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

[mars_armer]

I hate to be the bearer of bad news, but I just heard that there is a serious problem with Spirit's right front drive actuator after yestersol's drive. (This is the actuator that had high currents in the past and led to the backward-driving strategy.) It will take awhile to evaluate the situation, but early speculation is grim.

In a worst-case scenario, they can still drag the bum wheel along, but don't expect another summit view.

Best-case scenario would be a rock or debris jammed in the wheel.

This is a heads-up, sorry I can't really give more info at this time. I still thought you all would like to know.

[Guest_Myran_*]

Thank you for the heads up mars_armer.
With winter approaching which would mean lower temperatures, something might have jammed, but just as you say, lets hope its just a splinter of rock that can be wiggled loose.

[DFinfrock]

It will take awhile to evaluate the situation, but early speculation is grim.

The problem is, they can't spend a month trouble-shooting like they did with Oppy at Olympia. Spirit has to make progress toward McCool Hill, and that winter haven.

David

[Guest_Sunspot_*]

You mean the wheel will no longer turn at all anymore?

[Shaka]

I hate to be the bearer of bad news,

daaaaaaaaaaammmmmmmmm Thanx, Mars. I'd shoot you but I'm too depressed.
Finger crossing time, Guys! You know it has to happen, but still...

[mars_armer]

You mean the wheel will no longer turn at all anymore?

That's right, it stalled. So far the data is limited, so I may be jumping to conclusions. But based on what I've heard, the most likely interpretation is a failed motor, meaning the right front wheel would be steerable but wouldn't turn.

[Jeff7]

Yeah, let's really just hope that it's just a rock stuck somewhere. I think something like that happened before.
Either way, they know how to drive the thing in 5-wheel mode, which is good. So spin-round, get to safe ground, then analyze the thing thoroughly.

[Guest_BruceMoomaw_*]

Do you mean that the wheel won't turn even if its motor drive is disengaged, or just that the motor has failed?

[Shaka]

Do you mean that the wheel won't turn even if its motor drive is disengaged, or just that the motor has failed?

Do we have six clutches on this thing? Can we disengage the motor and free-wheel?

[Guest_BruceMoomaw_*]

Under ordinary circumstances that is possible. In fact, it's what they did when they had the earlier problem with high friction in one of the wheel drives, until they managed to redistribute the lubrication to get the motor working properly again.

[CosmicRocker]

Oh, no. So that is one reason why Spirit has moved so little recently. It would seem to be an appropriate time to pray to the engineers. It's not likely to be caused by a rock lodged in the wheel, since Spirit has been travelling over a fairly hard surface recently, and the few available hazcams show no suggestion that debris is in the wheel. It is curious though, that there are so few recent hazcams available if there is an issue with that wheel...3 pairs from sol 774, 1 pair from 776, and nothing else so far. Is that due to the MRO/MOI communication? I thought that would be finished by now.

But yes, that seems to be the $64,000 question. Can it still free-wheel as it once did, or is it locked? All I can tell from the images available so far is that Spirit was driving backwards on sol 774 and it left differently appearing left/right tracks. At some point it had turned around 180 degrees, and then it turned back and was in a somewhat different orientatation/location by sol 776.

Even if the wheel is shot, they should be able to drag it to safer ground, but it may take some learning along the way.

[djellison]

Oh, no. So that is one reason why Spirit has moved so little recently.

No - read the first post - this is a brand new thing - literally yestersol.

The comparatively little movement recently has been because of the DSN conflict between Spirit and MRO so all commands for Spirit have had to go up via UHF which has a very long lead time - it's like super-restricted sols.

Tosol looks like diag.

780 p0781.03 2 0 0 2 0 4 navcam_1x1_az_324_3_bpp
780 p0981.03 2 0 0 2 0 4 navcam_1x1_az_324_3_bpp
780 p1213.00 2 0 0 2 0 4 ultimate_front_hazcam_3_bpp_pri15
780 p1242.01 1 1 0 0 0 2 front_haz_front_right_wheel_subframe_pri_17
780 p1313.02 2 0 0 2 0 4 rear_haz_ultimate_3bpp_pri15
780 p2138.04 2 0 0 2 1 5 pancam_right_wheel_L27
780 p2138.04 2 0 0 2 1 5 pancam_right_wheel_L27
780 p2600.07 2 2 0 0 2 6 pancam_tau
780 p2630.03 56 2 0 0 2 60 pancam_saw_skysurvey_L4578R2478
781 p1585.00 4 0 4 0 0 8 navcam_cloud_4x1_dwnsmp_RVRAz_calstart

Doug

[Bill Harris]

Oh well, stuff happens. We're all a lot creakier than we were 30-40 years ago.

My suspicion would be that this is a geartrain failure. I forget the exact reduction ratio, but there many gears and bearings between the motor and the wheel and there has been a failure along the way. Remember, we are many hours past the design service life.

Spirit needs to get to an interesting north-facing site. She may be a 3-legged dog, but we still love her...

--Bill

[edstrick]

I note that both from Husband hill and from the drive to and around home plate, the driving on the north McCool "flats" and the lower flank of the hill look mostly pretty easy.... likely sand traps are rare and high-density large cobble areas are scarce. Some of that "diagonal" stripe of lighter and grayer colored terrain on McCool are pretty rubbly and cobbly, but they're not in the drive to get onto the hillslope.

[Marz]

Poor Spirit, just as she regains the lead in milage, she hits another bump in the road.

I suppose there is a plan to return to Homeplate in spring, so I expect the driving around McCool will be very conservative. Maybe if we're lucky, some of the Homeplate unit will be found along the east slopes of McCool.

I was half hoping we could get some closer images of the Chaos terrain that was next on the adjenda, but now I worry it's a rockbed too far.

[mars_armer]

Do we have six clutches on this thing? Can we disengage the motor and free-wheel?

The short answer: I'm 99% sure the answer is "no".

The long answer: There are two things that resist turning of the wheel when the motor isn't energized: dynamic braking and static detents. Dynamic braking occurs from back-emf in the motor electrical circuit, and provides a resistive torque when the wheel is turned but no force when the wheel is stopped. Dynamic braking can be disengaged in the electrical system. The static detents, on the other hand, are magnets that cause the motor to preferentially stay at certain turn positions. These are necessary to keep the wheels from rolling after the rover comes to a stop, and cannot be disengaged. Because of the high gear ratio of the drive gearbox, it takes a hefty torque to the wheel from the outside to overcome the detent.

Bottom line: assuming the motor stall can't be corrected, they will probably have to drive backwards dragging a stuck RF wheel. This is something they have done before in the West Spur area when they were afraid the RF motor was nearing end of life. Though at that time, I think they periodically turned the RF wheel a bit to drive over the buildup of dirt in front of the wheel.

[tty]

Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

[Bill Harris]

there should be some simple and reliable mechanism for unclutching a wheel...

Probably not do-able within the constraints of 'simple and reliable'. Given that the original service life of the Rovers was 90 days and they have lasted a long time, the optimum solution would be to upgrade the motor and geartrain to give a much much longer service life.

--Bill

[alan]

Something in there?

[Toma B]

That's good news...if it got in, it can posibly get out of there...Would not be the first time.

[helvick]

[quote name='alan' post='45573' date='Mar 14 2006, 07:49 PM']
Something in there?
[/quote]
Looks like a rock stuck in there to me. With some stretching and bending of the luminosity curves there seems to be a fairly irregular potato shaped object jammed in there.

If it is a rock is there any chance that it could be jolted loose with some creative driving?

B)-->

That's good news...if it got in, it can posibly get out of there...Would not be the first time.
[/quote]

The last one that I recall was
this one from Sol 345

[mars_armer]

Something in there?

That's really encouraging!

Now I think (hope) I overreacted to the initial description I heard of the problem. At that time it sounded like there was evidence in the telemetry that the motor circuit had failed "open", which suggested a broken wire or brush inside the motor. By comparison, unsticking a rock sounds easy.

I knew I should keep my virtual mouth shut and wait for more data.

[helvick]

I knew I should keep my virtual mouth shut and wait for more data.

Absolutely not ! If everyone waited until they were certain of what they were saying then we'd have nothing to do here.

[Shaka]

That's really encouraging!

Now I think (hope) I overreacted to the initial description I heard of the problem. At that time it sounded like there was evidence in the telemetry that the motor circuit had failed "open", which suggested a broken wire or brush inside the motor. By comparison, unsticking a rock sounds easy.

I knew I should keep my virtual mouth shut and wait for more data.

I hope that's a rock too, but none of it is out in the light looking clearly 'rocky'. I hate to suggest it might just be some internal reflection - like my...er...flying saucer.

[helvick]

Absolutely not ! If everyone waited until they were certain of what they were saying then we'd have nothing to do here.

And just in case we get too optimistic:
Example 1
Example 2

There's shading in both of these in exactly the same place and the lighting is from a similar direction.

[Shaka]

And just in case we get too optimistic:
Example 1
Example 2

There's shading in both of these in exactly the same place and the lighting is from a similar direction.

...And the pendulum swings... http://static.flickr.com/36/112580016_7b9d7405a1_o.jpg
Somebody in another forum doing some more intensive photoenhancement.
(Like looking for WMDs)

[helvick]

...And the pendulum swings... (Like looking for WMDs)

And finding just dust it would seem. Well time to wait for more news.

[Guest_Sunspot_*]

I thought it might have been a rock at first... but now i'm thinking it is probably some internal reflection too

[djellison]

At a first look - it just looks like dust to me - and the two sets of diagnostic images ( one presumes before and after a commanded rotation of the wheel ) show no change in the position of the wheel

Doug

[Bob Shaw]

Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

That's *exactly* how the wheels were organised on the Lunokhods - individual motors which could be popped to allow the wheels to rotate freely if required.

Perhaps old lessons should be *remembered*...

Bob Shaw

[Daba]

And just in case we get too optimistic:
Example 1
Example 2

There's shading in both of these in exactly the same place and the lighting is from a similar direction.

It looks like no rock to me.

Daba

Attached thumbnail(s)

 

[slinted]

There was a tiny bit of motion between sol 779 and 780, though I'm not sure it is very promising.


click through for a larger (2x) enlargement of the FHAZ images.

The wheel doesn't rotate, and it doesn't change its pointing (steering motor), but it does seem to roll with regard to the suspension which doesn't move. Is that even a commandable motion? We know the wheels can turn and can be pointed (yaw) but can they be rolled?

[djellison]

That's a very odd motion - at first I thought it might just be a change in lighting, but it's genuine movement.

I've got to give a talk to some students tomorrow that will end with "and here's Spirit's wheel appearing to start falling off"
Doug

[RNeuhaus]

The short answer: I'm 99% sure the answer is "no".

The long answer: There are two things that resist turning of the wheel when the motor isn't energized: dynamic braking and static detents. Dynamic braking occurs from back-emf in the motor electrical circuit, and provides a resistive torque when the wheel is turned but no force when the wheel is stopped. Dynamic braking can be disengaged in the electrical system. The static detents, on the other hand, are magnets that cause the motor to preferentially stay at certain turn positions. These are necessary to keep the wheels from rolling after the rover comes to a stop, and cannot be disengaged. Because of the high gear ratio of the drive gearbox, it takes a hefty torque to the wheel from the outside to overcome the detent.

Bottom line: assuming the motor stall can't be corrected, they will probably have to drive backwards dragging a stuck RF wheel. This is something they have done before in the West Spur area when they were afraid the RF motor was nearing end of life. Though at that time, I think they periodically turned the RF wheel a bit to drive over the buildup of dirt in front of the wheel.

Would you post the rover wheel in graphical description? I still have no a good idea about its design. By now, I tought that there are four motors for motion: 2 in front and 2 in back and the motor axis is connected to the wheel. The others motor are for turning control which are connected at the top of every four motors: 2 front and 2 back. Isn't that correct?

P.D. If that looks so, I think that design is the most elegant but not the most robust. Hope this would provide a good lesson for the next Mars rover : MSL (I am afraid that its wheel design is very similar to MER according to the very generic picture.)

Rodolfo

[RNeuhaus]

Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

Once time, one of the wheels of my truck was stuck by a small stone (between the brake and wheel) and it started to noise awfully. The only way to get rid off the small stone from the wheel was to use a long screwdriver and hammer. What might be done with MER?

As MER goes very slow and I don't think that any small stone would stuck any wheel and the most probably ones would be of dust, grain or sand. The use of any kind of shaking with pyro or anything else is not a good design. The best ones would be the wheels have a very tight seal that neither a water or powder can filter into it.

On the other hand, the rover wheel has smaller circunference and its 5 kilometers is like 1,000 km for a off road truck with its big tires (I don't exactly compare the cicunference distance). After that distance, a truck need a chasis wash to flush off the dust and other dirty things and some lubrications in their joints. The MER ones has no such service for more than two years. That is Amen!

Rodolfo

[ElkGroveDan]

The wheel doesn't rotate, and it doesn't change its pointing (steering motor), but it does seem to roll with regard to the suspension which doesn't move.

Interesting. That could be a good sign. It looks like it's torquing against a load, causing the suspension to shift, which would infer something jammed somewhere out of view. That would be a far better situation than a malfunctioning motor.

[Bill Harris]

Not at all good. Slinted's animated-GIF shows that there is radial motion of the wheel, which suggests to me that a wheel bearing has failed.

--Bill

[mars_armer]

Looks like a drive will be attempted on Sol 781 (dragging the right front wheel), after some diagnostics. Goal is to move toward an area ~14m away with a more favorable power situation.

There is no debris in the wheel, but also no explanation yet for the anomaly.

[monty python]

Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.

[Ames]

In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.

Cheers Monty

Now that has my warped sense of humour going

Couldn't have come from a better named contributor

But seriously, that is a good point - if a stuck wheel is an impediment - chop it off!

Nick

[edstrick]

quote: "I've got a little list..... I'm SURE it won't be missed!"

[Burmese]

Yeah, wheel bearing looks likely to me, or some other 'broken' component besides a motor winding. Does anyone know if the wheels have -any- free movement in a radial direction under normal circumstances?

[odave]

But seriously, that is a good point - if a stuck wheel is an impediment - chop it off!

It's just a flesh wound!

However, I think we'd run into some problems with balance and stability if a wheel gets blown off. Not so bad on the flats, but I think Spirit would lose her mountain goat abilities.

[MahFL]

Strange co-incidence......today the front left wheel bearing went kaput on our van, its fixed now though

[djellison]

I gave a talk to some 16-18 y.o. school students today - and I always finish my talks with the most recent image I can get before the talk starts...so today I finished talking about Spirit thus...

"To bring it bang up to date, this image was taken yesterday morning, and shows the front right wheel - the same one that was a temporary problem 600 sols ago, essentially stuck. A major stall of the motor suggest that something might be broken for good inside the mechanics of the wheel - so I'm sad to say that I leave Spirit with the news that yes, one of its wheels might be about to fall off"

For a bunch of typical teenagers, they got most of the space related gags, went oOoo at the right anaglyphs, wow at the right pictures - and indeed laughed at the idea of a dodgy wheel falling off. For the Brits ammoungst you, there's a joke about finding a Mars rover up on bricks with 6 missing wheels somewhere in there, with the mission engineers saying something like "I KNEW we shouldnt have had that engineering consultant from Liverpool in to do the job"


Doug

[lyford]

In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.

well, maybe just to blow open the clutch or something so it could freely turn - then dragging it wouldn't be dead weight.

[Guest_Sunspot_*]

Still limping along:

http://qt.exploratorium.edu/mars/spirit/fo...23P1210R0M1.JPG

[Burmese]

Good, they aren't going to sit still and spend a week analyzing the problem w/o moving. I suspect they just make best time possible to the slopes and then take a breather to see if they can do anything about it.

No updates from SS since Feb 5th, really could use another one by now.

[general]

Still limping along:

http://qt.exploratorium.edu/mars/spirit/fo...23P1210R0M1.JPG

Looks like she's returning to Home Plate

[Marcel]

Still limping along:

http://qt.exploratorium.edu/mars/spirit/fo...23P1210R0M1.JPG

Ohmy...this doesn't look good at all. Let us not forget, that dragging a blocked wheel is no problem in this loose material, but roving around rocks is a must in this situation. If it's really stuck (which is most certainly the case because of the high gear ratio indeed), rocks that could be driven over before are an obstacle now: draging along rocks isn't easy on 5 working wheels.

It might get us some interesting views under rocks though....something we did not see before ! I remember thread that was about turning rocks with the arm ! And: we'll get a loooong trench ! ALWAYS look at the bright side of life (I am trying to keep the corners of my mouth up !)

I hope this motor starts working again. I remember something about a gear ratio well within hundreds: this means it is going to be hard to force the motor back and forth by excerting force on the wheel itself. It might be done in combination with a high current boost through the actuator, while pushing the wheel to a stationairy surface (large, coarse rock, with the "cleats" of the wheel pushed on it): the other 5 might slip then....

Fingers crossed that they'll fix it....like they did before. That wasn't a complete stall however...it was a higher current, but still turning.

[elakdawalla]

Squyres did not mention the wheel trouble in his talk today about Spirit. In fact he said at the end "Spirit has just completed a drive in the direction of Oberth and Korolev, we hope in a week or so to be on one of those nice toasty slopes that will allow us to survive another winter at Mars."

For what that's worth.

--Emily

[imipak]

In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.

Pyros could malfunction, and go off early - or, worse, simultaneously...

Cue bad Micahel Caine impression -- "You're only s'posed to blow the bloody doors off!"

[Guest_Sunspot_*]

Ohmy...this doesn't look good at all. Let us not forget, that dragging a blocked wheel is no problem in this loose material, but roving around rocks is a must in this situation.

Maybe they were just testing it with a short drive.... and will try longer ones in the days ahead.

[centsworth_II]

"Looks like she's returning to Home Plate" -- General
Not if that's Husband Hill in the background.

"(I am trying to keep the corners of my mouth up !)" -- Marcel
If all else fails, try standing on your head.

[Shaka]

Squyres did not mention the wheel trouble in his talk today about Spirit. In fact he said at the end "Spirit has just completed a drive in the direction of Oberth and Korolev, we hope in a week or so to be on one of those nice toasty slopes that will allow us to survive another winter at Mars."

For what that's worth.

--Emily

It's not exactly the kind of note a scientific 'knight in armor' wants to conclude his latest progress report with, Emily. He would say it's too soon to evaluate the problem, so 'not worth mentioning' today. Fair enough, I suppose, but I'll bet he's wishing he'd made an update last week at his Mission to Mars site. Then it could have been entirely upbeat, now...
Obviously, those static detents, Mars_Armer described are doing their job too well, the bad wheel has not budged despite that long drag. Marcel may well be right, a protruding bedrock meeting the bad wheel might 'anchor' us fast, forcing a back-up. Might mean trickier drive programming and keeping to the sand where possible. Dam'n'Blast! Time's'a'wastin'! We've got to get North, FAST before we freeze!
Don't know about those pyrotechnic charges, boys. One short-circuit or static discharge might instantly convert us into a stationary 'rover'. Better to equip MSL with a powerful rock-biting sampler that could be programmed to gnaw the leg off.

P.S. Emily, do you mind if I ask a personal question? What is your avatar a picture of? I've guessed 'dented daisy', 'tattered tutu', 'mutant ephyra', but I'm still unsure.
Hope the weather's fine in Houston.

[Guest_AlexBlackwell_*]

P.S. Emily, do you mind if I ask a personal question? What is your avatar a picture of? I've guessed 'dented daisy', 'tattered tutu', 'mutant ephyra', but I'm still unsure.

It's a radar image of the venusian surface from Magellan.

[Shaka]

It's a radar image of the venusian surface from Magellan.

Awesome, AB. I see the obvious link with Venus,(Men are from Mars...), but what is the actual structure? A volcano or something? Anywhere I can see a blowup of the pic?

[helvick]

It's a radar image of the venusian surface from Magellan.

Lavinia ?
]

[djellison]

I see the obvious link with Venus,(Men are from Mars...),

The less obvious (but more accurate) link is that Emily did research on Venus with Magellan data before working at TPS.

Doug

[odave]

I see the obvious link with Venus,(Men are from Mars...)

See a previous post from Emily.

Is she busy or something this week?

[Bill Harris]

>Looks like she's returning to Home Plate

And not with Oberth, et al, in the Rear hazcam (forward-facing).

--Bill

[djellison]

I think they moved to the nearest patch that offered a slightly better tilt w.r.t. solar power for a few days of analysis - toward or away from HP, I doubt they cared much.

Doug

[alan]

First impression: the right front wheel looks like it is locked.
But if you look at images from last year, you can see that Spirit created trenches when it traversed soft material.
Image from sol 313 for comparison
http://marsrovers.jpl.nasa.gov/gallery/all...00P0745R0M1.JPG
I assume for now that the wheel will turn when it meets enough resistance.

[Shaka]

See a previous post from Emily.

Is she busy or something this week?

OH, Maannnnn. There is so much I don't know, it's scary!
OK I've never even dropped in at one of the other planets in UMSF. Until it went orbital, I'd never even seen the MRO section! My toolbar button goes straight to MER. The truth is I'm spending too much of my remaining 'fourscore and ten' already on the MER pages! But this is planetary science I can touch. This is almost as good as biology. (I can pay no higher compliment.) When I was an astronomer (age 7 - 10), I would have been able to quote chapter and verse of UMSF from A to Z. Time marches on.
Lavinia? Is that the ravishing name of that diaphanous 'flower' at upper left? Are they volcanoes? (I am as a newborn babe on this planet, but, PC be damned, I know a blessedly feminine place when I see it.)


Edit note: Now that I've studied the blowup, I assume they're impact craters. The radar makes the proximal ejecta look like flower petals! Cool.

[Shaka]

http://static.flickr.com/41/113051772_e40da86735_o.gif
Nice animated anaglyph from the other forum, if you haven't seen it.

[CosmicRocker]

Squyres did not mention the wheel trouble in his talk today about Spirit. In fact he said at the end "Spirit has just completed a drive in the direction of Oberth and Korolev, we hope in a week or so to be on one of those nice toasty slopes that will allow us to survive another winter at Mars."

For what that's worth.

--Emily

Jim Bell concluded his presentation in the morning session by mentioning that most recently they had taken diagnostic images of the wheel, and that Steve Squyres might have more to say when he speaks. After SS didn't mention it, all ll I could think was that they didn't know enough yet to speculate.

I had a short chat with Matt Golombek after the last presentation. Although I should have known better, I couldn't help but ask him if they had any ideas about the wheel problem. As you might expect, he told me it was too soon to speculate because it was such a recent development. He also said the engineers were investigating (again, something you might suspect). So, I wasn't able to learn anything new, but only confirmed what one would logically suspect.

...for what _that_ is worth.

[mars_armer]

The wheel is definitely looking dead (open circuit, consistent with a brush failure).

Without giving up on the motor, the most productive engineering effort will probably be enhancing the efficiency of 5-wheel-drive. The sol 781 drive took almost an hour to drive a total of ~4 meters, because of the need for visodom and other extra imagery. Their durrent energy budget only allows 1 to 1.5 hours of driving per day, so this gives you an idea of the pace you can expect.

Another drive is planned on sol 782.

I assume for now that the wheel will turn when it meets enough resistance.

My understanding is that it takes ~30 N-m (22 ft-lb) of torque on the wheel to overcome the detent. Good for holding position on slopes, but it now makes it unlikely that the wheel will ever turn again. Deeply embedded rocks could easily snare the RF wheel.

[Guest_Sunspot_*]

Their durrent energy budget only allows 1 to 1.5 hours of driving per day, so this gives you an idea of the pace you can expect.

Oh dear...that's very bad news... Spirit's roving days are pretty much over then.

[ToSeek]

See a previous post from Emily.

Is she busy or something this week?

She's at the Lunar and Planetary Science Conference.

[Guest_AlexBlackwell_*]

She's at the Lunar and Planetary Science Conference.

I was wondering where she had disappeared to.

[ToSeek]

Oh dear...that's very bad news... Spirit's roving days are pretty much over then.

Well, until next summer, at least.

[mars_armer]

> Well, until next summer, at least.

And don't discount their ability to come up with clever driving algorithms, that can improve efficiency without compromising safety.

[odave]

I'm sure the MER engineers will be able to squeeze more meters out of future 5 wheel drives, so I don't think Spirit will turn into a lander mission just yet. It just looks like I'll have to give up my hope of seeing a pan from Spirit at the mouth of Ma'adim Vallis

[helvick]

I'm sure the MER engineers will be able to squeeze more meters out of future 5 wheel drives, so I don't think Spirit will turn into a lander mission just yet. It just looks like I'll have to give up my hope of seeing a pan from Spirit at the mouth of Ma'adim Vallis

That may be hoping for too much but I don't think that losing one wheel is catastrophic. The 4m progress rate is more a consequence of the visodm drive mode. In a fully planned or blind drive she should be able to go further if and when the circumstances and terrain allow.

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

[odave]

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

[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.

[Guest_Sunspot_*]

Was Spirit supposed to drive today?

http://qt.exploratorium.edu/mars/spirit/fo...67P1211R0M1.JPG

No movement.

[helvick]

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?

Well you can read how SS phrased it in the April 17 2005 update on his blog. He isn't particularly explicit about what happens below that level just that "We think that the rovers can't survive at power levels much lower than 280 watt-hours". There have been other comments from the team to the rovers dying when power drops below 300whr but I can't find them at the moment.

There has already been some discussion on this in the Oppy Vs Spirit Power Consumption thread. Any additional insight would be welcome.

[djellison]

Was Spirit supposed to drive today?

Nope. Charging day

Doug

[akuo]

Was Spirit supposed to drive today?
http://qt.exploratorium.edu/mars/spirit/fo...67P1211R0M1.JPG
No movement.

That image is from yestersol, but there shouldn't be movement tosol anyway. The Spirit update says that tosol (783) is a battery recharging sol.

BTW, I like how they have started to add the plans for the next few sols in the rover updates.

[Bob Shaw]

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.

I think there *are* certain genuine limits, such as with regard to the batteries and the way they get charged/discharged. Certainly, if they get frozen then they'll be damaged, and may take no more charge. That might leave us with a MER which the DSN can ping, but does little else, ie EOM.

Bob Shaw

[Guest_Oersted_*]

I think we're all happy that the team was pretty conservative in their time estimates to reach a good slope on the hill. It is exactly that kind of planning that will make this situation most probably survivable. - Apart from that, this is reminding me more and more of Apollo 13's homecoming, when they were also scrounging for every little amp they could find anywhere, to power up the command module with the minimum power...

[nprev]

On the weakly positive side, I hope that the wheel motor circuit is dead open (if it has to be open at all, I mean...rats! ) This will at least remove a little bit of load from Spirit's energy budget, though I know that the other wheels will more than overwhelm this due to extra torque requirements. A short to any part of the vehicle chassis from a hanging wire or a blown winding could prove fatal at this point...

[marsman]

In today's press release below, there are a few additional tidbits of information about SPIRIT's wheel problem and current driving expectations.


Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown/Erica Hupp (202) 358-1726/1237

NASA Headquarters, Washington


News Release: 2006-039 March 17, 2006

Mars Rovers Get New Manager During Challenging Period

NASA's long-lived Mars rovers demand lots of care as they age and the Martian winter approaches.

Dr. John Callas, newly named project manager for NASA's Mars Exploration Rover mission, is coordinating the work to meet these challenges. He is a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. He was named project manager after earlier roles as science manager and deputy project manager for the Spirit and Opportunity rovers.

"It continues to be an exciting adventure with each day like a whole new mission," Callas said. "Even though the rovers are well past their original design life, they still have plenty of capability to conduct outstanding science on Mars. The JPL operations team and the remote science team working on the project are the best in the solar system at what they do. It is a pleasure and a privilege to lead such an outstanding team and great mission."

One of Spirit's six wheels has stopped working. Dragging that wheel, the solar-powered rover must reach a slope where it can catch enough sunshine to continue operating during the Martian winter. The period of minimum sunshine is more than 100 days away, but Spirit gets only enough power for about one hour per day of driving on flat ground. And the supply is dropping fast.

Spirit's right-front wheel became a concern once before, when it began drawing unusually high current five months after the January 2004 landing on Mars. Driving Spirit backwards redistributed lubricant and returned the wheel to normal operation. This week, during the 779th Martian day of what was originally planned as a 90-Martian-day mission, the motor that rotates that wheel stopped working.

"It is not drawing any current at all," said JPL's Jacob Matijevic, rover engineering team chief. One possibility engineers are considering is that the motor's brushes, contacts that deliver power to the rotating part of the motor, have lost contact. The motors that rotate Spirit's wheels have revolved more than 13 million times, far more than called for in the rovers’ design.

Spirit's solar panels have been generating about 350 watt-hours of electricity daily for the past week. That is down about 15 percent since February and less than one-half of their output during the Martian summer.

The best spot for Spirit is the north-facing side of "McCool Hill," where it could spend the southern-hemisphere winter tilted toward the sun. Spirit finished studying a bright feature called "Home Plate" last week and is driving from there toward the hill. It has approximately 120 meters (about 390 feet) to go. Driving backwards with the right-front wheel dragging, the rover needs to stop and check frequently that the problem wheel has not snagged on anything and caused other wheels to slip excessively. Expected progress is around 12 meters (40 feet) per day under current conditions.

Opportunity is closer to the equator, so does not need to winter on a slope like Spirit. Opportunity spent most of the past four months at "Erebus Crater." It examined layered outcrops, while the rover team determined and tested a strategy for dealing with degraded performance by a motor in the shoulder of its robotic arm. Opportunity left Erebus this week and is on a 2 kilometer (1.2 mile) journey to a giant crater called "Victoria."

Callas has worked on the Mars rovers' mission since 2000 and five other Mars missions since joining JPL in 1987. He succeeds Jim Erickson, who switched to a leadership role with NASA's Mars Reconnaissance Orbiter. Callas grew up near Boston and graduated from Tufts University, Medford, Mass. He earned his doctorate in physics from Brown University, Providence, R.I.

JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Exploration Rover and Mars Reconnaissance Orbiter projects for NASA's Science Mission Directorate.

[odave]

News Release: 2006-039
<snip>
The period of minimum sunshine is more than 100 days away
<snip>
It has approximately 120 meters (about 390 feet) to go. [...] Expected progress is around 12 meters (40 feet) per day under current conditions.

Those numbers make me feel better, though I know anything can happen at any time. I assume the 120 meter figure is to the nearest possible "good" slope. Here's hoping Spirit can make it to a windy spot too!

[SteveM]

NASA's long-lived Mars rovers demand lots of care as they age and the Martian winter approaches.

Dr. John Callas, newly named project manager for NASA's Mars Exploration Rover mission, is coordinating the work to meet these challenges. He is a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. He was named project manager after earlier roles as science manager and deputy project manager for the Spirit and Opportunity rovers.

Let me make a few off-topic comments.
This change must not have been unexpected. A biographical sketch of Callas appears in a recent report he co-authored: Distributed Operations for the Mars Exploration Rover Mission with the Science Activity Planner.

Dr. John L. Callas received his Bachelor's degree in Engineering from Tufts University in 1981 and his Masters and Ph.D. in Physics from Brown University in 1983 and 1987, respectively. After completing his doctorate in elementary particle physics in 1987, he joined the Jet Propulsion Laboratory in Pasadena, California to work on advanced spacecraft propulsion, which included such futuristic concepts as electric, nuclear and antimatter propulsion. In 1989 he began work supporting the exploration of Mars with the Mars Observer mission and has since worked on seven Mars missions. In 2000, Dr. Callas was asked to join the Mars Exploration Rover (MER) Project as the Science Manager. Dr. Callas continues as the Science Manager for the highly successful Spirit and Opportunity rovers. Recently, Dr. Callas has begun serving as a Mission Manager on MER, as an additional duty, as the rovers continue their great success on the surface of Mars. In addition to his Mars work, Dr. Callas is involved in the development of instrumentation for astrophysics and planetary science, and teaches mathematics at Pasadena City College as an adjunct faculty member. In his spare time, he mentors students interested in science and works with schools classrooms on science projects.

His 11 publications listed in the Astrophysical Data System (1983-2006) focus on remote sensing involving spacecraft using the radio and gamma regions of the spectrum.