Stuck, All six wheels in deep Options

[dot.dk]

Animation of todays drive:

[JES]

......If they were to go straight back down their own trenches, the wheels could end up just churning all the way. By turning the craft a little to 'push' against the left side of the trenches, it gives them something 'new' to have a bite at and pull up out the trenches I guess.

Doug

I remember reading that they were exiting on an arc. Wouldn't we be seeing the wheels biting into the side of the trench a bit and perhaps trying to ride up the side a bit? Or are they keeping the angle at a minimum to increase friction at the side without trying to push into the side. I would think that any displaced material from the side wall would fall into the oncoming track and help raise the wheels up as the rover backs out.

[maycm]

Apologies if this has already been posted.

Here's a polar shot of Oppys present-ish position.



There's a medium res version HERE

[dot.dk]

Interesting! In todays drive they seem to have turned the left front wheel slightly, perhaps the same amount as the 7 degree as the right front.

[Marcel]

Interesting! In todays drive they seem to have turned the left front wheel slightly, perhaps the same amount as the 7 degree as the right front.

Which is very smart i'd say ! Turning wheels in different directions only displace material unnecessary, which costs energy, that is not invested in movement !

[Guest_Sunspot_*]

How would you rate Opportunity's progress so far? Do you think things are going well or not?

It's interesting (as others have pointed out) that the rover doesn't seem to be rising up out of the soil. I wonder if the depth of the rear wheels is preventing the front wheels from climbing up out of the trenches.

[Tesheiner]

Interesting! In todays drive they seem to have turned the left front wheel slightly, perhaps the same amount as the 7 degree as the right front.

Perhaps they want to finish this "left arc" and go straight ahead.
As others pointed out, we can see the effects of this arc on the trenches made by the rear wheels and probably the contact with the side of these trenches add some drag to the forward movement.

But it is just a guess...

Tesheiner

[Marcel]

How would you rate Opportunity's progress so far? Do you think things are going well or not?

I'm not so pessimistics. Eventually, she'll come out I'd guess. But, this could take a long time.

There are three scenario's:

1 The wheels will lift (almost) on top of the soil as soon as she reaches the point where the wheels turned the soil over while digging in weeks ago (about 1 meter from her present position)
2 The wheels will keep on milling around for meters (slowly crawling on like she did last weeks) until one of the cleats of the wheels hits firm rock (evaporite), that will help her out.
3 She won't be able to climb out the dirt soon and keeps on going like this, which will sooner or later cause problems in her bearings/actuators in the wheel (with all these fines).

I hope it's the first one. The second one is fine to me too. The third is horror.



I think (hope) it does not have anything to do with a crust or something, but with the other nature of the last meters of soil.

[Cugel]

I'm new to this topic, so maybe it has been discussed before, however...
As I understand it the problem that Oppy is now in resulted not so much from getting stuck in the dune field, but more in persistent rotation of the wheels when the rover was actually not moving forward. I believe I have read somewhere that the rover got stuck roughly halfway in a long range drive, so after 40 or 50 meters in a 100 meter drive.
However, once it got stuck the software failed to notice this and simply 'completed' the drive. (Correct me if I'm wrong about this) I think this caused the wheels to really dig in deep, which is why it is so difficult to get out afterwards. Had the software stopped the wheels on time, the rover would have backed out much more easily. If this assumption is correct it would mean that driving deeper into the Etched Terrain would not be that risky, with the software properly configured that is... Or is this a bit too optimistic from my side?

[Marcel]

I'm new to this topic, so maybe it has been discussed before, however...
As I understand it the problem that Oppy is now in resulted not so much from getting stuck in the dune field, but more in persistent rotation of the wheels when the rover was actually not moving forward. I believe I have read somewhere that the rover got stuck roughly halfway in a long range drive, so after 40 or 50 meters in a 100 meter drive.
However, once it got stuck the software failed to notice this and simply 'completed' the drive. (Correct me if I'm wrong about this) I think this caused the wheels to really dig in deep, which is why it is so difficult to get out afterwards. Had the software stopped the wheels on time, the rover would have backed out much more easily. If this assumption is correct it would mean that driving deeper into the Etched Terrain would not be that risky, with the software properly configured that is...  Or is this a bit too optimistic from my side?

Yes, Cugel, this has been discussed before. Detecting slippage is only possible in autonomous navigation mode. This digging in probably happened during a blind drive command.

What i was wondering however: They KNOW where they came from in the last drive that ended in this deep. They KNOW at which point they started slipping from imagery. Subtract these distances and you'll get the ratio between wheel motion and actual displacement within this horrendous last meters. This gives us the function that has been posted earlier this threat.

What i was wondering: is this function while digging in the same as it is now, while trying to get out again ? If it is, i am confident that in the end she'll get out within the same amount of wheel revolutions as it took her to get in.

Then there's only one question left for me: how many meters was the commanded drive that got her in the deep ? This might give me the opportunity to win the mars bar in the other threat.......by guessing the sol she'll be up and running again !

[Cugel]

I'm new to this topic, so maybe it has been discussed before, however...
As I understand it the problem that Oppy is now in resulted not so much from getting stuck in the dune field, but more in persistent rotation of the wheels when the rover was actually not moving forward. I believe I have read somewhere that the rover got stuck roughly halfway in a long range drive, so after 40 or 50 meters in a 100 meter drive.
However, once it got stuck the software failed to notice this and simply 'completed' the drive. (Correct me if I'm wrong about this) I think this caused the wheels to really dig in deep, which is why it is so difficult to get out afterwards. Had the software stopped the wheels on time, the rover would have backed out much more easily. If this assumption is correct it would mean that driving deeper into the Etched Terrain would not be that risky, with the software properly configured that is...  Or is this a bit too optimistic from my side?

Yes, Cugel, this has been discussed before. Detecting slippage is only possible in autonomous navigation mode. This digging in probably happened during a blind drive command.

What i was wondering however: They KNOW where they came from in the last drive that ended in this deep. They KNOW at which point they started slipping from imagery. Subtract these distances and you'll get the ratio between wheel motion and actual displacement within this horrendous last meters. This gives us the function that has been posted earlier this threat.

What i was wondering: is this function while digging in the same as it is now, while trying to get out again ? If it is, i am confident that in the end she'll get out within the same amount of wheel revolutions as it took her to get in.

Then there's only one question left for me: how many meters was the commanded drive that got her in the deep ? This might give me the opportunity to win the mars bar in the other threat.......by guessing the sol she'll be up and running again !

OK, thanks for the response Marcel. I guess that would mean that any progress through this sort of terrain will be a lot slower in the future. By the way, I don't think that digging in can be considered the reversal of digging out. They actually do not dig out at all, just bulldozering a new trench all the way out.

[dvandorn]

Then there's only one question left for me: how many meters was the commanded drive that got her in the deep ? This might give me the opportunity to win the mars bar in the other threat.......by guessing the sol she'll be up and running again !

I believe she did wheel turns for about 40 meters of driving without moving at the end of that last blind drive. I also believe I have read that it will likely take more turns than that to get her out -- but the exact number, no one knows.

-the other Doug

[Marcel]

By the way, I don't think that digging in can be considered the reversal of digging out.

That's exactly what i am trying to find out by comparing nowadays attempts to get out with the numbers of getting in. And IF these (slippage)numbers are the same: you can get the best estimate when she'll be back to "normal".....assuming that only the last meter or so is loose material...

[dot.dk]

According to this:
http://www.space.com/imageoftheday/image_of_day_050527.html

Opportunity has now spun it's wheels for 48 meters and gained about 28 cm.

But the interesting thing in the image is that apparently the difference between the red and green areas is 70 cm!!

It's really not easy to see this big difference from the cameras on the rover because of the uniform terrain.
This means the difference between the area just in front of the rover and the area just behind it has a 70 cm difference in height!

No wonder it got stuck

[CosmicRocker]

dot.dk: Good catch on the wheel turn. That 70 cm of elevation change is also interesting news. I am guessing that they have already compensated for the right turn Opportunity made as it ploughed into this dune, and they now want to turn into the trough on the way back out.

Others have wondered how the progress has been so far. I posted some graphs of progress efficiency in another thread.

http://www.unmannedspaceflight.com/index.p...indpost&p=11238

In retrospect, I probably should have posted them here.

The plots display centimeters advanced versus meters attempted, and include data published by JPL and the recent article from space.com. The going has not been getting any better (as we all can see), but the data is a few sols old. As others have pointed out, the latest data point from space.com indicates that 48 meters of attempted driving has occurred, and Opportunity has not gone as far back as she had previously ploughed ahead in 50 meters of attmpted driving.

At least she is still making progress, but I really was expecting progress to get better by now. I would sure like to get some newer data to add to the plots.