More tests on Spirit: not encouraging

In case you missed this news about the intrepid little Mars Rover Spirit.

Further Tests Designed for Rover’s Right-Rear Wheel

December 07, 2009

A series of diagnostic tests on Spirit’s right-rear wheel on sols 2104 and 2105 (Dec. 3 and 4) investigated stalls that occurred on Sol 2099 (Nov. 28) and earlier. The rover team cannot draw any conclusions at this point, but the results are not encouraging, and further tests are planned.  [Ratz.]

The recent tests included rotor-resistance tests at three temperatures and a one-radian (about 57 degrees) forward motion test. The resistance tests indicate anomalously high resistance in the motor winding at all three temperatures. However, a curious transition from anomalously low resistance to high resistance was observed very briefly on the very first resistance test. The resistance remained high for the balance of all the testing. Control measurements on the left-rear wheel showed normal resistance for that actuator motor. For the forward wheel motion test, the right-rear wheel stalled immediately and did not produce any motion.

The plan ahead is to explore a set of hypotheses: possible motor failure, possible internal gearbox jam, possible external jam (e.g., a rock in the wheel). Commands being developed for Spirit’s activities on sols 2109 and 2110 (Tuesday and Wednesday, Dec. 8 and 9) will include more diagnostics to explore these hypotheses.

 

UPDATE:

December 10, 2009

Results of diagnostic tests on Spirit’s right-rear wheel on Sol 2109 (Dec. 8, 2009) continue to indicate a troubled wheel, which may leave the rover with only four operable wheels[ratz]
 
The Sol 2109 plan included a check of the grind motor of Spirit’s rock abrasion tool (RAT) because it shares the same motor controller as the right-rear wheel. It also included rotor resistance tests on the right-rear motor at three temperatures using opposite voltage polarity from earlier tests, backward and forward commanded motion of the right-rear wheel, and a check of rotor resistance on all other operating wheels. The RAT motor appears okay, although a more exhaustive test will be tried later. The right-rear wheel rotor resistance tests continue to show very elevated resistance, although not as high as in previous tests, and exhibiting a curious voltage-dependent effect. No motion of the right-rear wheel occurred during the backward commanded motion. The forward motion was not executed since the initial backward motion did not occur. The rotor resistances on all the other operating wheels are nominal.

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. Further ahead, steering tests will be considered to explore an external jam as a possible explanation.

Concurrent with this, the project is exploring whether any meaningful rover motion would be possible with only four operable wheels. Spirit lost the use of its right front wheel in 2006.

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. Even if extrication is not possible, some limited rover motion may be able to improve rover tilt and increase the chance of winter survival

 

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About Fr. John Zuhlsdorf

Fr. Z is the guy who runs this blog. o{]:¬)
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6 Responses to More tests on Spirit: not encouraging

  1. Just to put it simply, this isn’t a great day for science the world over. However, “Spirit” has given us many tidbits of information over its longer-than-expected lifespan, so it should still be useful, despite its current problems.

    Hope that it won’t die out too soon, though. Those are taxpayer dollars at stake here for the sake of science! :-)

  2. Aaron says:

    Too bad NASA didn’t adopt Robert Zubrin’s Mars Direct plan for cheap (by their standards) manned missions to Mars back in the 90s. By now, someone might be able to just walk over and fix it.

  3. Supertradmom says:

    So cute, too, like something the kids make with legos……

  4. Supertrad: And I saw one from Legos when I visited the Kennedy Space Center in Florida. I have a photo I think.

  5. Rob Cartusciello says:

    All good things must come to an end, and Spirit had a great run.

  6. MAJ Tony says:

    One thing I’ve noted from all of this is that these missions, most likely for economic reasons, always violate the “never send one (insert noun) alone; always go with a buddy” rule they taught us in the service.