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.

Comments

Why are nuclear fission systems too heavy?

[MillerHighLife21]

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?

[mark-t]

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.

Re:Why are nuclear fission systems too heavy?

[fuzzyfuzzyfungus]

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:Why are nuclear fission systems too heavy?

[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:Why are nuclear fission systems too heavy?

[fustakrakich]

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

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

No, but it costs about $10k to put 1kg into orbit (more to break orbit, naturally). Chemical fuel and/or solar panels don't have anywhere near the energy density of nuclear fuel, so it costs much more to send up. Besides, the efficiency of solar panels falls off with 1/r^2 from the sun, which adds extra ouch-factor to the equation if you want to send a probe to the outer planets.

Re:Why are nuclear fission systems too heavy?

[gstoddart]

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.

Re:Why are nuclear fission systems too heavy?

[ackthpt]

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-)

Re:Why are nuclear fission systems too heavy?

[h4rr4r]

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

Re:Why are nuclear fission systems too heavy?

[Joining Yet Again]

>it's

Land-lubber.

Re:Why are nuclear fission systems too heavy?

[Wookact]

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

I honestly dont know, just asking.

Re:Why are nuclear fission systems too heavy?

[vjoel]

>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?

[Joining Yet Again]

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

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

Re:Why are nuclear fission systems too heavy?

[gstoddart]

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?

[CrimsonAvenger]

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.

Re:Why are nuclear fission systems too heavy?

[Jeremiah Cornelius]

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.

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

Hmmm ... funny that the climate change denialists and the libertarians would have the same outlook on this ...

Re:Why are nuclear fission systems too heavy?

[CrimsonAvenger]

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.

Re:Why are nuclear fission systems too heavy?

[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.

Re:Why are nuclear fission systems too heavy?

[gstoddart]

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.

Re:Why are nuclear fission systems too heavy?

[hedwards]

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.

Re:Why are nuclear fission systems too heavy?

[WillAdams]

Water as a useful thing for blocking radiation actually comes up as a plot point in Charles Stross's recent short story _Zombies_. Available online here:

http://www.antipope.org/charlie/blog-static/2011/09/zombies.html

Re:Why are nuclear fission systems too heavy?

[TheCarp]

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.

Re:Why are nuclear fission systems too heavy?

[hedwards]

That's not surprising, the components are heavy and dense. Whereas the ISS is mostly air.

Re:Why are nuclear fission systems too heavy?

[ShanghaiBill]

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?

[ShanghaiBill]

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:Why are nuclear fission systems too heavy?

[ShanghaiBill]

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.

Re:Why are nuclear fission systems too heavy?

[CrimsonAvenger]

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 probe.

Re:Why are nuclear fission systems too heavy?

[Zemran]

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.

Re:Why are nuclear fission systems too heavy?

[jellomizer]

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

Re:Why are nuclear fission systems too heavy?

[cpt kangarooski]

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).

Re:Why are nuclear fission systems too heavy?

[CrimsonAvenger]

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.

Re:Why are nuclear fission systems too heavy?

[Zemran]

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

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

Behold! A soviet space nuclear reactor: http://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor

Re:Why are nuclear fission systems too heavy?

[gmuslera]

Maybe you can use poop as shield, 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.

Re:Why are nuclear fission systems too heavy?

[erice]

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 that much radiation, unlike an RTG, which is producing maximum output while still on the ground. Just wait until the probe is in space, extend an arm holding the reactor a good distance from the probe and then light it up. Inverse square law goes a long way toward reducing the required shielding. The main thing it needs is engineering and testing. A space worthy reactor is quite a bit more complex than an RTG, quite different from the heavy, human handled machines we have on Earth and there hasn't been much willingness to invest the resources to make it happen.

Re:Why are nuclear fission systems too heavy?

[garyebickford]

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).

Re:Why are nuclear fission systems too heavy?

[Jawnn]

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 every engineer knows that everything always behaves according to design. Right?

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

Your per Kg costs are a bit out of date. Space X is putting stuff into LEO for between $2,550 and $4,300 per KG per their published prices. Its still a lot, but less than half of what it was a few even a decade ago. But back to the subject at hand I don't think this is as big of a deal as the article is making it, Americium is the next viable RTG fuel, and I believe we have tons of the stuff. It would need some significant RTG redesign, and it doesn't provide the per kg power of Plutonium (about 1/4). But it would work find in space probes until we restart much needed reprocessing & production in Americas nuclear industry.

Re:Why are nuclear fission systems too heavy?

[TheCarp]

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?

[Anonymous Coward]

Finally someone remembered the talk like a pirate day!

Re:Why are nuclear fission systems too heavy?

[Gilmoure]

I usually resort to YouTube Walkthroughs when I run at Heroic Level.

Re:Why are nuclear fission systems too heavy?

[camperdave]

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.

Re:Why are nuclear fission systems too heavy?

[Lithdren]

So your argument is because its possible something might maybe happen, it should never be tried?

What excatly are you doing on a website like Shashdot?

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

http://what-if.xkcd.com/29/

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

s/it's/her/g

s/Land-lubber/Land-lubbers/g

Re:Why are nuclear fission systems too heavy?

[ChrisMaple]

Pu-238 decays to uranium-234 via an alpha particle emission

A process known as fission.

uranium-234 decays very slowly to thorium-230 via an another alpha particle emission

Also fission.

Fission, on the other hand...

Say what?

Re:Why are nuclear fission systems too heavy?

[necro81]

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).

Or, want to make sure your satellite keeps a low profile by not having large, shiny solar panels on it. This is why many spy satellites were nuclear powered - they were more difficult to track that way.

Re:Why are nuclear fission systems too heavy?

[SuperTechnoNerd]

You still need conventional rocket to get it up there. At about $10,000 per pound to lift something out of earths gravity well, every ounce counts.

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

That didn't stop Russia launching about 30 RORSAT satellites with nuclear power plants.

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

We plan for the unknown failures too:
http://en.wikipedia.org/wiki/Factor_of_safety

For example, the bridge you live under is probably designed for bumper-to-bumper semi-trailer trucks, not the typical fast moving well-spaced sedans.

So what do you think is more safe - a world where we risk small amounts of radiation, or a world that's ignorant of external threats?

Re:Why are nuclear fission systems too heavy?

[nojayuk]

Actually it IS radioactive decay. Fission is when a nucleus fractures into two or more pieces and emits neutrons, usually when it's hit by another neutron. There are only a few available isotopes that are fissionable, U-233 and -235 and Pu-239 and such. Pu-238 isn't fissionable.

Re:Why are nuclear fission systems too heavy?

[h4rr4r]

You should wear gloves or at least wash your hands after. Not because of the evil radiation, but because of heavy metal poisoning. Uranium is dusty stuff.

Re:Why are nuclear fission systems too heavy?

[nojayuk]

Maximum single-lift launch capability today is about 24 tonnes, a Delta-4 Heavy with all the go-faster bits usually reserved for NRO spy satellite launches. It might be possible to build a reactor in orbit from smaller modules and lift the fuel in a separate launch.

As for using a molten-salt reactor it would be simpler to just use U-233 in the fuel stream rather than have to breed up from non-fissile Th-232. I don't know if U-235 or Pu-239/240 could be used in a molten-salt reactor; the one that was built back in the 60s in the US used U-233.

Re:Why are nuclear fission systems too heavy?

[nojayuk]

At least five tonnes of plutonium has been vapourised and dispersed around the world, often at altitude by a long series of atmospheric nuclear and thermonuclear weapons tests by the Big Five (and possibly a couple of other nations) during the middle part of the last century. I doubt the addition of a few more kilos of Pu to the atmosphere would have any significant effect other than making some very sensitive radiation detectors read a bit higher for a time.

Re:Why are nuclear fission systems too heavy?

[turgid]

not the typical fast moving well-spaced sedans.

I thought they were goats?

Re:Why are nuclear fission systems too heavy?

[garyebickford]

I just read that the US is planning to spend 1/2 $billion to 'destroy' a few thousand tons of U-233 that were preserved for just exactly this use - in MSR reactors, to trigger the Thorium reaction. It's valued at $4600 per lb., and loss of this material will put any hopes for MSR development back many years and dollars. (From my most recent reading, once an MSR is running, the Thorium is converted (by neutron impact?) to U-233 which then fissions, so it 'breeds' its own fuel. But it needs U-233 or something equivalent to get it started. This is not my area of expertise...)

I do recall someone is working on a different trigger using a proton accelerator or something - they want to put a small MSR in automobiles. But I have no clue if that is feasible.

I did also find that NASA launched more than one fission reactor - the one called SAFE is most interesting. It is still floating around in a 3000 year orbit. It apparently lost some parts a long time ago, possibly due to a collision with something.

As for payload, I stand corrected. though at one time we could do almost that with Saturn V (ah, the good old days). From my reading since your reply, I see the Delta IV heavy is rated at almost 23,000 kg to LEO (and only about 9300 kg to lunar or escape velocity). The Apollo Command Module, lifted on a Saturn, was 33 tons by itself, and Saturn shipped the entire Apollo system to the Moon. It sez here on Wikipedia that Saturn's launch capacity to LEO was 260,000 lbs., 130 tons or 120,000 kg). So apparently the old Saturn V is still the big boy on the block. I think I got the 150 ton figure when I was out at SpaceTech Expo and they were talking about future launch systems. The Falcon Heavy, which has not launched yet, is projected to lift 53,000 kg or 120,000 lb to LEO.

For perspective on all this, it's interesting to consider that over-the-road trucks often have a GVW of over 50,000 lbs., a typical limit (set by the railroad) on gross weight of a single rail car is over 250,000 lbs, and the Costa Concordia - a large but not the hugest ocean liner, weighs over 100,000 tons - building a ship in space of that mass would take on the order of 2000 flights of the Falcon Heavy.

Re:Why are nuclear fission systems too heavy?

[FireFury03]

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?

Re:Why are nuclear fission systems too heavy?

[Atzanteol]

He can't leave his house since he *may* be hit by a car or eaten by a pack of wild poodles.

Re:Why are nuclear fission systems too heavy?

[nojayuk]

"I just read that the US is planning to spend 1/2 $billion to 'destroy' a few thousand tons of U-233"

Can you give me any sort of link to this? It sounds weird (and unbelievable) for a whole number of reasons. For one thing that amount of U-233 is enough to supply the US' entire demand for nuclear power for decades. For another making U-233 is not easy, it's not refinable from ore the way U-235 is so having "thousands of tons" lying around seems odd. MSRs and other reactor designs meant to breed U-233 from Th-232 can use anything as a source of fission neutrons including U-235 and Pu-239/240, indeed that's what the Indians are planning to use for their three-stage thorium burners. Other folks are also looking at conventional PWR fuel combos using Th-232 in a pelletised form along with copious neutron sources but not in unproven molten-salt systems. There was a Slashdot article about this a couple of weeks ago regarding initial experiments with eight such pellets in a Norwegian test reactor.

You may be suffering from conspiracy theory or conflating other stories in the news about 'destroying' nuclear material -- the US has funded an operation to secure weapons-grade uranium and plutonium from the former Soviet Union and downgrade it to be used in nuclear power plant fuel pellets, the "Megatons to Megawatts" project. Is this what you're thinking of?

Re:Why are nuclear fission systems too heavy?

[garyebickford]

Uranium-233 Inventory in Oak Ridge Lightened with First Shipment of Material from Building 3019 - press release from DOE, 2012-01-05.

OAK RIDGE, Tenn. - - The first shipment of inventory from Building 3019 at the Oak Ridge National Laboratory arrived at the Nevada Nuclear Security Site (NNSS) on December 22, marking the beginning of the end for the 50-year old Uranium-233 national storage facility. ...[snip]...
The U-233 Disposition Project is responsible for preparing 450 kilograms of fissile material stored in approximately 1,100 canisters for disposition. The transfer of the ZPR plates, and a future direct disposition campaign of a second inventory component, constitutes the first phase of the disposition program, which addresses approximately half of the inventory. A Phase 2 analysis is being finalized, and will set a path forward for eliminating the remaining inventory from Building 3019.

Also google "destroy U-233" you'll see dozens of articles at various thorium promotion sites, mostly from 2010. Again, this is not my area of expertise but it does indeed appear to be the case. My first response is to think this is the result of persuasion by the 'old' nuke industry (and/or maybe the old guard in the US nuke agencies, who were trained during the period when MSR reactors were on the verboten list - the politics in 1970 were pretty extreme), whose entire business model is based on fabrication of expensive fuel rods. If MSR reactors go into production, Westinghouse and a couple of other biggies will lose a huge revenue stream.

Re:Why are nuclear fission systems too heavy?

[garyebickford]

I should say, my recollection may be incorrect on the amount - I don't know where I got the 'few thousand tons' number either. :P

Re:Why are nuclear fission systems too heavy?

[nojayuk]

OK, a couple of tons (I keep on reflexively writing "tonnes" and have to backtrack since this is an Inperialist-based site) of U-233 stockpiled seems more reasonable.

One problem with U-233 is that it can be used to make quite functional nuclear weapons hence using up this stockpile in some manner is a boost for anti-proliferation efforts in the same way the "Megatons to Megawatts" project I mentioned earlier. The other side of the coin seems to be that it's not got any real purpose and it costs money to store and monitor. It's been sitting unused for fifty years and there's no real prospect of much or any of it being needed any time soon.

As for the thorium jihadists, well... If they can come up with a complete realistic design and operating plan for a thorium breeder molten-salt reactor, financial cover for waste-handling and end-of-life decommissioning, insurance etc. and jump through the NRC regulatory and licencing hoops for a decade or so then maybe they can get a thorium-based MSR built. They don't absolutely need kickstarter U-233 to fuel it though and it's questionable whether the US government would release bomb-grade material into private hands for this purpose.

Re:Why are nuclear fission systems too heavy?

[cjameshuff]

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?

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

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

You don't need to. We've already won...

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

"As others point out, things don't lose their mass just because they're in space."

Well, if they're used as a propulsion system, yes they do or they wouldn't work. Just... they lose mass very, very slowly.

Re:Why are nuclear fission systems too heavy?

[geekoid]

"they'll spew tons of radioactive particles all over the place. "
not with the casing they use. It would fall into the sea and probably be retrieved.

Re:Why are nuclear fission systems too heavy?

[geekoid]

Of course it is, you don't want a bunch of Hulks running around!

actually, that might be kind cool.

Re:Why are nuclear fission systems too heavy?

[geekoid]

The containment vessel would fall to the ground and be recovered.

Seriously, look at the containment vessel tests on youtube.

Re:Why are nuclear fission systems too heavy?

[cusco]

Several space craft with RTGs have suffered launch failures. For the most part they were fished out of the ocean or dug out of the tundra, refurbished, and launched on a later mission. The only way to "atomise" the plutonium in an RTG would be to to take that out that slug of metal, grind it into powder, mix it with something like magnesium and then burn it. A simple explosion won't turn it into dust. You really should listen to engineers rather than professional protesters and documented liars like Helen Caldicott when it comes to technology.

Re:Why are nuclear fission systems too heavy?

[BitZtream]

Arrrrrgh, Space has never been a vacuum.

Re:Why are nuclear fission systems too heavy?

[I'm New Around Here]

He can't leave his house since he *may* be ... eaten by a pack of wild poodles.

Can you imagine how long the hair on those things would be? Since they don't have traditional dog fur, but instead have regular hair that keeps growing year round.

You would be able to grab one by the hair, twirl it around and bowl it into the others, tangling them all up in a big snarling snarl.

Re:Why are nuclear fission systems too heavy?

[BitZtream]

One doesn't have to lift a FUELED reactor. Lift it unfueled. Add fuel in orbit. We launch radioactive elements all the time, RTGs are the main example I'm thinking off. You just lift the fuel in a heavy and expensive container, but much smaller than making the entire reactor capable of surviving an uncontrolled re-entry, fire or the abrupt stop at the end.

Still not going to be economical at this point, but its a solvable problem.

Re:Why are nuclear fission systems too heavy?

[Nefarious Wheel]

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.

Re:Why are nuclear fission systems too heavy?

[Zynder]

I would pay money to see that!

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

As for the thorium jihadists, well... If they can come up with a complete realistic design and operating plan for a thorium breeder molten-salt reactor, financial cover for waste-handling and end-of-life decommissioning, insurance etc. and jump through the NRC regulatory and licencing hoops for a decade or so then maybe they can get a thorium-based MSR built.

Well, back before the head of NRC, under serious pressure from the DOD and having his budget slashed and given the choice between breeders and MSRs (thanks to Nixon), chose to keep the breeder program and fired the major proponent of MSRs, the US had a very nice little 5KW (IIRC) MSR running. It ran without problems, generating electricity and, most notably, getting turned off every night by flicking a switch. Try doing that with a Light Water reactor.
Right now the Chinese and Indians are both building hybrid uranium/thorium reactors, although I don't think either one is an MSR - I think they're mixing the thorium in with Uranium to reduce costs. India has about 25% of the well-mapped reserves of Thorium.
So the designs have actually been evolving in the background for 40 years and are actually pretty mature. It's pretty well accepted now that in all respects that I recall, LFTR or MSR are safer, cleaner and easier to operate than the present systems. One of the primary reasons they were not of interest in the late 1960s is that it is difficult to use an MSR to make weapons material (although there is a small amount of U-233 made, it is mostly consumed). At that time the US needed more bombs, and any reactor that wasn't going to produce bomb material was a waste of resources. So MSRs have the advantage of reducing (not eliminating) the risk of weapons proliferation.

It also takes mining of about 40,000 tons of dirt and ore to acquire enough of the 'right kind' of Uranium for a 1 GW power reactor, vs. about 1 or 2 tons (I don't recall the exact number) of Thorium - it's actually sand on the beaches in eastern India.

As for waste, the total waste from a 1GW MSR is (from what I've read) on the order of a few pounds per year - IIRC about 0.1% of the waste from the typical present day reactors. And it's not long term waste that requires sequestration for 40,000 years - I think the major half-life is 200 years. I don't recall the details but it's all available.

As for insurance and the nuke regulatory system, well that's another story. You _do_ realize that over 90% of the actuarial risk of present day power reactors is covered by the government. The insurance problem should not be a big issue for an MSR, because present day reactors have more than 100 X more probability of catastrophic accident that poisons an entire state than any proposed MSR design. AFAIK nobody has figured out how to make an MSR that is capable of meltdown in the way that present day reactors are always one or two mistakes from suffering - they just can't do it. But the politics, driven at least in part by Westinghouse and that other company whose name I can't recall, are entirely against it.

The US has the second largest known reserves, by the way. And Thorium in the mine tailings is one of the big problems for the US-based rare earth mining efforts. So supporting use of that Thorium, instead of considering it a dangerous waste product, would kill two birds with one stone.

Re:Why are nuclear fission systems too heavy?

[nojayuk]

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.

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

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).

The advantage of fission power sources over RTG's is that you can dial their fuel spending down until you need more power. RTG is always on, until it burns out completely.

BTW, why can't we use solar radiation for proton bombardment of heavy nuclei to sustained production of radioactive isotopes? It may be infeasible (no pun intended) down on Earth, but throughout Solar system we usually have abundance of solar wind. If we start with common U-238, solar proton whacks it and we get Np-239+, and it soon undergoes a beta decay and turns into Pu-239 ... and then we are stuck, as far as RTG application goes! But, if we had a small neutron source, we could induce Plutonium to undergo fission.

Re:Why are nuclear fission systems too heavy?

[doccus]

Er...last time I checked, space was much much colder than the ocean. Exposure to the sun might be very hot, but f the ship is that close to a star it can temporarily use it's nuclear energy instead of generating it's own. Besides, any advanced system capable of bending space would be far more massive than a nuke engine.. Captain Kirk has been flying massive ships since 1966 or so , and what about plan 9 from outer space?

Re:Why are nuclear fission systems too heavy?

[cpt kangarooski]

Er...last time I checked, space was much much colder than the ocean.

Check again. Space isn't cold per se. It's a vacuum up there. Which means that any heat that a ship generates, it cannot get rid of it through conduction or convection. That only leaves radiation, which is very inefficient.

What you want to do, generally, is to build the ship so that it will radiate more heat than it can possibly generate or than it can absorb from something else radiating heat. Then, whenever you're not getting enough waste heat through normal operations, you turn on heaters to generate more. If you didn't do this, your ship would accumulate more and more heat and would eventually destroy itself.

You may recall how the Apollo 13 astronauts wound up having to deal with an interior temperature of around 40 degrees by the end of their mission. That's because due to power shortages, they had to turn off most of their equipment (which gave off waste heat) and the heaters, but couldn't prevent the ship from radiating heat as it was designed to do.

A naval nuclear reactor is designed to dump heat into the ocean; in the absence of the ocean, it would quickly meltdown.

Re:Why are nuclear fission systems too heavy?

[Optali]

I am sad, so sad.
This used to be a site filled with nerd wisdom and brainy people.

By the sake of Isaac Newton!

One more of such questions and I'm going to commit suicide.

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

If you get a thorium reactor going, you'll have a source of PU-238 as you can process it out of the reaction salt.

Re: Why are nuclear fission systems too heavy?

[nbritton]

Huh? Is space relatively close to absolute zero? Just put a heat exchanger on it.

Re:Why are nuclear fission systems too heavy?

[Anonymous Coward]

Gish Gallop? Jihadist? What an arrogant fuckface you are.

1985

[jimmydigital]

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

Re:1985

[Anonymous Coward]

This is where Mr. Fusion would really come in handy.

Re:1985

[JigJag]

beautiful BTTF reference. I applaud you, sir!

Re:1985

[Voyager529]

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.

Re:1985

[Anonymous Coward]

They said the same thing about ink and paper but we've had the digital revolutions and now tablets. No need for ink and paper.

Re:1985

[Guppy06]

No, but there's plenty of teapots out there you can use.

Re:1985

[Anonymous Coward]

It's in orbit, chucked out of shuttles, stations, rockets, and satellites over the years. Create an economic incentive to clean up space junk and you will be my hero.

Re:1985

[Anonymous Coward]

Maybe if we'd left Mir in Orbit.

Re:1985

[TechyImmigrant]

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

Just like sudafed.

Re:1985

[geekoid]

I am, but it would violate the Time Travel Convention of 1862, ratified 1 minute later by the Sol space colonies in 2378.

Upside

[ZombieBraintrust]

We are no longer creating bombs for a nuclear apocalypse.

Re:Upside

[smooth wombat]

But the zombie apocalypse is still ok, right?

Re:Upside

[Anonymous Coward]

Exactly.

I'd rather NASA (and other space agencies) have this problem than re-start production of something whose only other use is nuclear weapons. (Plus the large amount of nuclear waste that is created as a byproduct of Plutonium production.)

Re:Upside

[rubycodez]

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

Re:Upside

[Wookact]

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.

Re:Upside

[Baloroth]

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.

Re:Upside

[Anonymous Coward]

I find it hilarious that you both speak as if you are the ones (using the term "we") who are doing the bomb building, or bomb storing, or bomb dropping. You don't have the slightest control over any of that. Hell, a football fan using the term "we" to describe his favorite team has more control over the game than you have over war spending.

Re:Upside

[TheCarp]

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

Re:Upside

[necro81]

The only connection between Pu-238 and nuclear weapons, in fact, is that weapons production facilities naturally make good production facilities for Pu-238.

And without that nuclear weapons complex, humanity might never have synthesized Pu-238, or been able to separate and manipulate it. Our ability to use Pu-238 is due entirely to our history with nuclear weapons - it's a pretty freakin' tight connection.

(It didn't need to be that way - we could, maybe, have produced Pu-238 as an accidental or intentional byproduct of civilian nuclear power. And it certainly doesn't need to be the future. But that is the history.)

Re:Upside

[Wookact]

The original point was we are not making them anymore therefore we are not making the fuel in the same way that we used to. Whether or not we can dismantle the old ones and get the fuel from them is a completely separate matter.

Re:Upside

[necro81]

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.

Re:Upside

[geekoid]

Yes, it will be know as the most boring and short lived apocalypse.

Re:Upside

[rubycodez]

we pay the bill for it, it's ours

mine Pluto

[Anonymous Coward]

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

uh...

[Anonymous Coward]

Comrade Kim maybe? Send Dennis Rodman with a briefcase?

Just watch the movie UHF

[adric22]

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

112 tonnes enough?

[Anonymous Coward]

http://www.bbc.co.uk/news/uk-21505271

A shortage? right. That's enough to put a dent in a small moon.

Re:112 tonnes enough?

[Anonymous Coward]

Can you seriously not manage to add anchor tags to your link?

Re:112 tonnes enough?

[Virtucon]

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?

[compro01]

That's the wrong kind of Plutonium. RTGs need Plutonium-238. That stockpile is Plutonium-239, 240, 241, and a bit of 242.

Re:112 tonnes enough?

[Anonymous Coward]

That would be Plutonium-239. Plutonium-239 cannot be used in an RTG because it does not generate enough heat. Plutonium-238 has a shorter half life and generates much more heat for these generators.

Re:112 tonnes enough?

[CrimsonAvenger]

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).

Re:112 tonnes enough?

[tgd]

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.

Re:112 tonnes enough?

[sjames]

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.

Re:112 tonnes enough?

[Anonymous Coward]

On browsers that don't suck, you can highlight the text, right mouse click, then select "Go to web address" to go to the page without needing a link.

But yeah, he shouldn't be so lazy to not include tags.

Re:112 tonnes enough?

[camperdave]

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.

Re:112 tonnes enough?

[PolygamousRanchKid]

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.

This will be hoot and a half for future archeologists when they find this valuable stockpile:

"Hey, Zodan, do you have any idea why the Ancients buried all this fuel instead of using it . . . ?"

"I dunno, Ziffron, my guess is that they were total fuck-wits with shit for brains. Have a chat with Zaggon, who has found what appear to be primative computers. It appears that their devices were mostly used to collect porn and exchange meaningless banter with each other."

"What's really bizarre, is that their porn labeled 'Hentai' looks like our porn. We must have visited this planet before.

Re:112 tonnes enough?

[Kielistic]

"Open link in new tab" worked for me.

Re:112 tonnes enough?

[Anonymous Coward]

But on the upside, it'd last a heck of a lot longer. Just got to think of something where you'd need heavy-lift capability already, on a mission that you want to last decades.

Re:112 tonnes enough?

[Phrogman]

So we convert 6000 nuclear weapons into something useful and decrease the risk to the planet at the same time. We have 10s of thousands of extras right? Really a Swords to Ploughshares initiative :P

Re:112 tonnes enough?

[ChrisMaple]

I just did it in Firefox 24.0.

Re:112 tonnes enough?

[ChrisMaple]

Britain has accumulated the biggest stockpile of civil plutonium in the world.

The British, being very proper, have only civil plutonium. In the US, we use rude plutonium; civil plutonium won't fit in our reactors.

Re:112 tonnes enough?

[ChrisMaple]

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 (?)

Re:112 tonnes enough?

[compro01]

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.

Another reason to build LFTRs

[Anonymous Coward]

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

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

Re:Another reason to build LFTRs

[tgd]

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!)

Re:Another reason to build LFTRs

[mrspoonsi]

Also reprocessing:

http://en.wikipedia.org/wiki/Thermal_Oxide_Reprocessing_Plant

One of the reasons why the Sellafield reprocessing plant was built (not to reprocess, but to get plutonium for bomb making).

Re:Another reason to build LFTRs

[Anonymous Coward]

This is Slashdot. If you cant put in your own HTML tags then this is not the site for you. Reddit is ----> thataway

Re:Another reason to build LFTRs

[Anonymous Coward]

lol u so funny

Re:Another reason to build LFTRs

[Urkki]

This is Slashdot. If you cant write your own browser extension to automatically put in your own HTML tags then this is not the site for you. Reddit is ----> thataway

There, fixed that for you.

Except, sadly, I think 99% of /. readers can't.

bring back the real 9th planet!

[Anonymous Coward]

I knew downgrading Pluto from planet status would have unseen repercussions, first Plutonium, next what... no more plutocrats?

rather sensationalist

[rubycodez]

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

Re:rather sensationalist

[Anonymous Coward]

I am not a nuclear scientist so this may be a rather stupid question, but wouldn't an isotope with a longer half-life not be an alternative? I would imagine an isotope with a longer half-life emits substantially less energy over the same time period and thus would not be as useful as a Pu-238.

Re:rather sensationalist

[Anonymous Coward]

One of the reasons to use Pu-238 is its relatively short half life. It creates more heat through decay that way.

Re:rather sensationalist

[CrimsonAvenger]

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.

Re:rather sensationalist

[mirix]

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

[Xyrus]

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.

Re:rather sensationalist

[rubycodez]

that's why the three to five times the weight, but for centuries of useful output rather than decade (e.g. am-241)

be-be-beef or pork

[intermodal]

Only three more years to go! If you need a hand with finding the corner store, I'll be over at the Cafe 80s, where it's morning even if the aftern-n-noon!

Well then, there's an easy answer.

[Virtucon]

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?

Re:Well then, there's an easy answer.

[decipher_saint]

Do you know what this means?

Communists from the Red Planet!

TWO INVASION GENRES COMBINED INTO ONE!

Damn politics

[Anonymous Coward]

If it's so important, then why don't they just prioritize the next space mission to go back to Pluto and get some more? It seems pretty obvious, but I guess I just don't understand the politics of the situation. I guess it's because they don't consider Pluto to be a planet any more, so it's no good.

We are missing so many opportunties here

[WindBourne]

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.

Re:We are missing so many opportunties here

[MiniMike]

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.

Re:We are missing so many opportunties here

[Anonymous Coward]

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.

Unless the first alien civilization we encounter is radioactive sea bass. Then we'll blend in perfectly.

Re:We are missing so many opportunties here

[Anonymous Coward]

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.

Why not? I'm betting the sea bass is probably a lot more intelligent than most humans. :-)

Re:We are missing so many opportunties here

[Tablizer]

I'm betting the sea bass is probably a lot more intelligent than most humans. :-)

Better singers also

Voyage To The Bottom Of The Sea.

[gallondr00nk]

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.

[RevDisk]

Tapping undersea cables.

Re:Voyage To The Bottom Of The Sea.

[compro01]

What on earth do they need deep sea espionage for?

Tapping submarine cables.

Re:Voyage To The Bottom Of The Sea.

[Rhywden]

Tapping submarine cables.

I've heard of those drive-by-wire systems! What an ingenuous way to steer a military submarine!

Re:Voyage To The Bottom Of The Sea.

[Anonymous Coward]

What on earth do they need deep sea espionage for?

Although the NSA has complete knowledge of everything we communicate, the Crabby Patty formula eludes them

Re:Voyage To The Bottom Of The Sea.

[Impy the Impiuos Imp]

Like the one Brazil is laying to Europe so the NSA can't spy on Brazilians downloading Denmark stuff.

Re:Voyage To The Bottom Of The Sea.

[nojayuk]

Monitoring submarines, mostly. It would be kinda nice to know where the Other Guy's boomers and attack subs are at any given time. There are also stealth satellites which don't use big solar arrays highly visible from the Earth's surface.

Re:Voyage To The Bottom Of The Sea.

[Solandri]

Specifically, cable-tapping they used to do with NR-1 (the smallest nuclear-powered sub ever made). It was retired in 2008. In retrospect, it should've been obvious they retired it because they had a better, probably autonomous, method of accomplishing the same task.

We need another Cold War.

[Apharmd]

Problem solved!

Re: We need another Cold War.

[Anonymous Coward]

No, what we need are Dilithium crystals. Super efficient and safe

Re: We need another Cold War.

[Talderas]

What we need is naquadah.

Just start reprocessing spent fuel

[bobbied]

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...

Re:Just start reprocessing spent fuel

[denis-The-menace]

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.

Re:Just start reprocessing spent fuel

[Anonymous Coward]

b-b-b-but what about those super insightful laws that prevent breeder reactors needed to reprocess spent fuel rods.

Just FYI, but spent fuel rods aren't reprocessed in breeder reactors.

My understanding is that the fuel pellets are extracted from the rods by stripping off the cladding. Then the pellets are dissolved in some sort of nasty acid and the still useful Uranium and the not-so-useful nuclear waste are separated out chemically.

A nasty process with nasty chemicals and nasty byproducts and nasty radioactive elements.

Re:Just start reprocessing spent fuel

[Anonymous Coward]

the nuclear industry lobby isn't the ones doing that one.

it is the antiproliferation groups, environmentalists against anything nuclear, and sheer inertia that is stopping reprocessing. The nuclear industry in America would love it, as they could get rid of the giant liability that is guarding nuclear waste.

Re:Just start reprocessing spent fuel

[Zynder]

I'm sorry, I couldn't hear what you were saying over everyone else screaming "NOT IN MY BACKYARD!" Did you say "nasty"? I thought I heard you say nasty but I wasn't sure. My lack of hearing is a nasty problem that would require a pretty nasty fix to get it back to something useful. It's my own fault though. Years of nasty ass cars with loud nasty exhaust pipes on them, coupled with the nasty ass machine guns I had to fire in the Army at all those nasty targets. As a matter of fact, I should go shower- my ears are feeling kind of nasty. It's all this nasty dust in my nasty ass basement. I really should clean it up. My mom does say I'm a nasty ass alot of the time.

OH and one more thing:

NASTY!

Re:Just start reprocessing spent fuel

[bobbied]

Well.. Nasty as it is, we already have places where it has been done before. Just do it at one or more of those places and we won't be creating any new NASTY places... I sure hope that one of these places is NOT in your current backyard...

Re:Just start reprocessing spent fuel

[Zynder]

I'm posting this from a Superfund site. Ain't skeer'd buddy!

Ready supply

[Citizen of Earth]

We can always just buy weapons-grade plutonium from North Korea and Iran.

Re:Ready supply

[CrimsonAvenger]

Pu-238 is NOT "weapons-grade", and Pu-239 (which is) is NOT a useful substitute for Pu-238.

Re:Ready supply

[Hillgiant]

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

[Sla$hPot]

* 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!

Re:HowTo

[moteyalpha]

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 atmosphere, but exit and entry is still the limiting factor.
What do mean it went prompt, isn't it good to be prompt.

Re:HowTo

[cpt kangarooski]

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.

Re:HowTo

[Sla$hPot]

There is no such thing as a gravity well.
Space travel still follows the same basic rules since the forties.
Nobody understands gravity. I mean nobody! There is a lot of crazy theories out there.
Even the higgs boson haven't been finally confirmed yet.
Thinking about gravity well's for space exploration is not going to be productive until there is a better understanding of gravity.
Even if we understood gravity perfectly. It wouldn't necessary mean that we would be able to manipulate gravity at all.
We have to use what ever technology that is available today, if we wan't to push the boundaries in space travel.
The longer we sit and debate about star trek technology, the more we will miss out.

Re:HowTo

[Sla$hPot]

Then i will add an other bullet to the list. * Understand how a H3 fusion reactor works.
That part could actually be solved on earth.
However It's almost 35 years ago that i read an article that the scientists where almost there.
And I thought they actually cracked it, but just needed a steady supply of H3 . hmm.

Re:HowTo

[moteyalpha]

I beg to differ. I would say that in my estimation there is no way to cancel gravity but there are other ways. I don't think that the concept of space elevator is workable but I have begun doing the work to prototype a device that would have the same effect as a space elevator without the engineering limitations. I have already done tests and it works on the scale of my tests. The physics is just an extrapolation of a linear effect to scale. I am putting up the data, CAD, equations, and construction methods for anybody to call me out on the physics and I welcome any criticism , constructive or otherwise. I have worked in process engineering for decades as well as systems design so I have a bit of experience in developing systems and it looks good on paper and the tests match my expectations so I will go to the next step. It requires several new technologies, but each has already been tested and I am releasing the first part of the design and even have a video explaining it by an actress that did a decent job of making it. It has only been a week now that I have been getting the stuff ready to publish so a lot of it is ragged and I intend to polish the web info when I can spare the time from my regular work. In fact I have an appointment now and will be gone until tomorrow. Just saying that so that if I don't reply to further stuff, that is why.

Re:HowTo

[camperdave]

He3 fusion doesn't work. Other than that, we're good to go!

Re:HowTo

[Dunbal]

Nobody understands gravity but we're still capable of making highly accurate predictions of orbits of comets and asteroids far, far into the future. Not bad for something that's not "understood". If you want to be pedantic about it, no one understands subatomic particles or electromagnetic radiation, either. I mean, not really understands. Sigh.

Re:HowTo

[Anonymous Coward]

You forgot the wave magic wand step to produce enough money and resources to get past Step 1 and more importantly Step 2 without bankrupting the planet.

Seriously; it's not about having the technology to do it. It's about having the technology to do it with a reasonable economic cost.

Re:HowTo

[ChrisMaple]

Are you an idiot or a troll? Understanding that it takes a lot of energy to move a mass from the surface of the Earth to a few tens of thousands of miles higher does not require an understanding of the mechanism of gravity, but that energy requirement is what "gravity well" refers to.

Re:HowTo

[Sla$hPot]

Neither i mistook a gravity well for some fancy anti gravity device. Didn't look it up on google.
>Earth to a few tens of thousands of miles higher does not require an understanding of the mechanism of gravity
Are you an idiot or a troll?
Don't you think i know that. Huh : - ( )
I takes a massive amount of kinetic energy. That's why we need to run the whole operation from the moon.
moteyalpha: Sorry i missed your point :)

commercialize it

[stenvar]

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.

Re:commercialize it

[Sla$hPot]

I have a suggest to that problem.
We have already seen how golf clubs have driven up titanium production to the level were it almost stalled jet turbine blades production.
So why not make golf balls with plutonium cores?
They will be dead easy to find using a geiger counter.

Re:commercialize it

[stenvar]

We have already seen how golf clubs have driven up titanium production to the level were it almost stalled jet turbine blades production.

Huh? How can "driving up titanium production" stall anything?

In any case, over the last ten years, titanium has become cheaper than copper or brass.

Re:commercialize it

[Sla$hPot]

I should have said, when golf club production drove up titanium demand.
It actually was on the news back in 2005--2006 when production of titanium golf cubs surged and people stated to buy these insanely large drivers that sounded like half empty coke bottles.

Re:commercialize it

[stenvar]

Short term demand spikes create short term shortages. Long term, an increase in demand will be met by an increase in production, more efficient production methods, and lower prices. That's a good thing.

Re:commercialize it

[Grishnakh]

Part of the reason titanium has become so cheap is because the Soviet Union collapsed, and their immense supply of titanium became available on the global market. They used to build submarines out of the stuff because they didn't have many other domestic uses for it and they didn't trade with other nations, but now they'll sell it to the highest bidder, so with much greater supply comes much lower prices.

Reason: Price gouging by Dept of Energy

[Squidlips]

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

Re:Reason: Price gouging by Dept of Energy

[thrich81]

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."

Re:Reason: Price gouging by Dept of Energy

[timeOday]

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 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 money for the program in the Energy Departmentâ(TM)s budget. 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 Departmentâ(TM)s 2010 and 2011 budgets.

NASA officials did receive congressional approval last spring to use money in the space agencyâ(TM)s 2011 budget to begin working with the Energy Department to study resumption of Pu-238 production. Lawmakers authorized NASA to begin looking into the issue in 2011. That effort was delayed, however, because Congress failed to pass a 2011 budget bill and instead provided the space agency with money through a series of stopgap spending measures designed to support ongoing activities. To spend money on new programs, including Pu-238 production, NASA officials needed congressional permission.

Re:Reason: Price gouging by Dept of Energy

[Anonymous Coward]

Republicans at work. If they make the President look bad, they win, even if everyone else loses.

Re:Reason: Price gouging by Dept of Energy

[Anonymous Coward]

Republicans at work. If they make the President look bad, they win, even if everyone else loses.

You said it! The president doesn't need the Republican's help!

Re:Reason: Price gouging by Dept of Energy

[Anonymous Coward]

Way to shoehorn in an economics argument into something completely unrelated -- are you one of those libertarians by some chance?

Re:Reason: Price gouging by Dept of Energy

[Dunbal]

Oh here we go with the partisan bullshit circus yet again. Yeah remember which color flag you fly makes a HUGE difference! Morons. Maybe when you stop shouting at each other you'll realize that you have BOTH been had.

Re:Reason: Price gouging by Dept of Energy

[Anonymous Coward]

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."

Of course they did, we can't afford to spend money on pointless things like that.

We can, of course, put that money to "good use" blowing up brown people in other countries, especially in a country like Syria that's already blowing each other up anyways. It's the humanitarian thing to do, just like our humanitarian missions to Korea, Vietnam, Iraq, Afghanistan, and Libya. And then there's those (currently grounded) F-35 JSFs, we need a few dozen more of those.

Fear-mongering. We are restarting production.

[Robotbeat]

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

[charnov]

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/

Oog, why, why has thou forsaken us?!

[Anonymous Coward]

feature request - pirate troll.

Pssst... North Korea

[Anonymous Coward]

Figured out a source of income for y'all.....

Just ask al-Qaeda for more

[Anonymous Coward]

Simple solution, no?

Reminds me of that bumper sticker

[Anonymous Coward]

"You can't hug a child with milliparsec arms"

The Way of Things

[trongey]

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

No but

[gr8_phk]

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 bigger problem.

On the other hand...

[Anonymous Coward]

We have been running out of IPv4 addresses since 1999, and here we are.

Tell me again....

[gestalt_n_pepper]

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

Re:Tell me again....

[Overzeetop]

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

Re:Tell me again....

[gestalt_n_pepper]

The sun is an overly bright star and why would you have a singular parabolic mirror rather than a few hundred or thousand smaller mirrors with automated attitude adjustment to keep them focused on the space craft and provide a robust redundancy?

Re:Tell me again....

[cbhacking]

What part of "deep-space probe" looks like "satellite" to you? I mean, can you actually read? You can write well enough, I see, but can you *read* English?

Re:Tell me again....

[gestalt_n_pepper]

I guess it's the part that says, "Whoa! Way far away from the sun! Better add a *lot* more light mylar reflective surface area to focus on relatively tiny solar panel to maintain sufficient energy."

Not only can I read, but I can add too.

Obviously there are limits to this strategy too. Maneuvering attitude of a multitude of mirrors is probematic since they too require energy, and distance is distance. Once you get far enough away, there's just not much energy to play with, but you should be able to maintain systems for quite a while.

Irresponsible

[Radtastic]

It seems irresponsible to me to send a craft into space emitting unsafe radiation. U-238 has a half life of 4.5 billion years, U-235 700 million. (Sorry, I'm not an engineer and I'm too lazy to go look up which would be used in said spacefaring fission reactor.)

We'd be mighty pissed if some ancient alien probe showed up on doorstep spewing poison. (Although for all we know, said radiation might be sugary fuel to them.)

Re:Irresponsible

[rahvin112]

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

[Gilmoure]

Exactly!

Don't Pollute Space With Radiation!

Re:Irresponsible

[HornWumpus]

OMG we're contaminating space with radiation! Think of the space ponies and the lunar ecology.

Re:Irresponsible

[Shakrai]

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.

Re:Irresponsible

[fredmosby]

The longer the half-life the less radioactive something is. So isotopes with half-lives in the hundreds of millions of years aren't very dangerous.

Re:Irresponsible

[Anonymous Coward]

Pu-238, -239, and -244 are found in nature, though in trace concentrations. Most of what we use is manufactured and not collected directly.

Re:Irresponsible

[cbhacking]

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.

Re:Irresponsible

[FireFury03]

As others have already noted that P238 isn't really dangerous unless you are going to eat it.

And whilst it is radioactive, the real danger of eating it would be that you would die of heavy metal poisoning... so the radioactivity is probably not worth anyone worrying about :)

Re:Irresponsible

[TangoMargarine]

From the perspective of the sheer volume of space, radiation is all it is, mostly :)

Re:Irresponsible

[geekoid]

I would like to point out that space is big. really really big... a clever person might call it mind boggling big

Imagine I through a cork into the Atlantic ocean. Some time after that a person from the middle of Africa moves to Colorado. That person then drives to California and spend 1 minute at the beach.
He is far, far, far more likely to find the cork then a probe will find civilization before running out of fuel.

Re:Irresponsible

[Blaskowicz]

These long, hundreds millions or billions years half-lives are precisely why Uranium is not a big radiation hazard. Of course, an operating nuclear reactor or its waste products, that's another matter. The metal toxicity of Uranium is another problem, maybe that's what's causing all those deformed babies born or stillborn in Iraq.

Cables

[ThatsNotPudding]

What on earth do they need deep sea espionage for? Are they trying to spy on Cthulhu or something?

Phone cables don't cut and splice themselves, pal.

Many other isotypes and generator types

[kriston]

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.

Nuclear propulsion: Project Orion

[Anonymous Coward]

Oh, come on!

If Project Orion was planned in the 50's, with the "scarcity" of atomic bombs then, imagine what we could do with the current stock-pile!

 

US Nuclear reactor currently orbiting Earth

[Anonymous Coward]

US Nuclear reactor currently orbiting Earth:

http://en.wikipedia.org/wiki/SNAP-10A

Launched April 3rd, 1965.

Mirabile dictu!

[govett]

Zero-point energy? Neutrinos? Gravity?

Call Canada?

[Anonymous Coward]

CANDU allows for online refueling, and allows for different fuels in different tubes, shouldn't be too hard (compared to calculating other mixes) to set up a fuel-channel to be biased towards producing more Pu.

That will teach them

[Kinwolf]

They had the nerve to demote Pluto, so now it's pluto-nium offsprings are leaving in protest!

Re:I thought they restarted production back in Mar

[Anonymous Coward]

We are actively producing it at HFIR (DOE reactor at ORNL)

So what?

[Urkki]

Do we really need to send probes to the outer solar system for next half a century? Let's wait for better, lighter reactors and solar panels, and less power hungry electronics and more sensitive radios. In the mean time, let's mine some asteroids, send up better telescopes, practice human presence in space, send balloons to Venus and rovers to polar regions of Mercury...

Re:So what?

[jd]

Humans are staggeringly lazy. Nobody does anything unless they absolutely need to. This is why wars result in a lot of research and development being done. It's not because necessity is the mother of invention, it's because necessity is an axe-wielding psychopath that will slaughter anyone that doesn't do anything with all the projects, plans and papers that have been produced since the last war.

We need to explore the outer planets, less for the data that might be there (you can obtain the same volume of world-view-shattering data from many sources), but purely because it gives the engineers no choice but to actually get off their lazy collective arses and do something productive. (NB: I say engineers only because the managers are lost causes.)

Solar panels, no matter how good, won't help. All the sunlight falling on the entire of Jupiter would not power the computers, never mind ion drives, of an advanced probe, and there is simply no way of building solar panels larger than that. Lower power electronics are easy, we could do those tomorrow. Voyager 1 is running multiple instruments AND a long-range transmitter on a trace of power so low that most home multimeters wouldn't register it, and electronics are tens of thousands of times more efficient today than back then. (Further, if the probe is using an ion drive, you can store the data rather than sending it, which means you're not confined to bandwidth limitations or the horrible inefficiency of wireless.)

Reactors won't get lighter. Fission has gone as far as it can. Until someone develops working fusion, there will be no significant reactor development. In fact, most probes don't use reactors at all, they use nuclear batteries. Different technology.

Radio sensitivity won't help. Shannon showed that the retrievable information (even in theory) is not dependent on the sensitivity of the receiver or the power of the transmitter.

Mining asteroids is a waste of time. The cost will always exceed the benefit, even if you parked an asteroid made of solid gold in Earth orbit. Even if it could be made profitable, it merely encourages a waste of resources, and it is because humans waste resources so much that R&D never gets done until it's past too late.

Sending up better telescopes is seriously stupid. Crystals form better in microgravity and you won't get the mirror deformations that hindered Hubble so much, if you just build (from raw material) the entire telescope in space. In fact, park a disposable construction facility in orbit around the moon and you'd be able to build a defect-free optical telescope in space larger than the largest radio telescope on Earth.

Balloons to Venus would tell you nothing - we've already got a fairly decent surface map and the atmosphere would destroy any material you sent. No, if you send a probe to Venus, the only rational place to send it (and the only place we'd get new data) is below the surface itself. That means taking a small asteroid, putting your probe in the middle, then slamming the lot into Venus at a speed that'll vaporize most of the asteroid and put the rest plus probe deep enough underground to actually do real science on the planet prior to the utter destruction of anything left. This is way, way beyond what we can currently do, and even if it wasn't, we've far more to learn from asteroids than from Venus. Venus is a boring planet.

Mercury is also a boring planet. It's basically a lump of iron ore, with a few traces of other metals thrown in. Pretty much what you'd expect, given that the rotation of the accretion disc would have separated out the various elements very efficiently (which is why you see the types of planets where you do) and also given that Mercury shows strong evidence of being a planetary core with the outer parts of the planet blasted off at one time or another. It can tell you about planetary cores, if studied as a whole, but if you're limited to a few mm below the surface of two tiny, non-representative regions, then it can tell you nothing at all.

Re:So what?

[Urkki]

Uh, sorry but that was utterly unimaginative rant, so much so that I'll call it a stupid rant. Some points:

Asteroid mining is pre-requisite for sensible manufacturing in space, and has actual commercial interest in it too. And space manufacturing is pre-requisite of doing anything really interesting in space, hauling all the stuff up from gravity wells just will not do in long term.

More efficient solar panels could mean a nanofilm with area measured in square kilometers, and ability to power it also with (solar powered) lasers once even that gets out of useful range of solar radiation. This is just an example btw, not prediction of real deployed tech.

I'm fairly sure a fission-powered thermoelectric generator could be made lighter than radioactive decay powered RTG, already at power range and RTG lifetime of Voyager probes. In fact having "cheap" plutonium for building RTGs with stagnated technology is holding us back, with their limited power output and lifetime. We need incentive to develop something better.

Mercury is the best place for solar neutrino detector, thanks to inverse square law and required shielding, and sending rovers there would be first step into building one.

You should really read up on balloons at Venus, in the upper atmosphere, it's quite an interesting concept and technical challenges are interesting too. Also, if we want to really understand planetary atmospheres (including our own), we really have to spend some time in the atmosphere of Venus too.

About radios, just think how much audio and video data, with what kind of tiny antennas, and with how little energy per uncompressed bit, we can transmit with our consumer mobile devices today, compared to just 10 years ago, and it doesn't look like things are slowing down, quite the opposite. That relative improvement will trickle down to space tech too, in due time.

Time for a fast breater reactor (in lunar orbit.)

[MonsterMasher]

What a fast breeder reactor to multiply fuel supply - fine - I won't mind as long as it's in lunar orbit you assemble and run it. Any place else and I hope there will be non-stop shit storm.

Lets see what happens with the Japanese reactor storage building full of fuel. I expect a small quake will bring the entire thing down, exposing all that fuel to air, burning and carrying super toxic participial all over the Pacific ocean and our west food growing area.

I'm in the process of tracking down a gieger-counter as is. Fear your tuna fish meal!

Why is this a surprise?

[jd]

We already know from Doctor Who (Second Doctor, second story featuring the Ice Warriors) that humanity doesn't get beyond the moon until after transmat and weather control have been developed and we have a fully operational moonbase. Although the transmat part looks like it may be doable (despite incorrect calculations by cynics on how much data would be required), we're probably not going to see a moonbase and weather control is likely an impossibility.

Since these are prerequisites, I conclude that further travel than that will not happen. Since nobody will be going further, there will be no need to explore further. Whether, as Douglas Noel Adams' suggested, it turns out that leaving the oceans was a really bad idea is hard to say, but the lower 95% of the population seems determined to convince me that it was.

This is bullshit.

[Anonymous Coward]

America, Russia, Japan and the UK have programs to recycle plutonium in MOX reactor fuel, because they have no other use for it. There is still plenty in the stockpiles.

Re:I thought they restarted production back in Mar

[steelfood]

It's just the usual /. dupe and delay system at work.

Hydrogen Plasma Propulsion

[Shortguy881]

What about plasma rockets?

http://www.popsci.com/technology/article/2010-10/123000-mph-plasma-engine-could-finally-take-astronauts-mars?page=2

These are super efficient and super fast and the fuel is readily available.

Re:Hydrogen Plasma Propulsion

[joe_frisch]

The hydrogen is used to carry the momentum but the energy needs to come from some electrical power source. solar works near the sun but in deep space some type of nuclear is the only practical option. At the power levels required for nuclear powered rockeets (like plasma drives ) a nuclear reactor (not an isotope source) is probably the only practical solution.

NASA is working on Cold Fusion power source

[Anonymous Coward]

http://climate.nasa.gov/news/864
Apart from this there exist few commercial companies which are promising to sell Cold Fusion (LENR) devices soon.
Here is a weekly compendium of all related news:
http://pesn.com/2013/09/19/9602374_LENR-to-Market_Weekly_September19/

What a humbug posting...

[mynameiskhan]

The author(s) did not even care to read the papers by Zefram Cochrane and are blithering on about plutonium. Anything is possible with dilithium. https://en.wikipedia.org/wiki/Dilithium_(Star_Trek)

Unnecessary Weapons Building

[Anonymous Coward]

Yes, there's no better screen for a round of nuclear weapons proliferation than getting an obscure professor and a few retired NASA engineers to say "OMGZ WE'RE RUNNING OUT OF PLUTONIUM FOR SPACE MISSIONS!!!!11111!1!1 QUICK BUILD MISSILES!!!!!11!!1!1!1!1!!!!!"

What planet do *you* live on? Because it sounds like a planet where a triple-digit IQ would make you a king.

Re:Unnecessary Weapons Building

[cusco]

We've had two US presidential administrations in the past three decades run by guys with double digit IQs. I wouldn't be throwing stones.

Re:Unnecessary Weapons Building

[Anonymous Coward]

While I believe in criticizing stupidity wherever it's found this is a good point well made.

NASA made it a lot worse

[Anonymous Coward]

By using plutonium for Curiosity 1 and 2 in a mission to Mars, a place where solar panels have been shown to work for at least 9.5 years on the surface (Opportunity rover). The only thing they could have added to improve was something to clean the panels from the dust regularly instead of waiting for dust devils.

This shortsighted approach is now showing up. At least solar panels are now good enough for Jupiter missions. Not sure if they are good enough in the radiation environment around Europa though.

Not just probes

[Anonymous Coward]

But communications as well. I was simultaneously amazed and extremely disappointed with Curiosity's landing because, I mean hell, it was 2012 and we couldn't strap the equivalent of a GoPro on that sucker for the decent :( There's just not enough bandwidth available to transmit HD 60fps video through space -- the orbiters around Mars today offer very limited sending times and upload capacity. We should fix that before our next mission to Mars as the data upload rates will only increase.

For those thinking we don't need that type of camera for 'science' I'll say this. We're past the science stage with Mars... we need to start getting practical and marketable with it. It would be a mistake to send another 'science' only mission to that planet I think. Send some humans, give them a nice big upload capacity, and have them do science from that angle.

Re:Not just probes

[Anonymous Coward]

Interestingly, the "Mars One" project actually accounts for this to some extent. They only give some marginal information though -- hopefully they'll be powered by PU-238 and can deliver 200 channels of HD that no one on mars will end up watching :)

http://www.mars-one.com/en/communications-system

So what?

[gelfling]

Space science is over. Screw it. First manned spaceflight died off now we can kill this off 'for the greater good'. Who cares anymore.

How is their lack of pu238 my problem??

[Anonymous Coward]

Maybe mj12 can find you some.

Ah, but the peace-loving people of Iran...

[Anonymous Coward]

assure us that their medical research labs will soon be pumping out weapons grade...errr... ahhh.... "exploration" grade plutonium in large quantities any day now...

On a related note, President Obama assures us that his lack of action to stop this Iranian situation is, in fact, a very clever plan to obtain new low-cost RTGs for space exploration. This will also assist his new NASA mission of "outreach to the Muslim world", which he believes is much better than all those nasty plans to return to the moon and go on to Mars (which Bush started and Obama in his infinite wisdom cancelled)

Save the Helium!

[THE_WELL_HUNG_OYSTER]

Get in line, damnit. Helium gets saved first.

This is already happening!

[Zynder]

I saw a documentary the other day that showed that Nazis were in fact already doing this on the dark side of the moon.

Simple solution!

[Anonymous Coward]

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.

If you get Pu-238 as a by-product of making nuclear weapons, the solution to the Pu-238 shortage seems simple to me: Make more nuclear weapons!

What could possibly go wrong?

i've got a great idea!

[cas2000]

Outsource the production of Pu-238 to private industry and they can get it made cheaply in pakistan or china or ukraine or somewhere.

What could possibly go wrong with that?

Turtle IV to Major Tom...

[Tablizer]

There are other isotopes that have longer half-lives

Just make the probe go slower

NASA looked into fission power with Prometheus

[stiggle]

Nuclear fission reactor powered craft - assembled in space whose initial mission was out to the icy moons of Jupiter, where solar power would not be reliable.

Aswell as the JIMO (Jupiter Icy Moons Orbiter) it was also considered for an unmanned inner-planet ion drive delivery system, where you would launch cargo into orbit around the Earth which would then be collected and delivered to the inner planets where the cargo would be released. This would then be able to deliver satellites and landers to Mars aswell as return goods back to earth.

http://en.wikipedia.org/wiki/Project_Prometheus

http://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter

Buy it from Iran or NORK?

[Wizardess]

We could simply purchase it from Iran or North Korea, I suppose.

{O.O}

Re:Buy it from Iran or NORK?

[Blaskowicz]

Purchasing from Iran would be hard, as they don't have a nuclear weapons program.
NK does make plutonium based bombs, but just a handful. You won't get much from them. Pu 238 is the finest, most valuable nuclear waste around, rare and mostly obtained from the absurd nuclear weapons production of the US and Soviets. You'd better ask Israel for some of it. I dunno how much you would get, a guess would be maybe just enough for one deep space mission.

There is plenty of Pu

[Anonymous Coward]

Scattered around Fukushima. Just someone must collect.

Not really that hard ...

[yusing]

I'm pretty sure the DoD could scrape some together by looking under some rocks somewhere if it had to.

who has Pu

[Anonymous Coward]

Just buy some from the Iranians, they have tons.

BS

[Anonymous Coward]

There is plenty of Pu in spent fuel rods that the US does not recover (I'll let you speculate why) ... not to mention leftovers from recent political dealings.
Cooling in space is simple - use the vaccuum drop method.
The heaviest part is the shielding - you DO NOT NEED SHIELDING (as much) in space because there is no environment or people to protect from it ... just enough to reflect the neutrons and safeguard equipment. ... come on people - its not rocket science or nuclear engineering here

Red Pu?

[bbsalem]

Maybe the Russians and Chinese will corner the supply of Pu on earth and NASA and other space agencies will be forced to buy it from them to power their probes? Then we will have been probed by the Communists, yet again, and all due to our cheapscape policies. I think that Reds have figured out how to screw with Capitalism, just appear to the scarcity and miserly impulse in financial people. Beat them at their own game.