Extricating Spirit, Digging out from Troy Options

[Keatah]

This is one of the most singularly exciting and suspenseful missions of all time, and we all have a front row seat ... every day!

Cheers

That is true, I now sit down in the evening with a cup of hot cocoa in anticipation of reading this board and other sites. Like the ultimate soap opera!

My girlfriend was watching Aliens the other day and one of the soldiers in the APC on descent to the surface has an intermittent helmet camera, so he bangs his head on the bulkhead. GF says "hey! Maybe those mars guys can smash the arm into the rover!" Fix them electrical problems that seem to be coming and going. The moment was just so ridiculously funny!

Anyways, my armchair analysis says this is a mechanical problem; like a screw holding a grounding cable, or a cracked solder joint, or to a lesser extent and possibility a connector. I would imagine most connectors are double spring loaded to keep tension on the metal contacts.

[djellison]

We could play what-if till the cows come up.

Not using a wheel known to be dead, when further usage could endanger it's motor controller bed-fellows was the right thing to do at the time.

The only appropriate time to reverse that decision would be an in extremis situation, where the risk of damage to other components is worth the chance of finding the wheel working once more, which is what we have now. It may even transpire that the wheel has given is all it can already and may never turn again.

Trying to second guess a decision making process with 3 years of hindsight is, to be honest, silly.

[Tesheiner]

I checked the tracking web this morning and found the pattern of imaging sequences corresponding to another driving sol today i.e. sol 2118. Might it be?

[climber]

...of course, the rover could be free in a few days and this message will be moot...
Cheers

It is of GREAT value to me helping understand the issue, thanks a lot.

And thanks also to Oersted for his uplifting "spirit"

[Tesheiner]

Regarding today's drive: 1.5mm forward, 3mm down.

[fredk]

The fhaz shows that the RF did move again today (2118):
http://qt.exploratorium.edu/mars/spirit/fo...86P1235R0M1.JPG
http://qt.exploratorium.edu/mars/spirit/fo...92P1214R0M1.JPG
So whatever happened at the end of the 2117 drive wasn't fatal. Perhaps an intermittent problem.

[Floyd]

I'm not sure the rover gods are with us. Gain of RF in exchange for loss or RR is a poor deal. The RF wheel was sitting on the surface and could be dragges (or pushed) reasonably well with the other 5 wheels. The RR wheel is almost totally burried and will be most difficult to pull out of the sand--I think that is why we are sinking more than translating forward. Lets hope the RR comes back to life and we have 6 wheels for at least long enought to get free.

[MahFL]

Think positive...the RF digs in, grabs a nice rock, pulls Spirit out. Then we go mountain climbing again with all SIX wheels .

[fredk]

Or they try a different approach. Right now I think they're still checking the right wheels as much as trying to extract Spirit. If the electrical problem is understood, perhaps they'll be able to come up with a workaround that restores use of the RR. If not, pivoting forwards and to the right around the RR might be another approach to prevent it from holding us back.

[marsophile]

Is the electrical problem possibly a buildup of static electricity on the rover chassis? After 5 years in the cold dry Martian climate, I can imagine a significant static charge may have built up. If so, is there any way to discharge it? In any event, anything we can learn about the electrical issue with Spirit may be useful if a similar issue later develops with Opportunity. That is one of the benefits of having two rovers.

[Hungry4info]

I would think that the rover would be grounded to the surface, so I would guess "no".

[Deimos]

Grounding to the surface (through a light-weight mobility system) on Mars is difficult. A radioactive source that can create an ion path helps. My recollection from Pathfinder was that the Sojourner APXS was going to be used first if there was ever going to be contact between Sojourner and Pathfinder. That is also a concern (ie, a solvable problem, but something that needs attention) for future sample return operations. I'm not sure how conductive the IDD is vs. the mobility system, but I imagine the APXS and Mossbauer (plus contact plate) use has kept the static build up under control.

[mcaplinger]

Grounding to the surface (through a light-weight mobility system) on Mars is difficult.

Definitely an understatement. AFAIK, there is no guaranteed ground path between the rover chassis and Mars. The rover has a number of small "lightning rods" that help to discharge it (see http://www.nasa.gov/centers/glenn/moonandmars/mer.html ), but I could imagine that potential differences of a few volts could still be sustained. There may be a detailed description of the power bus grounding architecture of MER on the web someplace, but I don't have time to look for it right now. It doesn't sound to me like the current issue has much if anything to do with any potential difference between the rover and Mars anyway.

[climber]

Make sure you've checked Scott's blog here: http://twitter.com/marsroverdriver latest 5 or so entries are very interesting indeed.

[Guest_Oersted_*]

Make sure you've checked Scott's blog here: http://twitter.com/marsroverdriver latest 5 or so entries are very interesting indeed.

"# With RR failed(?) and RF working(???), Squyres has proposed that there's a law of conservation of working wheels on Spirit. ;-) #FreeSpirit 2:32 PM Dec 16th from web "