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Mars Rover Spirit Reaches Winter Tilt
Posted by
kdawson
on Tue Feb 26, 2008 04:21 AM
from the playing-pinball-on-the-fourth-planet dept.
from the playing-pinball-on-the-fourth-planet dept.
An anonymous reader writes "The Mars rover Spirit has been inching carefully down the north slope of the feature 'Home Plate' to tilt its solar panels into the sun to survive the long Martian winter. On Friday, it reached a tilt of 29.9 degrees, probably the final tilt it will reach for the winter. Although it's used the tilt strategy to increase power over the Martian winter twice before, this year it's especially critical, since a global dust storm last summer has left the solar-powered rover covered with dust and starved for power. Geoffrey Landis, one of the MER scientists, commemorated Spirit's trek to the winter haven with a sonnet on his blog. (The second of the two rovers, Opportunity, is at a landing site that's not as far into the southern hemisphere, and hence has less need to find a tilted surface.) OSU has a website explaining some of the software used to visualize the terrain to optimize the tilt, and for the latest news, the ongoing log of the rover status is updated weekly."
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Submission: Spirit reaches winter tilt by Anonymous Coward
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Rover Accidentally Uncovers Mars Hydrothermal Vent 53 comments
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Stupid but obvious (Score:4, Funny)
Re:Stupid but obvious (Score:4, Funny)
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Re:Stupid but obvious (Score:4, Insightful)
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Re:Stupid but obvious (Score:4, Funny)
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Re:Stupid but obvious (Score:5, Insightful)
For the original 90 day mission length, running out of juice due to dusty panels would not have been a concern. It would have just been another thing to break and would have added to the mass of the rover, quite possibly costing valuable capacity for other scientific tools.
[insert rant about how some of that war budget could do wonders for NASA]
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They have already been working on a few ideas [nasa.gov] in the labs.
Re:Stupid but obvious (Score:4, Informative)
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Re:Stupid but obvious (Score:4, Insightful)
No, it means no rovers will have an American dust cleaning device.
And as happens more and more, the rest of the world will laugh at us as we legislate ourselves into a third-world mediocrity.
As an aside - OSHA actually has guidelines for one of the rarest of human professions in all history, but they can't keep coal miners safe? Whiskey Tango Foxtrot?
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"I disagree" != "Troll" (Score:5, Insightful)
Though confusingly similar to the untrained eye, people can legitimately disagree with your personal worldview without trolling.
Although metamoderation almost always vindicates me, and I couldn't care less about my karma ("excellent", BTW) I do find it somewhat discouraging that zealots (whether religious, political, or Apple) manage to silence any discussion on topics they don't like by modding to below the default visible threshold.
If you disagree with me, say so. You might even convince me of the error of my ways. Modding me down just reinforces the view that those who silently disagree with me really have no rational arguments worth hearing.
Parent
I disagree... (Score:2)
If I had any mod points, I'd mod you down right now.
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Obviously, they were over-engineered because the environment on Mars was not known very well at design time.
If it had been known very well there would have been no point in sending them.
What I want to know is why the dust can't be shaken loose by rocking either the solar panel or the whole rover.
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Dust removal, hard but possible (Score:5, Informative)
With that said, let me note that dust removal is probably a bit harder than you realize. The optical data showed that suspended dust is extremely fine-- the cross-section weighted average particle radius is about 2.5 microns, so these particles are about the size of the particles in tobacco smoke. Particles this fine are predicted to adhere extremely well, by van der Waals and electrostatic forces. Picture trying to use your windshield wipers to clean the dust off your windshield, without using the wiper fluid. (and wiper fluid is tricky on Mars, too; you need it to stay liquid for long enough to run the wiper, and neither evaporate or freeze before it hits the panel). And blowing dust off is very tricky-- the atmospheric pressure is less than 1% that of Earth's. We could carry fluid, or compressed gas, but those would be consumables-- and if we had designed the mission and budgeted consumables for a 90 sol lifetime, we'd have run out of them years ago anyway, so we'd be in the same position we're in now anyway.
A feather duster might work, but feathers almost certainly violate the planetary protection policy :)
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For piezos, I'm thinking of the "dog shake" method. A little buzz from time to time to loosen the dust. If the panels are tilted, some of the dust might flow off. Clean the panels? Unlikely. But maybe keep the dust from exceeding some limit.
For electrostatic, someone might be clever enough to figure out how to do it with no moving parts. But all I can think of is to charge a small ribbon or wire and pass i
Re:Dust removal, hard but possible (Score:5, Informative)
Yeah, both of these were looked at. We thought about miniature piezo vibrators on the cells, but didn't actually get to the point of doing any tests under Mars conditions. We did a bit of work with electrostatics-- in fact, the mitigation technique I like best right now uses a DC glow discharge ("Paschen discharge") which is pretty easy to start at Mars pressure, very near the Paschen curve minimum.
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And, allow me to reiterate the sentiment -- kudos to the entire rover team. Coolest things in a long time.
Cheers
Re:Stupid but obvious (Score:5, Insightful)
- Weight
- Dust too fine to be brushed off easilly
- Chance to actually reduce power generation on failure by blocking the solar panels
- Needs power itself
And all this aside from the fact that asking someone to make a solar panel wiper for Mars is going to be an enormously expensive and involved operation. Windspeeds, airpressure, particle count, gravity, temperature all play a part in this. And anyone using windshield wipers on their car knows how unreliable they are to begin with.
Parent
Re:Stupid but obvious (Score:4, Insightful)
That being said, I think you are overstating the complexity and cost a little bit. Now that we do know it would be valuable and extend the lifetime of the mission, it would be trivial to add a kind of "dustbuster" if you will.
This will be true no matter what we are talking about doing with the rover, with the exception of its electronics and sensors. It is essentially a robot, and must have moving parts to achieve locomotion and carry out missions with its arms. So what you are saying is obvious. The question is if the value it adds to the mission justifies it costs.
Once again, this is a consideration with every aspect of the mission, from getting it there, to the energy expended while on the surface. The question should once again be if the value it adds to the mission justifies the costs.
Does it need to be brushed in the first place? I know the poster asked specifically about a brush, but they also asked about "something". It need not be a windshield wiper, but could simply blow whatever atmosphere there is against the panels like an air canister. Since the canister and pumping apparatus could provide variable amounts of pressure, it could be configured to blow the air just enough to start getting rid of the dust without doing significant damage to the solar panels, or at least no more significantly than the dust already did when landing on the solar panel itself.
Now this applies only if it was really designed like a brush (a large tool), and even less if it was a windshield wiper (very small tool). If it was a robotic arm with a "wand" it could be designed to only block a very small portion of the panels during use. Even windshield wipers block a very small percentage of any windshield if they are stopped in the middle of a sweep.
Heck, you could ditch the wand entirely, and just implant into the surface a bunch of raised nozzles like the ones we have on cars now that spray the windshield wiper fluid. A simple omni-directional nozzle could spray out the air onto the solar panel, and would not block the solar panel under any conditions.
Well thats kind of redundant and unnecessary as a comment, no offense. EVERY device on these Rovers is going to require power, either what it brings from Earth, or what it can generate on Mars. Not a reason to dismiss anything out of hand. Once again, if it is justified by the value it adds to mission, its energy costs are then factored in and must be worth it.
As for the power requirements, is it feasible to just reserve a small percentage of the incoming power to keep the air canisters pressurized at all times? I realize that it must use some of the same power it is attempting to protect, but air canisters can remain pressurized for extended periods of time. The amount of power that would be necessary to run pumps to "top off" the air canister should be minimal when spread over such a large duration of time.
There was also a recent post about a type of nanotech windshield that was wiper less and only required a power source. If the power required was low enough, it could be powered directly from the solar panels themselves. There would only be reduction in the amount of power delivered to the main systems. Another possibility, and one that is certainly solid state and required no
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Thanks for your post :) I pretty much agree on your points, and I wasn't trying to make a statement it would be too hard. I only tried to list a couple of things that could/should be taken into account with these sort of things.
In the original mission briefing the reduced power output of the solar panels due to dust buildup were actually mentioned, but it wasn't actually considered a serious problem, since it would only start
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Windshield wiper: may scratch panels, causing catastrophic or severe power-gathering capabilities. It's the $2 option on a Terran car, but only because the constraints are well-known and not mission-critical.
Transparent rolling film: works for NASCAR cameras, but film may tear or get caught in winding mechanism. Still needs squeegie (weight) or electrostatic squeegie (power drain) or mission-length supply of film (weight, estimation error). Material science: transparent film is likely plastics-based
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It doesn't need to be complexes. Just something that could effective provide enough wind to blow the dust and dirt off. I don't think they has to worry about moisture. Co2 tanks o
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Of course this would assume the panels would open up like a fan instead of unfolding like
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Re:Stupid but obvious (Score:4, Interesting)
I think the original rovers folded the panels on top of each other. I think if this were changed to stack and slide together like a sliding winder, at the points they meat, it could use the deployment motors to periodically retract the panels which would cause them to be brushed by the felt or velcro strip along the seems of the pannels. Then deploy the panel wings on the opposite side of the craft and you would essentially have swiped both sides the entire panel array.
The only draw back is that you would need to manipulate which panel was on top in order to ensure they could all three (or five or whatever) be cleaned by this maneuver. It appears that it only needs to happen a couple times a year. I'm sure even the simplest design could outlast the crafts.
It might not be as easy as this. Or whats that saying, sound easy until you try to do it. But I think that out of a few simple approaches, something might be able to be worked through relatively easily without costing too much weight or bulk.
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(temp -78C)
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I'm wondering of simply lining the Co2 cartridge with nickel or a nickel alloy and injecting a drop or so of hydrogen peroxide would work. The biggest draw back there would be the v
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It seems to me that something like http://science.slashdot.org/article.pl?sid=08/02/22/2342233 [slashdot.org] would be right up NASA's alley.
Of course I read WAY too much
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not obvious, but possibly stupid (Score:5, Informative)
What are the triboelectric properties of ostrich feathers? If rubbing an ostrich feather across a solar panel charges up the panel electrostatically (and think of rubbing something on Mars like petting your cat in the middle of a very cold winter, except Mars is really really dry) you are in deep trouble. (obSF: "Dust Rag," Hal Clement).
How do you sterilize an ostrich feather to get it past the planetary protection protocol?
What is your failure-mitigation mechanism for the case the mechanism jams when the feather is halfway across the solar panel? (keep in mind that shadowing just one solar cell in a string will take the entire string off line.)
The dust on Mars is preferentially attracted to magnets.
Mars is very cold, and very dry, and very dusty. What are you proposing to use to lubricate this mechanism? How are you keeping it from jamming? What's your plan to ensure that the acoustic environment inside the launch shroud doesn't vibrate it until the shaft bends? (That long ostrich feather looks like a cantelever that's going to resonate like heck. Tie downs? OK, another few moving parts; more failure modes, more wires connecting to D/A lines connecting to the computer.)
I don't even know what you mean here. There's no free lunch, even on Mars; if you have weights and pulleys moving it one way, you need exactly that much more energy to move it the other way.
Failure analysis is a difficult task, and it's the failure modes that you don't think of that kill you. I'm hard-pressed to think of mechanical devices that work reliably for ten years with no servicing in severe environments on Earth, and you're proposing close to zero chance of breaking on Mars. My car's windshield wipers get a little unreliable at merely 0F; I don't think I'd like to claim "no chance of failure" at, say, -50.
....although it may seem like it, my point here is not merely to poke holes at superficial solutions (to be fair, you did say "off the top of my head."). The point is that space is not like Earth, and there really are reasons that it is harder to do things in space than it is on Earth. Something like you propose probably could be made to work, but your offhand thought that oh, it would be simple and cheap and reliable is just offbase.
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Thanks for the update (Score:2)
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A Job well done. (Score:5, Insightful)
Great job rover team.
The two rovers are a constant motivator for all engineers on how a project can still be done right in this world, and how much affect that can have. Nowadays it's depressing when you hear about all the flaws in products people actually sell, and how returning broken shit out of the box is the norm. In business we get delayed projects and stupid alterations at whims sometimes.
But the rovers were done right, and were done for science. And they're still chugging well past their expiration date. I regret I wasn't alive for the moon landings, but in my humble opinion, i sometimes feel as if this was the greater achievement of the two. Especially that they're still going.
Good job. And keep it up.
Rover III (Score:5, Funny)
Sponsored by Dyson.
Wonderful (Score:3, Interesting)
Great to see these amazing robots still at work!
I read "Roving Mars" a couple of years ago and even back then the mission had superseded all of its goals.
Indeed a very inspiring episode in space exploration
29.9 (Score:4, Interesting)
I can't even know the angle of the keyboard I'm writing this, with such precision.
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Nah. They don't control the inclination - they measure the inclination and park the rover at the best possible spot within various limits. Even measuring to a tenth of a degree isn't all that spectacular, I was measuring to a hundredth with electronic equipment nearly twenty years ago.
nah, its no problem. (Score:3, Funny)
they'll need to get close to one of the canals if they want to wash of some of the sand clogging the treads as well.