mars rover and dusty solar panels
I was just reading this: http://www.newscientist.com/article.ns?id=dn6824
I'm wondering why they didn't install some sort of dusting device on the solar panels? Sure it would add some weight but it just seems weird to me that they send these things to Mars knowing the solar panels would get dusty and eventually stop producing enough power and didn't do anything about. I mean were they saying "it's dust, what can we do." Wouldn't a little blower or a brush work? It's not like it's damp or anything.
[522 byte] By [
dubwaia] at [2007-10-1 1:12:20]
The people at NASA can't be concerned with trivialities such as dust and wipers. Of course, they could've outsourced that part to BMW or another car company that was brilliant enough to come up with headlight wipers.
Although, my guess is that they didn't want to do that because it would end up causing more scratching and wearing away of the solar cells and their protective coating then the wind/dust will already do.
engineering specsbudget analysisprocurement protocols
Of course, we could just pull in to the corner space station and get a wipe while we're filling 'er up.
Don't knock NASA, we Brits can't even get the damn parachute to open and we make wonderful oscillating bridges!
> Although, my guess is that they didn't want to do
> that because it would end up causing more scratching
> and wearing away of the solar cells and their
> protective coating then the wind/dust will already do.
But the issue AFAIK, isn't that the solar panels are being damaged, it's that they are caked with dust. They think dust devils are cleaning one of the rovers' panels and it's seen as a great thing thast will extend the life of the rover. Why not include a little blower that clears the dust off in the morning or once the power drops?
> Don't knock NASA, we Brits can't even get the damn
> parachute to open and we make wonderful oscillating
> bridges!
Like Tacoma Narrows? Also wasn't it NASA that created a probe where one team used metric units and another used British units? They aren't infallible.
> Like Tacoma Narrows?
The Tacoma Narrows bridge was built at a time when the aerodynamics of bridges was still being understood. The Millennium bridge was built at a time when the designers should have known better!
> Also wasn't it NASA that
> created a probe where one team used metric units and
> another used British units? They aren't infallible.
In the sixties, an Anglo/French space project (that never go off the ground) had the first stage built using imperial and the second stage build using metric. When they tried to connect the two together they found that the conversion factors used were wrong and they were about a 1cm out! The solution - build a collar!
Why would anyone use anything but metric units for anything like this? It boggles my mind.
> The Tacoma Narrows bridge was built at a time when
> the aerodynamics of bridges was still being
> understood. The Millennium bridge was built at a time
> when the designers should have known better!
Both true, but stiffening anything in torsion can be tricky.
Still, don't they have finite element codes in England? If I recall correctly, there's a wonderful organization called NAFEMS based there that did good work on standards for analysis and such.
Maybe no one thought about the dynamic load imposed by people walking on it. Does anyone know the full story? I'd love to hear it.
Isn't it sorted out now? What changes did they have to make to stablize it?
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> Why would anyone use anything but metric units for> anything like this? It boggles my mind.I have worked on several multi-national projects and the French always want to do it their way, the British always want to do it their way and we end up doing the German way!
> Isn't it sorted out now? What changes did they have> to make to stablize it?I went over the bridge in August. They have added some new invention called 'dampers'!
> > Although, my guess is that they didn't want to do
> > that because it would end up causing more scratching
> > and wearing away of the solar cells and their
> > protective coating then the wind/dust will already do.
>
> But the issue AFAIK, isn't that the solar panels are
> being damaged, it's that they are caked with dust.
> They think dust devils are cleaning one of the
> e rovers' panels and it's seen as a great thing thast
> will extend the life of the rover. Why not include a
> little blower that clears the dust off in the morning
> or once the power drops?
Well, the first consideration they have to make is how long they expect the rovers to last once on the ground. They figured a couple months or so, and probably figured that the dust wouldn't be a problem for that long a time. Any other usage after that time is a bonus. Dust could cause lots of problems besides the solar panels as well. So why waste the money, weight, etc.
Also it's a likely assumption that the wind that puts the dust there is just as likely to blow it off. I would suspect that the assumption would be that dust on the panels isn't that big a deal unless it gets buried in a thick dust storm. And that type of storm would likely damage so much more, making it pointless to worry about it. Otherwise, casual dusting in the normal winds would not build up a significant thickness, since those winds would do as much cleaning as dirtying.
But if you have wipers that clean the dust off, that will cause scratching... well, I'm not sure how bad, cuz I don't know what the panels are coated with, and I'm sure they could've used something highly scratch resistant. But most likely, that would eventually damage the panels. A lot depends on the courseness of the dust or sand. I'm not sure that it wouldn't be after months or years, though. So maybe they should've created some wiper system that could run every few days.
of course, I could be talking out my ass here.... :-)
> I have worked on several multi-national projects and
> the French always want to do it their way, the
> British always want to do it their way and we end up
> doing the German way!
But metric units are so much better. They are all tied into each other in logical ways.I don't remember exactly, but I do remember in Physics that trying to figure things out in slugs, feet, calories and horsepower is a nightmare especially when you are going to keep the correct precision.
I would like to think that engineers would use metric universally....I would like to think a lot of things, though.
The amazing thing is that America is still using British units, while England is firmly metric.
The US Congress passed a law during the Nixon administration mandating a switch to metric. There was a terrible hue and cry, with politicians saying that American consumers would never stand for using metric units.
The truth is that American housewives have no trouble buying goods in liters now. It was American business that didn't want to retool their factories and engineers from British to metric.
Another generation of engineers was trained to have a "feel" for British units. *sigh* Too bad. I learned both, but a modulus of elasticity of 30e6 PSI for carbon steel means something to me. I can't tell you what that should be in MPa without doing a lookup and conversion.
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> Well, the first consideration they have to make is
> how long they expect the rovers to last once on the
> ground. They figured a couple months or so, and
> probably figured that the dust wouldn't be a problem
> for that long a time. Any other usage after that
> time is a bonus. Dust could cause lots of problems
> besides the solar panels as well. So why waste the
> money, weight, etc.
Yeah I can see that but if you read the articles about the rovers it seems to me like the assumption was always that the dust on the solar panels would be the death of the rovers. As long as they can power up they can go as long as the batteries and mechanical parts last.
> Also it's a likely assumption that the wind that puts
> the dust there is just as likely to blow it off.
Again, I could see that but that's not what they've said they assumed in interviews.
> But if you have wipers that clean the dust off, that
> will cause scratching... well, I'm not sure how bad,
> cuz I don't know what the panels are coated with, and
> I'm sure they could've used something highly scratch
> resistant. But most likely, that would eventually
> damage the panels.
But a blower would do just what the wind does to remove the dust, you don't need a wiper necessarily.
A lot depends on the courseness
> of the dust or sand. I'm not sure that it wouldn't
> be after months or years, though. So maybe they
> should've created some wiper system that could run
> every few days.
If the dust scractes the panels, the wind blowing the dust would probably be worse. Like a sandblaster.
> of course, I could be talking out my ass here.... :-)
I don't know what the answer is. These are feasible except for what I've read about what they assumed.
> I went over the bridge in August. They have added
> some new invention called 'dampers'!
BRILLIANT! ;)
My cousin was the last person to walk on the bridge before it was closed. She stumbled her way across and phoned her brother when she reached the other side. He told her that they were announcing the closure of the bridge just when she called!
It sure was spectacular. I'm glad that they've fixed it.
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Regarding the solar cells, yeah, I haven't read too many articles about it. I remember reading once about that being a potential problem, but what I read didn't suggest that NASA was giving too much weight to that being the a likely ultimate cause of failure.
Maybe they figured that a blower would require more power for itself then would make it worthwhile.
> The amazing thing is that America is still using
> British units, while England is firmly metric.
irony abounds...
> The US Congress passed a law during the Nixon
> administration mandating a switch to metric. There
> was a terrible hue and cry, with politicians saying
> that American consumers would never stand for using
> metric units.
Alabama still has Km markers on several highways.
> The truth is that American housewives have no trouble
> buying goods in liters now. It was American business
> that didn't want to retool their factories and
> engineers from British to metric.
We should be very well versed in metric conversion. All packaging I see around the US has both metric and English. Of course, some things are mixed up....
Beverages are sold in 12 oz cans or 24 oz bottles, or 1 or 2 liter bottles, for example. Weird.
> We should be very well versed in metric conversion.
> All packaging I see around the US has both metric
> c and English. Of course, some things are mixed
> up....
Right, but that's my point. It's not the American public that's the problem. It's American manufacturers still clinging to British units on tooling, fasteners, etc.
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> Right, but that's my point. It's not the American public that's the problem.
> It's American manufacturers still clinging to British units on tooling, fasteners, etc.
Surprisingly, actually, cuz they could convert it to metric, use slightly smaller packaging, and raise the price cuz no one would know!! Ha HA! Marketing 101....
God bless America! :)Merry Christmas to all who frequent this forum. It's been a pleasure and an education this year. Sincerely, %
> The truth is that American housewives have no trouble
> buying goods in liters now. It was American business
> that didn't want to retool their factories and
> engineers from British to metric.
I had a teacher in highschool who suggested that the reason was that people associated metric weights with drugs. Normally, when some one refers to a kilo in the US it means cocaine. I don't know how true that is though.
I think now that computers are so integrated in our lives we'll probably just use whatever unit we like because conversion is not a problem. What's really weird to me is that units can mean different things given different substances. IIRC, a ton of gold weighs less than a ton of feathers.
I have a book that lists (as far as I know) every major unit. It's weird, some of them have really weird names.
> Right, but that's my point. It's not the American> public that's the problem. It's American> manufacturers still clinging to British units on> tooling, fasteners, etc.It would be nice to only have to have one set of sockets for my socket
> I had a teacher in highschool who suggested that the
> reason was that people associated metric weights with
> drugs. Normally, when some one refers to a kilo in
> the US it means cocaine. I don't know how true that
> is though.
Your teacher was a bit too active in the drug trade. ;)
> I think now that computers are so integrated in our
> lives we'll probably just use whatever unit we like
> because conversion is not a problem.
The problem's never been the calculations, IMO, because that's easy enough to do.
When you grow up as an engineer using a particular set of units, you develop a "feel" for how large or small numbers ought to be, what "looks" right. It's your intuitive check that tells you when your calculations are off.
That's what we lose when we don't commit 100% to metric conversion.
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That's why I don't understand why all engineering isn't done in metric. No one I know of uses anything else in physics. Not for anything serious.
> That's why I don't understand why all engineering
> isn't done in metric. No one I know of uses anything
> else in physics. Not for anything serious.
I agree. Perhaps it's because physics crosses international boundaries, but manufacturing is done locally. I'm sure that Ford cars built overseas use metric units in their factories. It's just the ones that come out of Detroit that still cling to English units.
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> I agree. Perhaps it's because physics crosses
> international boundaries, but manufacturing is done
> locally. I'm sure that Ford cars built overseas use
> metric units in their factories. It's just the ones
> that come out of Detroit that still cling to English
> units.
Isn't that a pain in the ass? Or do they use decimals with Brtitish units?
> I had a teacher in highschool who suggested that the reason was that
> people associated metric weights with drugs. Normally, when some
> one refers to a kilo in the US it means cocaine. I don't know how true
> that is though.
I doubt that. I think it's been shortened to a key (or would it be ki) of cocaine... at least that's how I hear it on TV the last several years.
> IIRC, a ton of gold weighs less than a ton of feathers.
huh? When did a ton mean different things?
What's illogical is that women should want to switch to metric so that they weigh less in kilograms then in pounds. ;-)
[snip]> > IIRC, a ton of gold weighs less than a ton of> feathers.> > huh? When did a ton mean different things?> Troy vs avoirdupois weight.
> huh? When did a ton mean different things?
Precious metals are measured using the troy system. 1 pound troy is 12 oz vs. 16 for a pound of feathers.
> What's illogical is that women should want to switch
> to metric so that they weigh less in kilograms then
> in pounds. ;-)
If that's what they want, they should use stones.
> > Why would anyone use anything but metric units for
> > anything like this? It boggles my mind.
>
> I have worked on several multi-national projects and
> the French always want to do it their way, the
> British always want to do it their way and we end up
> doing the German way!
Try working in electronics, the tracking is done usually in imperial as most components are designed in imperial (except for the ones that are in metric)
>
> I had a teacher in highschool who suggested that the
> reason was that people associated metric weights with
> drugs. Normally, when some one refers to a kilo in
> the US it means cocaine. I don't know how true that
> is though.
Yet in the UK cannabis keeps imperial and fraction alive. ie a sixteenth of an ounce.
If a teenager understands fractions and ounces then its a safe bet he smokes, and if he knows how to knock the bottom out of a milk bottle...
> > huh? When did a ton mean different things?
>
> Precious metals are measured using the troy system.
> 1 pound troy is 12 oz vs. 16 for a pound of
> feathers.
I see....
> Yet in the UK cannabis keeps imperial and fraction alive. ie a sixteenth of an ounce.
in the US too, I believe... I could ask someone who knows....
>
> When you grow up as an engineer using a particular
> set of units, you develop a "feel" for how large or
> small numbers ought to be, what "looks" right. It's
> your intuitive check that tells you when your
> calculations are off.
>
> That's what we lose when we don't commit 100% to
> metric conversion.
Huh?
By mandating an immediate switch wouldn't that guarantee that intuitive check would be wrong for most engineers for a number of years? Probably at least 10.
> By mandating an immediate switch wouldn't that
> guarantee that intuitive check would be wrong for
> most engineers for a number of years? Probably at
> least 10.
Here's an example of how metric conversion confusion can have serious real-life effects:
http://en.wikipedia.org/wiki/Gimli_Glider
my favorite line:"Seconds later the right side engine stopped and the 767 lost all power, leaving the cockpit suddenly silent and allowing the cockpit voice recorder to easily pick out the words "Oh, f***!"."
> The amazing thing is that America is still using British units, while England is firmly metric.
Nonsense. Google "metric martyr".
The EU still lets us buy milk and beer in pints. I still bake sponge cakes using Imperial units for the ingredients. I know my height in inches more accurately than in cm, although my weight more accurately in kg than stone. We use miles for distances, and mph for speeds.
I'm off for Christmas, so won't be around for a while: don't expect me to defend any assertions or answer any questions for a couple of weeks. Best wishes, all, for Christmas and New Year.
> Huh?
>
> By mandating an immediate switch wouldn't that
> guarantee that intuitive check would be wrong for
> most engineers for a number of years? Probably at
> least 10.
Of course it would, but if we'd done it back in the Nixon admin we'd be through it by now. It'd be painful no matter when we did it, so why not start now?
I think there's an economic cost to not using the system that the rest of the world does. US should switch.
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> The amazing thing is that America is still using> British units, while England is firmly metric.> The official name is Imperial units. If this were more widely known in the USA, it might encourage a faster changeover.
> I'm wondering why they didn't install some sort of dusting device on the solar panels? It's not in their enviroment Spec..that would be saved for the realse of Rover 2.0
At the university where I am studding they are involved in developing dust removal tools using CO2 jets. I was involved in a mars rover project my self during my final year Beng. I was only involved in building the software and electronic interfaces not particularly in the department of developing space-qualified hardware. Its a good idea to use dust removers but must consider the redundancy of rest of the system. For example something like the mars sprit rover is more redundant than the sojourner (mars path finder) rover, which was much simpler in design and didnt have to carry all that bulky instruments around on its back
