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Mars NASA Science

NASA To Try Powering Mars Rover "Spirit" Out of Sand Trap 118

Posted by Soulskill
from the calls-to-onstar-have-gone-unanswered dept.
coondoggie writes "NASA's long-running Mars rover Spirit is stuck in a sand trap — a situation the space agency would like to fix. Yesterday NASA said it will begin what it called the long process of extricating Spirit by sending commands that could free the rover. Spirit has been stuck in a place NASA calls 'Troy' since April 23, when the rover's wheels broke through a crust on the surface that was covering bright-toned, slippery sand underneath. After a few drive attempts to get Spirit out in the subsequent days, it began sinking deeper in the sand trap. Driving was suspended to allow time for tests and reviews of possible escape strategies, NASA stated."
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NASA To Try Powering Mars Rover "Spirit" Out of Sand Trap

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  • mars rover blog.. (Score:5, Informative)

    by Frogg (27033) on Saturday November 14, 2009 @07:40AM (#30096446)

    here's a link to a blog by someone on the mars rover team, Mars and Me [blogspot.com]

    i've been following it for a while now - it's truly fascinating

  • by barzok (26681) on Saturday November 14, 2009 @08:16AM (#30096588)

    The panel-clearing brush was considered. Then discarded. They didn't intend for the rovers to last more than 90 days, and determined there wouldn't be a significant dust build-up in that time, so they used the weight & space for items more valuable to the mission.

  • Re:Use the arm ? (Score:3, Informative)

    by DerekLyons (302214) <fairwater@gmai l . c om> on Saturday November 14, 2009 @01:23PM (#30098756) Homepage

    The end of the arm is a cluster of scientific instruments, not a bucket like your excavator. Not only can it not pick up anything, using it to push rocks/soils around or to lift the vehicle risks damaging or destroying the very instruments that are the rovers reason for being. It's akin to sticking your head into a grinder to save the tip of your little finger.

  • Re:Use the arm ? (Score:5, Informative)

    by ScottMaxwell (108831) on Saturday November 14, 2009 @02:14PM (#30099264) Homepage

    Using the arm to help isn't completely off the table, but pretty close, largely for reasons you conjectured about in your post. First, we can't actually push while driving, because the motor controllers are shared between the arm and the wheels -- you can run one or the other, but not both at once.

    We could, potentially, push down with the arm to lift Spirit slightly, then run the wheels. But Spirit's just not strong enough to make much difference. :-) In the best case, we can push down with maybe 70N of force, and that's if we had a hard surface to push on. (But if we had a hard surface to push on, we probably wouldn't be mired in this stuff in the first place.) For comparison, you'd need to apply ~ 650N to completely lift Spirit, so the arm can apply only about 1/10 of the needed force. As you can see, she wasn't designed to do one-handed push-ups. :-)

    Further, doing so would pose a high risk of damage to the arm itself, and since four of Spirit's science instruments -- about 2/3 of the total science payload -- live on the end of that arm, the potential downsides are quite significant.

    In addition, it's not completely clear that pushing down with the arm to partially lift Spirit would actually help: one effect of that would be to reduce the traction on the wheels, and not having enough traction is one of our big problems here.

    Resculpting the terrain is a less unlikely scenario, but something we're keeping in our back pocket for now. There are few suitable rocks within reach, we've never tried it and (again) would risk damaging the arm by doing so, and on top of all that we don't even know if it would actually help, since the rocks might simply slip quickly under the wheels without moving us forward much. Even so, if things get desperate enough, we might possibly try that one.

    The soil we're stuck in is very weird, and has some counterintuitive properties. It doesn't work like dirt or mud. We mixed up a batch of simulant to drive our test rover in, and while there are known differences between the simulant and the real soil, the experience of working with the simulant is quite illuminating. The stuff feels like flour and flows like water: run your hand through it, and it flows away from you like water does, it just stops moving sooner. Weird, weird stuff.

  • Re:Use the arm ? (Score:5, Informative)

    by ScottMaxwell (108831) on Saturday November 14, 2009 @04:17PM (#30100386) Homepage

    It's equal parts -- can't remember if that's by weight or by volume, but I think it's by volume -- of Lincoln 60 fire clay and food-grade diatomaceous earth. (FGDE is normally used for, among other things, de-worming horses and killing centipedes. I tasted it. Bleah.)

    One entertaining afternoon a few months back, when we were testing out different mixes, fellow rover driver Paolo Bellutta and simulant designer Kim Lichtenberg (the mix is called "KimSim" :-) and I drove out to a local ranch, picked up a huge bag of food-grade diatomaceous earth, and drove back to Lab. Later, I was up to my elbows hand-mixing a batch of the stuff in a wheelbarrow. Ah, the things I get paid to do!

With all the fancy scientists in the world, why can't they just once build a nuclear balm?

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