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MSL's Power Source
Marslauncher
post Nov 30 2005, 12:47 AM
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QUOTE (mcaplinger @ Nov 30 2005, 12:34 AM)
Seems to me that the 2006 NASA budget I cited is clear proof that they have selected the MMRTG.  And I'll just leave it at that.
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Sir has there been any more development on the Skycrane issue? Just curious to find out when we would likely see initial work done on the system.

Thanks

Marslauncher

John Cooke
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Guest_BruceMoomaw_*
post Nov 30 2005, 02:29 AM
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It's about to be declared the officially, firmly selected landing system -- despite the fact that the actual desert tests won't start until 2007. They seem to have that much confidence in it.
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mchan
post Nov 30 2005, 02:43 AM
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QUOTE (exobioquest @ Nov 29 2005, 10:49 AM)
those nuts and their logic its scares me so, how likely you think they will make a effective stink?
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They will be flatulent, you will hold your nose, the smell will pass, and NH will launch.
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Guest_exobioquest_*
post Nov 30 2005, 02:48 AM
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Well if the MMRTG is set I can only hope they can get enough fuel, really hope no problem that dooms the mission happens during cruise or EDL because of a thermal management issue. mad.gif
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RNeuhaus
post Nov 30 2005, 03:34 AM
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QUOTE (helvick @ Nov 29 2005, 06:10 PM)
I'm of the opinion that the biggest speed boost will actually come from the RAD 750. It has 10x the integer performance and about 20x the fp performance of the RAD6000's on the MER's. Combined with the increased on board storage that alone should allow MSL to do safely drive much faster.
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I think that the CPU capacity of MER along with the low bandwidth communication was the hidering factors to slow the advance of the Mars mission. The CPU capacity is a very important thing for analyzing the land obstacles before steping an advance for every around 40 seconds and then take some 15 seconds in analyzing the same task and over.

About the bandwidth of the communication of MER is no more than 128 kbits/sec that is enough to send at least 80 pictures per day (between 1kBytes to 350 kBytes each one). The MSL will take the advantage of greater bandwidth transmission capacity of MRO that might send from Mars to Earth between 1 to 3 GBytes depending upon to the distance between the Earth and Mars.

The others things that I expect the the new MSL incorporates three new instruments after taking the advantage of greater power supply capacity. These new instruments requires very few watts and they might be activated whenever they are needed.

1) Microphone to listen the environment sounds. It would be a very interesting thing and it might be a very valuable device after the camera. This is a good thing to improve the PR. Many people would get exited to listen the sounds from the other words. Very few words can be listen except to Venus, Mars, Titan, and what else more?

2) Two extra arms at both sides as an useful support to help any situation such as to shove, drill, lift MSL from emergency, scratch, hammer, or anything else on the surface. I feel deseperated that MER has no arms to touch, push (from Purgatory Sand) and neither grasp any thing from the surface. It is like a more complete geologist with eyes (ok), ears (not yet), legs (ok), smell (ok -miniTES, x-ray, spectrometer, etc.) and arms (not yet)

3) Anenometer to measure the wind speed and direction in order to help to understand better the geology (the wind also plays an important rol as an aeolian erosion).

Rodolfo
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Guest_exobioquest_*
post Jan 15 2006, 04:57 AM
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What is this:
"NASA is considering nuclear energy for powering the Mars Science Laboratory. The rover would carry a U.S. Department of Energy radioisotope power supply that would generate electricity from the heat of plutonium's radioactive decay. This type of power supply could give the mission an operating lifespan on Mars' surface of a full martian year (687 Earth days) or more and in extreme seasonal conditions such as those at high latitudes. NASA is also considering solar power alternatives that could meet the mission's science and mobility objectives." -- MSL Home Page

What, what, what! Solar is still a option can somebody clear this up? I thought things were a little more well defined on what the power supply was going to be.
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mcaplinger
post Jan 15 2006, 06:12 AM
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QUOTE (exobioquest @ Jan 14 2006, 08:57 PM)
Solar is still a option can somebody clear this up?
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You'll also note that all the images of MSL on the website appear to have the power source "airbrushed out". As far as I can tell, this is NASA PIO's way of dealing with anti-nuke sentiment.

I haven't seen any indication that the MMRTG is not the power source. Solar would require a complete redesign of the system, if it was viable at all (certainly the MER experience is that you can go for a long time on solar, but I don't think one can count on random wind cleaning events for mission success.)


--------------------
Disclaimer: This post is based on public information only. Any opinions are my own.
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djellison
post Jan 15 2006, 09:09 AM
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Yes - it's clearly just being 'polite' about it until they have to start with the 'it's actually quite safe and you have nothing to worry about' efforts in a few years. I've not seen any mention of anything other than an RTG, and no mention anywhere of Solar Arrays.

Doug
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helvick
post Jan 15 2006, 09:35 AM
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QUOTE (mcaplinger @ Jan 15 2006, 07:12 AM)
I haven't seen any indication that the MMRTG is not the power source.  Solar would require a complete redesign of the system, if it was viable at all (certainly the MER experience is that you can go for a long time on solar, but I don't think one can count on random wind cleaning events for mission success.)
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The MER's have proven that Solar power for Mars surface operations isn't as marginal as had been thought but it would take one hell of an array to reliably equal the reliability of an MMRTG.
Even with a 50% improvement in solar cell and power management technology you would need a 10m^2 array in order to allow reasonable landing site selection.
The only rationale I can think of for going solar would be to limit the mission life time to something around the 90-120 Sols length which makes no sense for MSL. You could get away with an array of around 3m^2 for such a short mission starting in Summer that needed 2.4kwh per sol.
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Guest_exobioquest_*
post Jan 15 2006, 06:06 PM
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Well what is the max the MERs gets? what 900-1000w per day? And for MSl we want 2400w so assuming the same cell efficiency we would need 2.4 times more area of solar cells just to get 2400w on a really good day on the equator. How much square area does the MERs solar arrays take up? Give me that and maybe I can draw up what a fugly MSl with solar arrays would look like!
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helvick
post Jan 15 2006, 06:57 PM
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QUOTE (exobioquest @ Jan 15 2006, 07:06 PM)
Well what is the max the MERs gets? what 900-1000w per day? And for MSl we want 2400w so assuming the same cell efficiency we would need 2.4 times more area of solar cells just to get 2400w on a really good day on the equator.  How much square area does the MERs solar arrays take up? Give me that and maybe I can draw up what a fugly MSl with solar arrays would look like!
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MER's have somewhere between 1.35 and 1.3m^2 of cell surface area (499 cells of ~4x6.5cm). The cells are 26.8% efficiency triple junction units from Spectrolab.
The maximum reported power out per sol was from Spirit on Sol 581 (956 watt hours).

Total daily Insolation in mid winter is ~46% of the Midsummer value when you exclude atmospheric effects, when you include them the variance is lower and idwinter insolation is ~56% of the summer maximum at Gusev, mostly because the midsummer numbers are reduced by increased Tau.

For a long term mission (like MSL) you'd need to have arrays that can generate 2.4 kilowatt hours in midwinter. So you need at least 7m^2 of array.
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RNeuhaus
post Jan 16 2006, 03:04 AM
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QUOTE (mcaplinger @ Jan 15 2006, 01:12 AM)
I haven't seen any indication that the MMRTG is not the power source.  Solar would require a complete redesign of the system, if it was viable at all (certainly the MER experience is that you can go for a long time on solar, but I don't think one can count on random wind cleaning events for mission success.)
*

MER's experience is that MSL must not depend upon to winds. It must incorporate own dust blowers which will be used whenever it is necessary.

Rodolfo
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RNeuhaus
post Jan 16 2006, 03:14 AM
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QUOTE (helvick @ Jan 15 2006, 01:57 PM)
For a long term mission (like MSL) you'd need to have arrays that can generate 2.4 kilowatt hours in midwinter. So you need at least 7m^2 of array.
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Not so practical. 7 mē is like a small bathroom of the size 2.5 x 3.0 meters. The present technology solar power has improved by 50% so the present MER would reduce its solar panel from 1.3 mē to 0.75 mē now and the MSL would need at least 3.5 mē instead of 7 mē, Not correct?

Rodolfo
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helvick
post Jan 16 2006, 03:26 AM
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QUOTE (RNeuhaus @ Jan 16 2006, 04:14 AM)
Not so practical. 7 mē is like a small bathroom of the size 2.5 x 3.0 meters. The present technology solar power has improved by 50% so the present MER would reduce its solar panel from 1.3 mē to 0.75 mē now and the MSL would need at least 3.5 mē instead of 7 mē,  Not correct?
Rodolfo
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Yes but only if MSL was intended for a short mission close to the equator.

Any long term mission will have to be built to handle a major dust storm. The MER's haven't had to deal with one yet but the frequency is about 1 major storm every 5 Martian years, any sensible long duration mission must be able to survive when insolation drops to around 20% of normal.

Even at 21deg S the minimum winter insolation is 30% lower than at Gusev (14deg South) so choosing Solar severely limits your ability to explore outside of equatorial regions.

The Northern hemisphere is even worse because the high tau season coincides with winter.
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Guest_Analyst_*
post Jan 18 2006, 10:06 AM
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Mike Griffin said at the NH press conference MSL will be the next RTG powered spacecraft. No solar arrays.

Analyst
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