Wheel Trouble, ...down to 5 good wheels? Options

[Bob Shaw]

On the plus side the rovers are scheduled to get a software upgrade in June. So the planning is still for the long term.

Oh no! Not Vista!

Can Autostitch make Blue Screen Of Death screens into panoramas?

Bob Shaw

[Marz]

Yeah, I know that Ma'adim Vallis is not a realistic goal - I've just always fantasized about what a killer desktop image it would make

lol - when you dream, why not dream big!

Let me try some quasi-irrational optimism: is there any possibility that the wheel-freeze is a side-effect of much cooler temperatures? Could warmer summer temperatures suddenly result in a working wheel again?

My kingdom for a well-placed drop of oil!

[djellison]

The day time temps might be getting to -60 instead of say, -20 - but it still goes down to lots more than -100 at night. And even then - all the wheels have heaters.

Doug

[Jeff7]

Can't they just use the routines they developed before when Spirit's one wheel acted up? I thought that they'd figured out a fairly decent method of compensating for the navigational problems caused by a stuck wheel.

[djellison]

Spirits wheel wasnt stuck back in the 150-350 sol region.The motor pulled more current when driven, 3x more than the others, and they thought that if it got worse they'd kill the motor - but it DID work when commanded to.

So - they commanded it to not turn about 90% of the time, and just turn it 10% of the time to clear the little trench it was digging.

What we have here is when you command the wheel to turn, it doesnt, a different problem, and possibly not even a related problem to the trouble of 500 sols ago.

Doug

[Shaka]

lol - when you dream, why not dream big!

Let me try some quasi-irrational optimism: is there any possibility that the wheel-freeze is a side-effect of much cooler temperatures? Could warmer summer temperatures suddenly result in a working wheel again?

My kingdom for a well-placed drop of oil!

Mars_armer's authoritative report that the motor circuit failed "open" indicates a break in the circuit - a broken wire or a broken motor brush. A technician with a soldering iron might be able to fix it in a jiffy, but we ain't got one unless Marvin the Martian shows up. The motor is not straining against a blockage or frozen bearing - it's lifeless

[GregM]

.

[ddeerrff]

Mars_armer's authoritative report that the motor circuit failed "open" indicates a break in the circuit - a broken wire or a broken motor brush. .....

Are the wheel drive motors really DC motors with brushes?!? I would have expected stepping motors.

[Shaka]

My biggest concern about all of this is that if the Rover cannot climb the hill on 5 wheels, it will not gain enough altitude to catch the wind, and therefore not be able to clean off the solar panel. Even if it gets to the base of the hill and gets on a tilt that alllows better positioning with respect to the sun, it is only buying a little time. Eventually the dust will accumulate on the panel and starve Spirit anyway. Sooner or later it will need wind. The wind is up high on the hill. It needs to be able to climb somehow.

Be brave, Greg! We don't know yet what Spirit can do on 5 wheels. Maybe it will be able to climb McCool, slowly and with frequent roadblocks when the Bad Wheel (TBW) catches on a rock. Then we will have to back up, turn, and go around the rock. It will be slooowwww progress. But we have all the time the gods of space probes have allotted Spirit.
As to catching the wind, we could see a huge improvement as soon as we get into the Pass between McCool and Husband Hills. If you aren't familiar with the wind power they can provide, Google on wind farms, and Tehachapi, San Gorgonio, and Altamont Pass. We don't have to reach the peak of McCool to get the wind. On the contrary, it may be extra strong down in the pass.
To be the final, ultimate, SuperHero of Mars exploration, Spirit needs to slowly climb the north face of McCool Hill. If it gets even half way to the summit, it should have a bronze statue in every city park in America!

[RNeuhaus]

As to catching the wind, we could see a huge improvement as soon as we get into the Pass between McCool and Husband Hills.

That is true. I have observed it on the Earth experience. The highest point of a valley, goes a strong wind tunneled by the lower valley. Hope that the point of junction of two hills: Husband and McCool there would be windy.

Rodolfo

[MahFL]

"We're now in a drive or die situation," says Steve Squyres of Cornell University, Ithaca, New York, who leads the rover science team. "Our current focus is to drive like hell and get to a safe winter haven."

I did not realise the situation was that dire...............

[helvick]

"We're now in a drive or die situation," says Steve Squyres of Cornell University, Ithaca, New York, who leads the rover science team. "Our current focus is to drive like hell and get to a safe winter haven."

I did not realise the situation was that dire...............

Power is at 350 watt hours per sol now with daily insolation at 3630 whr per m^2. Insolation drops to its winter minimum of 2770 on August 24th (Sol 909). If they do not move and there is no additional dust deposition power would drop to 267 whr by then. Factoring in dust deposition causes an additional 0.08% per sol loss so the power level will probably drop to 241whr. 280whr is the number that we suspect is the minimum survival level, SS has said this in the past. A good slope (15-20% tilt approximately facing the noon sun) would add 20-30% to that bringing Spirit back to a level where she can survive and possibly even do some work.

[djellison]

<360 Whr's per sol and decreasing quite rapidly

Doug

[ToSeek]

Power is at 350 watt hours per sol now with daily insolation at 3630 whr per m^2. Insolation drops to its winter minimum of 2770 on August 24th (Sol 909). If they do not move and there is no additional dust deposition power would drop to 267 whr by then. Factoring in dust deposition causes an additional 0.08% per sol loss so the power level will probably drop to 241whr. 280whr is the number that we suspect is the minimum survival level, SS has said this in the past. A good slope (15-20% tilt approximately facing the noon sun) would add 20-30% to that bringing Spirit back to a level where she can survive and possibly even do some work.

Even the extra 20% would make it only up to 290 whr. Sounds like one cloudy day could be the end of Spirit....

[mars_armer]

How sure are we of the 280 Whr "death" number? It's hard to believe that Spirit couldn't hunker down with overnight deep sleeps and infrequent comm passes and at least survive with much less than that. Could it be that SS was really talking about a minimum power level for usability, rather than a survival limit?

Edit: Plenty of discussion on this subject in this topic. My impression is that we know a lot more about power availability than about power requirements.