-21, 03:41 AM
Amazing how much we've gotten from that robot.

galacsi
2014-Aug-21, 08:07 PM
Amazing how much we've gotten from that robot.

Er .... What exactly , except an enormous amount of hype ,and $ 2.5 billions less in Nasa's budget ?

That there is phosporus in the martian rocks ?? !!!! Give me a break !!!

NEOWatcher
2014-Aug-21, 08:11 PM
Curiosity big discoveries (http://www.space.com/20396-mars-rover-curiosity-big-discoveries.html)

We won't know until we try.

Strange
2014-Aug-21, 08:27 PM
Er .... What exactly , except an enormous amount of hype ,and $ 2.5 billions less in Nasa's budget ?

Yeah! Science is such a waste of time and money.
/sarcasm

galacsi
2014-Aug-21, 09:07 PM
Yeah! Science is such a waste of time and money.
/sarcasm

Sarcasm is easy , evidences are not . What are your evidences that this robot did any good ?

Swift
2014-Aug-21, 09:13 PM
May I suggest that if you wish to discuss the usefulness (or lack there of) of the Curiosity rover, that you start a new thread about such a discusion, and leave this thread to a technical discussion of the wheels. Thanks.

Strange
2014-Aug-21, 09:13 PM
Sarcasm is easy , evidences are not . What are your evidences that this robot did any good ?

What is your evidence that it didn't and will not? How do you define "good"?

Torsten
2014-Aug-22, 03:10 AM
That was a very good article. Interesting how the suspension design and the unexpected, cemented-in-place ventifacts act together to cause the damage.

JohnD
2014-Aug-22, 08:37 AM
Hear, hear Torsten!

There have been previous threads on this subject, as above and including mine http://cosmoquest.org/forum/showthread.php?149845-Shurely-shome-mishtake&highlight=Curiosity+wheel in which my pitiful attempts at humour drew the ire and fire of a moderator, but also disbeliving incomprehension from others. There were measured comments too. So I am delighted to read Ms.Lackdawalla's article, which answers all the questions I had raised, with clear exposition of what has happened and why. I congratulate NASA for their skill in remote diagnosis and openness.

As always mass trumps other challenges in space exploration, and the Oppo/Spirit experience showed that ultra low mass wheels would do. Curio's wheels and suspension were designed to overcome problems already seen, such as the bogging that killed Spirit, but also for a much, much longer mission than the MERS. 90 days, wasn't it? And still going strong - Go Oppo! But it looks as if Curio's mission could be drasticly shortened, long before that, by wheel failure. I hope that NASA will think more "Rolls-Royce" for future missions, and set a policy to build into its vehicles reliability to match the mission, at the expence of mass for experiments or other facilities in the probe.

JOhn

cjameshuff
2014-Aug-22, 11:09 AM
Fortunately, it sounds like the wheel durability could be substantially improved by mostly moving mass around to avoid concentrations of force that lead to fatigue, using a thin outer coating that adds little mass, and perhaps a different selection of alloy. It sounds like the biggest limit to useful lifetime is the central stiffener ring, with the wheels eventually splitting in half alongside that ring, forming a hazard to cables. I'm betting something as simple as a more rounded transition between the stiffener ring and the skin would largely eliminate that tendency.

Also, perhaps narrower wheels are in order, allowing more thickness to be used. This would make the wheels perform more poorly in sand traps...but while we have lost a rover to a sand trap, it performed 7.73 km of driving first, and its twin has done over 40 km. Maybe the need for performance in sand was overestimated, and trading some for durability would give a better balance.

Swift
2014-Aug-22, 01:20 PM
Given the trade-offs between wheels designed for sand and wheels designed for pointy rocks and bedrock, I suspect that the next rover will be designed for its specific landing site. Which means the landing site will have to be picked early in the process, or, if picked later, the choice of the landing site will be partially governed by wheel design.

Squink
2014-Aug-22, 02:49 PM
Curiosity is generally looking pretty good (http://www.faz.net/aktuell/wissen/weltraum/curiosity-auf-dem-mars-ganz-schoen-mitgenommen-13109551.html) for two years without a bath.

LotusExcelle
2014-Aug-23, 04:21 AM
I volunteer to wash and wax it. I'll even change the tires. And give it an undercoating. Also grease the muffler bearings.

Eadfrith
2014-Aug-25, 11:23 AM
Hmmm... so it's not just the "pointy" rocks that are causing this problem then, there's an engineering/design issue. I still think the wheels are simply not robust enough for the size and weight of the rover.

If you look at Spirits wheels toward the end of the mission, they still looked completely pristine, despite all the driving issues: http://www.midnightplanets.com/web/MERA/image/02143/2F316612115MRDB2D8P1248R0M1.html