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A Nuclear Probe to Explore Earth’s Interior
- curtis 12y agoThis sounds like a more practical version of David J. Stevenson's 2003 earth probe proposal: http://news.nationalgeographic.com/news/2003/05/0514_030514_earthcore.html http://news.nationalgeographic.com/news/2003/05/0514_030514_...
- ChuckMcM 12y agoDid this go anywhere? The only papers if find that reference the original ideas (2005 and 2008) mention nuclear waste that melts itself into the Earths core.
- ISL 12y agoProbably not. That's a scary thing to build. Cobalt-60 gammas are hard to shield, and 2000K is really hot. The laws of physics don't forbid building such a thing, but I wouldn't want to be in the same building with it. Okay, so you have something that's so self-heating that it'll easily melt rock. In fact, it's hot enough that it self-liquifies quickly at STP. Cobalt reacts weakly with oxygen, but you'll still have to be careful with it in air, so you'll have to seal it in something; at 2000K, there are only a few materials with which you can hold and seal it, tungsten being one. Also, it's radioactive, and the tungsten sphere you put it in isn't nearly sufficient to stop the gammas. So, you get your tungsten sphere all ready to go, let the cobalt liquify itself, pour it into the sphere, and then lower/drop it into a borehole. Better not be any water down there, or it might come back up. Once you've got it doing it's melting thing and it's really deep at the bottom of a borehole, it probably can't hurt anyone. I can't imagine a funding agency being ballsy-enough to fund it, and _really_ can't imagine a nuclear regulatory agency being interested in letting you build a source that could get itself so thermally hot. TL;DR -- lots could go wrong.
- Crito 12y agoI imagine the safe way of deploying the thing would be to assemble it on-site, over the bore hole, robotically. Don't have any humans anywhere near the entire operation as long as all of that cobalt is in the same place (deliver it to the site with several delivery missions, each only having a relatively safe amount of cobalt). (Apparently the cobalt would be inserted into the tungsten sphere as a not-yet-liquid sphere. That would make the multiple deliveries and robotic assembly more difficult, so maybe a liquid-assembly like you suggest could be arranged.) How the hell do you weld tungsten anyway? Maybe make the sphere in two halves, then spin them up in opposite directions and push them together, to friction weld them?
- ISL 12y agoTungsten is usually sintered with a binder. I'm unaware of any welding techniques that work with it. For a similar fabrication job, check out the LARES satellite (which is awesome, elegant, and the densest free-falling object in the Solar System): http://www.esa.int/Our_Activities/Launchers/Launch_vehicles/Vega3/LARES_Laser_Relativity_Satellite http://www.esa.int/Our_Activities/Launchers/Launch_vehicles/...
- msds 12y agoLaser, electron-beam and atomic-hydrogen (no, not crackpot-conspiracy-theory "HHO" atomic hydrogen) welding can work with tungsten, in theory...
- kefka 12y agoInteresting that you mention HHO as crackpot theory. What I am familiar with are kits to generate HHO gas for hydrogen welding. Mainly, they rely on electrolysis of water and gathering of H2. Of course, the amateur kits have blowback preventers and other tech to prevent gas explosions. But nothing crackpot. Guess I don't read the cranks documents.
- VLM 12y agoAtomic hydrogen welding is basically taking a COTS plasma cutter and blowing H2 thru it and welding with it, not welding with H2 but with hydrogen ions. On a scale of hazardous welding technologies, its up there. Possibly the only thing I'd less enjoy doing by hand would be explosive welding or some of the thermite processes. Its not "is there going to be a fire" but "how much damage will the inevitable fire cause vs the cost of alternative fabrication" On the bright side (oh the pun) during the welding its pretty efficient at preventing weld pool oxidation. On the bad side, if long term hydrogen embrittlement is an issue with the base metal, this is an interesting way to find out. Also you can get some gas porosity problems as the weld bubbles while cooling, exactly CO2 in soda water, although hydrogen is better than the noble gasses (like argon in a plasma cutter) Burning homemade H2 in a modified acetylene torch like you're talking about is comparatively harmless with the exception that H2 can find leaks that acetylene can't find, although its not that much worse. Oh and the regulator is different because acetylene comes out of a coke bottle solution like CO2 out of soda, but hydrogen comes out of a tank like O2 so the pressures are a bit higher.
- ISL 12y agoI spoke too-quickly regarding the radioactive shielding requirements, they're more manageable than I thought [1]. For the 10-cm thick tungsten wall, following [1], it looks like the shielding factor is ~25,000. That's more significant than it sounds, because only the gammas emitted at the surface of the cobalt see that shielding factor. The rest are better shielded, up to factors of 10^11 in the best case (propagating all the way across the sphere). It's still a spooky thing to assemble, but it does appear that if the shielding is preserved, that it could be done without ridiculous quantities of assembly/launch shielding.
- cstross 12y agoIt's utterly insane! A 30cm sphere has a volume of around 1.1 x 10^5 cm^3. Cobalt's density is about 8.9g/cm^3, so we're looking at roughly 10^6 grams of 60Co, or about a ton of the stuff. 60Co puts out 1100 Curies of radiation per gram, so this sphere represents about 1.1 billion Curies. To put this in perspective, a nuclear weapon detonation releases on the order of 1-5 MCuries of fallout: the Chernobyl disaster vented about 200 MCuries into the environment: total contamination left behind by the Soviet nuclear weapons program is estimated at around 3 GCuries. I am not sanguine about a research experiment that requires assembling multiple Chernobyl's worth of high level gamma emitters in a red-hot capsule, dropping it on the ground, and hoping it stays intact ...
- wmeredith 12y agoWhat a fascinating proposition. FYI: This blog article is from 2013 and is about scientific papers written in 2008 and 2005. A few minutes of cursory Googling turns up nothing else.
- valarauca1 12y agoIt was actually used as the basis of a Young Adult book in 2005 [1] or a very similar idea. The book uses a large molten ore body created from explosive charges. [1] https://en.wikipedia.org/wiki/Artemis_Fowl:_The_Opal_Deception https://en.wikipedia.org/wiki/Artemis_Fowl:_The_Opal_Decepti...
- cpeterso 12y ago"... and they were never heard from again!"
- 3327 12y agowow this is actually genius cheap and doable can some please forward this to Jeff Bezos?
- rdmcfee 12y agoWith the accelerating change in the earth's magnetic field it would be fantastic to drop a few of these bad boys and see what's actually going on down there.
- gipp 12y agoWouldn't get anywhere near the dynamo, sadly.
- cromwellian 12y agoSeems that the technique would also work on Europa to melt its way into the ocean underneath the ice.
- panzi 12y agoBut if there really is live down there, how do you then explain to them that you just dropped some nuclear waste into their ocean?
- rational-future 12y ago"We have reasons to believe you posses weapons of mass destruction" Worked fine with all the depleted uranium dropped on Iraq.
- TeMPOraL 12y agoEuropeans (pun intended) could be much better equipped to retaliate than Iraqis.
- Crito 12y agoIt has definitely been suggested: http://en.wikipedia.org/wiki/Cryobot http://en.wikipedia.org/wiki/Cryobot http://www.jpl.nasa.gov/releases/2002/release_2002_6.html http://www.jpl.nasa.gov/releases/2002/release_2002_6.html
- grecy 12y ago> As the probe descents deeper, the rate of descent will gradually slow until the probe reaches a depth of 100 km after ~30 years The article doesn't mention - why will the probe stop descending?
- toomuchtodo 12y agoIncrease in density as you get closer to the core.
- TallGuyShort 12y agoOn top of which gravity is going to lessen as you get to the center of mass, so even a little resistance will eventually become extremely significant...
- privong 12y agoOnly 100 km down, the gravitational acceleration would not be reduced by very much. Assuming the Earth is spherical and has uniform density, the probe would only be below ~3% of the mass and would be less than 2% closer in distance. So the acceleration felt by the probe would only vary by a few percent.
- 4ad 12y agoAt 100km, the gravitational acceleration is actually higher than at the surface. http://www.wolframalpha.com/input/?i=gravitational+acceleration+at+100km+below+surface http://www.wolframalpha.com/input/?i=gravitational+accelerat... In fact, it increases until 3500km below the surface (2800km radius). http://en.wikipedia.org/wiki/Gravity_of_Earth#mediaviewer/File:EarthGravityPREM.svg http://en.wikipedia.org/wiki/Gravity_of_Earth#mediaviewer/Fi...
- S4M 12y agoThe article also suggests using the probe to analyze the composition of other planets. Is that doable? It seems pretty tough to me to carry on a space ship a nuclear probe hot enough to melt rocks.
- jessriedel 12y agoIf you're going to carry a probe powerful enough to melt rocks on a spaceship, the probe better damn well be nuclear powered. There's no other way to get the energy density to make the launch costs feasible.
- S4M 12y agoI agree that the prob will have to be nuclear powered. What I find risky is to put it on a spaceship.
- jerf 12y agoIf we're to the point where we're even considering this, presumably we're in a position to obtain the materials from either local sources, or possibly asteroid sources. This presumes a level of tech much higher than our current one since at our current one we can barely land probes that can drill semi-aimlessly into rocks. (And don't get me wrong, that's a hell of an achievement that gives me the Warm Science Fuzzies that we can pull it off... but it's also a long way from being able to do this sort of probe on other planets.)
- ars 12y ago"Subsequent re-crystallisation of the molten material will generate intense acoustic signals." Why would it make any noise?
- ejr 12y agoI imagined to be like ice which does make crackling noises when it freezes due to expansion, except cooling rocks will shrink causing the same. Re-solidifying rock would probably sound louder and the acoustic signature may travel further.
- ars 12y ago"transform some of the energy from radioactive decay" Not so simple. You need a hot source and a cold sink to transform energy. Where's your cold sink? This thing is intended to melt what's around it, and the outside of the probe is not that different in temperature from the inside.
- gipp 12y agoErm. If it's melting the rock around it, then the rock is your cold sink. By the time the temperature of the rock catches up with the probe, it's already molten anyway.
- ars 12y agoThe rock would not work as a cold sink - the cold rock is too far from the probe. The rock right near the probe is at almost the exact same temperature.
- kijin 12y agoAnd that's exactly why the probe will take 30 years to move 100km. It's going to be a very slow process.
- dredmorbius 12y agoMore specifically: the interior of the probe is 2000F, the surrounding rock melts at 1000F. That's a pretty good temperature gradient right there.
- cperciva 12y agoYou need a hot source and a cold sink to transform energy. Only if it's thermal energy. Given the small amount of power needed, they could easily use a betavoltaic generator.
- InclinedPlane 12y agoCo-60 decays via beta (and then gamma) decay. It's a straightforward matter to convert the beta decay into electrical power.
- doctorKrieger 12y agowhy cant we dispose our nuclear waste in this way?
- mikeash 12y agoI don't think most nuclear waste gets nearly hot enough.
- JetSpiegel 12y agoIf it did, we could just harvest it.
- mikeash 12y agoExcellent point. If you have a sphere that can maintain 2000C and melt through rock, toss it into a steam turbine and hook it up to the grid.
- cpeterso 12y agohttps://en.wikipedia.org/wiki/Deep_borehole_disposal https://en.wikipedia.org/wiki/Deep_borehole_disposal
- kimonos 12y agoBrilliant idea!
- bediger4000 12y agoA Caltech professor, David Stevenson, proposed a temperature-resistant probe immersed in a blob of molten iron: Stevenson, David J. Mission to Earth's Core - A Modest Proposal. Nature, 423, 239-240, 2003a. No radioactivity necessary, and the PDF is here: http://mathcs.albion.edu/~mbollman/Honors/ToTheCore!.pdf http://mathcs.albion.edu/~mbollman/Honors/ToTheCore!.pdf
- RachelF 12y agoWhat prevents it from cooling down?
- ridgeguy 12y agoThe post states that tungsten "...has a low corrosion rate at elevated temperatures." This is not accurate. Tungsten oxidizes in air beginning around 600°C and as the temperature increases, the tungsten oxide layer scales off, exposing underlying metal to further oxidation. (see, for example, http://labfus.ciemat.es/AR/2011/C_004/AM_4x.pdf http://labfus.ciemat.es/AR/2011/C_004/AM_4x.pdf) Tungsten is great for high temperature use in vacuum, neutral (the inert gases) or reducing environments (hydrogen, for example). You can use it nearly up to its melting point in those conditions if you aren't too dependent on structural integrity. In oxidizing environments (air, oxygen, water, halogens, silicates, etc.) it fails quite rapidly. Molten rock is replete with chemical species that react with tungsten at elevated temperatures. At 2000°C, the tungsten blanket covering the Co60 heat source would be corroded away, I'll guess, within a week of launch on its journey to the center of the earth. Although it would be incredibly costly, they might have better luck with iridium or rhenium. Nevertheless, a fun mission to think about.
- Natsu 12y ago> A self-sinking probe is basically a dumb probe measuring less than 100 cm in diameter - a lump of nuclear waste encapsulated in a tungsten sphere and sunk into the ground. Even more so if you wonder if it couldn't be a way to dispose of waste. Also, if corrosion was an issue, perhaps they could coat it with something?
- gambiting 12y agoNuclear waste is waste because it doesn't produce enough heat anymore to be useful in production of electricity. So I doubt that spent nuclear fuel would be able to produce 1000C+ temperatures for 30 years to bury itself deep enough.
- DCKing 12y agoIANAG, but it probably doesn't need to get 100km under the ground. It only needs to go to the depth at which the nuclear waste stops being a problem. With a good amount kilometers of rock between the surface and the waste, the danger is already gone. Furthermore, melting the waste and have it move thorugh the mantle will lower its concentration and will over time have the heavy materials fall into the core. My guess is that the point at which the nuclear waste becomes less problematic than current methods will probably occur quite quickly, just a few kilometers if that. The point at which the tungsten corodes and the waste can be swept away doesn't seem to be that deep either.
- BorisMelnik 12y agoif they get to the center they will find the gnomes, which won't end well.
- gulpahum 12y agoThis sounds like a controlled version of the China syndrome. http://en.wikipedia.org/wiki/Nuclear_meltdown#China_Syndrome http://en.wikipedia.org/wiki/Nuclear_meltdown#China_Syndrome
- entangledqubit 12y agoA patent for a similar device from back in the 60s: http://www.google.com/patents/US3115194 http://www.google.com/patents/US3115194 Happened to see it while archiving the inventor's papers. :)
- spingsprong 12y agoWould this produce a new volcano? Or would the magma just freeze as it travels through the relatively cool hole?
- dredmorbius 12y agoMy read is that the rock would re-fuse above the probe, so no: "Heat generated from the decay of radioactive cobalt-60 allows the probe to melt its way into the Earth. The probe is estimated to melt down to a depth of 20 km in ~1 year. As the probe descents deeper, the rate of descent will gradually slow until the probe reaches a depth of 100 km after ~30 years. By melting its way into the Earth, the probe will leave behind a wake of molten material. Subsequent re-crystallisation of the molten material will generate intense acoustic signals."
- youaredoomed 12y agoWhy not place the sphere into a pre-made hole so it will make it to the center of the planet faster?
- jimmyswimmy 12y agoA couple reasons, I'd bet - first, a hole wide enough to fit the probe is pretty unusual, and would be an expensive research project all on its own. Second, the probe near the surface will emit the largest signal, so you get some really good SNR data to calibrate your algorithms against. If you don't understand the signals you're receiving when it's shallow, you won't understand them any better when it's deep - a regime where we have more theories than data. Or maybe something else.
- nacnud 12y agoDrop it into a volcano, for example?
- msane 12y agoWhat was that recent speculation based on seismic resonance about there possibly being a large amount of previously un-theorized water, rather than rock, somewhere in the interior?
- deleted 12y ago[deleted]