Oppy hasn't moved much lately and now they are looking at the front right wheel...



What are they doing?

If I had to guess, I'd say they're looking at Oppy's tracks more than the wheel. I'm seeing a lot of bright compressed soil in the tracks, just like we saw at Gusev where the soil had very high salt content.

I think we're seeing the dust and sand from the eroded evaporite mixed in with these soils, which is causing the spotty bright compressed soil in Oppy's tracks. I think maybe they're taking a close look at the tracks to see if that's what is, in fact, happening. Wouldn't surprise me to see a two or three day session of Mossbauer and APXS integrations on the soils around here sometime soon. Maybe even a trench.

-the other Doug

The only other time I remember seeing these hazcam subrames was when Spirit had a rock stuck in the wheel and they were unable to move....

They've driven a little further than I thought:

http://qt.exploratorium.edu/mars/opportuni...00P1607R0M1.JPG

And the wheels get deeper in the soil than before ! Toplayer seems less dense around here. Less crusty also. Younger ? Other composition ? Thicker layer (=deeper bedrock) ?

No, there's another time when they do these subframes: when they're starting a trench.

I bet dvandorn is right, though.

Opportunity's right front steering actuator stalled near the end of the drive on sol 433 (after 150 meters of driving). On sol 434, they backed up a meter or so and tried to straighten the wheel, but the steering motor stalled again without moving at all. Imaging doesn't show any reason for the stall. The wheel is about 7 degrees off from straight, which would still be driveable if they can't resolve the problem.

I take it back.

I 'm keeping my fingers crossed. We shall overcome

uh oh. I had been lulled into a false sense of security by that 18 month extension. Here's hoping that it doesn't turn out to be a permanent/major problem. At least they have experience at dragging a wheel. Looks like it could come in handy on Oppy.

Onward backwards to Victoria!

Damn.....I thought there might be a problem Lets hope they can get moving again, they're not exactly parked in a very scenic spot lol

Yeah, kind of looks like Nebraska. (Sorry, regional humor.) But seriously, we need to keep moving. Come on, Oppy! At least we've already been through something like this with Spirit. In fact, isn't this the same wheel that acted up on Spirit? I know it's a different component, but still, that would be an odd coincidence, if coincidence it is.

This could be pretty serious. If that wheel cannot be straightened, Oppy's progress could be critically impacted! I hope they figure this out!!!

I suppose driving backwards with the wheel in it's current state would be even less of a problem?

mars_armer,

Where do you get this information?

Even with the wheel completely inoperable, they should be able to continue to drive good distances, especially with the flat terrain. But if the info is correct, this sounds like a mechanical malfunction which would be far more serious than Spirit's lubrication problem.

gregp1962, mars_armer is correct what he said. But that's pretty much all I can say at this point

You mean it's bbroken down? lol

well thats not good. It may take a little longer to drive if there is no fix. Anybody wanna change rovers on the "who will die first" thread?

On a brighter side nasa has people that can do amazing things. Just a bump in the road. (i hope)

scott

The sad thing is that in terms of forward progress, BOTH rovers have ground to a halt

Somebody speak up please. All we have is a bunch of pictures of the wheel. With that we're all assuming that something is wrong. How do we know this?

No, we also have information that mars_armer wrote, which is exactly what's happening, and what we all now know.

I suppose the rovers have to stop functioning (die) eventually, but it would be nice if they lasted forever, wouldn't it? Even after people land on Mars and walk around, the rovers could be used for taking pictures of tourists (for a pittance).

If Opportunity's wheel really is 7 degrees off-kilter, it's hard to imagine any way to 'fix' it a la Spirit's wheel. Maybe it's just a software glitch. You know, that dreaded '7 degrees off' bug..?

All they need to do is turn her around and drive backwards. The trailing wheel would apply some lateral drag, forcing constant steering adjustment, but certainly not enough to disable the vehicle.

! do we have any detailed diagrams of this area on the rover? Is this something that can be fixed by blowing a fuse like with the spirit actuator problem?

And, how do we now know this? It isn't anywhere in the news yet.

I guess they could tell us, but then they'd have to kill us.
News through, let's say, "informal channels" presented in this board in the past have always been accurate. In fact this is one of the main advantages of this place.

I prefer not to ask many questions and just enjoy the priveleges of being part of this community Doug kindly provided us with

Yes - from time to time, you just have to take things on face value from a couple of very reliable sources who have lines thru to some interesting people. Pando and Mars_Armer are examples of this.

I havnt got any insider contacts unfortunately- but here's my take on Oppy wheel issue..

If the steering motor is stalling, it could well be a mechanical issue in which case it may well be a drive-backwards-and-drag issue. However - it could be a software glitch as well, essentially a 'soft' stall ( if current >Xamps, turn off),

Spirit dug some dangerous holes when trying to climb STRAIGHT up the ridge towards HH - so they're simply heading east and the SE along the NE side of Cumberland Ridge to find more accesable routes up to the ridge - just the same as when we first arrived at the hills.

Doug

Yikes :

http://qt.exploratorium.edu/mars/opportuni...03P1214R0M1.JPG

This doesn't look good lol

http://qt.exploratorium.edu/mars/opportuni...03P1893L0M1.JPG

Or maybe they were testing the driving ability, it's facing backwards ready for a dackwards drive?, It turns on the spot ok, but makes a bit of a mess of the soil

Yeah - it's going to dig little trenches if it cant steer the wheel.

Just a thought - couldnt they drive it like a tank? Turn the wheels on the left faster than the right to turn right - turn the wheels on the right faster than those on the left to turn left?

A technique like that could certainly compensate for a stuffed FR steering actuator!

Doug

Well at least it moves ok. I think your right doug. Steering that thing like a tank would be way better than "trenching" with the wheel every time they turn. Altho it would creat trenching from all the wheels if kept straight. Good thing spirit had the lube problem. Gives a baseline to work from with oppry draging

scott

Didn't Spirit have 2 problems with its wheels? The current spike caused by lubricant moving around, which has since been resolved - they turned the wheel off for the most part only turning it occasionally while drivning to clear the debris that built up in fornt of it while being dragged. And also the same problem Oppy has right now of a problem with the steering actuator?

Spirit steering problem thread:
http://www.unmannedspaceflight.com/index.p...eering+actuator

I believe the trench is a byproduct of trying to resolve the mechanical problem by having some force on the wheel from the side. Driving back didn't help, so maybe turning will.

How much for a tow?

How far is the next filling station?

This is definitely going to require a rotation of the tires soon.

That's what we get for being to cheap to buy the Martian "onstar" package.

I hope the trade in is still good enough for a down payment on a new one.


scott

Ok, I just want to get this right.

It is the wheel steering motor for changing direction that maybe is broken?
The actual drive motor is still working right?

If it is only turned 7 degrees I think they still could drive pretty good backward not even dragging the wheel, just making some corrections from time to time.

The good thing is that it is not turned much more than it is. If it was turned 90 degrees it could really have been difficult to drive

Completely agree with you!
This is exactly the reason I'm proud to partecipate to this Forum!
Here I found deep knowdlege, experienced (and patient) people and timely informations.
Really, cannot ask anything better, I'm very lucky and I strongly hope discussion level will remain always so high!
Thanks to all this fantastic people! (and good luck to Oppy!!!!!! )

I suspect turning in place would be more difficult when oppy reaches solid ground. Are there steering actuators on all six wheels or just the four on the corners? Could it be possible to turn all the wheels 7 degrees to match then drive at an angle like a car with a bent frame, probably have to rewrite the navigation software again.

They can only steer on the fronts and rears

For the turning, just switch to "tank mode"

True, this forum has been able to keep the nuts out. I haven't followed it closely enough to know that certain people have inside knowledge and their info has always right. I'll take your word for it.

One thing to keep in mind -- we are not the press release people

They actually do exist somewhere, they are just really slow at times...

yes. definitely the best Mars Rover related forum out there

also very good: the mars board at Phil Plait's great "Bad Astronomy" site
...but not so much traffic over there ...

Would a solution to keep the rover driving in a straight line not be to drive with the same 7 degrees of "toe in" on the left front wheel?

Like this:


And perhaps doing it while driving backward for the best efficiency.

Any thoughts?

It seems to me like that would work, though it seems to me it would drag a bit..

If the motor is purposely disabled so that the rover can move forward (or backward), will the wheel then be locked at 7 degrees? Or will it turn freely, flopping whereever fate takes it? Or can the software simply be updated to not try to adjust the right front steering motor, thereby allowing it the possibility of 'fixing itself' while not requiring Mission Control to permanently disable the motor?

Were famous.... On spacedaily here is the Article.....

Mars Rover Opportunity Has Broken Wheel Motor

Opportunities right wheel actuator stalled on Sol 433.
Los Angeles, CA (SPX) Apr 16, 2005
NASA's Mars Exploration Rover Opportunity has experienced a significant breakdown with the suspected failure of the front right wheel motor.
According to a report posted on Doug Ellison's renowned Mars forum Unmannedspaceflight.com, "Opportunity's right front steering actuator stalled near the end of the drive on sol 433 (after 150 meters of driving).

"On sol 434, they backed up a meter or so and tried to straighten the wheel, but the steering motor stalled again without moving at all. Imaging doesn't show any reason for the stall. The wheel is about 7 degrees off from straight, which would still be driveable if they can't resolve the problem."

In the immediate period to the breakdown, Opportunity has reached Viking Crater, before continuing to Voyager Crater, taking panoramas of each crater and conducting detailed surface inspections.

During this period the Mars Odyssey orbiter also went into safe mode causing a suspension of data relay to Earth.

Driving resumed on sol 428 with data downlinked via the direct-to-Earth link. With the exception of the miniature thermal emission spectrometer (analysis is still in progress), Opportunity is in excellent health.

Does anyone have an update on where things stand now.

The latest images are available for Sol 437. More end of the track pixs. With a complete panorama.

I assume there will be a workaround soon enough for MER-B and onward it shall be.

simon at spacedaily.com

Hopefully we might get some idea of whats going on after the latest images are posted.......they shouldn't be too long

I spoke too soon lol..... the one day new pics are late in being posted lol

...kinda like the one wheel on that bum shopping cart I always seem to end up with?

I confident the MER engineering team will come up with something, it seems like there are several avenues for a workaround/solution.

Well........no update today, so I gues they're still tinkering with it.

I just saw this and thought I would pass it on:

OPPORTUNITY UPDATE: Steering Tests After a Long Drive - sol 430-437, April 18, 2005



The terrain that Opportunity is crossing has been steadily getting more wavy. After a long drive southward from "Voyager" crater, Opportunity's right-front steering motor stalled out on sol 433 during an end-of-drive turn. While performing tests to help the team diagnose the condition of that motor, the rover also continued to make remote-sensing observations. Testing in sol 435 did show motion in the steering motor, but analysis is still underway. The rover resumed normal science and driving operations on sol 436, but with restrictions on use of the right-front steering motor. It drove 30 meters on sol 437. Opportunity and Spirit are capable of driving with one or more steering motors disabled, though turns would be less precise. The latest revision in flight software on both rovers, uploaded in February, gives them improved capabilities for dealing with exactly this type of condition. It gives them upgraded ability to repeatedly evaluate how well they are following the intended course during a drive, and to adjust the steering autonomously if appropriate.

And also very assuring note:

Sol 437:
The team planned a southward drive of about 45 meters, but Opportunity curved left, sensed it was off course, and ended the drive after 30 meters. The same driving commands produced the same results in a software testbed at JPL, indicating that the curving resulted from how software parameters were set, rather than a hardware problem. Observations with the panoramic camera were completed as planned.

Odometry total as of sol 437 (April 16, 2005): 5,225 meters (3.25 miles).