Mars Rovers Update

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."

Comments

Solar problems

[LotsaCaffeine]

NASA should have installed wiper blades on the solar panels.

Re:Solar problems

[hottoh]

I understood Nasa to say 'wiper blades' would not be effective due to the nature of the fine dust chemically sticking to the surface of the solar cells. Mechanical sweeping does not solve the real problem of the dust sticking to the solar panel.

Just a guess based on Nasa commentary is the batteries will fail before the solar panels fail to charge them.

Re:Solar problems

[ModernViking]

First, my credentials. I have worked on the field trials of the FIDO rover. It is the science test bed for the MER rovers that has been tested in various parts of the western United States over the past 6 years.

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.

Re:Solar problems

[IgnoramusMaximus]

A vibrator? Might work although probably could be destructive...

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.

Fan

[RetroGeek]

Is there some reason why these rovers do not have a fan to blow away the accumutating dust on the solar panels?

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?

[KewlPC]

Java is only used on the ground. They'd be stupid to use it in the flight software.

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

[blamanj]

A nice photo from the Cassini mission.

Seasonal changes

[Dan East]

The blurb fails to mention that seasonal changes on mars are resulting in less sunlight per sol. That is one of the main power issues.

Dan East

The Martian Dust

[Chris Tucker]

The big problem is that the dust is so fine, it'd be very difficult to wipe it off with anything akin to a windshield wiper. You might remove the dust, but the grit would scratch the glass, eventually causing enough opacity that the panels would eventually be rendered useless.

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.

Re:The Martian Dust

[Scorillo47]

>>> The big problem is that the dust is so fine, it'd be very difficult to wipe it off with anything akin to a windshield wiper. You might remove the dust, but the grit would scratch the glass, eventually causing enough opacity that the panels would eventually be rendered useless.

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...

The whole solar thing...

[Paddyish]

I have a bunch of questions about this stuff.

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:The whole solar thing...

[vbdrummer0]

One suspects that NASA decided to go solar because of the potential disaster to be had if there was a 'mishap' during launch and radioactive material went everywhere in the upper atmosphere. Public protest against putting nuclear fuel on top of a controlled bomb grew steadily over the years, to the point that, if I recall correctly, Cassini hardly got off the ground due to some people protesting it. Probably, there wouldn't be much of a problem, but better safe than sorry (especially when you're funded by taxpayers).

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.

electrostatic dust

[dpilot]

Arthur C. Clarke wrote a story reminiscent of this, set on the moon. Two explorers in a dusty area, and some of the dust sticks to their faceplates. Wiping the dust off builds electrostatic charge, attracting more dust, so they're soon blind.

***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.

They don't want long life for rovers

[Katz_is_a_moron]

Ok, hear me out.

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?