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Unmanned Spaceflight.com > Mars & Missions > Past and Future > MER > Spirit
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fredk
We may have the same scenery for quite a while. From the latest release:
QUOTE
The rover team... has suspended driving Spirit temporarily while studying the ground around the rover and planning simulation tests of driving options with a test rover... "Spirit is in a very difficult situation," JPL's John Callas... said Monday. "We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again."

In the past week, the digging-in of Spirit's wheels has raised concerns that the rover's belly pan could now be low enough to contact rocks underneath the chassis, which would make getting out of the situation more difficult.
alan
I've been seeing this listed on the tracking site recently

01904 p2568.22 0 0 0 0 0 0 pancam_light_disturbed_soil_L6R1
01904 p2569.22 0 0 0 0 0 0 pancam_undisturbed_soil_L6R1
01904 p2570.22 0 0 0 0 0 0 pancam_dark_disturbed_soil_L6R1

Watching for signs of wind gusts?

By the way with the new found energy and the apparent decrease in activity why isn't the backlog of images being downloaded?
RoverDriver
QUOTE (alan @ May 11 2009, 07:51 PM) *
I've been seeing this listed on the tracking site recently

01904 p2568.22 0 0 0 0 0 0 pancam_light_disturbed_soil_L6R1
01904 p2569.22 0 0 0 0 0 0 pancam_undisturbed_soil_L6R1
01904 p2570.22 0 0 0 0 0 0 pancam_dark_disturbed_soil_L6R1

Watching for signs of wind gusts?
...


No. We are trying to gather mechanical properties of the soil under the wheels. Actually where the wheels are buried. We have observe from the RHAZ that although the wheels have churned up the soil pretty badly, the left side soil is bright in color while the RR wheel has churned up dark material. We believe the dark toned material could provide more traction than the light tone material. We will try to replicate the soil properties in the testbed, evaluate which strategies might work better and go from there. The situation is compound by the issue of high-centering. We are not sure we are high centered, but if we are not, we are cose to it. There is a single frame NAVCAM taken on sol 1870 which shows the terrain the rover is currently sitting. By comparing that NAVCAM frame with the NAVCAMS taken from the current location we are trying to figure out exactly where the rover is and determine if we are high-centered. The last fly in the ointment is that during the last executed drive (sol 1899) the LM wheel stalled. We do not have a cause yet, could be a rock stuck in the wheel well, could be bedrock underneath the wheel, could be an actuator problem.

This is a pretty big mess: embedding event + high-centered vehicle + stalled wheel. Since I have been asked to lead this investigation, you know why I won't be posting much during the next few weeks.

Paolo
nprev
Oh, boy. sad.gif Thanks for the update, and good luck, Paolo. We're rooting for you!
alan
My guess for the location of the wheels.
Click to view attachment

Also identified are the original location of the rock that was flipped after being dragged and one that appears to have gone missing during all the churning.

ETA:
the pancam site has a color image of this location,
http://marswatch.astro.cornell.edu/pancam_..._L257_pos_5.jpg
(about a third of the way up and a third of the way to the right from the lower left corner)
Sunspot
Looks like some people think we may be here for the rest of the mission.
RoverDriver
QUOTE (alan @ May 11 2009, 10:45 PM) *
My guess for the location of the wheels.


Good guess!

QUOTE
ETA:
the pancam site has a color image of this location,
...
(about a third of the way up and a third of the way to the right from the lower left corner)


I believe this PANCAM is at a higher elevation than our current location.

Paolo
RoverDriver
QUOTE (Sunspot @ May 11 2009, 11:20 PM) *
Looks like some people think we may be here for the rest of the mission.


Hmm... maybe it is a language barrier, but I do not understand the point of your remark.

Paolo
djellison
He's being the worst kind of pessimist...a pessimist who also thinks everyone else is pessimistic.
alan
QUOTE (RoverDriver @ May 12 2009, 04:47 AM) *
I believe this PANCAM is at a higher elevation than our current location.

Paolo

???

Do you mean it was taken from a higher position (its from the edge of Homeplate) or that the location is wrong?

Perhaps my explanation of the specific location in the image wasn't clear. I've circled what I meant in this image.

Click to view attachment

I can clearly see the two flat rocks which were run over during the drive on sol 1871(arrowed)
ElkGroveDan
Here's a wild thought that would be more a later move of desperation. I'm not certain what kind of mass ratios we are dealing with but would it make sense to extend the arm and IDD to slightly shift the CG, and add to the traction/load on a preferred wheel or wheels?
charborob
Seeing how the rovers are so vulnerable to getting stuck in soft ground, I wonder if that possibility had been taken into account when designing the rover wheels. With hindsight, it might have been better to equip the rovers with large balloon-type wheels, allowing them to "float", so to speak, over the sand. Maybe it would have caused other problems (storage space for big wheels, less traction?).
I can't help thinking about MSL, which seems to be equipped with somewhat similar wheels, although wider to account for the higher mass. I hope the experience gained with the MERs will be put to good use on MSL. We know there are sand traps on Mars. Lets hope MSL doesn't suffer the same fate as the MERs, getting stuck all over the place. (OK, the MERs aren't getting stuck all over the place, but you see what I mean.)
MahFL
If anyone on the planet Earth can get us out, it is Paolo !

wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif huh.gif
SpaceListener
I still believe we can rescue Spirit. The things that must be studied carefully are about the relieve of the soil around the Spirit. We must take the advantage of the help of gravity direction to be unstuck. According to Alan's picture, I am not able to see precisely about the inclination of the surface. As the rule of thumb, the lower land, has softer soil than the higher ones. The picture has show that the left side, close to the slope, the surface is very smooth but I doubt it would be a firm soil.

Is Spirit capable to turn around by 90 degree to change the scape route toward left side (close to the slope) toward the Braun hill?

Maybe, lower soil, has another kind of layer, a firmer soil which might help to improve the traction?
Stu
Is this roughly the right position?

http://cumbriansky.files.wordpress.com/2009/05/stuck.jpg
nprev
You got that right!!! wheel.gif wheel.gif wheel.gif Go, Paolo!

BTW, back in Montana during my wild youth I nearly high-centered a few times in slippery terrain. IIRC, any sort of tilt along the longitudinal axis is a huge help in extraction (since you're normally pretty level along the lateral axis in this situation).
Phil Stooke
"Is this roughly the right position?"

No, it's more like this:

Click to view attachment

Phil
Stu
SO wrong to laugh at that Phil, but I couldn't help it. You're a very bad man! laugh.gif
Phil Stooke
A very, very, very bad man! (waggles finger)

Phil
nprev
laugh.gif

Well, if worst comes to worst, just land MSL nearby & program the SkyCrane to hover over & yank her out after it drops off MSL!
Stu
QUOTE (nprev @ May 12 2009, 06:27 PM) *
laugh.gif

Well, if worst comes to worst, just land MSL nearby & program the SkyCrane to hover over & yank her out after it drops off MSL!


I think you're confusing MSL with Thunderbird 2... laugh.gif
Oersted
I suggest a new thread called "Getting unstuck in West Valley" or something to that effect... - This will take a while.
imipak
From an article Tweeted by MarsRoverDriver:

QUOTE
"This is a really big concern. We've never been in a situation like this when we've been at risk of high centering the rover," project manager John Callas said. "There is a real danger of it getting permanently stuck."


MahFL @390 thirded; you posted the words out of my head. Stu - my impression (FWLIW!) is that the front wheels (near side in your image) is a little less deeply embedded, and that the site's a few cm further away to the south. Been wrong before, YMMV, etc.

ISTR that after the first day or two of trying to back Oppy out of Purgatory didn't work, things looked pretty scary. In retrospect, that was mostly because it was the first time it'd happened, and the way out wasn't immediately obvious. Hopefully, the same applies now.
djellison
Now I wish I'd made building a 1/4 scale mobility model my Winter '08-09 project rather than my project for NEXT winter.

RoverDriver
QUOTE (alan @ May 12 2009, 05:24 AM) *
???

Do you mean it was taken from a higher position (its from the edge of Homeplate) or that the location is wrong?
...


I meant to say that it looked like this pancam was aimed at a higher elevation, with the PMA aimed at an area that is visually above the NAVCAM.

What Sol is this? [edit: never mind, I see what sol # it is. Thanks!]

Paolo
RoverDriver
QUOTE (ElkGroveDan @ May 12 2009, 05:24 AM) *
Here's a wild thought that would be more a later move of desperation. I'm not certain what kind of mass ratios we are dealing with but would it make sense to extend the arm and IDD to slightly shift the CG, and add to the traction/load on a preferred wheel or wheels?


The IDD is about 2-3 Kg and about 1m long, the rover is about 200Kg. You do the math. :-(

Paolo
RoverDriver
QUOTE (MahFL @ May 12 2009, 06:00 AM) *
If anyone on the planet Earth can get us out, it is Paolo !

wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif huh.gif



Thanks for your trust in my capabilities, but I have assembled a team that will actually do the work. Since we will be doing some testbed analysis, you won't see much changes in the scenery for a while, don't interpret this lack of mobility activity as unsuccessful motion.

Paolo
RoverDriver
QUOTE (SpaceListener @ May 12 2009, 08:18 AM) *
I still believe we can rescue Spirit. The things that must be studied carefully are about the relieve of the soil around the Spirit. We must take the advantage of the help of gravity direction to be unstuck. According to Alan's picture, I am not able to see precisely about the inclination of the surface. As the rule of thumb, the lower land, has softer soil than the higher ones. The picture has show that the left side, close to the slope, the surface is very smooth but I doubt it would be a firm soil.

Is Spirit capable to turn around by 90 degree to change the scape route toward left side (close to the slope) toward the Braun hill?

Maybe, lower soil, has another kind of layer, a firmer soil which might help to improve the traction?



Brief description of the rover attitude:

1) the rover is aligned more or less north-south (front of the rover north)
2) the rover is on a slope about 10-12 degrees, left side of the rover is lower than the right side
3) pitch is almost zero

The soil under the left side is cohesionless, the soil under the right side seems to provide more traction.
The two middle wheels are only partly embedded, the RF is on top of the surface, LF, and rear wheels are fully embedded.

Turning in place was tried (CW) but was unsuccessful. We might try to revisit this technique.

Paolo
alan
QUOTE (RoverDriver @ May 12 2009, 02:56 PM) *
I meant to say that it looked like this pancam was aimed at a higher elevation, with the PMA aimed at an area that is visually above the NAVCAM.

What Sol is this?

Paolo

The image was taken as part of the West Valley pan on sol 1367
http://marswatch.astro.cornell.edu/pancam_...WestValley.html
http://marswatch.astro.cornell.edu/pancam_..._L257_pos_5.jpg
RoverDriver
QUOTE (Stu @ May 12 2009, 08:18 AM) *



Roughly, yes. The roll of the rover is not very accuratly represented as well as the precise state of each wheel, but the position itself is quite accurate.

Paolo
RoverDriver
QUOTE (alan @ May 12 2009, 12:15 PM) *


Thanks. This exactly the kind of posting I'd like to see. THANK YOU!!

Paolo
lyford
Pardon my ignorance, but what does the term "high centered" mean? Is it referring to center of gravity? A 4WD phrase? Both sides are equally dug in??? unsure.gif
nprev
"High-centered" usually means that the vehicle's center of gravity is being supported on something other than the drive surfaces, so there's little or no traction, Lyford.

Paolo, it's good that there's some significant lateral slope. Are there any transducers or some indirect means to measure how much of Spirit's weight is resting on the wheels? That would be good to know for strategy development.

Based on your description of the situation, if it was me in a truck or something I'd gun it forward, expecting the left wheels to slip & hoping that the right wheels would grab enough to spin me downslope (leftwards) & pick up dual traction again.
HughFromAlice
QUOTE (imipak @ May 13 2009, 04:26 AM) *
"....risk of high centering the rover," project manager John Callas said. "There is a real danger of it getting permanently stuck."

Purgatory ...looked pretty scary.......wasn't immediately obvious



From one who has been bogged in remote places many times during their driving career, I would say thinking it through and - above all - patience pay high dividends!!! I'm sure that they'll test, retest and reretest....... over many many weeks if necessary.

Paolo, besides getting thermoses of strong black coffee air freighted to your team, is there any small thing at all that UMSFers could do that could be of support? (Like the v useful posts above of exactly where Spirit was bogged - or some thread similar to the Drivability Analysis etc.) Very frustrating to have to just sit here while the wheels spin!!!!
marsophile
This is maybe grasping at a straw, but is the soil traction affected by temperature? Is there any reason to think a night move, when it is colder, might have better traction?
RoverDriver
QUOTE (nprev @ May 12 2009, 01:35 PM) *
"High-centered" usually means that the vehicle's center of gravity is being supported on something other than the drive surfaces, so there's little or no traction, Lyford.


That is correct. Sorry for using terms that are unfamiliar.

QUOTE
Paolo, it's good that there's some significant lateral slope. Are there any transducers or some indirect means to measure how much of Spirit's weight is resting on the wheels? That would be good to know for strategy development.


Not that I know of. The rocker-bogie system since it is passive is an indirect measurement, but it is affected by the mechanical properties of the soil.

QUOTE
Based on your description of the situation, if it was me in a truck or something I'd gun it forward, expecting the left wheels to slip & hoping that the right wheels would grab enough to spin me downslope (leftwards) & pick up dual traction again.


A car or truck is not really representative of the type of motion we have on the rover. It is mostly a sequence of quasi-static moments rather than a dynamic event.

Paolo
nprev
Got it; I used the truck analogy for illustration only.

What I was thinking was something like a 30 sec run on all drive wheels (forward or backward!) Even churning the soil on the left side provides some impulse via reaction. If you can get the nose to swing to the left enough, you're probably home free.
nprev
Here's another unsolicited silly idea: Can you turn the 3 operable front & back wheels 90 deg with respect to the lateral axis of the rover & try to translate it to the left (not a spin, all driving the same direction)? That might drag you clear of whatever's presumably underneath & reseat the wheels.
RoverDriver
QUOTE (nprev @ May 12 2009, 02:30 PM) *
Here's another unsolicited silly idea: Can you turn the 3 operable front & back wheels 90 deg with respect to the lateral axis of the rover & try to translate it to the left (not a spin, all driving the same direction)? That might drag you clear of whatever's presumably underneath & reseat the wheels.



Nope. The max is 60deg, we tried to turn them 30deg and drive forward (1894-1899) and made some (slowly diminishing) progress.

Paolo
SpaceListener
A question, when MER landed on Mars, its six wheels were kept inside. I wish I would have seen the movie on how MER unstowed their six wheels before rolling out from the lander bag to see whether the below idea would be feasible.

Depending upon to its technical characteristics, is possible to perform stow the 2-4 or 6 wheels until its belly touches on the surface and again perform to unstow the wheels very slow trying to turn around somewhat so that the wheels can pose on better firmness soil?
Stu
QUOTE (RoverDriver @ May 12 2009, 09:16 PM) *
Roughly, yes. The roll of the rover is not very accuratly represented as well as the precise state of each wheel, but the position itself is quite accurate.


Thanks Paolo, appreciate that. It was just a thrown-together thing, so glad to know I wasn't too far out.

All the best to you and your team as you start looking at this. Hard days ahead of you, to be sure, but you're the guys to get our gal free.
nprev
Hmm. How about rocking it? That would be a 60 deg all wheels right short move going aft, followed by 60 deg all wheel left going fwd, repeat a few times & see if her nose begins to point downslope.

(BTW, thanks for your patience with my amateur suggestions, P; you're busy, and your replies are kind, but no worries if you got better things to do! smile.gif I'll post whacko thoughts as I get them just for fun.)
BrianL
Paolo, could you move your seat forward a bit? I don't think nprev has enough legroom back there. biggrin.gif
nprev
laugh.gif ...fortunately, my legs are retractable!

BTW, Paolo, don't forget to adjust your rear-view mirror before backing up!!! tongue.gif
Oersted
I wonder if the arm could usefully push against the ground in any way, to take weight off wheels? Would that be helpful? That would obviously be a last-ditch (no pun intended) effort. The arm is pretty strong and the rover weighs less on Mars...
fredk
Here are a couple of anaglyphs showing our current location, above the clump of rocks near centre of each image (refer to the previously posted maps for our precise location). First is navcam from sol 1870, second pancam from HP on sol 1367:
Click to view attachment
Click to view attachment
You can clearly see how the ground slopes downwards on the west (left) side of the rover. If only we could make it a bit in that direction and let gravity help pull us out from there...
RoverDriver
QUOTE (nprev @ May 12 2009, 02:40 PM) *
Hmm. How about rocking it? That would be a 60 deg all wheels right short move going aft, followed by 60 deg all wheel left going fwd, repeat a few times & see if her nose begins to point downslope.

(BTW, thanks for your patience with my amateur suggestions, P; you're busy, and your replies are kind, but no worries if you got better things to do! smile.gif I'll post whacko thoughts as I get them just for fun.)


This is a variation on the theme of turning in place and I will keep it in the list of things to try. The immediate reaction is that I would be concerned of digging the wheels in with this type of back and forth motion, but the sandbox testing will tell us something. Thanks.

Paolo
nprev
You're welcome! smile.gif Hope it helps; looks like the main idea is to precess the nose downslope somehow.

Re wheel digging: Any idea if those nasty soils on either side compress worth a hoot? If so, then rocking on a patch might make it a bit firmer.
Tesheiner
Good luck with the testing, Paolo. Fingers crossed. smile.gif

QUOTE (SpaceListener @ May 12 2009, 11:36 PM) *
Depending upon to its technical characteristics, is possible to perform stow the 2-4 or 6 wheels until its belly touches on the surface and again perform to unstow the wheels very slow trying to turn around somewhat so that the wheels can pose on better firmness soil?

They are locked in place. AFAIK, impossible to stow the wheels.

QUOTE (BrianL @ May 13 2009, 12:02 AM) *
Paolo, could you move your seat forward a bit? I don't think nprev has enough legroom back there. biggrin.gif

laugh.gif laugh.gif laugh.gif

QUOTE (Oersted @ May 13 2009, 12:34 AM) *
I wonder if the arm could usefully push against the ground in any way, to take weight off wheels? Would that be helpful? That would obviously be a last-ditch (no pun intended) effort. The arm is pretty strong and the rover weighs less on Mars...

Already answered on yesterday posts.
climber
Crazy idea, but well...
On Earth, to get free from this situation, we'll put "something" under the weels to get back some traction.
Is there anything we could drop under a weel? (don't blame me for the idea, I try to be creative smile.gif )
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