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MSL reasons for delay
centsworth_II
post Mar 6 2009, 02:14 AM
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QUOTE (stevesliva @ Mar 5 2009, 07:06 PM) *
You're forgiven.

Actually it's to algorimancer that the apology is due.
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dvandorn
post Mar 6 2009, 03:27 AM
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Let's face it, guys -- anything that has moving parts can fail. And a bunch of stuff without moving parts can fail, too.

There is a difference between equipment that fails because it's poorly designed and equipment that fails because it's poorly made or just because things happen that you can't prevent and wouldn't be expected to foresee.

It's not, I don't think, that anyone thinks that any given organization is incompetent at making any given piece of equipment. I think Steve is right, we tend to get more nervous about devices with more moving parts than we do about devices with less moving parts (witness the greater worries about Sterling RTGs and their moving pistons vs. the more classic thermocouple-based RTGs with no moving parts).

It is important to remember that almost all moving parts on almost every spacecraft we've ever launched have worked perfectly. My feel for it is that more spacecraft have died because of electronics failures than have died because a moving part broke or stuck. But we seem to remember and worry about the moving part failures more than about fried electronics... unsure.gif

-the other Doug


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mcaplinger
post Mar 6 2009, 03:43 AM
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QUOTE (centsworth_II @ Mar 5 2009, 06:14 PM) *
Actually it's to algorimancer that the apology is due.

Asking for forgiveness is different than apologizing, I think. rolleyes.gif

One last (?) word on the Mastcam mechanisms. A mechanismless system would be more reliable, certainly. But it would also have compromised performance. We looked at fixed-focus systems like Pancam and concluded that the performance hit was too great (Pancam is really slow optically and it's only in best focus at 2m target distance.) Our mechanisms are as reliable as we know how to make them and make as much use of MER heritage as possible. We tested them for 3x mission life and they passed with no issues. If people have residual reliability concerns, I'd be curious to know how they think we could address them. But you'd probably have to know more details of the mechanisms than is publicly available to have a well-founded opinion.

If our cameras fail there will be plenty of B&W Navcam images. smile.gif


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algorimancer
post Mar 6 2009, 01:41 PM
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QUOTE (mcaplinger @ Mar 5 2009, 03:34 PM) *
Did you trust the MER Pancam filter wheel or the MI cover to not lock up?...

As a matter of fact, I have had doubts about that as well smile.gif My perspective is reflective of my experience with commercial digital cameras -- true, the engineering quality isn't the same, but it's also true that every actuator-driven motion is a potential failure point, and I worry about that abrasive wind-blown dust. I'd lean towards solid-state systems, perhaps an optical phased array smile.gif

Seem to have touched a bit of a nerve here. I'm afraid that I am indeed guilty of playing armchair engineer -- and I've had a lot of fun doing it smile.gif
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jmcdesign
post Mar 6 2009, 04:23 PM
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"In retrospect they might simply have placed a dedicated third camera with fixed telephoto capability centered between a pair of stereo wide angle cams on the mast head with rather less trouble and similar capabilities as the dual zoom system."


There are no unused MSSS camera interfaces in the MSL rover. If you want to lobby for an additional camera mention there are three unused engineering camera interfaces. smile.gif
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djellison
post Mar 6 2009, 04:41 PM
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Of course, we have ChemCam as an ultra high res imager - but it's not the same as a pair of matched, zoomable, focusable Mastcams.
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Cruzeiro do Sul
post May 6 2009, 12:45 PM
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One question about the RTG in MSL: in front of the natural decay of plutonium, will be the amount of power available for MSL lesser with the two years delay of launch?
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SpaceListener
post May 8 2009, 12:42 AM
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QUOTE (Cruzeiro do Sul @ May 6 2009, 06:45 AM) *
One question about the RTG in MSL: in front of the natural decay of plutonium, will be the amount of power available for MSL lesser with the two years delay of launch?

It was previously discussed. The answer was that the loss of power is not of concern since it is very small. smile.gif About how much, I don't remember but the reference is to take in account that the half life span of this type of radiative is of 88 years.
Wikipedia about Plutonium
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monitorlizard
post May 8 2009, 09:56 AM
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http://mars.jpl.nasa.gov/msl/mission/technology/power

Above website states that the"MMRTG (used on MSL) optimizes power levels over a minimum lifetime of 14 years".

And if I recall correctly, the MSL delay press conference last December stated that the RTG power loss during the two year delay would be on the order of 5%
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Cruzeiro do Sul
post May 11 2009, 02:34 PM
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5% is a small amount of lost, so we can hope that it will not be a seroius concerns in case of a possible extended MSL mission. Thanks for the information!
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SFJCody
post Jul 11 2009, 07:01 AM
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Very interesting document over at nasawatch. Amongst other things, it looks like MSL may need a supplementary solar array.
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climber
post Jul 11 2009, 10:38 AM
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You'll be interested in this .pdf presentation by Doug Mac Cuistion: http://images.spaceref.com/news/2009/PSS.Jun.09.Mars.pdf
Among news, they envisione adding solar panels.


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SpaceListener
post Jul 11 2009, 03:06 PM
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And hope that these probably existence of solar panels must have their own self cleaning mechanics by applying the learned lessons from MER's experience.
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centsworth_II
post Jul 11 2009, 03:48 PM
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QUOTE (SpaceListener @ Jul 11 2009, 10:06 AM) *
...solar panels must have their own self cleaning mechanics...

My favorite solution is to mount the panels on vertical surfaces, like the sides of the electronics box. They would give less power with the sun overhead, but more with the sun near the horizon. Best of all, they should stay clean with no additional cleaning apparatus needed.
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djellison
post Jul 11 2009, 04:45 PM
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QUOTE (SpaceListener @ Jul 11 2009, 04:06 PM) *
the learned lessons from MER's experience.


The lessons learned from MER experience is that actually, you can get away without cleaning solar arrays.(to a certain extent)

If having a vertical panel is the answer, how come we still have to clean our TVs and Monitors?

We've already got threads on solar array cleaning - this isn't the place.
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