How Much Driving Time? Options

[djellison]

And look at the power trend - essentially sustainable at between 400 and 700 whrs. That's basically enough.

It wont be a lack of power that kills these things - it'll be a mechanical failure.

Doug

[AoftheN]

A simple dust removal mechanism maybe isn't such a giant leap from the MER already on Mars. Most of the elements of such a system can be adapted from parts of the science payload. The RAT spins at 3000 RPM - why not integrate some kind of impellor unit that blows air out the back while it’s spinning (like my power drill, jigsaw, orbital sander etc..!). Then adapt the reach of the IDD to reach the deck, engage the RAT, compressed air blows out the back, and move the arm for total coverage.

/back to lurking

[djellison]

To enable the IDD to reach the whole of the solar arrays would mean making it three times bigger and three times heavier. It wouldnt fit.

Doug

[Marcel]

To enable the IDD to reach the whole of the solar arrays would mean making it three times bigger and three times heavier. It wouldnt fit.

Doug

True.

All the options thought trough (and reading GL's articles) it might not have been such a good idea for MER after all. It seems to work out fine indeed with the nowadays array output in mind (which is purely due to being lucky).

It might be an option for future missions without RTG's however. What about Phoenix ? Still 2 years till lanch window....and we're talking about a pretty tight energy budget up in the shivvvvvering north.

[Guest_Analyst_*]

If there is no sun at all (in northern winter), you can have the cleanest arrays on the planet. Won't help.

[Guest_Edward Schmitz_*]

...It might be an option for future missions without RTG's however. What about Phoenix ? Still 2 years till lanch window....and we're talking about a pretty tight energy budget up in the shivvvvvering north.

The energy budget up north is not that bad. They just have to point the solar arrays at the sun. The main difference is how much atmosphere they have to look through. Now consider that no amount of cleaning will help when the northern winter arrives and solar panel cleaning becomes a non-issue.

RTG's are the way to go...

[Bill Harris]

it will accumulate dust anyway: just like sides of rocks (Gusev) and the pole on the sundial are dusty on the sides as well.

I've wondered about the lenses on the Haz-, Nav- and Pancams; I guess that they accumulate dust, also. That would add a degree of "softness" to the images, which could be compensated for with image processing. The Hazcams (rear, especially) do show some "blotchiness", but I've not noticed image degradation on the other cameras. Are there lens covers or cleaners on the cameras?

--Bill

[Marcel]

Are there lens covers or cleaners on the cameras?

--Bill

On the Microscopic imager is a lens cover (probably because the RAT is so close to it) and i don't think the rest of the camera's have special covers.

[um3k]

By the way, there's been quite some research on it by the way by Geofrey Landis et al., indicating to me that it is an issue that's worth considering (at least) for future missions. 

I've met him. In person.

[RNeuhaus]

Interesting discussions about different options on how to improve the power of array solars in order to avoid in using the heavy and "relatively" dangerous RTG.

What happens if there is a planetary dust storm that might last a long time?
- The Sun power will be more restringued during these days. The RTG is favored
for this situation.

On the other hand, about my comments about on this topic:

1) Windshield. Forget it. It need water to clean away perfectly the sun power panels.
2) Raising to vertical position and shake the wings sun power. Extra weight due the adding electrical motors to raise and also to shake wings.
3) Martian air compressor. The best solution for its simplicity and about the weight, it might be lower than the option 2.
4) Go for a zone of dust devils and wait of being hit. Never know when! and not all place has dust devils. (Gusev has most often dust devil than Meridiani Planum). Not good solution.
5) Look for some big stone and climb on it so that its position is, as an example, 40 degree of inclination and turn an vibration engine to shake off the dust. Not as effective as the solution 2 but it add less weight to the rover.

Anyway, I think that the best solutions to extend the power supply are not only of one idea but any more ideas:

1) On the surface of the sun power must have some kind of magnifying optical in order to absorbe more light and hence provide more sun power. I am not sure of that this idea is valid. The magnifying optical concentrates the tenue light ino an radius of strong linumination. But I doubt the result would be the same for both ways.

2) As the Martian has wind, the top of mast must have some kind of helix. The martian is somewhat windy (around 10 m/s on the surface). It might add some weight to Rover but in some places, it would be very helpful to provide "aeolein???" power (air power). I doubt if that solution might be effective since the martian air is so light to push the helix to rotate...some very light material and very low friction, it might be rotating and thus hope to provide some few worths of wats/hour.

Rodolfo

[rschare]

Isn't this all kind of a moot point?

I thought that the batteries only have a maximum number of charges they can handle (and we're coming up on that limit soon). So, even if you could get a cleaning of the array's, and a larger electrical charge, the batteries are eventually going to die anyway.

[helvick]

The "To Clean or Not To Clean" discussion again. :-)

Just remember that the primary mission objective was 90 days with only the very optimistic thinking even one rover would survive twice that long. The best estimates they had at design time showed they should have been getting into serious power budget problems at around Sol 200-250. And they did - Spirit hit rock bottom at that stage (288 Watt hours on Sol 204), Opportunity fared better because it was sheltered in Endurance and angled nicely for optimum solar power but still dropped below 450 watt hours in mid winter. Every kilo spent on a cleaning system would have impacted somewhere else, maybe fewer cameras, less mobility, no mossbauer or what ever. I really think the design trade offs that were made were excellent and the fact that the rovers are still operating after 500+ sols is an amazing achievement.

SS's latest comments about the Mossbauer's Cobalt-57 gamma ray source [half life of 271 days] shows that many of the non mechanical components are destined to continually degrade and a lifetime of 500+ Sols was really on the outer limits of anything they thought would be achievable. It's been pointed out before that the Li-ion batteries probably have a useful life of no more than 1000 charge cycles and that might be the thing that finally does them in.

Vertical\Sun tracking arrays have been considered, This study goes into a lot of detail on the factors being considered for a Polar Rover .

Phoenix is a short term mission being done on the cheap with already proven technology- I don't think any amount of gymnastics with solar arrays is going to allow it to last much beyond it's 90 sol primary mission and would add both cost and risk with no benifit - 70 days or so after the end of the primary mission it's going to be in near darkness 24.66 hours per sol and solidly frozen.

[glennwsmith]

I didn't intend to jump into this discussion about solar cell cleaning, but if you wiggle a lure in front of a fish long enough, somethimes it will strike out of frustration.

At any rate, aren't the solar cell panels equipped with hinges and motors that lowered them into a horizontal position in the first place? And if so (and I don't mean on this mission), wouldn't it be possible to use this same mechanism to raise the solar panels back to a vertical position -- perhaps several times -- to at least shake off much of the dust?

I realize this is a stupid idea, so someone please set me straight.

Glenn

[Marcel]

I didn't intend to jump into this discussion about solar cell cleaning, but if you wiggle a lure in front of a fish long enough, somethimes it will strike out of frustration.

At any rate, aren't the solar cell panels equipped with hinges and motors that lowered them into a horizontal position in the first place?  And if so (and I don't mean on this mission), wouldn't it be possible to use this same mechanism to raise the solar panels back to  a vertical position -- perhaps several times -- to at least shake off much of the dust?

I realize this is a stupid idea, so someone please set me straight.

Glenn

Hey you, it's a stupid idea !
No, seriously, the participants in this discussion (which know a hell of a lot about the machines) stated, that the amount of energy from the arrays is not going to be the bottleneck. I might as well go for that opinion, since, indeed, after almost 550 sols of ops., there's STILL no reason to be concerned about the dust on the solar panels. Next year there will be, probably, but what the heck, we will have had such a treamendous amount of data......we should be satisfied.

If, however, both rovers would have ended after 100 sols (just after primairy mission) due to dust cover on the arrays, I AM SURE the next solar powered rovers would be equipped WITH a cleaning system.

But the great experience they have now with the energy budget of these two sweeties does not require elaborate effort for that.

Better to invest in optimization of EDL, RTG's, instrumentation and mobility performance for the next generation rovers.......

Marcel.

[djellison]

At any rate, aren't the solar cell panels equipped with hinges and motors that lowered them into a horizontal position in the first place?  And if so (and I don't mean on this mission), wouldn't it be possible to use this same mechanism to raise the solar panels back to  a vertical position -- perhaps several times -- to at least shake off much of the dust?

As I undestand it - THIS misison couldnt as the arrays locked into place when they were rotated into position. Runing those motors backwarsd wouldnt work.

the next solar powered craft is Phoenix - and it has some fairly funky arrays that dont really fold 'up', but more concertina in a circle. But the misison is going to be killed off by the lack of light before dust ever becomes an issue

Then we're on MSL and it's RTG-o-rama



Doug