Given the MSL has a constant power source does that mean it can operate 24hrs and 40 minutes a day? Do they have driving lights or can drive with IR or other sensors? If so they could get a lot more science done than the MER mission. Or do they have to channel the power into heaters each evening?
How the Curiosity Rover's Nuclear Battery Works
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Re: How the Curiosity Rover's Nuclear Battery Works
#82Earlier quoted context omitted.
when we start building "breeder" reactors again. Plutonium is a byproduct of the breeder reactors when they create the type of uranium that can be used for nuclear bombs (this is one of the reasons that breeder reactors aren't popular). I was talking with one of the scientists at Ames last night, and apparently this is pretty much the last of NASA supply, since the US has significantly cut down on their production of…
That's not really accurate, but rather than explaining why, I'll just give the abbreviated rundown on plutonium: Plutonium 238 is a powerful alpha emitter with a half-life of 87.7 years, making it a great element for powering mars rovers. It's produced by exposing Neptunium 237 to neutron flux. You can get Np-237 out of nuclear waste from ordinary reactors. The US has mostly been buying Pu-238 from Russia, but we're…
well, i guess i learned not to blindly trust NASA scientists today. thanks for the info; that was pretty interesting.
Re: How the Curiosity Rover's Nuclear Battery Works
#83Earlier quoted context omitted.
Well it does - it stores nuclear binding energy that's unstable enough to be extracted and stable enough to last for x years. It's a nuclear battery just like convential ones are chemical batteries.
You're not clipping leads to the ends of it and getting current, though -- you're using thermocouples. It's more of a "heat battery", I suppose.
And now draw a black box around that whole system. What do you get? A voltage source, right?
Engineers usually don't care much about the principles of how something is made. As long as it can be abstracted to a known concept you're all good and you can integrate it with your given tools, e.g. a combinational circuit plan.
Re: How the Curiosity Rover's Nuclear Battery Works
#84NASA has almost run out of U238: http://www.popsci.com/military-aviation-amp-space/article/20... People promoting liquid thorium reactors have been pointing out that they could supply it: http://flibe-energy.com/products/
Plutonium 238 is NOT Uranium 238. There's shitloads of U238 in the world.
Crap, that's what I meant. Thanks.
Re: How the Curiosity Rover's Nuclear Battery Works
#85Earlier quoted context omitted.
The same safety implications as launching 10 pounds of anything twenty miles in the air, over an ocean, and subjecting it to an explosion. 10 pounds divided by any realistic footprint is negligible. Plutonium is dangerous stuff, sure, but it isn't 10 orders of magnitude more dangerous than anything else the way some people act like it is. It's just dangerous, not imbued with an evil malevolent spirit that wants to ir…
Per wikipedia[1]: A commonly cited quote by Ralph Nader, states that a pound of plutonium dust spread into the atmosphere would be enough to kill 8 billion people. However, the math shows that one pound of plutonium could kill no more than 2 million people by inhalation. So no need to worry. [1] https://en.wikipedia.org/wiki/Plutonium#Toxicity
You know what the problem with pulling something from Wikipedia is? It has citations. Specifically, for your pulled quote it cites this: http://www.phyast.pitt.edu/~blc/book/chapter13.html , and the section on "Plutonium Toxicity" about halfway down the page.
In particular, I commend to you the paragraphs starting with "In response, I offered to inhale publicly many times as much plutonium as he said was lethal." But more to my point:
"In summary, a pound of plutonium dispersed in a large city in the most effective way would cause an average of 19 deaths due to inhaling from the dust cloud during the first hour or so, with 7 additional deaths due to resuspension during the first year, and perhaps 1 more death over the remaining tens of thousands of years it remains in the top layers of soil. This gives and ultimate total of 27 eventual fatalities per pound of plutonium dispersed."
I can't quite get a direct cite, but I'm pretty sure the claim that a pound of plutonium dust can kill two million people is for a pound of plutonium dust being carefully doled out to two million people in precisely the quantities that will just barely kill them, because the previous paragraph is the description of what happens if you just sort of fling it at a city.
And an explosion from a rocket would actually be dispersed over a much larger area than merely a large city if it were going to hit anybody at all, because we don't launch anything immediately upwind of large cities. Think state-sized dispersal and you'd be closer.
"There have been fears expressed that we might contaminate the world with plutonium. However, a simple calculation show [26] that even if all the world's electric power were generated by plutonium-fueled reactors, and all of the plutonium ended up in the top layers of soil, it would not nearly double the radioactivity already there from natural sources, adding only a tiny fraction of 1% to the health hazard from that radioactivity."
"I have been closely associated professionally with questions of plutonium toxicity for several years, and the one thing that mystifies me is why the antinuclear movement has devoted so much energy to trying to convince the public that it is an important public health hazard. Those with scientific background among them must realize that it is a phony issue. There is nothing in the scientific literature to support their claims. There is nothing scientifically special about plutonium that would make it more toxic than many other radioactive elements. Its long half life makes it less dangerous rather than more dangerous, as is often implied; each radioactive atom can shoot off only one salvo of radiation, so, for example, if half of them do so within 25 years, as for a material with a 25-year half life, there is a thousand times more radiation per minute than emissions spread over 25,000 years, as in the case of plutonium.
"No other element has had its behavior so carefully studied, with innumerable animal and plant experiments, copious chemical research, careful observation of exposed humans, environmental monitoring of fallout from bomb tests, and so on. Lack of information can therefore hardly be an issue. I can only conclude that the campaign to frighten the public about plutonium toxicity must be political to the core. Considering the fact that plutonium toxicity is a strictly scientific question, this is a most reprehensible situation."
And thanks for leading me to the awesome link to post next time this comes up.
Re: How the Curiosity Rover's Nuclear Battery Works
#86Earlier quoted context omitted.
I think the OP is looking at using their stove as the heat source, not a nuclear battery. On that note, the idea you're talking about was actually considered for a little while for public use until the dangers were found to outweigh the benefits.
Right now I'm thinking about a stove, but this nuclear battery has me thinking. I am wondering if it would be possible to buy or build such a nuclear battery.
Governments tend to frown on the personal acquisition of radioactive isotopes. Well, there's a tiny bit in your smoke detector, but if you managed to get the eleven pounds that are in the MSL's RTG you'd make the international news.
Pu-238 isn't naturally occurring, and nobody makes it anymore. The US bought the plutonium that went into the MSL from the Russians, who are starting to run out themselves.
The other problem with RTGs is they get less efficient as they get larger. The one in the MSL only produces 125 watts, which will decay to about 100 watts at the end of its 14 year lifetime. That's not a lot of power.
Re: How the Curiosity Rover's Nuclear Battery Works
#87So, when can I get a nuclear car? And what's the insurance gonna cost?
when we start building "breeder" reactors again. Plutonium is a byproduct of the breeder reactors when they create the type of uranium that can be used for nuclear bombs (this is one of the reasons that breeder reactors aren't popular). I was talking with one of the scientists at Ames last night, and apparently this is pretty much the last of NASA supply, since the US has significantly cut down on their production of…
The type of Uranium used in nuclear weapons (fissile U235) isn't created in reactors; it's purified from natural Uranium, which is almost entirely non-fissile U238 but contains a small proportion of U235.
Most commerical enrichment of Uranium uses gas centrifuges to separate the heavier isotopes from the lighter.
Re: How the Curiosity Rover's Nuclear Battery Works
#88Earlier quoted context omitted.
Right now I'm thinking about a stove, but this nuclear battery has me thinking. I am wondering if it would be possible to buy or build such a nuclear battery.
Certainly to build one the theory behind it wouldn't be tough, it'd operate on the same principles as the stove setup. To buy though? There's a story of a boy scout who did something similar as part of a personal experiment in the 90's. (Before getting raided out of fear by the FBI) Will have to find that story again. In almost every country the materials required are tightly regulated and getting permission even in…
The book is The Radioactive Boyscout
http://www.amazon.com/The-Radioactive-Boy-Scout-Backyard/dp/...
I read the book. from what I remember he started with smoke detectors and worked his way up from there. Just a few letters to some supply houses saying he was a researcher or something. he effectively mail ordered his radioactive sources I think.
Re: How the Curiosity Rover's Nuclear Battery Works
#89Earlier quoted context omitted.
That's a good point... while in theory is probably could drive at night, it probably isn't a good idea to have a rover on a different planet driving around in the dark.
Is radio communication with the rover even possible at night? We only have line of sight to mars during the martian daytime.
Not sure about this specific mission but I think we have had satellites around mars in the past that have helped relay messages when line of sight isn't available.
Re: How the Curiosity Rover's Nuclear Battery Works
#90Earlier quoted context omitted.
Per wikipedia[1]: A commonly cited quote by Ralph Nader, states that a pound of plutonium dust spread into the atmosphere would be enough to kill 8 billion people. However, the math shows that one pound of plutonium could kill no more than 2 million people by inhalation. So no need to worry. [1] https://en.wikipedia.org/wiki/Plutonium#Toxicity
You know what the problem with pulling something from Wikipedia is? It has citations. Specifically, for your pulled quote it cites this: http://www.phyast.pitt.edu/~blc/book/chapter13.html , and the section on "Plutonium Toxicity" about halfway down the page. In particular, I commend to you the paragraphs starting with "In response, I offered to inhale publicly many times as much plutonium as he said was lethal." But…
The quote was pulled to put the "same risk as 10 pound of anything" claim into perspective, not to give an exhaustive treatment of plutonium ( and specifically Pu 238) dispersement.
The claim of 2 million cancers per pound of Pu is sketched out just at the start of the subchapter "Plutonium Toxicity" in your reference, it depends on a model how long the Pu remains in the lung. ( I suspect Naders number of 8e+9 death is obtained by dividing 1 Pound by an estimate of the lethal dose.)
Additionally the source talks presumably of Pu 239 (at least the numbers in the appendix are for Pu 239) while the activity ( and therefore the dosage) of Pu 238 is about a factor of 200 higher. So we can estimate 4000 death per pound of Pu 238 dispersed in the atmosphere over an city. ( Dispersing over an Ocean instead of a city would lower this estimate of course considerably. What could possibly go wrong ...)
And you are welcome, this seems to be one of the better texts one can cite about the dangers of Pu. (I will be happy to point out the several best case estimates the text makes.)