-
#1100
by
meekGee
on 27 Dec, 2013 19:40
-
Looks like the rims constitute the "hoops" you are talking about. I dont think any of that is going to really break, but you might start straining the wheel motors a bit more if sharp corners of stones in the surface stick into the holes.
Yes - but if the tear propagates to the rims, you have an almost total disconnect, and the two edges of the tear can shear with respect to each other. If they'd have left internal hoops, it would have stopped the tears from being able to propagate, and the mass penalty would have been much smaller than a thicker skin. Every skin puncture would have been limited to no more than the area bordered by two treads and two hoops.
I don't know if that large hole was punched to full size, or whether it is growing when there's pressure on a point on its circumference.
I wonder if the software can be taught to steer clear of protrusions that will hit that specific hole in the wheel.
-
#1101
by
veblen
on 27 Dec, 2013 20:35
-
The largest hole damage is not as big as the ones designed into the wheel (JPL Morse tracks). Using an abundance of caution the engineering team has uplinked new navigation software that will take Curiosity over smoother terrain.
-
#1102
by
meekGee
on 27 Dec, 2013 21:39
-
The largest hole damage is not as big as the ones designed into the wheel (JPL Morse tracks). Using an abundance of caution the engineering team has uplinked new navigation software that will take Curiosity over smoother terrain.
The engineered holes seem to have edges around them that exactly prevent them from growing. The new holes naturally do not, and the biggest of them seems to be at least as large as the engineered holes.
The new software IIRC will avoid rocky areas in general. I was talking about fine steering to protect the damaged wheel from specific rock protrusions.
I worry more about the existing holes growing than I am about more holes. You could punch a grid pattern of holes in the wheel, remove 70% of the skin, and it would still perform its structural purpose. But if this hole keeps growing you'll get stress concentration around its edges. I hope the Aluminum is ductile enough that this area will deform inwards and that will help mitigate further damage.
I betcha the next wheel will have hoops on the inside.
-
#1103
by
Star One
on 27 Dec, 2013 21:54
-
How do they differ to Opportunity's wheels being as that has been driving on Mars for almost a decade?
-
#1104
by
PahTo
on 27 Dec, 2013 21:56
-
I think more than anything this is a function of the size/mass of the vehicle...
How do they differ to Opportunity's wheels being as that has been driving on Mars for almost a decade?
-
#1105
by
Star One
on 28 Dec, 2013 10:25
-
I think more than anything this is a function of the size/mass of the vehicle...
How do they differ to Opportunity's wheels being as that has been driving on Mars for almost a decade?
A case of smaller is better in this instance.
-
#1106
by
Dalhousie
on 29 Dec, 2013 19:29
-
As far as I can tell Opportunity's and Spirit wheels were essentially undamaged. Clearly Curiosity has a much higher ground pressure.
While this isn't a problem yet, Curiosity is only just into the mission and has covered less than 5 km. It is had as far to go again before it reaches the foothills. Conditions are going to be much rockier there and that is where the work really starts.
So I do think this is an area of concern for the future.
-
#1107
by
hop
on 29 Dec, 2013 20:19
-
As far as I can tell Opportunity's and Spirit wheels were essentially undamaged. Clearly Curiosity has a much higher ground pressure.
They are a very different design, you can't just scale dimensions and get equivalent performance (cube / square and all that.) They also have different requirements, IIRC the MSL wheels were designed to have some give when acting as the landing gear.
So I do think this is an area of concern for the future.
Agreed. They stated from the start that dents and holes are expected, but it seems pretty clear that it is happening at or above the upper end of expectations. MSL can drive on very damaged wheels, but even if it doesn't look like major problem, being outside of expectations is a good reason stop and look at things very carefully.
-
#1108
by
Star One
on 29 Dec, 2013 21:56
-
There must be a limit to how much easier a route they can choose for it, looking at the terrain whatever way they pick to go is going to increase the damage on the wheels and that's before they have even reached the foothills.
-
#1109
by
Dalhousie
on 29 Dec, 2013 22:00
-
There must be a limit to how much easier a route they can choose for it, looking at the terrain whatever way they pick to go is going to increase the damage on the wheels and that's before they have even reached the foothills.
And it is going to be very rocky in the foothills let alone climbing the lower slopes of Mt Sharp.
-
#1110
by
Star One
on 29 Dec, 2013 22:02
-
There must be a limit to how much easier a route they can choose for it, looking at the terrain whatever way they pick to go is going to increase the damage on the wheels and that's before they have even reached the foothills.
And it is going to be very rocky in the foothills let alone climbing the lower slopes of Mt Sharp.
I wonder if the damage continues at this rate on the journey to the foothills that it could move to the status of endangering the mission objectives?
-
#1111
by
meekGee
on 30 Dec, 2013 03:51
-
For a long time now, I noticed that each press release made very sure to emphasize that "mission objectives have been met already". Scientifically, I think they were - Yellowknife bay was a very unexpected boon. From the public perspective though, people expect it to "get to the mountain". (Hell, most people expect it to get to the top of the mountain, even though that's not in the plans, and not scientifically interesting)
That almost boilerplate statement always made me feel nervous, as if they're aware of an engineering issue. If this is it, then so be it. Could have been worse.
-
#1112
by
Dalhousie
on 30 Dec, 2013 07:30
-
Yellowknife was a great site, but it was plain dumb luck that it was encountered so early in the mission. Much like Opportunity landing in Eagle crater.
IMHO the mission objectives are very low key given the cost and proposed capabilities of MSL. Only a dozen post landing science papers have been published.
Also note that the primary mission has been variously reported as being one martian year/two earth years, so we are well short of that.
Combined with how far and long we have to go and the low productivity, these signs and admissions of greater than expected wear and tear concerns me.
-
#1113
by
Star One
on 30 Dec, 2013 09:10
-
Would be somewhat embarrassing if Opportunity outlasted it.
-
#1114
by
notsorandom
on 30 Dec, 2013 12:49
-
Would be somewhat embarrassing if Opportunity outlasted it.
Opportunity has show its self to be not only an incredible machine but quite lucky too. Spirit managed to trek a good distance with a bum wheel so I suspect that Curiosity is not close to stopping. Even without wheels Curiosity can last for a long time and do useful science.
-
#1115
by
hop
on 30 Dec, 2013 19:21
-
A nice long guest post on the planetary society blog by Grotzinger
http://www.planetary.org/blogs/guest-blogs/2013/20131221-habitability-taphonomy-and-curiositys-hunt-for-organic-carbon.htmlIMHO the mission objectives are very low key given the cost and proposed capabilities of MSL. Only a dozen post landing science papers have been published.
"Only"? It seems to me they have published results from the major instruments on the first two sites they've investigated, and with the recent papers also started to describe the broader context of the lake environment. I'm not sure what else you would expect this far into the mission.
-
#1116
by
savuporo
on 30 Dec, 2013 19:26
-
Would be somewhat embarrassing if Opportunity outlasted it.
I think it would be more embarrassing if it got the budget axe, same with Cassini.
-
#1117
by
Dalhousie
on 30 Dec, 2013 19:37
-
IMHO the mission objectives are very low key given the cost and proposed capabilities of MSL. Only a dozen post landing science papers have been published.
"Only"? It seems to me they have published results from the major instruments on the first two sites they've investigated, and with the recent papers also started to describe the broader context of the lake environment. I'm not sure what else you would expect this far into the mission.
[/
Yes, only. The number of papers has been broadly equivalent to Spirit or Opportunity in the same period which had half the number of instruments and much smaller science teams. Only two locations have been investigated in detail. There has been nothing from the meteorology team, nothing from the neutron team, no systematic overview of the traverses, despite thousands of images and hundreds ChemCam shots.
-
#1118
by
Dalhousie
on 30 Dec, 2013 19:41
-
Would be somewhat embarrassing if Opportunity outlasted it.
Opportunity has show its self to be not only an incredible machine but quite lucky too. Spirit managed to trek a good distance with a bum wheel so I suspect that Curiosity is not close to stopping. Even without wheels Curiosity can last for a long time and do useful science.
However a 2.5 billion stationary rover will be something of an embarrassment, it will be the most expensive semi-functional weather station, radiation monitor and remote camera in history. Especially if it fails before it gets to Mt Sharp.
-
#1119
by
savuporo
on 30 Dec, 2013 19:49
-
..There has been nothing from the meteorology team, nothing from the neutron team, no systematic overview of the traverses, despite thousands of images and hundreds ChemCam shots.
I saw some pretty good engineering reads about the EDL sequence though and analysis of MEDLI data. From what i saw, their previous models matched the measurements with remarkable accuracy.