A teeny weeny bit of movement in Spirit's right front wheel
Posted by Emily Lakdawalla
14-12-2009 13:12 CST
The ever-vigilant Doug Ellison of unmannedspaceflight.com just posted this animation, which really actually does show a teeny tiny bit of motion in the right front wheel. If you don't notice any motion, look closer. It's eensy, but it's there. Cause for celebration? I don't know. But it can't be a bad thing.
Now, Spirit's right front wheel has turned a little bit since it seized up in 2006; as it's been dragged along the ground, the wheel has occasionally encountered enough resistance to rotate it on its axle, passively, along with the active motion of the other wheels. However, this is a different sort of motion. Spirit hasn't been moving anywhere fast since she got mired at Troy, so this motion isn't passive. This wheel motion is commanded motion. The wheel! It's alive!! I think. I await further news from the rover team.
If it's true that the right front wheel can be commanded, that still may leave Spirit with only five operable wheels, because the completely sunk-in right rear wheel has been stalling since they started attempting to extricate Spirit from Troy. The latest "Free Spirit" update says "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." A great deal more detail on the troubleshooting can be had by following the link to the update. Stay tuned.
Several weeks ago a reader wrote me to ask for my frank opinion about Spirit's situation. Spirit's been stuck for so long, and after seemingly endless testing, mission managers elected to go with what seemed the most obvious choice -- rolling Spirit back the way she came. Since the start of the effort, little progress has been made, and more trouble has been discovered. What do I really think about the Free Spirit effort? Is it even worth the attempt?
So, here's the honest truth about what I think, based on what's out there for everyone to see and also my private conversations with various people who are involved on the mission. Spirit is in a bad place. If this were not a very difficult situation, Spirit would be out by now. Given how deeply buried she is, it would have been irresponsible for the team to just try rolling out the way she came in without exploring all the other possible extrication methods they could think of. And their testing has hopefully led to deeper understanding of what it means when Spirit digs in a few millimeters this way or yaws a few degrees that way. Unfortunately, the testing doesn't seem to have led to confidence that the extrication effort will work.
I do take it as a mildly bad sign that there is no video for JPL to post on their website showing the engineering model of the rover successfully rolling out of the sand trap. But do remember that their sandbox version of the sand trap was meant to be a worst-case scenario of the conditions where Spirit is stuck. And also that the extrication effort is likely to take months -- my assumption is that they learned what they needed to from their simulations but did not want to take the time to do a full-on simulation of the entire extrication effort, since things on Earth cannot possibly go precisely the same as they will on Mars. It was time to get started on Mars, so they started.
I don't think anybody knows whether Spirit will get out or not. But I do believe it's possible. If there were not a reasonable hope that Spirit could get out, they wouldn't be bothering to try. Believing that they can get Spirit out is different from knowing that they will, but that's what the mission is riding on now. It may not be possible to extract Spirit from the sand trap, but if it is, the rover drivers and engineers at JPL are the people who can do it.
I'm glad they think it's possible, because the more trouble Spirit has, the more I attached I get to her. Y'all have probably noticed that for a long time I've followed the Society's convention of using "it" to name all spacecraft, including the rovers, but I can no longer bring myself to do that consistently for Spirit. She may be a hunk of metal and plastic that does not care in the end whether she ever moves again, but the emotional attachment that her drivers and her fans feel to her just grows with every passing year. I do believe that NASA and JPL would make the decision to shut down the effort if analysis revealed that it was hopeless. But I also believe that while her drivers and managers might think the effort has an uncertain chance of success, they will spend every ounce of their strength to save Spirit as long as that chance exists.
We got her in to this mess; we have to try to get her out. Even if it's just to risk her again as she continues to drive. Especially that, actually. Spirit is on Mars to take risks that humans can't bear. Here's to hoping she'll face, and survive, many more challenges on Mars.
Go Spirit, go!