Jan's comment about an RTG is fairly apt, though. I wonder how much work went in to their selection of a very short-lived battery system for Philae.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Brings a new meaning to the term "range anxiety".
There are plenty of discussions of that very subject out on the Net.
One summary I read said something of the following sort. Initially, a combined US/ESA comet landing mission was under discussion, and an RTG was "on the table". However, the US canceled its mission, and the ESA decided to "go it alone".
The EAS countries did not have the technology base to manufacture their own RTG or provide the necessary plutonium. Only the US and the Soviet Union (or was it already just Russia at the time?) did, and they did *not* make RTGs available for sale. There was, apparently, a shortage of the necessary isotope at the time (Pu-238?) and the countries which could make and refine it, weren't being very generous with it.
The cost to the ESA of developing their own RTG technology would have been prohibitive - it would have "blown" the budget for the mission. And (as has been alluded to) there was concern about accidents with the RTG, especially during launch. There have been several known accidents involving RTG-powered spacecraft, and at least two of them have resulted in earthly contamination by the radioactive "fuel".
So, it sounds like "best-available battery plus best-available solar panels" was the best ESA could do, with the budget and resources available for the mission. Less than ideal from the power- survivability point of view, it's now clear... but if going for an RTG would have killed the mission due to *either* cost or political pressure, it would have been a poor choice.
I see that David Platt responded to this thought. They had a plan and if it had gone well no one would have questioned it.
To be honest, I think the idea of harpooning the meteor sounds like something from a sci-fi movie but I guess had it deployed it could have worked.
I think they still have a shot at the solar panels charging the batteries which improves as they get closer to the sun. But I guess the chances of moving it to a better spot are done, no?
-- Rick
The Mojave has been more overcast than usual for at least the last five years. If they based the data on solar power from a decade ago, they would not meet their goals.
On the other hand, the desert is soggy and green, which may be beneficial to somebody. In my experience, the soggy desert has led to more cattle eating by the highway due to water displaced by the crowned impervious roadway. I've seen some might nasty "cattle mutilations" in Nevada. Not from hungry space aliens, but bovine-automobile collisions.
As you know, global climate change has put more moisture in the atmosphere. When it used to be just baking hot in Las Vegas, it is now muggy with lightning. Sometimes rain, but more often virga.
There is a lot to be said for what Germany is doing regarding solar power, basically lots of photovoltaic. Even with overcast, they still provide some power. There is no complicated steam cycle to maintain.
I always find it entertaining that the tea baggers love spending money on the DoD. Yet the DoD is all in on climate change. This has been true for years.
Of course consistency is not something the tea baggers excel at.
The largest heliostat based solar power plant running is the PS20 in Spain (20 MW).
Apparently scaling up to 400 MW was not that easy.
Sounds like they built it in the wrong place and/or that they underestimated the wind loading on the tracking mirrors. Maybe they just need more window cleaners to keep the mirrors clean of dust!
Parabolic solar trough design is probably the way to go. Personally I favour preheating in a mechanically simpler non focussing concentrator first which still works to some extent even with diffuse light.
BTW: I am impressed that you haven't sided with the Luddites!
-- Regards, Martin Brown
In areas, in which CSP is sensible, the peak load is in the afternoon due to air conditioning.
Being able to run the CSP for a few hours after sunset should be enough, no need for all night operation.
Neither did the sampling hammer which apparently broke when they used it to hit the surface hard to try and dislodge the lander from its boulder trap. Basically they were dealt a poor hand after the lander bounced and came to rest inevitably against some outcrop and at a weird angle. It did rather well considering that it was 1990's imaging technology that had been in suspended animation for almost a decade.
The effective weight of the lander was so small in the asteroids gravity field that they hoped that the hammer and sample drill would serve as a means to short hop if needed. As it was the asteroid surface proved to be much tougher and rugged than anyone had expected.
Most people were expecting to see a fairly smooth dirty snowball of mostly ice not something angular that looked like a quarry spoil heap!
I did wonder if they had a mass spec capable of doing a rare earth signature for the rock to see what type of meteorite it would be.
That and sleep deprivation of the key players in the command centre.
It was still a very good outing for a robotic probe although a bit sad that it ended prematurely with "out of battery warning". It is possible that as the comet approaches the sun and it starts to outgas that the landers PV array will then get enough sunlight to recharge the battery.
Previous comets like Hale-Bopp which have been surveyed from the ground had very interesting core behaviour which is captured in this video clip by CCD camera maker Terry Platt:
This time with an orbiter tagging along we will get a closeup view of what actually happens at the nucleus in fantastic detail as a tail develops. Assuming that is that it develops a tail. Comets are amazingly fickle and predictions of their brightness notoriously difficult (usually erring on the too optimistic side). Several trumpetted loudly as "comet of the century" have been damp squibs.
-- Regards, Martin Brown
and can store enough hot molten salts in insulated tanks to keep on genera ting electricity all through the night.
all and only stores about six hours worth of after-dark generating capacity - bigger tanks have longer thermal time constants for the same level of in sulation.
nough when there's high altitude haze, it's an additional expense (and tric ky to do after you've put the system together) but it's something you can d o.
They did build a pilot:
The molten salts have to be heated to 550oC to stay molten, so some kind of aux power source has to be used when they're used as heat transfer fluids. Ivanpah may not be using molten salt heat storage because of the over-abun dance of sunlight and its peak output capacity. There's nothing preventing them from using the excess thermal/electric energy production to power an a dd-on storage system later:
On a sunny day (Mon, 17 Nov 2014 15:52:14 -0800 (PST)) it happened Bill Sloman wrote in :
You can buy large flexible freshnel lenses to cook food out in the boonies. Some of those were ment as magnifiers for TV panels as projectors I think, for example (there are hundreds of different ones):
On a sunny day (Mon, 17 Nov 2014 17:47:26 -0800 (PST)) it happened Bill Sloman wrote in :
Down under there is lots of Uranium too. It should be used, not only exported.
Sydney would be a good place for a nuke plant.
On a sunny day (Mon, 17 Nov 2014 18:19:18 -0800) it happened snipped-for-privacy@coop.radagast.org (David Platt) wrote in :
Yea, I do not see any real RTG on ebay yet, but with the Chinese building nuculear plant after nuculear plant maybe it will happen soon.
Have not checked Alibaba yet...
Not in my back yard. But it already has a research reactor at Lucas Heights - two in fact, one dating from 1958 which is now in the process of being decommissioned, while it's replacement started up in 2007.
Both are about 30km southwest of where we live, which is a little closer than I really like. But they are Australia's only nuclear reactors - nobody ever bothered to build any for power generation.
One of my friends from undergraduate days was a member of the team that worked out a way of dealing with nuclear waste
I wouldn't dream of trying to talk to him about it.
-- Bill Sloman, Sydney
Sounds like they had no idea what the surface characteristics were like, within a huge factor, so they tried to include a few options.
'E's not dead.. no, no, 'e's uh,...he's resting.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
That bloody thing already looks like the Tower of Sauron...
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
You can buy trtium stuff online (not in the US), but apparently it takes a fair bit to get the kind of boost one might want. A South African guy told me it was a fair percentage of the total cost of the entire firecracker.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On a sunny day (Tue, 18 Nov 2014 08:49:08 -0500) it happened Spehro Pefhany wrote in :
Yes I have bought tritium 'fishing lights' online.
After posting that, I remembered many many years ago seeing RTGs for sale on internet (some company sells them). The price was not that high, and I think they were used in some US military vehicles. Forgot the details. ESA should have googled. Basically, on this side of the universum, everything is for sale.
The main problem would be cooling (works on temperature difference) you need to radiate that heat out into vacuum, and also keep radiation sensitive components away. Size would be bigger. IIRC the Voyagers have the RTG on some extended boom.
Five years is sort of approaching "usual."
Germany is ramping up its coal-fired power generation. They are phasing out nukes and can't trust the Russians for gas.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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