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Without Plutonium, Deep-Space Probe Missions May Sputter Out
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.
I'm sure that in 1985, plutonium is available in every corner drugstore, but in 2014, it's a little hard to come by.
Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats. -HLM
We are no longer creating bombs for a nuclear apocalypse.
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.
File under 'M' for 'Manic ranting'
We could have mined plutonium on Pluto, but they went and demoted it to a dwarf planet.
Launch price.
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.
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.
Yes, lifting facilities like Three Mile Island and Chernobyl off the ground takes a bit of effort
“He’s not deformed, he’s just drunk!”
Apparently Philo gives the secret of how to make plutonium from common household objects.
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.
Lost at C:>. Found at C.
One of the helpful byproducts of a Liquid Floride Thorium Reactor (LFTR) is Pu-238
Source: http://flibe-energy.com/?page_id=64
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-)
A feeling of having made the same mistake before: Deja Foobar
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
>it's
Land-lubber.
Fire up Rocky Flats and Hanford 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, amoebas in our water and a third of us with Toxoplasmosis, what's a little radiation folks?
Harrison's Postulate - "For every action there is an equal and opposite criticism"
Japan is LOADED with a number of beta emitters that are perfect for making nuclear batteries. 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. And this is actually safer than Pu.
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.
I prefer the "u" in honour as it seems to be missing these days.
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?
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.
Harrison's Postulate - "For every action there is an equal and opposite criticism"
That's the wrong kind of Plutonium. RTGs need Plutonium-238. That stockpile is Plutonium-239, 240, 241, and a bit of 242.
upon the advice of my lawyer, i have no sig at this time
>it's
Land-lubber.
Twasn't an apostrophe, ye dog. It be the stray mark of a sharp cutlass.
What part of `yes no` don't you understand?
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.
"I do not agree with what you say, but I will defend to the death your right to say it"
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...
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
* 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!
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.
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 think it's an excuse to put nukes into space.
But, technically putting something the size of a nuclear reactor from a sub into orbit should be doable.
The problem is that the Dept. of Energy, although hugely wasteful, cannot "afford" to make plutonium for NASA/JPL. Yet another way this and previous admin is trying to gut planetary science: http://www.planetary.org/blogs/casey-dreier/2013/20130913-the-doe-is-full-of-wasteful-spending-but-forbidden-to-help-nasa-make-plutonium-for-space-missions.html
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....look at the radioactive boyscout, anything he can do NASA can do better.... but the question becomes.... how long can it output power at a workable rate? A space probe kind of needs to be "set it and forget it", you want as few adjustments needed as possible, not the least of which because any adjustment mechanism has weight and can degrade or break.
Its not just about making fission happen, its about extracting consistent predictable energy over a period of decades with no maintenance.
"I opened my eyes, and everything went dark again"
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.
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 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/
[RIAA] says its concern is artists. That's true, in just the sense that a cattle rancher is concerned about its cattle.
Pu-238 is NOT "weapons-grade", and Pu-239 (which is) is NOT a useful substitute for Pu-238.
"I do not agree with what you say, but I will defend to the death your right to say it"
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, without any significant release of radiation.
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 probe.
"I do not agree with what you say, but I will defend to the death your right to say it"
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.
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.
I love stacking my barbecues in the shed at the end of summer - you can't beat a bit of grill on grill action.
0 G doesn't mean 0 Mass. The correct term would have been Nuclear Fission is too massive.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
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 and the USSR had BES.
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).
-- This and all my posts are in the public domain. I am a lawyer. I am not your lawyer, and this is not legal advice.
No, Plutonium is an alpha emitter. When it goes bang it gives off gamma, quite a lot.
I love stacking my barbecues in the shed at the end of summer - you can't beat a bit of grill on grill action.
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).
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
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
But there is another type of electro-mechanical rotating generator designed for Russian craft, TOPAZ-II, but, unfortunately, it's far too heavy.
Kriston
I usually resort to YouTube Walkthroughs when I run at Heroic Level.
I drank what? -- Socrates
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.
Exactly!
Don't Pollute Space With Radiation!
I drank what? -- Socrates
OMG we're contaminating space with radiation! Think of the space ponies and the lunar ecology.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
Neither of those substances are overly dangerous or radioactive. It's the stuff with shorter half lives that you have to worry about. It decays faster, and pound-for-pound will release a greater amount of radioactivity in a shorter time scale.
PU-238 has a half life of 87.7 years. It will be cold and inert thousands of years before entering another star system.
I want peace on earth and goodwill toward man.
We are the United States Government! We don't do that sort of thing.
Most probes use a boom rather than a tether. Look at pictures of pretty much any probe, like Voyager, Galileo, Pioneer and you'll see RTGs mounted out on booms away from the main body of the probe.
When our name is on the back of your car, we're behind you all the way!
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?
-
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.
There's no place I could be, since I've found Serenity...
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 survived the breakup of Challenger, so a solid lump of plutonium is basically just going to leave the scene of a similar accident a bit like a canonball - intact, not atomised. So its not going to disperse anywhere - it'll drop into the ocean where it can be fished out by the navy.
So why don't you like the odds?
http://blog.nexusuk.org
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's big enough to use one, a reactor makes much more sense than an RTG, but they only make sense for big missions. One example is the SAFE-400, which masses 512 kg but puts out 400 kW thermal and 100 kW electrical. A GPHS-RTG masses 57 kg and produces 4.4 kW thermal, 300 W electrical at the start of the mission. The reactor's a lot lighter for its output, but if you need 1 kW, what do you choose?
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 out of range of the DSN before then.
2. If it's a short mission, you wouldn't use an RTG to start with. Short==Not far away from the sun, so PV panels are a much better (and cheaper) source of power.
3. An RTG with that little power density is completely and totally impractical.
upon the advice of my lawyer, i have no sig at this time
Cherenkov radiation makes the fuel rod containment pools a really pretty shade of blue.
Speaking of CR, I recommend "Man of Steel, Woman of Kleenex" by Larry Niven. He mentions its display in Smallville, and why. Worthy.
Do not mock my vision of impractical footwear
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 then everything was being tried, pebble beds, helium coolant, liquid metals coolant, odd geometry cores etc. all under a very lax regulatory regime which doesn't exist any more.
The Indian plans to use thorium in fuel are real although the actual implementation is a bit fuzzy with no actual operations in train as it's still experimental and very theoretical. The proposed fuel mix is very nasty though with up to 20% of the fuel being 20%-plus medium-enriched uranium and also some plutonium in order to transmute the thorium into U-233 since the neutron economy of breeding thorium into U-233 and then fissioning it in an otherwise-conventional PWR is somewhat lacking hence the extra neutron sources in the fuel mix. Other folks are working on the idea of using fuel able to breed thorium up to U-233 in-situ in regular reactors too but it's long-term -- the first experiments recently announced to see what happens physically and chemically to a few test fuel pellets will take four or five years of low-energy exposure in a test reactor in Norway.
The thorium-breeding MSR is perfect for making bomb-grade material. It produces lots of U-233, it has to because thorium by itself in not fissile. The whole idea of the thorium MSR is to breed thorium-232 up into U-233 and then fission that, hopefully getting enough neutrons to keep the chain reaction going and also breed up more U-233 (not something lower-economy PWRS have to achieve) while generating lots of electricity. Since U-233 is the only isotope of uranium in the fuel mix if it's chemically extracted during the operating cycle then the operator ends up with pure weapons-grade uranium. There are complications but it can theoretically be done, and thorium MSRs require continuous chemical extraction of neutron-absorbing waste isotopes anyway to keep the neutron economy healthy enough for the breed-burn cycle to continue.
As for the supposed decision to go for uranium-fuelled PWRs for their bomb-making ability, by the mid-60s the major nuclear powers had already made as much Pu-239 as they'd ever need using dedicated breeder reactors for their stockpiles of tens of thousands of warheads. The decision to not implement thorium MSR as a power-generating technology was nothing to do with weapon-making capability. PWRs are steam-engine simple in design and operation, no breeding required, no super-high temperatures, no molten fuel circulating in and out of a carbon moderating core, no continuous processing of the fuel to extract contaminants etc. That's why basically, it's a bit like whining about the Wright Brothers decision to use an internal-combustion engine in their Flyer rather than a jet engine.