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Going To Mogollon..., ...and points South
Bill Harris
post Jan 20 2006, 02:30 PM
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QUOTE (Tesheiner @ Jan 20 2006, 05:38 AM)
It was already said that those structures seen on previous hazcam pics (well, in all sort of cameras and filters...) were delicate.

[attachment=3535:attachment] (138k)
But what about these ones? It looks like the smallest touch could broke them.

[attachment=3536:attachment] (138k)
PS: It's time to open a new thread, don't you think so?
*


Good idea. That topic was "tired" and had the cord showing. smile.gif biggrin.gif tongue.gif

Delicate, to be sure. One thing I've noticed is that the "ledge-forming" rocks are a layer and extend to the right and left of where we camped out. I wonder if that feature is related to the bluff at Mogollon Rim?

We need to check out the "mobile dust" at that site and see if there has been more movement during the stopover.
--Bill


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Guest_Sunspot_*
post Feb 17 2006, 09:33 AM
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Guests






sad.gif The tech probs are really stacking up...Im begining to think that Opportunity will spend her last days around Erebus.
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djellison
post Feb 17 2006, 09:43 AM
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QUOTE (Sunspot @ Feb 17 2006, 09:33 AM) *
sad.gif The tech probs are really stacking up...Im begining to think that Opportunity will spend her last days around Erebus.


Mobility wise, Opportunity is in fairly good health. Once they get that arm stowed, we'll be under way I'm sure.

Doug
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Marcel
post Feb 17 2006, 08:09 PM
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QUOTE (djellison @ Feb 17 2006, 10:43 AM) *
Mobility wise, Opportunity is in fairly good health. Once they get that arm stowed, we'll be under way I'm sure.

Doug


I don't understand why they completely stow the arm as soon as a long drive needs to be done. Why is this so important ? Do they really think something will break while the arm is in "half stowed" position (over the solar panel) ? They drive 5 mm's a second. It's not " bumping", it is like a snail creeping across the terrain ! I've been asking this to myself for a long time. Maybe i oversee something, but the risk of another winding breaking in the faulty joint (thereby completely disabling the possibility to UNstow the IDD for the rest of the mission) looks much higher to me, than the chance of breaking something because of driving in the alternative (half stowed) position. There are two primairy windings in these motors aren't there ? There's only one left. And forcing a higher current trough it at this stage (while materials are getting old) doesn't make sense to me. I'm puzzled. It has been unstowed AFTER a pretty bad situation of stalls and erronous behaviour. LEAVE IT THERE ! Or maybe i'm not informed well enough.... unsure.gif
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djellison
post Feb 17 2006, 08:32 PM
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QUOTE (Marcel @ Feb 17 2006, 08:09 PM) *
I don't understand why they completely stow the arm as soon as a long drive needs to be done. Why is this so important ? Do they really think something will break while the arm is in "half stowed" position (over the solar panel) ? They drive 5 mm's a second. It's not " bumping", it is like a snail creeping across the terrain !



If you hunt back in the movie archive at the JPL site, you'll see some rover driving videos - ditto the NOVA programs - and given that there's essentially a tiny tiny bit of suspension within the wheels but nothing else - it's quite a rough ride even over the fairly flat rocks and terrain we have here.

Given that suprisingly bumpy ride, the mass of the instruments on the IDD, and the leverage they'd have on the joints and motors when in the 'hover' position, there is a real risk of damage to IDD joints, motors, even the front of that array and the nearest instrument.

Hence the high-park for short drives, and the proper drive for longer driving campaigns.

Doug
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mars_armer
post Feb 17 2006, 09:54 PM
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The simulations that have been run with an unstowed arm involve a single wheel sideslipping off a rock and free-falling some distance. This scenario isn't too unlikely, even when driving slowly. And Doug is right, the "suspension" is very hard so the rover and arm get a good jolt when that happens. The worst thing is that the unstowed arm gets thrown sideways as well.

The arm design was highly optimized to stay within a very tight mass budget (~4 kg for the arm, and the instrument package is ~2 kg). Because of those constraints, the arm was never designed to take these kinds of loads. A single-wheel drop off a 3-centimeter rock edge gets pretty close to the documented capability of the arm when in the hover-stow position.

Something else to remember is that the joint 1 winding failure was almost certainly caused by thermal cycling (remember the stuck heater on Oppy's shoulder). So the expectation is that the joint will fail completely from a thermal cycle, not from operation. So for longer drives, where they can't see the terrain in advance, it is considered fairly safe to stow the arm before driving and then unstow after the drive. (Of course, there's still the occasional stall because it's tricky operating the motor with a broken winding.)

Hope this helps explain the logic behind what they are doing.
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jamescanvin
post Feb 17 2006, 10:14 PM
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QUOTE (mars_armer @ Feb 18 2006, 08:54 AM) *
The simulations that have been run with an unstowed arm involve a single wheel sideslipping off a rock and free-falling some distance. This scenario isn't too unlikely, even when driving slowly. And Doug is right, the "suspension" is very hard so the rover and arm get a good jolt when that happens. The worst thing is that the unstowed arm gets thrown sideways as well.

The arm design was highly optimized to stay within a very tight mass budget (~4 kg for the arm, and the instrument package is ~2 kg). Because of those constraints, the arm was never designed to take these kinds of loads. A single-wheel drop off a 3-centimeter rock edge gets pretty close to the documented capability of the arm when in the hover-stow position.

Something else to remember is that the joint 1 winding failure was almost certainly caused by thermal cycling (remember the stuck heater on Oppy's shoulder). So the expectation is that the joint will fail completely from a thermal cycle, not from operation. So for longer drives, where they can't see the terrain in advance, it is considered fairly safe to stow the arm before driving and then unstow after the drive. (Of course, there's still the occasional stall because it's tricky operating the motor with a broken winding.)

Hope this helps explain the logic behind what they are doing.


Perfect!

I am surprised how tricky it seems to be operating the broken motor, I would have expected it to be very predictable. But then what do i know, I'm a scientist not an engineer!

James


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Posts in this topic
- Bill Harris   Going To Mogollon...   Jan 20 2006, 02:30 PM
- - lyford   Does it look like there was any piled deposition o...   Jan 20 2006, 05:28 PM
- - Bill Harris   Ed, it may very well be that sand has piled up n t...   Jan 20 2006, 07:03 PM
- - Tesheiner   An article at Space.com: http://www.space.com/mis...   Jan 21 2006, 06:10 PM
- - Sunspot   ..week or so?   Jan 21 2006, 07:40 PM
- - ilbasso   They didn't say which week.   Jan 22 2006, 05:16 AM
- - CosmicRocker   Well, that pretty much confirms that more MIs of t...   Jan 22 2006, 06:48 AM
- - Bill Harris   > I am really anxious to get to Mogollon, but i...   Jan 22 2006, 07:54 AM
|- - ElkGroveDan   QUOTE (Bill Harris @ Jan 22 2006, 07:54 AM)We...   Jan 22 2006, 03:20 PM
- - Bill Harris   Foo. --Bill   Jan 22 2006, 06:30 PM
- - alan   QUOTE (Tesheiner @ Jan 21 2006, 12:10 PM)An a...   Jan 29 2006, 08:54 PM
|- - Shaka   QUOTE (alan @ Jan 29 2006, 10:54 AM)Oppy leav...   Jan 29 2006, 09:26 PM
- - dot.dk   QUOTE (alan @ Jan 29 2006, 08:54 PM)Oppy leav...   Jan 29 2006, 09:42 PM
|- - Shaka   QUOTE (dot.dk @ Jan 29 2006, 11:42 AM)From: h...   Jan 30 2006, 01:27 AM
- - jvandriel   The last images are down and here is the 360 degre...   Jan 30 2006, 09:50 AM
- - slinted   Since this is the thread for "...and points s...   Jan 31 2006, 12:21 AM
|- - jamescanvin   QUOTE (slinted @ Jan 31 2006, 11:21 AM)Since ...   Jan 31 2006, 01:52 AM
- - Bill Harris   I have long commented jokingly that the "rout...   Jan 31 2006, 12:39 AM
- - SigurRosFan   No Mogollon Rim close-up's?? http://athena.co...   Jan 31 2006, 09:47 PM
|- - Toma B   QUOTE (SigurRosFan @ Feb 1 2006, 12:47 AM)No ...   Jan 31 2006, 09:57 PM
|- - Shaka   QUOTE (SigurRosFan @ Jan 31 2006, 11:47 AM)No...   Jan 31 2006, 09:59 PM
- - Sunspot   According to the latest rover article at the Plane...   Feb 1 2006, 06:32 PM
|- - Nirgal   looks like they finally decided to switch the prio...   Feb 1 2006, 09:15 PM
|- - tacitus   QUOTE (Nirgal @ Feb 1 2006, 03:15 PM)looks li...   Feb 1 2006, 10:12 PM
|- - Nirgal   QUOTE (tacitus @ Feb 2 2006, 12:12 AM)Don...   Feb 2 2006, 12:53 AM
|- - Tesheiner   QUOTE (Nirgal @ Feb 2 2006, 01:53 AM)What I...   Feb 2 2006, 08:46 AM
- - RNeuhaus   The real interesting thing from Mogollon rim is th...   Feb 1 2006, 09:59 PM
- - Bill Harris   I will agree. If it hadn't been for the IDD p...   Feb 2 2006, 11:04 AM
- - Bill Harris   Presented here is a 3x vertical exaggeration from ...   Feb 16 2006, 02:01 PM
|- - Bob Shaw   Anyone know what the strategy is for Opportunity r...   Feb 16 2006, 02:32 PM
- - Tesheiner   QUOTE (Bob Shaw @ Feb 16 2006, 03:32 PM) ...   Feb 16 2006, 02:45 PM
|- - helvick   QUOTE (Tesheiner @ Feb 16 2006, 02:45 PM)...   Feb 16 2006, 03:47 PM
- - Burmese   http://www.newscientistspace.com/article.ns?id=dn8...   Feb 16 2006, 03:33 PM
- - Bill Harris   Also since this site a only a couple of degrees So...   Feb 16 2006, 03:49 PM
- - djellison   Power 19% further out will be 41% lower, I think ...   Feb 16 2006, 03:51 PM
|- - helvick   QUOTE (djellison @ Feb 16 2006, 03:51 PM)...   Feb 16 2006, 07:02 PM
|- - Nirgal   QUOTE (helvick @ Feb 16 2006, 08:02 PM) T...   Feb 16 2006, 07:45 PM
- - Phil Stooke   Burmese quoted a story from New Scientist, ...   Feb 16 2006, 05:26 PM
- - Tesheiner   Not only that, but the rover would have to make th...   Feb 16 2006, 05:35 PM
|- - Toma B   QUOTE (Tesheiner @ Feb 16 2006, 08:35 PM)...   Feb 16 2006, 06:59 PM
||- - Marcel   B)-->QUOTE(Toma B @ Feb 16 2006, 07:59 PM...   Feb 16 2006, 07:47 PM
||- - Nirgal   QUOTE (Marcel @ Feb 16 2006, 08:47 PM) Bu...   Feb 16 2006, 08:16 PM
|||- - Marcel   QUOTE (Nirgal @ Feb 16 2006, 09:16 PM) Im...   Feb 16 2006, 08:37 PM
||- - helvick   Victoria is apparently somewhere between 2500 and ...   Feb 16 2006, 08:29 PM
|||- - Marz   QUOTE (helvick @ Feb 16 2006, 02:29 PM) V...   Feb 16 2006, 10:48 PM
|||- - Marslauncher   So didnt I read that we should have had a drive? h...   Feb 17 2006, 02:20 AM
||||- - Shaka   QUOTE (Marslauncher @ Feb 16 2006, 04:20 ...   Feb 17 2006, 03:49 AM
||||- - jamescanvin   QUOTE (Shaka @ Feb 17 2006, 02:49 PM) ......   Feb 17 2006, 05:58 AM
|||||- - tacitus   Are they still trying to stow the arm completely o...   Feb 17 2006, 07:11 AM
|||||- - Tesheiner   QUOTE (tacitus @ Feb 17 2006, 08:11 AM) A...   Feb 17 2006, 09:07 AM
||||- - Tesheiner   QUOTE (Shaka @ Feb 17 2006, 04:49 AM) The...   Feb 17 2006, 08:56 AM
|||- - helvick   QUOTE (Marz @ Feb 16 2006, 10:48 PM) Yike...   Feb 18 2006, 10:16 PM
||- - bergadder   QUOTE (Marcel @ Feb 16 2006, 02:47 PM) --...   Feb 17 2006, 04:23 AM
||- - Marslauncher   I fully support science days and investigation, I ...   Feb 17 2006, 05:38 AM
|- - djellison   QUOTE (Tesheiner @ Feb 16 2006, 05:35 PM)...   Feb 16 2006, 08:44 PM
- - Sunspot   The tech probs are really stacking up...Im beginin...   Feb 17 2006, 09:33 AM
|- - djellison   QUOTE (Sunspot @ Feb 17 2006, 09:33 AM) ...   Feb 17 2006, 09:43 AM
|- - Marcel   QUOTE (djellison @ Feb 17 2006, 10:43 AM)...   Feb 17 2006, 08:09 PM
|- - djellison   QUOTE (Marcel @ Feb 17 2006, 08:09 PM) I ...   Feb 17 2006, 08:32 PM
|- - mars_armer   The simulations that have been run with an unstowe...   Feb 17 2006, 09:54 PM
|- - jamescanvin   QUOTE (mars_armer @ Feb 18 2006, 08:54 AM...   Feb 17 2006, 10:14 PM
|- - Jeff7   QUOTE (jamescanvin @ Feb 17 2006, 05:14 P...   Feb 18 2006, 01:47 AM
- - Bill Harris   QUOTE Imo, it's one of those two outcrops at t...   Feb 17 2006, 11:10 AM
|- - Tesheiner   QUOTE (Bill Harris @ Feb 17 2006, 12:10 P...   Feb 17 2006, 12:23 PM
- - Bill Harris   "We'll get there eventually..." ...   Feb 17 2006, 01:33 PM
- - Bill Harris   I picked up a "proper" L2 Pancam today a...   Feb 17 2006, 05:02 PM
- - djellison   Looks like a little slice of a baby Burns Cliff in...   Feb 17 2006, 05:10 PM
- - Marz   I was just surfing the sol 734 images and noticed ...   Feb 17 2006, 07:55 PM
- - Bill Harris   The dark-toned dune is Payson. Zane Grey is the l...   Feb 17 2006, 08:06 PM
- - tacitus   I suppose one thing the stowing problems might mea...   Feb 18 2006, 08:37 AM
- - mars_armer   Actually, the present strategy means the arm is ne...   Feb 18 2006, 04:17 PM
|- - Cugel   QUOTE (mars_armer @ Feb 18 2006, 05:17 PM...   Feb 18 2006, 06:34 PM
||- - hugh   QUOTE (Cugel @ Feb 18 2006, 06:34 PM) can...   Feb 19 2006, 07:30 AM
|||- - Nirgal   Question: does this mean that when the joint motor...   Feb 19 2006, 10:27 PM
||- - Toma B   QUOTE (Cugel @ Feb 18 2006, 09:34 PM) Que...   Feb 20 2006, 07:03 AM
|- - RNeuhaus   QUOTE (mars_armer @ Feb 18 2006, 11:17 AM...   Feb 19 2006, 03:49 AM
|- - djellison   QUOTE (RNeuhaus @ Feb 19 2006, 03:49 AM) ...   Feb 19 2006, 09:35 AM
- - Holder of the Two Leashes   Probably get just a little bit more science done t...   Feb 19 2006, 09:13 PM
- - Sunspot   We're a couple of days away from spending 3 mo...   Feb 20 2006, 12:41 AM
- - alan   QUOTE (Nirgal @ Feb 19 2006, 04:27 PM) Qu...   Feb 20 2006, 12:51 AM
|- - tacitus   QUOTE (alan @ Feb 19 2006, 06:51 PM) I su...   Feb 20 2006, 02:23 AM
|- - hugh   QUOTE (tacitus @ Feb 20 2006, 02:23 AM) W...   Feb 20 2006, 08:39 AM
|- - djellison   QUOTE (hugh @ Feb 20 2006, 08:39 AM) Not ...   Feb 20 2006, 09:12 AM
- - Bill Harris   It would be nice to have the IDD instruments, but ...   Feb 20 2006, 02:48 AM
|- - ElkGroveDan   QUOTE (Bill Harris @ Feb 20 2006, 02:48 A...   Feb 20 2006, 03:17 AM
- - neb   QUOTE (Bill Harris @ Feb 19 2006, 07:48 P...   Feb 20 2006, 03:21 AM
|- - Shaka   QUOTE (neb @ Feb 19 2006, 05:21 PM) Bill:...   Feb 20 2006, 04:46 AM
|- - ElkGroveDan   QUOTE (Shaka @ Feb 20 2006, 04:46 AM) I w...   Feb 20 2006, 04:28 PM
- - djellison   If the IDD breaks, then do what can be done with w...   Feb 20 2006, 08:34 AM
|- - JTN   QUOTE (djellison @ Feb 20 2006, 08:34 AM)...   Feb 20 2006, 02:00 PM
|- - jabe   QUOTE (JTN @ Feb 20 2006, 02:00 PM) Could...   Feb 20 2006, 02:09 PM
|- - djellison   QUOTE (JTN @ Feb 20 2006, 02:00 PM) Could...   Feb 20 2006, 03:11 PM
- - jvandriel   A panoramic view of Mogollon. Taken on Sol 734 wi...   Feb 20 2006, 11:50 AM
- - Bill Harris   QUOTE They need to find a way to stow it and get m...   Feb 20 2006, 12:20 PM
|- - sranderson   Unfortunately, we haven't found anything new w...   Feb 20 2006, 07:28 PM
- - centsworth_II   If the IDD breaks while extended they could drive ...   Feb 20 2006, 03:28 PM
- - odave   I hate contributing more negative waves to the dis...   Feb 20 2006, 03:31 PM
|- - djellison   QUOTE (odave @ Feb 20 2006, 03:31 PM) I h...   Feb 20 2006, 04:50 PM
- - Tesheiner   Will we see "Oppy leaves Olympia (aka Purgato...   Feb 20 2006, 05:30 PM
- - djellison   Again - you're making the mistake in assuming ...   Feb 20 2006, 08:00 PM
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