I trust that some cannot pass any opportunity to bemoan the state of mankind.
My personal theory is that misanthropy is sparked in the mirror, not in the media.
It seems the comet probe's solar panels suffer from unexpected shading, severely limiting available power. I guess they will need to further prioritize their data gathering. Hope it goes well. It's been an incredible accomplishment.
My personal theory is that misanthropy is sparked in the mirror, not in the media.
It seems the comet probe's solar panels suffer from unexpected shading, severely limiting available power. I guess they will need to further prioritize their data gathering. Hope it goes well. It's been an incredible accomplishment.
Yes there is a mountain in the way..
..Just a joke...I do hope they move it...However I would not like to be the person that does it..
With such a weight resting on your shoulders of 10 years + work going down the toilet..OK whos going to push the button..
It is a fantastic achievement..it will be even more so if they manage to rescue it!
Regards
M. Gregg
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For interest,
I was sure they said the harpoons had deployed now they say they didn't fire. Perhaps its lucky, they would not be able to move it if they had worked.
Three touchdowns for Rosetta?s lander / Rosetta / Space Science / Our Activities / ESA
Is it on the edge of a cliff? or on its side?
http://www.esa.int/spaceinimages/Images/2014/11/First_comet_panoramic
Just downloaded the pic but its hard to tell...
http://www.esa.int/var/esa/storage/...eng-GB/Comet_panoramic_lander_orientation.jpg
Regards
M. Gregg
I was sure they said the harpoons had deployed now they say they didn't fire. Perhaps its lucky, they would not be able to move it if they had worked.
Three touchdowns for Rosetta?s lander / Rosetta / Space Science / Our Activities / ESA
Is it on the edge of a cliff? or on its side?
http://www.esa.int/spaceinimages/Images/2014/11/First_comet_panoramic
Just downloaded the pic but its hard to tell...
http://www.esa.int/var/esa/storage/...eng-GB/Comet_panoramic_lander_orientation.jpg
Regards
M. Gregg
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Granted with enough budget, very high purity raw materials, and controlled slow charging, you can build a long lasting NiCad cell. Cells for extreme duty high cost applications will recapture all of the hydrogen and oxygen generated during charging and convert it back to water needed for operation.
A low cost "sealed" cell will lose some of these elements to reaction with impurities, and some will escape through the vent during charging due to heat build up. over time the electrolyte paste inside just dries up and the cell ESR goes up.
I spent the last 30 years designing two way radios for public safety and military use at Motorola except for the 5 years I worked in the cell phone group. We designed our radios for "mission critical" applications where human life is on the line if the radio malfunctions (police, fire, and military applications). These "walkie talkies" sell for $1200 USD to $7000 USD each.
The batteries used to be made in house including the cells. We had a NiCad battery cell production line in the building where I worked. It was a nasty, dirty place. Ever see a 3 phase Variac about 2 feet in diameter and 3 feet tall? Ever seen a Crescent wrench (adjustable spanner) glow red hot? I used to be the guy that fixed the power supply in the polarizing rack. 2 volts at 1500 amps!
The cell line was shut down because of EPA regulations in the 80's, moved offshore, then closed down completely a few years later. The battery line was still in place until the 90's or maybe early 2000's, I don't really remember, but all the cells were purchased from different suppliers.
There was an extensive testing program that vendors went through to get their cells qualified, and a lot of internal testing is performed under extreme operating conditions.
The commercial quality NiCad cells that we tested all lost as much as 50% of their capacity in two years of daily police use (discharge for an 8 hour shift, recharge overnight). The Japanese cells were the best at that time (Sanyo, Panasonic).
The consumer grade cells are even worse due to impure materials. I am sure we can all find outliers, I have a 12 year old Makita drill and two out of six of the original battery packs still work at about 2/3 capacity, The drill will run at nearly full speed for about an hour of sheetrock work. One is totally dead, and the other three will run for 5 to 15 minutes.
The standard battery pack wad NiCad up until the mid 90's when NiMh cells became capable of higher capacity for a given cell size. Self discharge is not an issue for a radio that is used every day for 10 to 15 years. NiMH became the dominant battery chemistry for those products, and remains dominant today.
All current Lithium chemistries are unsuitable in low temperature environments. Our radios are guaranteed to operate at -25C and we test everything at -40C. Most Lithium chemistries would not pass our destructive testing either.
LiFePo4 is Lithium Ferric Phosphate also called Lithium Iron Phosphate or Lithium Ferro Phosphate. I think Ferro is technically correct, but the batteries I have say Lithium Ferric Phosphate on them. This may be a poor translation from Chinese, like the early Shuguang 845 "Election Tubes, made in Chian" that I have.
I have 2 13 volt 12 AH packs wired in series. They will run a Core I7 PC including a 24 inch screen for 2 to 5 hours depending on workload. 5 hours doing nothing but the screen is lit, 1 hour 57 minutes cranking Prime 95 at 4.2 GHz.
Yep this sounds more like it, I think that nearly every single NiCD battery out there was placed on an overnight charge profile where the battery literally cooked/vented gradually.
Very interesting!
I've never seen a crescent wrench glow in person only on Youtube but I did melt some wires as a teenager, since then I've sucessfully learnt the proper lesson of calculating wire gauge to the load and properly fusing a DC/AC circuit.
I have heard this story before just how dangerous high amp delivering circuits can be. I maintain a 12 volt nominal 400AH battery system (made of 2x200AH AGM SLA batteries wired in parallel with high copper content 35mmSQ wire), they're fused according to load and the battery terminals are covered with electrical tape to prevent wrench-throwing occurances.
Would be nice if you could clarify these testing circumstances for me.
Yep, I believe this is where NiCD has lost a significant amount of its reputation, simply leaving the cells on a timing charge I believe is why they've been cooked and lost half of their capacity within 2 years.
I can still find Varta and other various assorted brands on eBay from the late-80s-early90s along with the overnight chargers for them.
I'm finding it difficult to find AA NiCD cells, 99% of them available for sale come from China and aren't the greatest quality, infact they are so poor quality that they feel physically lighter, which is kind of nice in a flashlight but not so nice for runtime.
So I use NiMH AA's for my Maglite 2AA torches and various other devices.
As I've stated before in the last reply I made I have a Maglite 2C with 2x Sanyo Eneloop NiCD cells, so far it hasn't had a single issue and I hope that it lasts for a long time.
For every other size besides C I use Sanyo Eneloop. Great low self discharge means that their full capacity is available whenever its needed.
The C Cell Sanyo Cadnica cells actually outdo the performance of equivalently sized NiMH cells because NiMH cells have such a higher self discharge rate, so I believe that the combination of a Maglite 2C and NiCD cells is a match made in heaven because Sanyo doesn't make C-cell sizes in Eneloop type.
Yeah NiCD has the nice feature of a low self discharge rate, perfect for use in a flashlight, remote control, clock, etc.
The low cell voltage is a detriment to its use though.
So I'm gathering from what you've said that NiMH is the victor and is the most sucessful battery for use in so-called mission-critical situations. However this doesn't mean that I can simply go out and buy off the shelf NiMH batteries, instead I need to buy high quality brands like Sanyo, which leaves Eneloop. And I'm already very well invested in that brand/type of cell.
I hope to be able to run a 30 watt draw continuiously (24/7) (core i3 2120-T) from my 12v 400AH AGM SLA battery bank and recharge it during the day from the sun. The math checks out anyway
http://www.rpc.com.au/solar-systems/off-grid-solar-power/residential-systems.html
www.rpc.com.au/information/faq/system-design/solar-power-calculator.html
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Not by a long shot buddy.
Ye have little faith in Solar power!
I'm sure they can program it to sleep until it reaches 90% of battery capacity or some such like that.
If thats the case then they can wait until it recharges completely and complete the mission.
It may take weeks or months though. How much time has it got left on that rock before its obliterated by something?
Yeah those SNAP modules are pretty big.
http://en.wikipedia.org/wiki/Radioi...ediaviewer/File:RTG_radiation_measurement.jpg
http://en.wikipedia.org/wiki/Radioi...ediaviewer/File:RTG_radiation_measurement.jpg
I believe atomic powered space craft has been outlawed internationally for a few reasons.
Every now and then rockets explode during take off like the last one destined to resupply the ISS in late October.
I think we are all better off if they do not carry nuclear reactors.
Also in space solar panels are cheaper, lighter and usually much more reliable and efficient than other forms of energy supplies.
Due EU politics/regulations.
More information in this video
https://www.youtube.com/watch?v=7Xm6y0LzlLo
For your question see min 50:00
Regards,
Tibi
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Even if nuclear batteries were allowed, they would probably not fit with the mission. Look at voyager and notice how far away the source is from the rest of the craft...
As Philae will only last a few months at best as the comet heads towards the sun and its facing the sun solar seems a good thing. shame a cliff got in the way
As Philae will only last a few months at best as the comet heads towards the sun and its facing the sun solar seems a good thing. shame a cliff got in the way
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