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NASA Power Space

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.
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Without Plutonium, Deep-Space Probe Missions May Sputter Out

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  • 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?

    • by mark-t ( 151149 ) <markt@nerdfl[ ]com ['at.' in gap]> on Thursday September 19, 2013 @12:18PM (#44894385) Journal
      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.
    • by fuzzyfuzzyfungus ( 1223518 ) on Thursday September 19, 2013 @12:20PM (#44894405) Journal
      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.
    • Re: (Score:2, Insightful)

      by Anonymous Coward

      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.

    • Re: (Score:3, Funny)

      Yes, lifting facilities like Three Mile Island and Chernobyl off the ground takes a bit of effort

      • Shouldn't they be able to lift the reactor from a nuclear sub?

        I honestly dont know, just asking.
        • Re: (Score:2, Informative)

          by Anonymous Coward

          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 thi

        • by cpt kangarooski ( 3773 ) on Thursday September 19, 2013 @01:36PM (#44895171) Homepage

          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).

    • by gstoddart ( 321705 ) on Thursday September 19, 2013 @12:26PM (#44894483) Homepage

      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.

      • by h4rr4r ( 612664 )

        Why not shield the humans instead? Then just keep them away from it during launch. Not like irradiating space is a concern.

        • Stop it! you'll give the climate change denialists ideas.

          "It's not a tragedy - it's a MARKET OPPORTUNITY for radiation shields!"

        • 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.

          • by ShanghaiBill ( 739463 ) on Thursday September 19, 2013 @01:16PM (#44895001)

            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.

          • by Zemran ( 3101 )

            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 also don't know enough about them to say if an unshielded reactor is essentially a bomb.

            It isn't.

            What it is is unsafe to stand near, where "near" is any closer than several hundred yards.

      • And as far as I recall, you essentially need lead to block the radiation.

        Actually, water works quite well to block neutrons (better than lead, in fact), alpha and beta radiation. The lead is mostly for the gammas.

        • 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.

          • But it's the gamma radiation which is the one we're most concerned about, no?

            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

          • by Zemran ( 3101 )

            No, Plutonium is an alpha emitter. When it goes bang it gives off gamma, quite a lot.

      • by TheCarp ( 96830 )

        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..

      • 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.

      • by gmuslera ( 3436 )
        Maybe you can use poop as shield [pcmag.com], not sure how efficient it is, but if is something that you produce and don't change the overall weight of the ship. But you will have better shielding at the end of the trip than at the start.
        • by TheCarp ( 96830 )

          "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.

    • by CrimsonAvenger ( 580665 ) on Thursday September 19, 2013 @12:50PM (#44894731)

      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?

      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.

    • 0 G doesn't mean 0 Mass. The correct term would have been Nuclear Fission is too massive.

    • by erice ( 13380 )

      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

    • by garyebickford ( 222422 ) <gar37bicNO@SPAMgmail.com> on Thursday September 19, 2013 @01:48PM (#44895307)

      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).

    • 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

  • 1985 (Score:5, Funny)

    by jimmydigital ( 267697 ) on Thursday September 19, 2013 @12:16PM (#44894359) Homepage Journal

    I'm sure that in 1985, plutonium is available in every corner drugstore, but in 2014, it's a little hard to come by.

  • Upside (Score:5, Insightful)

    by ZombieBraintrust ( 1685608 ) on Thursday September 19, 2013 @12:18PM (#44894381)
    We are no longer creating bombs for a nuclear apocalypse.
    • Re:Upside (Score:4, Funny)

      by smooth wombat ( 796938 ) on Thursday September 19, 2013 @12:25PM (#44894471) Journal

      But the zombie apocalypse is still ok, right?

    • Re:Upside (Score:4, Insightful)

      by rubycodez ( 864176 ) on Thursday September 19, 2013 @12:32PM (#44894547)

      eh? we're maintaining thousands of bombs for just that

      • Re:Upside (Score:4, Informative)

        by Wookact ( 2804191 ) on Thursday September 19, 2013 @01:07PM (#44894931)
        We are not creating any new ones is the point he was making. It had nothing to do if we were still maintaining them. Maintaining them doesn't give the fuel that is needed.
        • by TheCarp ( 96830 )

          While you are correct that maintaining them doesn't, dismantling them does.

          • Re:Upside (Score:4, Informative)

            by necro81 ( 917438 ) on Thursday September 19, 2013 @03:32PM (#44896271) Journal

            While you are correct that maintaining them doesn't, dismantling them does.

            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.

    • But we're keeping tons of spent nuclear fuel in swimming pools and occasionally encasing it in giant blocks of cement and arguing about where to put it. Instead we could just put all that "waste" in a different kind of reactor and use it as fuel while also creating a chain of material that can have some plutonium pulled out for the occasional space probe or whatever. Problem is people are too scared of the "whatever" part to even allow this to happen - they'd rather pretend the spent fuel isn't an even bigg
  • mine Pluto (Score:2, Funny)

    by Anonymous Coward

    We could have mined plutonium on Pluto, but they went and demoted it to a dwarf planet.

  • by adric22 ( 413850 ) on Thursday September 19, 2013 @12:23PM (#44894447) Homepage

    Apparently Philo gives the secret of how to make plutonium from common household objects.

  • by Anonymous Coward on Thursday September 19, 2013 @12:32PM (#44894541)

    One of the helpful byproducts of a Liquid Floride Thorium Reactor (LFTR) is Pu-238

    Source: http://flibe-energy.com/?page_id=64

  • by rubycodez ( 864176 ) on Thursday September 19, 2013 @12:39PM (#44894603)

    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

    • 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.

      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.

    • by mirix ( 1649853 ) on Thursday September 19, 2013 @01:08PM (#44894937)

      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.

    • by Xyrus ( 755017 ) on Thursday September 19, 2013 @02:40PM (#44895845) Journal

      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.

  • by Virtucon ( 127420 ) on Thursday September 19, 2013 @12:45PM (#44894671)

    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?

  • by WindBourne ( 631190 ) on Thursday September 19, 2013 @12:46PM (#44894685) Journal
    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.
  • by gallondr00nk ( 868673 ) on Thursday September 19, 2013 @12:47PM (#44894687)

    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?

  • by bobbied ( 2522392 ) on Thursday September 19, 2013 @12:57PM (#44894813)

    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...

    • 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.

  • We can always just buy weapons-grade plutonium from North Korea and Iran.
  • HowTo (Score:3, Insightful)

    by Sla$hPot ( 1189603 ) on Thursday September 19, 2013 @01:01PM (#44894859)

    * 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!

    • This is the only suggestion that I saw that was at least creative. I think you jest, but all of those things would be bypassed with a cheap way to get in and out of the gravity well, as things can just be moved about where they are needed. It is assumed that cheap exit and entry from a gravity well is an intractible problem. It is a dependeny issue. The great cost and delay in space exploration hinges on the cost of entry and exit from the gravity well. It is less difficult on a body without such a thick at
    • 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.

  • 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.

  • by Squidlips ( 1206004 ) on Thursday September 19, 2013 @01:05PM (#44894899)
    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 [planetary.org]
    • by thrich81 ( 1357561 ) on Thursday September 19, 2013 @01:28PM (#44895093)

      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."

    • That's a rather misleading way to put it - as if Congress just backs up a truckload of cash at DOE HQ each year and then they get to decide how to spend it and whether to be generous with NASA. Your article links to another one [spacenews.com] that explains it in a more factual manner:

      The most recent setback for efforts to restart Pu-238 came Sept. 7 when the U.S. Senate Appropriations Committee followed the example set by U.S. House of Representatives appropriators in June and approved a 2012 spending plan without any mo

  • by Robotbeat ( 461248 ) on Thursday September 19, 2013 @01:17PM (#44895007) Journal

    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.

  • by charnov ( 183495 ) on Thursday September 19, 2013 @01:19PM (#44895033) Homepage Journal

    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]

  • So what they're saying is, "No war - No fun."
    Isn't that the way it's always worked?

  • why a square mile of reflective mylar and a high efficiency panel won't power a satellite for a good long while?

    • Ignoring all the challenges of creating an parabolic shape a mile across, have you seen what the sun looks like from Voyager 1?

  • by kriston ( 7886 ) on Thursday September 19, 2013 @01:51PM (#44895349) Homepage Journal

    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.

The unfacts, did we have them, are too imprecisely few to warrant our certitude.