Getting Unstuck in West Valley Options

[HughFromAlice]

uptodate as Q&A come along.

Thank you guys for all your work on the FAQ! Great resource for all of us who don't have much time.

[CosmicRocker]

... and the straight-line wind event was on sol 1953. ...

I'm not convinced it was one of those.

I can't say I see convincing evidence of rotation in those dust clouds, but there does appear to be evidence of front and back side dust clouds. I think that very well could have been a DD roaring over Spirit. Other DDs were evident in the background, indicating that it was an active sol for them.

BTW, thanks for that wonderful, enhanced animation, Fran. It was one of the most fascinating rover observations I've seen in quite a while. It often goes unsaid, but many thanks to those who had the foresight to program Spirit to watch for such wind events.

Awesome...It's almost as if Mars was in my back yard.

[briv1016]

Possibly, the best way to tell on earth is the debris field. Not really an option in this case.

[Marz]

[edit]
The RF drive actuator shares the motor controller with one of the IDD joints and the failure was an open circuit indicating that at some point along the wire there is a break in the cable or interconnects.
[/edit]

I'm sorry if this falls under the "stupid question" catagory:

From reading the mission updates for Opportunity, I thought prior to the RF failure on Spirit there were a series of sols with increased voltages indicating the actuator was drawing more power than normal because it was under stress. If the failure on Spirit was due to a broken connection, then perhaps wheel-resting to resdistribute lubricant on Opportunity is not accomplishing much?

Perhaps keeping a low and steady current could help anneal contacts in the wire/circuit (prevent failure on Opportunity and with amazing good fortune, restore the connection on Spirit)? Anneal might be too strong a word, but perhaps allowing the wire to warm keeps it more flexible and perhaps expand enough to restore a weak/broken connection?

[RoverDriver]

...
then perhaps wheel-resting to resdistribute lubricant on Opportunity is not accomplishing much?

Unfortunately we do not have clear indication of what is the source of high currents there, so we don't know how to fix it. We do know that there is clear evidence that rest seems to help to solve the problem temporarily.

...
perhaps allowing the wire to warm keeps it more flexible and perhaps expand enough to restore a weak/broken connection?

On Spirit, we do not know where the open circuit is. It could be at any location along the wire, any connector or it could even be one of the brushes in the motor. We typically have heaters near actuators not on cables or connectors, so we could not actively warm them, but we could use them at different times of day. Still the hesitation in attempting to use the wheel again stems from the fact that the open circuit might also be due to a loose wire that potentially could contact unintended components, damaging the rover irreparably.

Unfortunately, there is only a limited set of things we can try to analyze a failure, and we have to be conservative whenever we have potential for permanent damage.

Paolo

[centsworth_II]

I can't say I see convincing evidence of rotation in those dust clouds, but there does appear to be evidence of front and back side dust clouds. I think that very well could have been a DD roaring over Spirit.

Also, there seem to be sharp borders at either side. If it was a "straight line" wind, it was very narrow and well defined like a blast from an air gun. It looks like a DD to these untrained eyes.

[eoincampbell]

Are any official odometry readings from the test bed rovers kept? Would the team expect the RF wheel problems on the test bed rovers eventually? Also, is that SSTB1 featured in the Roving Mars(IMAX) movie? (scene where SS shows the rover to school kids, and some other scenes). Apologies if this has been mentioned already but my search didn't seem to yield these topics.
Thanks in advance and good luck!
Eoin

[fredk]

Part of your question, Eoin, was answered in this post by Paolo.

[eoincampbell]

Thank you fredk, did you use the search function to find that? Any quick tips on narrowing searches? The answers to the other parts are bound to be here too
Eoin

[RoverDriver]

Are any official odometry readings from the test bed rovers kept?

Not that I know of.

Would the team expect the RF wheel problems on the test bed rovers eventually?

Possibly but the environment of the SSTB is quite different from Mars ;-)

Also, is that SSTB1 featured in the Roving Mars(IMAX) movie? (scene where SS shows the rover to school kids, and some other scenes).

No, that is the SSTB Lite.

Paolo

[fredk]

I remembered Paolo answering that question some time ago. So I searched for keyword "testbed" and member name "RoverDriver" for posts older than 2 months old, with "Show results as posts" selected under "Result Type". It showed up very quickly.

[HughFromAlice]

looks like a DD to these untrained eyes.

To these untrained eyes it looks like the very early stages of a dust devil in formation when the hot air is starting to punch up through the cooler layers immediately above and before rotation starts.

In my part of the world (Central Australia) we see quite a lot of these. Quite often rotation never starts and a line of dust blows onwards for short distances before dissipating or sometimes it goes on for a few kilometers. The disturbance shows itself through a jagged rough line of dust which has all the appearance and feel of a small squally wind front. Occasionally the front can be suprisingly broad - 100 meters or so. The pic that Fran posted really reminded me of these broad fronts.

Alaska sounded the most appropriate place to go for a ref!!
http://www.gi.alaska.edu/ScienceForum/ASF2/227.html
http://science.nasa.gov/headlines/y2005/14jul_dustdevils.htm

I have actually walked into the middle of a large dust devil on a calm day when it was almost stationary. About 10 metres wide - 300 metres high. I got to the centre after getting sandblasted by a wall of roaring sand (100kph?). The centre was completely calm - very clear air - about 6 metres wide. Could see right up to a point of blue sky at the top of the funnel. Kept walking along with it for a few minutes. I'll never forget the utter calm of the centre eerily contrasting to the tight wall of roaring sand whipping so close around it. Amazing!!

Whatever's happening here, it's been a fantastically good factor in taking time pressure off getting Spirit unstuck.

[nprev]

Too right. If she had to get stuck for awhile, Trojan is certainly proving to be a great place for it what with the unusual soil composition & favorable + interesting winds!

[PaulM]

I understand that it is currently high summer in Gusev. It is concievable that Spirit may not be extracted over the whole of the next Earth year.

What I wondered is whether the soil in Gusev crater would become harder and so easier to drive through during the martian winter?

What prompted me to ask this question is the report around one year ago during the martian autumn that liquid salty water may have been present at the Phoenix landing site. I presume that driving a rover on frozen soil at the Phoenix landing site during a martian winter would be easier than driving a rover on damp soil at the Phoenix landing site during a martian summer.

I am of course assuming that my hypothetical polar rover would be far more resistant to cold than an MSL or MER rover.

[SpaceListener]

What I wondered is whether the soil in Gusev crater would become harder and so easier to drive through during the martian winter?

Only after Spirit is alive again, the rover driver would be more aware of the tricks of land between the Troy to Von Braun hill. This is due to the fact that the RF is causing more troubles in driving on somewhat loose surface. The tracing path would be on the firmer surface, or close to bedrock as the preference path. By seeing the picture, it is rather hard to guess for the best route. Well, it is still to soon to talk about!