Mars Winds Clean Spirit's Solar Panels Again 269
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.'"
How much longer? (Score:3, Interesting)
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:Amazing (Score:5, Interesting)
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.
Re:Next time . . . (Score:5, Interesting)
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 . . . (Score:5, Interesting)
Re:Next time . . . (Score:5, Interesting)
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 . . . (Score:5, Interesting)
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 . . . (Score:4, Interesting)
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:Include cleaners next time? (Score:3, Interesting)
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 [nasa.gov]
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:How much longer? (Score:2, Interesting)
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? (Score:3, Interesting)
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? (Score:4, Interesting)
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:Next time . . . (Score:3, Interesting)
As well as hope that you aren't sandblasting your panels with it when the barrel gets clogged.
Re:Only on Slashdot! (Score:3, Interesting)
On exactly how many sites can a post be modded "+3 Interesting"?
Rover Driver Blog (Score:4, Interesting)
Anyone interested in the Mars Exploration Rovers' mission should check out Mars And Me [blogspot.com], 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.
Re:Next time . . . (Score:3, Interesting)
Re:Next time . . . (Score:5, Interesting)
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:the next lander is nuclear powered (Score:3, Interesting)
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.
Re:Next time . . . (Score:2, Interesting)
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 . . . (Score:2, Interesting)
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.