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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.'"
Yep - there are pools at JPL and Caltech. Go Beavers!
Did you ever wake up in the morning, with a Zombie Woof behind your eyes? -- FZ
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.
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.
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?
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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.
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
Not 240 watts; 240 watt-hours. With 24.6 hours per Martian day, that's about 9.75 watts average consumption.
Only on Slashdot can a post that confuses power (watt) and energy (watt-hour) be modded +3 Interesting.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
The next one will be; the Mars Science Laboratory will use radioisotope thermoelectric generators.
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Given the thin martian air, it could take a lot of power to build up sufficient pressure to be effective. Also, see this post.
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.
Well, there's spam egg sausage and spam, that's not got much spam in it.
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.
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".
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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.
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.
18 minutes. Sheesh.
Semi-automatic amateur armchair Australian philosopher; conjecture ready at any moment...
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.
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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.
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.
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