Mars Winds Clean Spirit's Solar Panels Again

Titoxd writes "In a blast from the past, NASA reports that Spirit's solar panels have received a much-needed cleaning courtesy of the Red Planet. The report states, 'The cleaning boosts Spirit's daily energy supply by about 30 watt-hours, to about 240 watt-hours from 210 watt-hours. The rover uses about 180 watt-hours per day for basic survival and communications, so this increase roughly doubles the amount of discretionary power for activities such as driving and using instruments.'"

Comments

Next time . . .

[OhHellWithIt]

. . . don't forget to pack the broom.

Re:Next time . . .

[Tubal-Cain]

They decided that a windshield wiper didn't have a good benefit/cost (in both money and weight) ratio. Especially for a 90-day mission. I understand that the best they could get the wipers to do was smear the dust around (something about static cling keeping it from coming off), so it wasn't going to do much good, anyways.

Re:Next time . . .

[SilverJets]

So what about an air cannon or something? Small pump to take in Martian air, build up pressure, and a small nozzle directed at the panel to blow the dust off.

I know, every ounce of weight and every bit of energy has to be calculated and accounted for. But they had to know that dust would accumulate on the panels and should have accounted for that with some type of design.

Re:Next time . . .

[solafide]

90 days.

Re:Next time . . .

[blueg3]

They did know. They also knew that all the possible solutions had significant costs and/or chance of failure. (As far as the air cannon, Mars air is very thin, so you have to have a quite significant wind to move the dust.)

Re:Next time . . .

[sremick]

I don't see how the benefits are minor, considering how much press and excitement is triggered each time the winds clean the dust off. Also considering the massive longevity to the mission that more runtime creates. More life = more science, and since the whole point of these missions is "science", that's more bang for your buck.

It's not easy to get stuff to Mars, and there are only occasional windows of opportunity. Best to get as much as you can out of the missions you DO send.

I don't see how there can be much "static cling" if just wind can dust them off.

Re:Next time . . .

[Tubal-Cain]

Given the thin martian air, it could take a lot of power to build up sufficient pressure to be effective. Also, see this post.

Re:Next time . . .

[dpilot]

Arthur C Clarke wrote a nifty short story that encapsulated some of this. I can't even remember the title, so spoilers are uselss, and I'll just give the gist.

Two astronauts were exploring on the moon, and the wandered into a dust bowl. They got a little dust on their faceplates, and made the mistake of wiping them. The generated static transferred all of the dust to the faceplate, and they were still deep enough in the dust that it attracted more. So even though the dust bowl is shallow enough to simply walk out, they can't see, and so far they haven't found anything they could rub the faceplate with where the static electricity would go the other way, taking the dust off.

Solution:

They rubbed faceplates together. One faceplate takes the charge that takes the dust, the other cleans. Then the astronaut with the clean faceplate can see the way to the buggy, leading the other.

Re:Next time . . .

[Tubal-Cain]

The wind is (somewhat tongue-in-cheek) taking the level of dust from "almost thick enough to grow weeds in" to merely "heavy".

Re:Next time . . .

[Gerzel]

They never expected the mission to go this long. Things were calculated at a success level of 90 days.

Indeed because of the success of these two rovers the next missions will be similar. The next mission may or may not benefit as often it is the failures that teach better than the successes.

It may be that the rover happened to have landed in a particularly windy part of the planet, or a part with a particularly un-clingy(love my technical wording!) local dust conditions and the next mission may be different and fail even if the exact same equipment is used.

Re:Next time . . .

[UnknowingFool]

Your post advocates a

(X) technical ( ) legislative ( ) market-based ( ) vigilante

approach to Rover problems. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)

(X) It requires too much power
( ) It may make situation worse
( ) It doesn't solve the problem
(X) It works here on Earth but not on Mars
(X) It will work for two weeks and then it might get stuck
(X) It does not account for the climate of Mars
(X) Marvin the Martian will not put up with it

Specifically, your plan fails to account for

(X) Weight limitations on mission payload
(X) Space limitations on mission payload
(X) Extreme cold of Mars
(X) Atmosphere of Mars
( ) Difference between Mars gravity and Earth gravity
( ) Materials don't exist yet
(X) Survivability of materials on Mars
( ) Distance between Mars and Earth
( ) NASA bureaucacy
(X) Technically illiterate politicians
(X) Marvin the Martian
(X) Democrats
(X) Republicans
(X) Ralph Nader

and the following objections may also apply:

(X) Ideas similar to yours are easy to come up with, yet none have ever been shown practical
(X) Solution is beyond mission scope
( ) Solution solves the wrong problem
( ) Only delays the inevitable
( ) Cost limitations
(X) Requires redesign
(X) Scientific instruments may have to be excluded
( ) Feel-good measures do nothing to solve the problem

Furthermore, this is what I think about you:

(X) Sorry dude, but I don't think it would work.
( ) This is a stupid idea, and you're a stupid person for suggesting it.
( ) Nice try, assh0le! I'm going to find out where you live and burn your house down!

Re:Next time . . .

[UnknowingFool]

2 practical problems with that. (1) The horizontal placement of the panels insure maximum solar efficiency so slanting them would be less efficient and the rover wouldn't get as much power. (2) The dust is super clingy due to electrostatic forces. Slanting them probably won't solve anything.

Re:Next time . . .

[Chyeld]

As well as hope that you aren't sandblasting your panels with it when the barrel gets clogged.

Re:Next time . . .

[Chris Burke]

90 days.

Which is how long they estimated it would take for the rovers' solar panels to be covered in too much dust for the rover to function. Dust is why the mission was scoped at 90 days. They didn't know that the Martian wind would be of any use whatsoever in cleaning off the panels.

Yet even though dust is what was limiting the scope of the mission, NASA still decided not to put on a brush, wiper, or (sorry but lol) air compressor. Given there's enough obvious tradeoffs in mass/space/power use for anything you add, I'll give NASA the benefit of the doubt and assume they actually calculated the tradeoffs and said "not worth it".

Re:Next time . . .

[thenickdude]

Two astronauts, one faceplate?

Re:Next time . . .

[93 Escort Wagon]

They decided that a windshield wiper didn't have a good benefit/cost (in both money and weight) ratio. Especially for a 90-day mission. I understand that the best they could get the wipers to do was smear the dust around (something about static cling keeping it from coming off), so it wasn't going to do much good, anyways.

Okay, so they needed to include a windshield wiper AND a bottle of 409.

Re:Next time . . .

[ElizabethGreene]

Am I the only one that read this and said "That is effing awsome?"

Re:Next time . . .

[Chris Burke]

Thank you for responding to the first half of my post with a simplified version of the second half of my post. That was very informative.

Re:Next time . . .

[CecilPL]

I'm almost positive you're thinking of Hal Clement's short story "Dust Rag". That's exactly the plot you described. Clarke did write a similar story called "A Fall of Moondust" which dealt with the perils of moon dust, but not quite in the same way.

Re:Next time . . .

[dgatwood]

Actually, it's pretty easy. We've discussed this before every time the subject comes up. Put a continuous roll of clear plastic at one end of the panel and a take-up roll on the other end. Make the plastic travel in a track with brush seals so that nothing can easily get in behind the plastic. Periodically roll the plastic to keep the portion atop the panel clear. When you get to the end of the roll, reverse the direction. You'll have less power that pass, and eventually this won't be practical, but it will work for a really long time. For that matter, you could have a series of brushes along the path of the plastic beyond the panels that would significantly reduce the dust level on the plastic even on the second and subsequent passes. And because it is just a simple motor on a spool, it is about as mechanically trivial as you can get, unlike... say a windshield wiper... and best of all, if you scar the plastic, you're not scarring the panel itself and risking causing a panel failure.

Re:Next time . . .

[Anonymous Coward]

Not Arthur C Clarke. "Dust Rag" by Hal Clement. Astounding Science Fiction 1956. Reprinted in Clement collection known as either "Small Changes" or "Space Lash". One of the spacemen tore open a plastic specimen bag and stretched it across his faceplate, excluding dust from beneath it. Then he rubbed his helmet, bag and all, against his companion's faceplate. Since bag and faceplate were of different materials, one of them HAD to acquire the correct charge to repel the dust.

Re:Next time . . .

[dwywit]

Dirt bike riders have been using this principle for years - they're called tear-offs, but the idea is the same.

A package of n clear plastic panels fits over the eye-goggles, each with a tab for easy removal. Dirt and mud build up until you can't see properly, and instead of stopping, taking off the goggles, cleaning them, putting them on and starting again, or just attempting to wipe it off with one hand while still riding, you reach up, grab a tab, tear it off, throw it away, and keep charging on.

No reasons why a continuous roll wouldn't work the same way.

And this might sound ignorant, but why not have an earthing strap trailing on the ground, like some cars here on earth? I suppose the entire rover would need to be designed to allow drainage of static, but would that be a problem? I mean, if there's a static buildup, and no way to drain it off, won't it become a problem when the potential difference between rover and the surface gets large enough?

Re:Next time . . .

[SilverJets]

NASA still decided not to put on a brush, wiper, or (sorry but lol) air compressor.

There is a thin atmosphere on Mars. It may be enough for a very small air compressor to build up enough pressure to simply blow the dust particles off the panel. We're not talking about moving anything large. Just a small burst to clear the panel. The problem with a brush or wiper is that the moving parts would be exposed to the dust which would most likely result in them breaking. If all that was exposed was a nozzle which the burst of air would come from it would be less prone to breaking.

Re:Next time . . .

[SilverJets]

So you think a tiny air nozzle would sandblast the panels compared to the dust storms on Mars?

Re:Next time . . .

[AmigaMMC]

I understand that the best they could get the wipers to do was smear the dust around (something about static cling keeping it from coming off)

They could have coated the panels with a layer of Snuggle :)

Re:Next time . . .

[NightLamp]

What about a vibrator?

This is the mechanism used to clean the CCD in many high-end digital cameras and since the rovers are obviously built to withstand very high magnitude vibrations why not use a similar system on them?

The rover could be parked on an incline, identical to the technique used to get them maximum solar exposure during "winter", and then vibrate the dust off the panels.

Even the smallest cell phone has a vibrator, they are small and light-weight I'm not sure how energy-efficient they are but I'd wager the power generating improvement would more than offset the expenditure.

Re:Next time . . .

[apostrophesemicolon]

enough kids...

now WHO gave these two too much candy??

Re:Next time . . .

[UnknowingFool]

First of all the dust is not only super clingy, it may also be abrasive. Physically removing the dust via brush may scratch surfaces.

Second, if the dust isn't abrasive what materials would the brushes and plastic film be made of. Remember they have to be softer the the panels or they'll scratch them. Typically on earth they are made of a synthetic like nylon and HDPE. Would such materials survive the harsh environment of Mars? The extreme shift of cold and hot of Mars days would make most soft material brittle after a short time period. For the plastic film the transparency would also be affected by the extreme conditions.

Third you are using a motor. Motors will fail after certain amount of time. For example 2 wheels on each rover have failed. If the motor fails, the rover is no better off than it is now. Such a device would cost weight and space on the rover.

Fourth are you planning to cover all the solar panels or just a few? The rover was packed with as many panels at it would allow. Such a system would necessitate fewer panels just to implement for weight and space considerations. That would reduce the amount of power the rover can gather in a day.

Squeegee kid

[macxcool]

That's much better than NASA's alternative plan of sending a Squeegee Kid to do the job.

Re:Squeegee kid

[GargamelSpaceman]

It was a martian. You see about a billion years ago, the Martian civilization discovered the secret of consiousness. Eventually the robots they created displaced them, and then when the planet's resources were depleted, they left for the stars leaving behind some curators. These curators are not really consious, their robotic creators ensured this so that they would be reliable in their task of preserving their martian heritage, but sometimes they do act in ways that are, almost uncannily lifelike.

This was the case here. The Martian curator bots find the rovers interesting, or rather, they find their controllers interesting. They periodically dust the solar panels so that they will be able to keep roving. They are curious as to what they are doing, maybe even appreciative that someone has visited to appreciate what they have devoted the past eon to preserving. For them, watching us look is most gratifying. They really ache to communicate with us and show us all the Martian history in their underground vaults, but because of their programming to remain inconspicuous, they can't. Still, they are helpful when they can be and not give themselves away.

Re:Squeegee kid

[JCSoRocks]

if only NASA had sent a homeless fellow with some newspaper...

Re:Squeegee kid

[The Great Pretender]

Actually it was a Mexican. You didn't realize that we had made it that far did ya! To hell with finding water on Mars, we already have a Taco truck with the best horchata in the solar system there waiting for NASA.

How much longer?

[i.r.id10t]

How much longer can this thing go? I mean, it was "designed" to only go a few months, and we are years beyond that. Anyone have a pool on when it will really stop working?

Re:How much longer?

[al0ha]

Yep - there are pools at JPL and Caltech. Go Beavers!

Re:How much longer?

[jellomizer]

Rule 1 of engineering: Underestimate your estimates.
The thing was designed to run for years. However they gave it a 90 Day limit to save their butts if it breaks in 85 days. as well the mission spec was for 90 days, so they made sure it would last that 90 days as much as possible. It is not like you going to put up a million dollar probe and skimp on parts. You are going to make it as robust as possible as estimating 90 days of operation in the unknown is quite hard.

Re:How much longer?

[Chabo]

And of course, the scene from the TNG episode "Relics":

"Starship captains are like children. They want everything right now and they want it their way. The secret is to give them what they need, not what they want."

"I told the Captain I would have this diagnostic done in an hour."
"And how long will it really take you?"
"An hour!"
"Oh, you didn't tell him how long it would really take, did you?"
"Of course I did."
"Oh, laddie, you have a lot to learn if you want people to think of you as a miracle worker."

Re:How much longer?

[dlevitan]

NASA probably has a good idea. Published estimates were likely wrong on purpose from the start to give them the opportunity for more media coverage and subsequently budget opportunities.

Not exactly. Estimates are based on worst case scenarios. What would have been the public's reaction if NASA had said that the rovers would last 1 year but they only lasted 6 months? NASA guidelines require that when something is supposed to last x months/years, then it's engineered such that it will last that long, no matter what. Specifying mission requirements is actually a tricky problem for the scientists on a mission because you want the most possible science that fits within a budget and that will last for as long as you say it will last. And usually the only way to convince NASA that something will last is if you add in backup systems. With new, expensive technology this becomes even harder.

So yes, the rovers were conservatively estimated to last 3 months. I'm sure the scientists on the mission expected that they would last longer, but 3 months was a good benchmark that provided a good amount of science for a reasonable cost. Everything else has just been icing on the cake (and in this case, a lot of icing). Personally, I think they did a great job and cannot fault them at all.

(I am a grad student working on a NASA mission and have seen a bit of how this process works)

Re:How much longer?

[osu-neko]

Published estimates were likely wrong on purpose from the start to give them the opportunity for more media coverage and subsequently budget opportunities.

Bzzt. Wrong. First of all, what you're quoting (90 days) never was an estimated lifespan. If the estimated lifespan of a craft was 90 days, that would mean there's a substantial chance you'll only get 60 days out of it, or 120 for that matter. 90 days was never the expected lifespan. 90 days was the promised minimum lifespan. They were very certain it would last at least 90 days. If you think about that a minute, that means they estimated it would probably last much longer than that, or else they couldn't be that certain it would last at least 90 days. In fact, they expected it to last about three times that -- they expected the rover would keep going until the Martian winter. They just weren't terribly confident it would survive the winter...

Re:How much longer?

[buserror]

I think there should be a nobel of engineering or something similar, given to whomever designed that rover.

It /never/ happens in real life that you can get away with designing a piece of equipment that outlasts it's fail-by-date by so much. In most companies nowayday, these guys would be in trouble !

It sort of ought to be encouraged somehow...

Re:How much longer?

[2short]

Exactly. "Designed to last 90 days" presumably means something like "Designed to have a 95% chance of lasting 90 days". Which probably means it has a 90% chance of lasting 180 days, an 80% chance of lasting 360 days...

I don't know what confidence threshold NASA uses, maybe more than 95%. So the 5 years these lasted is lucky, but not so completely off the charts as it might seem.

Re:Include cleaners next time?

[CompMD]

Weight = money. At $10,000 per pound, it would have been a waste of money for a vehicle designed to last only three months.

If the vehicle were designed to last five years, it might be a different story.

Re:Math?

[Samalie]

Jesus, can you fucking read? Not even the article, but the summary...

"to about 240 watt-hours from 210 watt-hours. The rover uses about 180 watt-hours per day for basic survival and communications, so this increase roughly doubles the amount of discretionary power for activities such as driving and using instruments."

180wh for survival. They were generating 210wh. Now they're getting 240wh.

210wh-180wg=30wh discretionary.
240wh-180wh=60wh new discretionary.

No wonder you're not a rocket scientist. Or if you are, you're one of those fucks who confused imperial and metric, aren't you?

Re:Include cleaners next time?

[smooth wombat]

Maybe next time, NASA should include some type of cleaning devices,

This comes up every time the rovers are mentioned. Here is a detailed explanation why there are no wipers, or any other cleaning device, on the rovers.

Re:Amazing

[Chabo]

My computer uses nearly that much power under full load, and it doesn't even have to move!

Re:Amazing

[evanbd]

Not 240 watts; 240 watt-hours. With 24.6 hours per Martian day, that's about 9.75 watts average consumption.

Re:Amazing

[Kjella]

Cruise is something of an exaggeration... they've gone 13 miles in 5 years, put together. The Lunar Rover missions each went longer than both combined in 3-4 hours, at top speed they'd pass the rovers within the first hour. Semi-stationary crawlers is a more accurate description, but of course they've been loaded up with scientific equipment rather than for showing off.

Only on Slashdot!

[blind biker]

Only on Slashdot can a post that confuses power (watt) and energy (watt-hour) be modded +3 Interesting.

Re:Only on Slashdot!

[Zenaku]

For redundancy. If the Joules run out, it can still run off the watt-hours, and vice versa.

Re:Only on Slashdot!

[Chabo]

On exactly how many sites can a post be modded "+3 Interesting"?

Re:should've gone with ...

[Glendale2x]

The next one will be; the Mars Science Laboratory will use radioisotope thermoelectric generators.

Re:Amazing

[cavtroop]

because I don't want to pay $456,784 for a lightbulb :)

More amazing is that it keeps going

[WindBourne]

What I really want to see is a glider, or a ballon/lander combo survive that long. Something of that nature would be really useful if it could pop all over.

Re:Include cleaners next time?

[Cheeko]

The next rover uses an RTG for power, so there won't be a need for wipers or any other such thing:

Mars Science Lab

I guess the radiator portion of the RTG could get enough dust on it to cut down on its effectiveness, but Mars in general is still pretty cold, so I doubt there is nearly as big of an issue as dust on solar panels.

Re:Include cleaners next time?

[NerveGas]

How dare you inject a useful, explanatory article into the armchair quarterbacking? I don't know where you think you are, but this is [i]Slashdot[/i], kid. Take that stuff somewhere else.

Phoenix lasted as planned

[peter303]

The Phoenix polar probe landed in late May 2008 and died early November 2008. It was funded for the first 90 days, then for another 90 days. Because it was so far north, it was expected to die in late November due to too short battery-charging hours. An unexpected dust storm covered the panels causing it to die two weeks early. However, there were other portents of doom: Mars went into solar conjunction in late November, so the device would be on its own for three weeks near its death date. I recall just about now its perpetual night at Phoenix latitude. Its expected to accumulate about a one meter of dry ice frost through the winter, which will crush it. Satellites will photograph it periodically.

Phoenix mostly worked as planned. I think about three of the dozen chemical stoves wouldnt open their latches wide enough. The stoves heat the soils to various temperatures and chemically measure the expelled gases. An stove grate shaker shorted out. Phoneix's arm had trouble getting ice samples beacuse the ice was harder than expected. If you dont gather ice flakes quick enough they evaporate and disappear. The soil was much more sticky than expected and balked at going into the stoves.

the next lander is nuclear powered

[peter303]

The Mars Science Lander is two years late and a billion dollars over budget because it has developed lots of new technology. It was supposed to launch during the 2009 optimal planetary configuration, but will have to wait until the 2011 one. The next lander uses a nuclear source and rocket landing instead of airbags. I'm a little fearful all the new stuff may not work as planned. I am also fearful NASA budgetary troubles may still kill it.

Re:the next lander is nuclear powered

[Tablizer]

The poster didn't say that those things were the new technologies of the new rover.

The fanciest, and most problematic, is a laser system that cooks rocks several feet away so that a spectrograph can analyze the chemical signature of the plasma from the heated area remotely. Pretty cool if it works. This would allow the rover to inspect several rocks without having to navigate to each and every one. A major increase in productivity if it works.

But it does look like they are putting a lot of big eggs in one basket. Perhaps they should be sending a smaller rover to test the idea first. A lot of people will be nervous during the landing of this big one.
   

Rover Driver Blog

[TrekkieTechie]

At night, there's a small red light in the sky. On that light lives four hundred pounds of thinking metal sent from Earth. I tell that metal what to do, and it does it.

Anyone interested in the Mars Exploration Rovers' mission should check out Mars And Me, the unofficial diary of a Mars rover driver. Scott Maxwell is blogging his daily work at JPL exactly five years later. A very interesting and well-written look at the day-to-day operations of a truly amazing scientific expedition.

Screw Next time . . .

[Capt.DrumkenBum]

How about we all stop thinking that we have better ideas than the guys who built these incredible pieces of machinery?
I mean the designers built two rovers that had to survive a launch from earth, months in deep space, a bouncy landing on another world, and then operate correctly with a 10 minute (Or longer) radio delay.
That is an incredible accomplishment! Then for it to continue to operate for YEARS! I am in awe of the designers.
Now here on /. we have a bunch of armchair engineers believing they could do better?
Do you honestly believe that the same people who built these incredible machines didn't think of a solar panel wiper? A can of compressed air? A fan? A compressor?

To the designers: If any of you are reading this. My hat is off to you. Well done!

Re:Screw Next time . . .

[Hucko]

18 minutes. Sheesh.

Re:Screw Next time . . .

[NotmyNick]

How about we all stop thinking that we have better ideas than the guys who built these incredible pieces of machinery?

Yes, lets stop all this thinking and just worship our JPL overlords as we are meant to do.

Remember that bit about a week into things, Spirit went dumb because they filled up the flash memory? Remember how surprised(pleasantly so) they were when the solar panels were scrubbed the first time?

If you've done any bit of reading on these guys' blogs you would know that they are not the omniscient beings that you give them credit for being. There have been many head-slappers and OMG-we-almost-lost-the-rover moments on the way. These rovers didn't just go up to Mars and deterministically last over five years. New ideas got them there.

Furthermore, I'm not sure if it was you that ridiculed it, but the idea that an air cannon would be ruled out by Mars' low atmospheric pressure.... Laughable. In fact, that would favor the approach. Less stuff in the way of the relief tube of the particle accelerator that way. The adiabatically generated heat might even be useful as a side bene.

Re:Include cleaners next time?

[IICV]

I don't know where you think you are, but this is [i]Slashdot[/i], kid. Take that stuff somewhere else.

Exactly! This is Slashdot, so leave the BBCode to the forums and use HTML like a real nerd!

Re:Math?

[aquabat]

oven light

Re:I am so glad you did the math for me.

[iNaya]

Reading some of the comments here shows, that some people, when all the math is done for them, still don't get it.