Mars Rovers Update 320
BoldAC writes "CNN is reporting that engineers will upload a software hack to decrease the recent power drain plaguing the rover Opportunity. The hack works by reducing the power supply to a poorly functioning switch." p3tersen writes "Opportunity has photographed a blue martian sunset (it's blue because of the optical scattering properties of dust in the martian atmosphere). In other news, the rovers are beginning to experience power supply problems due to the accumulation of dust on their solar panels."
Planning Ahead (Score:1, Interesting)
Solar problems (Score:5, Interesting)
Re:Solar problems (Score:2, Interesting)
I know you are joking, but I'm actually surprised that they haven't thought of a way to keep the solar panels clean.
I mean, they can get the thing to mars, they should be able to do that, no?
Fan (Score:4, Interesting)
The weight penalty should be offset by being able to work longer.
Or is the dust sticky? Maybe something akin to a wiper?
Re:Java problems? (Score:5, Interesting)
That isn't a slight against Java. It's just that they need real-time software, which can't be had with an interpreted language (even if it is only interpreted from bytecode).
How fast do you think a 20mhz processor could run a Java app?
This just in from Saturn (Score:5, Interesting)
Seasonal changes (Score:5, Interesting)
Dan East
Re:Fan (Score:4, Interesting)
Re:Solar problems (Score:4, Interesting)
Stack 10 sheets of this and voila, lifetime of the rover multiplied x10.
Re:Solar problems (Score:3, Interesting)
Say, a step motor and some mechanical jiggery-pokery ending with a stiff wire, a hook on its end, the layers would have tabs with holes in them to pull at.
Or.. a glue between layers that deteriorates on contact with Martian athmosphere and so the layers will peel off after a fixed (based on chemistry) time.
I mean, give me a break, those took less then 10 seconds to come up with and I am sure NASA engineers could have thought up much more effective methods.
Re:Solar problems (Score:4, Interesting)
Just a guess based on Nasa commentary is the batteries will fail before the solar panels fail to charge them.
Re:Solar problems (Score:5, Interesting)
There have been many ideas tested for the solar panels, including removable plastic coverings, wiper blades, etc. None of them have proven practical. The dust on Mars is extremely fine and electrostatically charged. It sticks to the panels , and every other surface, amazingly well. Figuring out a way to remove Martian dust from surfaces is a field that a lot of thought and experiment has gone into, without discovering any feasible solutions, so far.
During the Pathfinder Mission in 1997, it was found that, by driving the rover over 'large' rocks (large for the rover), some of the larger dust can be shaken off. This is, as I've heard from members of the engineering team, something they intend to try with the MER rovers when needed. It doesn't make a huge improvement, on the order of a couple percent, but every little bit helps.
The Martian Dust (Score:5, Interesting)
One thought I had was to gradually apply a charge to the solar panels and then suddenly apply an opposite charge, causing the dust to be repelled from the surface, to be carried away by the Martian winds.
I've no idea if it would actually work or not, but it seemed an elegant solution that didn't require any moving parts.
The whole solar thing... (Score:5, Interesting)
Why did NASA stray from 'nuclear' batteries, like they've used with the Pioneer, Galileo, Voyager and Cassini missions? Those could power a rover for years.
And what's stopping them from making a way to keep the panels clear? This is what contributed to the end of the Pathfinder mission...What is it about solutions to this problem that make them so difficult to implement?
Wipers add an extra mechanical system to worry about, but what about static fields? Maybe there could be a way to attract the dust to a specific area while keep the the panels clear?
Re:Solar problems (Score:3, Interesting)
Re:Solar problems (Score:5, Interesting)
Hmm, after another 15 minutes of mental effort: a thin brush on an arm mounted to the side of the camera mast. You lower the (very thin and light single file brush) with a small step motor to the horizontal position and then you rotate the camera mast to create a sweeping motion on the panels. You could brush the 2 side panels that way, since if you planned for it, there would be no portruding gear to get in the way of the brush (all such gear would be back of the mast).
And so on...
I am really flabbergasted why there is absolutely no provision for any sort of cleaning (even a partial one) on the rovers. Its not like this wasnt expected. I smell some sort of hidden agenda in shortening the life of the rovers.
Re:Solar problems (Score:4, Interesting)
Re:agreed (Score:2, Interesting)
Re:agreed (Score:2, Interesting)
At least you have an appropriate nickname. There are many cool features that NASA engineers would like to have included on the rovers. But at some point, decisions have to be taken on what things will not fly. These decisions are based on many criteria including weight, complexity, cost, etc. There is no hidden agenda here and the missions have been a great testament to the competence of NASA engineers.
Re:Java problems? (Score:2, Interesting)
This is why there's been work for a real-time version of Java for a number of years now (see here [rtj.org]). Incidentally this is what kicked of the JCP (it's JSR-001
Compressed Gas to blow the dust off? (Score:1, Interesting)
It might not be 100% effective, but surely it could get most of the dust off? There is already a manipulator arm on the robot... maybe add a little hose & nozzle attachment to it? Dunno...
And if there's an issue of contaminating the martian environment... cant you sterilize the gas? Is introducing any type of gas into the martian atmosphere an issue?
Re:The Martian Dust (Score:4, Interesting)
Probably using a vaccum would not damage the glass. Although this approach also adds more complexity...
>>> One thought I had was to gradually apply a charge to the solar panels and then suddenly apply an opposite charge, causing the dust to be repelled from the surface, to be carried away by the Martian winds.
Unfortunately this will not work since the electrical charge is not uniformy applied in only one direction on the surface glass. The small irregularities of the surface will cause a variation in the electrical distribution over time - for example a small peak in the glass might be more positively charged compared with inner of a nearly-located scratch. The same thing happens on some dust particles - due to their free movement in the air, their electrical distribution will end up non-uniform as well. So they will end up attracting as magnets - the small peak will attract particles on their negative-charged part, and the scratch will do the same on positively-charged surfaces. Now, since all these materials are good electrical insulators, the non-uniform distribution will stick on for a long time.
Probably what would help is to use a blower that would wipe off the dust with martian air. The blown air needs to be ionized to prevent more electrostatic charge to add up by just blowing. The ionized air will have a weak electrical conductivity which will tend to "shortcut" the charged areas. Now, since the martian air is mostly CO2 this pre-ionization process shouldn't require too high voltages - the energy consumption would be pretty low...
Re:The whole solar thing... (Score:4, Interesting)
And I'll give the NASA geeks the benefit of the doubt that if there were a reliable and cost-effective wy of cleaning the solar panels, they would have implemented it long ago.
Re:The Martian Dust (Score:3, Interesting)
Degauss the solar panels? Brilliant!
~UP
Re:Solar problems (Score:4, Interesting)
Concerning charged particles... (Score:3, Interesting)
Re:The Martian Dust (Score:2, Interesting)
Re:Solar problems (Score:3, Interesting)
Tilting and vibrating them might, possibly, shake some of the dust off?. Obviously this has to be balanced against the wear caused by the vibration so it may not be possible...
Re:Solar problems (Score:2, Interesting)
Re:This just in from Saturn (Score:2, Interesting)
To me, Saturn is the most beautiful cosmic creation that I know of. I wonder if there have been any other planets found with rings on them.
electrostatic dust (Score:5, Interesting)
***SPOILER ALERT*** (and suggestion)
Since rubbing causes static electicity, they rub their faceplates together. One charges one polarity, the other the opposite. So one faceplate comes out even dustier, the other clean. The explorer with the clean faceplate can lead the other back to the vehicle.
Actually I always though static electricity came from rubbing dissimilar materials, so I wouldn't expect rubbing two identical-material faceplates to do squat. But there may be a lesson here. If the primary problem is really electrostatic, might there be some sort of electrostatic solution? (on future rovers) The most extreme would be an ion-wind generator with the 'benign' (dustwise) polarity attached to the panel. Another might be a charged wiper blade. I'm sure there could be other simpler electrostatic-based solutions.
Re:Planning Ahead (Score:2, Interesting)
They don't want long life for rovers (Score:4, Interesting)
Cost aside, there most likely is a way to greatly extend the life of a rover.
From the noises NASA has been making, there will be a series of unmanned missions to Mars before an attempt to send humans will be made (I don't necessarily agree with the premise of sending humans to Mars).
NASA has said the limiting factor is power, because of the dust accumulation on the solar panels.
Let's say that the cost of implementing a way to eliminate the dust doubled the cost of the mission (probably would be less). If dust were eliminated, then the rovers could operate until the batteries could not longer hold a sufficient charge to do science.
What I'm getting at here is politics. A solution could be engineered to greatly extend the life of the rovers. But that would result in a reduced number of missions and *less funding*.
Ok, I've removed my tinfoil hat. Comments?
Re:Solar problems (Score:2, Interesting)
The questions shouldn't be on how to extend these pissant solar panels, but on why they didn't put an RTG in in the first place.
Re:mainly because people are ignorant (Score:1, Interesting)
Try Pu236, the most toxic substance on earth -- fatal at a dose of one microgram. (i.e. a single airborn dust particle.) Billions of fatal doses widely dispersed. Fun fun fun. That said, with Cassini the concern was not with launch but rather with the earth flyby, when an accident could have been energetic enough to rupture the reactor. The next series of rovers (scheduled to use the reactors) will not do the near earth flyby. Still, I expect that NASA has contingency plans. When they discuss the reactors I notice that they revert to very diplomatic language.
Re:The Martian Dust (Score:3, Interesting)
It's called fines, not dust! (Score:3, Interesting)
That's like calling dust gravel, jeeze.
(with apologies to KSR's Red Mars)
Re:Sunset (Score:3, Interesting)
The sky would be red as normal, but sometimes there would be a halo of blue sky surrounding the sun. Only sometimes because it depends on the amount of dust in the air. The Pathfinder mission saw sunsets with and without the halo. The halo may also happen during the daytime. There have been no colour pictures of the sun when it's high in the Mars sky.
I remember seeing a program on BBC once that tried to show what sunrise would look like on the different planets. Pritty cool stuff!
Re:Solar problems (Score:2, Interesting)
Solar panel in a dust storm? (Score:2, Interesting)
It's called nuclear power folks, and you can use it to create extremely reliable electric generators with a shelf life on the order of decades, and extend the life of sattelites and roving projectiles for years, not days. Day or night 'til the wheels fall off.
In fact, if you use said nuclear/electric power generators to power ion drives, you can use less than half the propellant to get to [insert planet here].
I don't get it. When did NASA become a jobs program for morons? I mean, morons have to make a living too, but shit, can't we let them execute water fountain projects instead?
Re:Solar problems (Score:3, Interesting)
Being particularly curious, I dug a couple out of the soil. Being covered in dust, the first thing they would do is make a loud buzzing noise to warm up (and which would shake off the dust) and then open their wing case and take off.
Would this method work with solar panels?
Re:Solar problems (Score:3, Interesting)
look at the tape cleaning systems that have been around for oh, about 100 years... those problems have long been solved.
Re:Fan (Score:3, Interesting)
Besides, as has been pointed out, any solution adds power requirements, weight, and complexity/points of failure. Does the extra power provided by clean solar panels outweight the added risk of equipment failure?
Re:Solar problems (Score:3, Interesting)
Why oh why would someone coat the panels with something that can even remotely be prone to chemically binding with soil?! And I am going to repeat the million times mentioned simple solution of a peel-off film! And guess what? ONE coat of peeloff film means twice the lifetime of the rover. Ponder that!
BTW, the RTGs are so politically loaded that noone is going to send any anywhere anytime soon. Besides they are apparently much heavier then they wanted the rovers to be for the types of boosters they could afford.
Re:Solar problems (Score:4, Interesting)
(1) Vibration.... the panels are lifted sideways and a motor at the top vibrates them for a few minutes. This will cost(1) the vibration motor (2) the lifting motor (3) lifting arm and hinges.
(2) Clapping two solar panels together.
(3) Compressed air. This is my fav. A small cylinder onboard could blow air across the panels about 10 times... increasing the life of the rovers 10 times. If theres enough gas in the atmosphere, replace the cylinder with a compressor. Its mechanically easy, less risk, and with a tiny compressor will add just a tiny bit of weight.
(4) Wiper blades. The blades will have feathers on them like a feather duster.
(5) Rotating panels. The panels would be disc-shaped and are rotated real fast like a CD to shake off the dust.
(6) Flippin panels. Turn the panels upside down for a little while. Optionally, jerk them.
(7) Roller film. Unlike camera film, one loop of film covers the panel and two axels at the panel ends loops the film around. Small brushes at one end will keep cleaning the film.
(8) Driving into rocks. The rover can tilt its panel forward facing and drive into a large rock with a bumper. That way the martians wouldnt think much of our intelligence and cancel the invasion.
(9) Tiny micro-rovers built by MIT undergrads to wander over the panels cleaning it. The micro-rovers will themselves have connectors to recharge. I'm thinking 2mm^2. Tricycle-shaped with a trailing brush.
(10) Drive over a high dune just before losing power. That way when theres a wind storm, enough dust will be blown away to allow the rover to communicate with the satellite. Hopefully, most of the dust will be blown away.
Some of the above ideas were taken from other posters. I believe they could have been used to build a rover that could in theory work forever.
Re:Solar problems (Score:1, Interesting)
This is a clever method, but it requires air to work. As the radiation from the polonium passes through materials, it ionizes them. Because air molecules have a reasonably long mean free path, the ionized air will drift, and will preferentially drift so as to neutralize static charges on the bristles of the brush. Thus the static charge has effectively been transferred to the air.
Mars does have some atmosphere, but it is considerably thinner than Earth's. You may be able to do the same trick, but you may need to use a strong source.
The other problem is: it seems that these brushes use polonium-210, which has a half-life of only 138 days. [[But on the other hand, it may be that a lot of the constraints that go into choosing which element & isotope to use (toxicity, cost, etc.) would not apply to a Mars mission.]]
Re:As nice as it would be... (Score:4, Interesting)
There are 2 types of cost involved in this daily figure, those that are 'out of pocket' and those that are 'just accounting'. Take for example, the DSN time used to retrieve data from the rovers. Yes, it's very expensive I'm sure, those deep space monitoring stations cannot be cheap to build and operate. Every hour they spend pointed at mars collecting data from the MER vehicles is surely tracked, and cost accounted to the MER program, and rightfully so. BUT, it's not like they wouldn't cost anything if they were not pointed at the mars probes, the actual cost of operating the DSN system is for all practical purposes a known and fixed cost, and it's gonna be paid, no matter where they are pointed. This is why I'd call that portion of the daily cost 'just accounting', because the taxpayer is going to foot the bill for the deep space network, regardless of where it's pointed. But, when it's pointed at mars, the mars programs are being accounted as the 'cost', and rightfully so.
While the rovers are on active surface mission, there are a lot of extra people hanging around jpl, and i'm sure most of them are 'rather expensive' to keep on hand. this type of expense is 'out of pocket', it's an expense that wouldn't be happening if the rovers were not on surface mission. My own guess offhand is that the 3 million a day is probably half and half, one half true 'out of pocket' expenses, and the other half just accounting for equipment/personnel that would be on hand anyways, but are currently involved in the MER program. For the sake of easy math tho, I'm gonna suggest 1 mill is 'accounting' and 2 mill is 'real cost'.
Now take a look at the overall value proposition. the entire program is running in the 850 million range, and it's targetted for 2 rovers on surface, for 90 days each. That's 180 science days for a total cost of 850 million, or 4.72 million per active rover science day, as per mission parameters. this was the value proposition of the original mission, and the mission(s) were launched on this basis.
Now that surface operations are in progress, the daily burn rate is 3 million, for 2 rovers on surface. If a million of that is stuff like accounting for dsn time, then 2 million is the actual 'out of pocket' expense, or approximately 1 million per rover science day. this is 21% of the projected overall cost per day of science returned on the original budget.
The up front cost of placing the equipment on the surface of mars has been absorbed, and is planned to amortize over the first 90 days on surface. After 90 days, it becomes a simple value proposition. The 'real cost' of maintaining full operations earthside is 21% of the original budget. In terms of the 'accounting costs' for things like the dsn time, it's the same type of value proposition. The dsn network WILL be kept busy, it's simply a case of determining where there is more value. The 70 meter dish can point out at voyageur and get engineering data from the deep space probe (which will still be there in another 2 months), or it can point at mars, and take advantage of the 'limited time offer' of recieving martian data at 79% discount off the 'full retail' price that was paid for the first 90 days of surface time.
This is a large project, with lots of accounting involved, and surely there's more than its fair share of 'pork' buried in the 850 million price tag. BUT, it's real right now, and the real cost of retrieving a day of data from a single rover is in the range of $1 million. Considering the 'full retail' price for that runs 4.72 million after you amortize in all the launch costs etc, this is one time when a significant budget overrun due to 'extended surface time' is an absolute bargain.
This is kind of a double edged sword though. A design life of 90 days means there is budget for 90 days of operation. An overrun of 90 days on operational time represents a huge value proposition for
Re:Planning Ahead (Score:2, Interesting)