Why is it that energizing the RR wheel in the current diagnostics does not carry the same risk of propagating a short as would energizing the RF wheel? What was the basis for suspecting a short in the RF wheel and why does that not apply to the RR wheel?

Elevated current. I don't know if any elevated current has been seen in the RR.

Edit: Actually, from this report, it looks like the RR may have the opposite of a short:
"The resistance tests indicate anomalously high resistance in the motor winding..."

Since the RR wheel is submerged completely, have they thought of possible soil particles that may have found its way into the gearbox itself? Does the resistance test's show that signature?

The report says: "a curious transition from anomalously low resistance to high resistance was observed very briefly..." Doesn't that suggest an initial short followed by a broken circuit?

If so, there may be no further risk of short circuit. But I don't know what all the data suggests.

New update on the Free Spirit site.

http://www.jpl.nasa.gov/freespirit/index.cfm


Two interesting quotes:

"The plan ahead, still being developed, will likely include more rotor resistance tests, an attempt to apply higher voltage to the right-rear wheel to see if any movement will occur, and a check of the right-front wheel to confirm its status and to see if it may offer insight into the right-rear wheel's condition."

"Because of the current rover tilt, the environmental conditions and dust accumulation on the solar arrays, Spirit is at risk of inadequate power for surviving through the next southern Mars winter, which reaches solstice on May 13, 2009."

One presumes they mean 2010

The check of the RF wheel definitely sounds interesting. I wonder if that means an attempt to drive it.

We'd heard about the danger of the coming winter, but not this bit:

Given the current position, how would that be possible other than to intentionally dig the front in even deeper to get more northerly tilt? Perhaps the statement might better read, once we determine that extrication is impossible, some limited rover motion....

One of the new hazcam images suggests NASA has called in extra help as it attempts to free Spirit...

Click to view attachment

What's he doing up there? He's got lots of work to do this month!

Good job on the lighting Stu.

Good news on the RR wheel would be the best present I could get this year... hmmm, I haven't resorted to posting notes up the chimney yet. Perhaps I should!

Heave...ho! Ho, ho, ho...

(Good one, Stu!)

I ran that new spirit image through the 'enhance-o-matic' machine...
Click to view attachment
My first impression is that we are about to get unstuck...
It also looks like the repair guy is experiencing 95% slippage...but it could be an illusion
any way, happy holidays!

Here is an animation of a panorama of Spirit's underbelly taken on Sol 2013
I will try to make a stitched panorama next (the animation kinda jumps?!)
Click to view attachment
Cheers

Here is my first attempt at a pan stitch using PS-C2
(those stripes!)
Click to view attachment
Cheers

What happened to Santa?

This happened

Click to view attachment

Sol 2113 - FHAZ - RF wheel.

Motion.

Not a lighting change. Motion.

Not a typo. RF wheel.

Commanded?
Could the impossible happen?!
GO SPIRIT!

Edit: From Dec.10 update: "and a check of the right-front wheel to confirm its status and to see if it may offer insight into the right-rear wheel's condition"

(Maybe Santa's visit is going to pay dividends after all )

We know the wheel has moved before while it's been dragged over the last three years.
eg: http://www.unmannedspaceflight.com/index.p...st&p=104788

Very good eyes, Doug!
Took me some time but I agree. I cannot see the soil moving (because of the shadow?) but the motion is visible on the top of the wheel.

Holy crud! How much was the RF wheel told to rotate? What does this mean for its potential use in this situation?

( I love the new forum banner, by the way )

I had a bit of a tip off so not really creditable to my eyeballs.

Seriously - this girl is invincible.

OMG - Santa's not a man to take time out of a busy schedule for no reason . Even if he didn't leave behind a spanner or two, talk about solid empirical evidence of his being there!!

How could that wheel possibly move ? Since you have inside info Doug, perhaps you might be first to put forward a hypothesis ?

How could it move?

They told it to.

If they told it to move, and it moved, could they tell it to keep moving? In concert with the other wheels?

(If we get out of this trap with six working wheels, I don't know what I'm going to do).

I was taught by my old gramps that if you have been running an electric motor with brushes for a long time under moderate load that it is always good practice to remove all loads and let the motor run freely. This, he said, would allow the commutator contacts and brushes to reseat and re-burnish. And that doing so would lead to a much longer life. He explained all this to me when I was building stuff with my erector set as a kid.

..and you can read about the concepts here:

http://www.reliance.com/prodserv/motgen/c7090/#whatcanwedo
http://www.maintenanceworld.com/Articles/K...shes-rotor.html

There's more, but those articles should give you an idea of the environmental effects on a brushed motor.

So in light of that, what sort of maintainance has (or will) been done to prolong the life of the rover motors. Or are these just simply give'em power and let'em roll type deals.

I don't know; but I would think that a brushless motor *still* would have been the better choice, even if a bit more expensive and slightly heavier. And we would not need to run a mass of cables from the web to the hub. Just two power lines and perhaps a signal line. The control circuitry can easily be built into the motor.

Any way in finding out how much motion was commanded?

Jumping in line ahead of Doug here. That place is rich in iron. The dust is full of it. If you ask me, whatever "gap" caused the malfunction previously is now being closed by conductive dust build up. I think there is enough iron in that dust and enough dust built up now to allow the electrons a path to the other side. Moreover, depending on the resistance of this new bridge, if it gets warm enough you might even see those grains start to fuse, creating a better path over time (if it doesn't burn itself out first) That's my hair-brained theory.

Not a bad guess, but unfortunately most iron oxides aren't very conductive.

My guess: A floppy wire connection that has flopped back to a happy spot. If we're REALLY lucky, there was a small arc during initial contact that spot-welded that sucker back into place.

Worth trying, but I'd be gobsmacked if the RF "fixed itself" since being dragged around HP from Tyrone. Half a degree of rotation doesn't equal a usable wheel. (Why yes, I AM a subscriber to the "be a pessimist to ensure only pleasant surprises" school.) "inwincible!" ? Well, maybe.

The lubricant has had plenty of time to redistribute itself!

8 years ago - they were not ready to fly. The decision they made would have been the right one at the time.

Dunno of any other one then wait for a status report.

<especulative mode>
IMO only a tiny motion was commanded since the motor status was unknown after all the time it was left unused. I would do that. Now, if the "drive" ended normally instead of aborted due to high current or high resistance I would expect more tests with this wheel motor. My 2c.
</especulative mode>

Good Newes from Mars! I hope the JPL team gets a servicable RF wheel for extrication.

In French, "conductive" is "conductif" and "to drive" is "conduire" so... let's condu(whatever) the rover out of this trap

Rover driver Paolo talked about the possibility of trying out the RF wheel again a while ago in this post. He talked about the risks of damage to other parts of the rover and then said:
I really, really hope that they only commanded the RF for a fraction of a second, in addition to at a low voltage.

In the tealeaves category, here's a doozy of a cryptic tealeaf from this blog:

Hmm, maybe they should try to send some commands to Oppy's Joint-1 azimuth motor now...

No, that one still functions, but it is not reliable.
The rover team have parked it so that is does not permanently fail in the stowed position.

Not to be Captain Bringdown, but the RF wheel could just be settling into a pocket. I certainly hope not; can anyone refute that thot?

Hmm. Yeah, possibly. Dunno what kind of mechanical/magnetic internal friction there is to deal with there, but certainly such a small amount of movement could be due to that.

However, IIRC there was a command to rotate. Doesn't mean that it might not have jumped a bit & stopped, though would have expected a rollback to the original position if that were the case...?

Yeah, I think the timing is the clincher - what are the odds that the RF would settle into a pocket on the ground just when it's commanded for the first time in years? Plus if it settled, it shouldn't rotate, because of the huge gear ratio (although it did rotate a bit when dragged before).

I think it's a safe bet that this tiny motion was associated with the RF being commanded. The wheel was determined to have an open circuit after it first failed. That would mean something has changed. That doesn't mean the wheel is fixed though. Maybe one strand of a wire made a brief connection before burning out. I can't wait to hear something from the team on this.

*If* the RF turns out to be functional, what would the next course of action be? another round of testing in the sandbox to see what the best strategy would be for the new configuration of broken/fixed wheels? Or is there not enough time before winter entombs us?

It may take them a week to determine if the wheel -appears- to be functional(as well as the full status of the RR wheel). If it is, and there are no unexpected operational restraints, I don't think they need much additional time to plan and execute extrication sequences. Everyone knows which wheel is on solid ground and needs to be pulling its' weight.

Even assuming we have a miraculous wheel healing here...

What about the possibility that the RF wheel is also sitting on a crust, and spinning it might cause it to break through into the sand? Might they not be better to try and continue to advance Spirit with the RF wheel sliding until there is a greater expectation of solid ground on which to drive it?

It's a case of trying and experimenting and simulating and then biasing sequences to what appears to work best. That experimentation might occur mainly in the ISIL or on Mars - or both.

I just hope they post some information soon, before the ratio of analysis to wheel motion approaches infinity again

10,000 words / mm Get typing.

I can't remember whether RF is still in the drive direction or tilted to the left or right.