Without Plutonium, Deep-Space Probe Missions May Sputter Out 268
cold fjord writes with this excerpt from Wired: "Most of what humanity knows about the outer planets came back to Earth on plutonium power. ... The characteristics of this metal's radioactive decay make it a super-fuel. ... there is no other viable option. Solar power is too weak, chemical batteries don't last, nuclear fission systems are too heavy. So, we depend on plutonium-238, a fuel largely acquired as by-product of making nuclear weapons. But there's a problem: We've almost run out. 'We've got enough to last to the end of this decade. That's it,' said Steve Johnson, a nuclear chemist at Idaho National Laboratory. And it's not just the U.S. reserves that are in jeopardy. The entire planet's stores are nearly depleted. ... what's left has already been spoken for and then some. ... Political ignorance and shortsighted squabbling, along with false promises from Russia, and penny-wise management of NASA's ever-thinning budget still stand in the way of a robust plutonium-238 production system." The plutonium shortage has been deepening for a long time, leading to some creative solutions. The Wired article alludes to the NASA project underway to create more, but leans toward gloom.
Why are nuclear fission systems too heavy? (Score:2, Interesting)
I don't know anything about them, but I have to ask why anything is too heavy in space? Is it too heavy when assembled on earth?
Re:Why are nuclear fission systems too heavy? (Score:5, Informative)
Re:Why are nuclear fission systems too heavy? (Score:5, Funny)
Mass doesn't disappear just because something is in outer space. That mass carries with it a certain amount of inertia, and the heavier something is on earth, the more energy will be required to manipulate it with any kind of acceleration, even in space.
Avast, ye swab, once ye space corsair be a'sail in deep space, it be carried along on it's momentum as thar be little friction in a vacuum. Life support, unless ye enjoy sippin yer tea at 4 K, be yer greater concern. Also, ye be needin' a wee bit o' energy for changin the tack of yer corsair. Arr. ox)P-)
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>it's
Land-lubber.
Re:Why are nuclear fission systems too heavy? (Score:5, Funny)
>it's
Land-lubber.
Twasn't an apostrophe, ye dog. It be the stray mark of a sharp cutlass.
Re:Why are nuclear fission systems too heavy? (Score:5, Informative)
Shoving something out of ye olde gravity well is always expensive, if you go over the weight/size limit of one of the reasonably-commodified launch systems, things go from 'expensive' to 'heroically expensive'.
Depending on exactly what trajectory you have in mind, a more massive craft may also require more fuel/more powerful thrusters if you are making any course corrections along the way.
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I usually resort to YouTube Walkthroughs when I run at Heroic Level.
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Two issues
1) You have to get the things into space
2) Stuff still has mass in space and thus a higher mass requires a higher force to accelerate compared to a less massive object.
Hope that helps.
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Yes, lifting facilities like Three Mile Island and Chernobyl off the ground takes a bit of effort
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I honestly dont know, just asking.
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A design concern for nuclear reactors is cooling. Nuclear subs are conveniently surrounded by an infinite heat sink of cold water, so cooling them is easy. A nuclear reactor desgined for space would need a completely different cooling system, which is a major part of the design.
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They would, most of those facilities is dedicated to cooling and shielding. They may not be able to use the reactor from a sub, and I'm pretty sure they couldn't, but that's merely because they're designed for terrestrial use and aren't designed to be put onto a rocket.
The other issue is that putting nuclear things into orbit is something that has to be done cautiously. If they blow up or fail to make it into orbit, they'll spew tons of radioactive particles all over the place. And paranoid states might thi
Re:Why are nuclear fission systems too heavy? (Score:5, Interesting)
Probably not; a sub's reactor would likely depend on the presence of the ocean for part of its cooling system (cooling is always a big problem in space -- basically it can only be done with radiators, which isn't very efficient), and is surely way overpowered for most missions.
The US and Russia have sent up actual reactors before. The US had SNAP [wikipedia.org] and the USSR had BES [wikipedia.org].
But you really don't need nuclear power sources at all unless you're either far from the sun (beyond the orbit of Mars, usually), have serious power needs that modern solar power isn't sufficient for (the recently landed Curiosity rover on Mars uses an RTG for main power), or need heat to keep systems from getting too cold (the solar powered Mars rovers had small RTGs in them for heating purposes, IIRC).
Re:Why are nuclear fission systems too heavy? (Score:5, Insightful)
Likely because they need to be wrapped up in so much stuff so they're not killing everyone nearby.
And as far as I recall, you essentially need lead to block the radiation.
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Why not shield the humans instead? Then just keep them away from it during launch. Not like irradiating space is a concern.
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Stop it! you'll give the climate change denialists ideas.
"It's not a tragedy - it's a MARKET OPPORTUNITY for radiation shields!"
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You know, my practical experience in nuclear shielding is non-existent. My theoretical knowledge only slightly less non-existent. :-P
But I should think the minimum safe distance from an unshielded reactor would preclude anybody actually getting near enough the spacecraft to prep it for launch.
I also don't know enough about them to say if an unshielded reactor is essentially a bomb.
I'm sure if it was a viable alternative, someone at NASA would be considering it.
Re:Why are nuclear fission systems too heavy? (Score:5, Informative)
But I should think the minimum safe distance from an unshielded reactor would preclude anybody actually getting near enough the spacecraft to prep it for launch.
A fission reactor that has been assembled, but never operated, does not produce much radiation. Enriched uranium and/or pure plutonium are not particularly dangerous (unless inhaled or ingested). It is the fission byproducts from actually operating the reactor that are dangerous. Even this minimal radiation could be avoided by using temporary shielding that is removed (possibly by a robot) immediately before the launch.
Re:Irresponsible (Score:5, Insightful)
That big yellow ball in the sky is emitting more radiation than that little chunk of P238. You might not be aware of this but without the earths magnetic field and atmosphere in the way that little ball of light would kill you very very quickly.
As others have already noted that P238 isn't really dangerous unless you are going to eat it. Though plutonium is believed to be an entirely a man-made material uranium and all the other naturally occurring radioactive elements exist outside the earth as well as on it. The several ounces on a space probe used as a thermolytic generator is insignificant entirely.
Re:Irresponsible (Score:4, Funny)
Exactly!
Don't Pollute Space With Radiation!
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OMG we're contaminating space with radiation! Think of the space ponies and the lunar ecology.
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Re:Irresponsible (Score:5, Insightful)
See, this is why people who don't understand radiation shouldn't talk about it.
4.5 billion years of half-life means that the decay rate - the actual process that emits radiation - is so absurdly slow that the material itself is just not dangerous. The dangerous stuff is, almost by definition, the stuff with *short* half-lives. A gram of material with a millisecond half-life will release more radiation in one second than a kilo of U-238 will in a century, assuming they undergo the same types of decay. Secondary decay of the uranium will be a bigger problem, and still not much of one.
In fact, people have incorporated U-238 into everything from building bricks for houses to the glaze on pottery. Let me make that clear for you again: people have built houses out of material containing uranium ore. They have then lived out their natural lives - and sometimes the lives of several generations of a family - in those houses.
Calling it "spewing poison" is bullshit of the first degree. It's probably more dangerous to eat bananas (which contain radioactive potassium isotopes, in tiny amounts, but with much shorter half-lives) than it is to have U-238 all around you. Even pure, enriched U-235, while not something you'd want to hold in your hand, is not particularly dangerous to handle so long as you keep it away from neutron guns or reflectors, and below critical mass.
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The safe distance for plutonium before it is being used is that you can hold it in your hand. I have handled Uranium, been there when Plutonium was handled (although not 238). If they transport the reactor into space conventionally and build it up there the only problem is the weight. There are lots of viable options available for consideration, I think that this is just smoke to prepare us for another round of unnecessary weapons building.
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It isn't.
What it is is unsafe to stand near, where "near" is any closer than several hundred yards.
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Actually, water works quite well to block neutrons (better than lead, in fact), alpha and beta radiation. The lead is mostly for the gammas.
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But it's the gamma radiation which is the one we're most concerned about, no?
Blocking the least dangerous stuff isn't the issue.
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In a space-borne system? I would think that neutron-embrittlement of your spacecraft would be more a concern than a few more gammas.
Admittedly, the gammas might interfere with those excrutiatingly sensitive sensors you're using in your deep-space probe, but a patch of lead between the power source and the sensor would deal with that nicely - you don't need spherical coverage of the power source, unless it's the center of the pro
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No, Plutonium is an alpha emitter. When it goes bang it gives off gamma, quite a lot.
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Nah you could block the radiation with any number of materials, its just that lead happens to be dense enough to do it reasonably. Little is to be gained by pushing concrete walls several feet thick into space.
Frankly I think its as much about complexity as anything. an RTG is fairly simple, basically a nuclear battery, with radioactive materials as a stand in for chemical bonds... when they break down, they cause heating, which is harvested for energy...simple.
Now a nuclear fission pile can be simple too..
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And as far as I recall, you essentially need lead to block the radiation.
Not necessarily. Instead of shielding, you can use distance. Fission reactors produce little radiation until they start operating. So you launch into space, then separate your main payload from the reactor using a long conductive tether. Then fire up the reactor.
Re:Why are nuclear fission systems too heavy? (Score:4, Informative)
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What.....
"Dehydrate them as much as possible, because we need to get the water back. Those solid waste products get put into a bag, put right back against the wall,"
Huh? Isn't the very reason its a good radiation shield because...it contains a very high percentage of water...which is an excellent radiation shield? It seems to me that when you dehydrate it, you would lose that.
Re:Why are nuclear fission systems too heavy? (Score:5, Informative)
A very long time ago I was in the Navy, sailing about in a nuclear submarine.
The power plant of that submarine outmassed the ISS.
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That's not surprising, the components are heavy and dense. Whereas the ISS is mostly air.
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0 G doesn't mean 0 Mass. The correct term would have been Nuclear Fission is too massive.
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I imagine it is because of the shielding required.
Pu-238 decays to uranium-234 via an alpha particle emission
uranium-234 decays very slowly to thorium-230 via an another alpha particle emission
Alpha emissions are really easy to shield against because they are charged particles. They don't even penetrate skin.
Fission, on the other hand produces abundant neutrons and gamma rays. The only way to stop them is with a lot of mass.
Still, it shouldn't be all that bad. A yet to be started reactor doesn't produce
Re:Why are nuclear fission systems too heavy? (Score:4, Informative)
Consider it costs from $2000 (Falcon 9) to $30,000 (Pegasus) per lb. to launch a payload from Earth. And the present maximum launch capability is, IIRC, about 150 tons. Anything bigger has to be launched in pieces. For probes going anywhere besides Earth orbit, that 150 tons has to include the additional rocket stage to push the probe out of the Earth's gravitational influence. So the probe itself is likely to be under 1/2 ton. Now, make a reactor that fits.
Having said that, I've been casually wondering if a small MSR (Thorium) reactor could be used. It provides both heat and power, and its characteristics make it plausible that an under-10-ton reactor could be made. Such a reactor could provide the heat for propulsion of the probe, plus lots of electricity, and it can be turned on and off at will, or throttled. So this might work in a large vehicle. Of course nobody has even started on the engineering required to make a liquid reactor work in microgravity (no convection, no heat conduction to dump waste heat).
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There's so much wrong with this that it's difficult where to start. It's a Gish Gallop of half-remembered anecdotes and self-reinforcing delusions...
No-one has built and operated a thorium-based molten-salt reactor. The US had an molten-salt reactor fuelled purely with U-233 in intermittent operation for a few years back in the 60s, it produced no electricity and ran at operating levels up to about 7MW thermal output which was dumped to air. It proved that fissioning U-233 in molten salt will work but back
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As others point out, things don't lose their mass just because they're in space.
However, the problem with reactors isn't that they're "too heavy", they're lighter than an RTG with equivalent power output would be. The problem is that they're too big. An RTG is a lump of passively decaying material surrounded by thermoelectric converters and heat sinks, there's no hard lower limit in size. A reactor has to have enough material to sustain a chain reaction, which imposes a stricter minimum mass.
If your mission
Re:Why are nuclear fission systems too heavy? (Score:5, Informative)
WHAT WOULD HAPPEN?
The reactor would mostly likely fall into the ocean, where it would be retrieved intact. RTGs are designed to survive a launch failure, and several accidents have
already happened [wikipedia.org], without any significant release of radiation.
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WHAT WOULD HAPPEN?
What? Say your Plutonium-Powered Satellite rides up on a booster, that does the same thing as "Challenger".
How far does the atomised Plutonium disperse?
I for one, really don't like the odds.
Nothing in Challenger exploded - the vehicle turned broad-side in the supersonic airstream, ripping the fuel tank open and the exposed fuel just burnt in the air. The crew compartment remained intact and continued on a ballistic trajectory and there's evidence that the crew even survived the midair disassembly of the shuttle.
So what would happen if you had a few kilos of plutonium on board? Well... not much - you've got a solid lump of plutonium weighing a few kilos. Remember, the crew compartment surviv
1985 (Score:5, Funny)
I'm sure that in 1985, plutonium is available in every corner drugstore, but in 2014, it's a little hard to come by.
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beautiful BTTF reference. I applaud you, sir!
Re:1985 (Score:5, Funny)
This is where Mr. Fusion would really come in handy.
I beg to differ...unless you happen to be aware of a stash of beer cans and banana peels in space.
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No, but there's plenty of teapots out there you can use.
Upside (Score:5, Insightful)
Re:Upside (Score:4, Funny)
But the zombie apocalypse is still ok, right?
Re:Upside (Score:4, Insightful)
eh? we're maintaining thousands of bombs for just that
Re:Upside (Score:4, Informative)
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While you are correct that maintaining them doesn't, dismantling them does.
Re:Upside (Score:4, Informative)
Not correct - the plutonium in nuclear weapons is Pu-239, not the Pu-238 that we desire for RTGs. You can't extract useful quantities of Pu-238 from a nuclear weapon. Conversely, you can't use Pu-238 to make a nuclear (fission) weapon. You could make a dirty bomb, I suppose, but that's more due to plutonium being a toxic heavy metal than its radioactivity.
No but (Score:2)
Re:Upside (Score:5, Informative)
Pu-238 isn't usable for nuclear weapons. The only use to which it is put is power generation. The only connection between Pu-238 and nuclear weapons, in fact, is that weapons production facilities naturally make good production facilities for Pu-238.
mine Pluto (Score:2, Funny)
We could have mined plutonium on Pluto, but they went and demoted it to a dwarf planet.
Just watch the movie UHF (Score:5, Funny)
Apparently Philo gives the secret of how to make plutonium from common household objects.
Another reason to build LFTRs (Score:5, Interesting)
One of the helpful byproducts of a Liquid Floride Thorium Reactor (LFTR) is Pu-238
Source: http://flibe-energy.com/?page_id=64
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Can you seriously not manage to add anchor tags to your link? A few extra characters to make everyone's life a bit easier, is that so much to ask?
After 15 years of Slashdot adding features no one wants to the site, could they not manage to add one they did? Like auto-linking?
(Although, if we're going down that route, please add story moderation first!)
rather sensationalist (Score:5, Informative)
there are alternative isotopes, with much longer half lives even if battery weight is three or five times what a pu-238 one would be. not the heaviest thing in a spacecraft...anyway, the equipment to make the pu-238 exists, just a matter of getting serious about making the stuff
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Longer half-life = heavier battery. More or less in direct proportion. If you use something with a 1000 year halflife, the battery will mass 11+ times as much, for a given power output.
Re:rather sensationalist (Score:5, Informative)
The Russians always used strontium 90. Slightly lower heat output and shorter (~30 vs ~90 yr) half life. Much cheaper.
Of course the reduced half life means power will drop off sooner, but I'd think thermocouple aging factors weigh more heavy anyway (for the first decade or two, at least). Maybe not?
So for long missions You'd want something else, I guess.
Re:rather sensationalist (Score:5, Informative)
There are other isotopes that have longer half-lives, but they are not alternatives.
In order to be a decent RTG power source, and isotope needs to have:
1. Good power density
2. Good half-life
3. Require little to no shielding
Plutonium 238 is the ideal fuel because it is the best (or close to it) in all three categories. Strontium-90 has a much shorter half-life and lower decay energy. Polonium-210 has a high power density but comes at the cost of an extremely short half-life (138 days). Curium-242/244 is a gamma and neutron emitter so requires heavy shielding.
The only reasonable alternative at this time is the same material they put into smoke detectors: Americium-241. It has a much longer half-life than plutonium, however due to that half-life it only has about 1/4 of the power density. It does emit more penetrating radiation but doesn't require a lot of shielding.
Well then, there's an easy answer. (Score:4, Informative)
Fire up Rocky Flats [wikipedia.org] and Hanford [wikipedia.org] again to start building the next generation of nukes! That way we can get enough Pu-238 to power our deep space ambitions! I read on "The Onion" that the North Koreans are already building their deep space probe Kim Il Wang 1 which will reach out and spread communism to our neighboring galaxies! We can't afford to have a deep space probe power gap! We must contain the Red Menace!
Frankly with all the carcinogens in our air [yahoo.com], amoebas [go.com] in our water and a third of us with Toxoplasmosis, [wikipedia.org] what's a little radiation folks?
We are missing so many opportunties here (Score:3)
Now, with that said, we STILL need plutonium. In particular, deep space probes need not just power, but heat. Plutonium is far better for both of that.
Re:We are missing so many opportunties here (Score:4, Funny)
If we start filtering that water over by their nukes, we can create a number of batteries that can provide power for mars and the moon.
Except we don't want our first probe to make contact with an alien civilization to be powered by radioactive sea bass. There's just no good explanation for that.
Voyage To The Bottom Of The Sea. (Score:5, Funny)
By 2005, according a Department of Energy report (.pdf), the U.S. government owned 87 pounds, of which roughly two-thirds was designated for national security projects, likely to power deep-sea espionage hardware.
What on earth do they need deep sea espionage for? Are they trying to spy on Cthulhu or something?
Re:Voyage To The Bottom Of The Sea. (Score:5, Informative)
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What on earth do they need deep sea espionage for?
Tapping submarine cables.
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Tapping submarine cables.
I've heard of those drive-by-wire systems! What an ingenuous way to steer a military submarine!
Cables (Score:2)
Phone cables don't cut and splice themselves, pal.
Just start reprocessing spent fuel (Score:3)
Problem solved.. Actually, multiple problems get solved with this one.
Reprocess existing spent fuel rods that are soaking away in cooling pools world wide. We literally have tons of this material if we would just go process the spent fuel we already have on hand.
As a bonus, we will get a lot of useable fuel out of the process PLUS drastically reduce the size of the high level radioactive waste we have to store...
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b-b-b-but what about those super insightful laws that prevent breeder reactors needed to reprocess spent fuel rods.
It would take a-lot of money to out-"lobby" nuclear industry insiders to change those laws.
Ready supply (Score:2)
Re:Ready supply (Score:5, Insightful)
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The way I see it, we just need to shave one of those neutrons off. Like, say, with another neutron. What could possibly go wrong?
HowTo (Score:3, Insightful)
* Build a moon base
* Setup solarpanels for lots of power generation
* Build infrastructure
* Extract lots of Helium 3
* Build a monorail assisted launch system
* Build space ship parts
* Build a Tokamak in parts, small enough to assemble in space
* Launch all the s#!+ into space and assemble all the parts
* Remember to launch a couple of tons of H3 too
* Go!
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It might help if we figured out how to make a working fusion reactor on Earth first. The problem with an 3He reactor is not simply a shortage of 3He.
commercialize it (Score:2)
There are lots of uses for RTGs (including medical devices), but they have been hamstrung by anti-nuclear hysteria. If Pu 238 was more widely adopted commercially, these shortages would disappear.
Reason: Price gouging by Dept of Energy (Score:4, Informative)
Re:Reason: Price gouging by Dept of Energy (Score:4, Informative)
If you go through the link you posted to one more deep you get this statement, "The administration of President Barack Obama asked for $20 million for the Pu-238 program in 2012, split evenly between NASA and the Energy Department. Lawmakers also denied funding for the program in the Energy Department’s 2010 and 2011 budgets."
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Fear-mongering. We are restarting production. (Score:3)
This is fear-mongering. We are restarting production, and the new Advanced Sterling Radioisotope Generators we have developed produce three times the electricity for the same amount of Pu-238. ...that is, if NASA's budget isn't cut by the Republican house. Sequester is really hampering what NASA can do.
I thought they restarted production back in March (Score:5, Informative)
I thought NASA struck a deal with DOE back in March to do 2 kilos per year of Pu-238 back in March. Did it get de-funded or something? http://www.universetoday.com/100875/u-s-to-restart-plutonium-production-for-deep-space-exploration/ [universetoday.com]
The Way of Things (Score:2)
So what they're saying is, "No war - No fun."
Isn't that the way it's always worked?
Tell me again.... (Score:2)
why a square mile of reflective mylar and a high efficiency panel won't power a satellite for a good long while?
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Ignoring all the challenges of creating an parabolic shape a mile across, have you seen what the sun looks like from Voyager 1?
Many other isotypes and generator types (Score:4, Informative)
Many other isotypes and generator types.
Strontium-90 is a good substitute for shorter trips. Americium-241 is very close to being a reality for longer trips. There is also the Safe Affordable Fission Engine project https://en.wikipedia.org/wiki/Safe_Affordable_Fission_Engine [wikipedia.org]
But there is another type of electro-mechanical rotating generator designed for Russian craft, TOPAZ-II, but, unfortunately, it's far too heavy.
Re:112 tonnes enough? (Score:5, Funny)
Wrong Plutonium! We need US Plutonium which uses a different plug configuration and is only 120V, not that funny 204V stuff you use in the UK you insensitive clod! Shit, NASA would have to buy like one of those travel adapters or something to make UK plutonium work in NASA probes and that would probably like throw off the gyroscopes or something.
Re:112 tonnes enough? (Score:5, Informative)
That's the wrong kind of Plutonium. RTGs need Plutonium-238. That stockpile is Plutonium-239, 240, 241, and a bit of 242.
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That's the wrong kind of Plutonium. RTGs need Plutonium-238. That stockpile is Plutonium-239, 240, 241, and a bit of 242.
Yeah, but dat shiz is da BOMB.
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Pu-238 has a half-life of 87 years; I'm guessing they use enough that the reaction speeds up a bit, otherwise Voyager wouldn't be running out so soon.
Pu-241 has a half-life of 14 years; if the fission is energetic enough, would it be suitable for shorter missions?
Pu-240 has a half-life of 6500 years; this would seem to be suitable for long missions but would require 75 times as much fuel (?)
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1. No. The half life remains constant. It's not running out per se, but rather there's not that much margin for loss available. The Voyagers need a significant amount of their RTG's output just to maintain their basic functions, leaving the remainder to power any instruments, so they're approaching the point (sometime in the next 10-15 years) where they won't have enough spare power to run any of them, and then eventually won't have enough power to function at all, though I believe they will have gone ou
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That's Pu-239 they're talking about. Fissionable, 25KY halflife.
The 25KYear halflife means you'd need 284 times as much Pu239 as you'd need Pu238.
So, for Voyager, we'd need about 3800 kg of Pu239. Which is enough to manufacture ~600 nuclear weapons (Fatman used only 6.2kg of Pu-239 - we've gotten better designs since).
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Wrong kind for this. RTGs need Pu238.
But as for that article, it's just more evidence that you're not allowed in politics unless you beat your skull with a brick until your IQ falls below 60.
Here we are with this energy shortage and on top of that we're stuck with this massive stockpile of free fuel we have no idea what to do with. I guess we'll bury it.
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Can you seriously not manage to add anchor tags to your link?
Seriously! You don't even have to go whole hog with anchor tags: just tack a <url: on the front and a > on the end.
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What we need is naquadah.