A Nuclear Probe to Explore Earth’s Interior

http://beyondearthlyskies.blogspot.com/2013/09/a-nuclear-probe-to-explore-earths.html

by mike_esspe • 12 years ago

111 64 12 years ago

beyondearthlyskies.blogspot.com

ChuckMcM• 12 years ago

Did 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.

ISL3• 12 years ago

Probably 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.

Crito2• 12 years ago

I 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?

ISL3• 12 years ago

I 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.

wmeredith• 12 years ago

What 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• 12 years ago

It 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_Decepti...

cpeterso2• 12 years ago

"... and they were never heard from again!"

3327• 12 years ago

wow this is actually genius cheap and doable can some please forward this to Jeff Bezos?

rdmcfee• 12 years ago

With 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.

gipp2• 12 years ago

Wouldn't get anywhere near the dynamo, sadly.

cromwellian• 12 years ago

Seems that the technique would also work on Europa to melt its way into the ocean underneath the ice.

panzi• 12 years ago

But 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• 12 years ago

"We have reasons to believe you posses weapons of mass destruction"

Worked fine with all the depleted uranium dropped on Iraq.

Crito2• 12 years ago

It has definitely been suggested: http://en.wikipedia.org/wiki/Cryobot http://www.jpl.nasa.gov/releases/2002/release_2002_6.html

curtis• 12 years ago

This sounds like a more practical version of David J. Stevenson's 2003 earth probe proposal: http://news.nationalgeographic.com/news/2003/05/0514_030514_...

grecy• 12 years 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• 12 years ago

Increase in density as you get closer to the core.

TallGuyShort• 12 years ago

On 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...

S4M2• 12 years ago

The 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• 12 years ago

If 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.

S4M2• 12 years ago

I agree that the prob will have to be nuclear powered. What I find risky is to put it on a spaceship.

jerf• 12 years ago

If 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.)

ars4• 12 years ago

"Subsequent re-crystallisation of the molten material will generate intense acoustic signals."

Why would it make any noise?

ejr• 12 years ago

I 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.

ars4• 12 years 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.

gipp2• 12 years ago

Erm. 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.

ars4• 12 years ago

The 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.

dredmorbius2• 12 years ago

More specifically: the interior of the probe is 2000F, the surrounding rock melts at 1000F. That's a pretty good temperature gradient right there.

cperciva• 12 years ago

You 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.

InclinedPlane2• 12 years ago

Co-60 decays via beta (and then gamma) decay. It's a straightforward matter to convert the beta decay into electrical power.

ars4• 12 years ago

Is it really that simple? You can't have any active electronics - they would melt.

And the tungsten is touching the cobalt, with no air gap (i.e. to opportunity to harvest power from the electrons returning to the cobalt to neutralize charge).

How would you harvest the electrons?

doctorKrieger• 12 years ago

why cant we dispose our nuclear waste in this way?

mikeash2• 12 years ago

I don't think most nuclear waste gets nearly hot enough.

JetSpiegel• 12 years ago

If it did, we could just harvest it.

cpeterso2• 12 years ago

https://en.wikipedia.org/wiki/Deep_borehole_disposal

bediger4000• 12 years ago

A 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

RachelF• 12 years ago

What prevents it from cooling down?

ridgeguy• 12 years ago

The 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)

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• 12 years 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• 12 years ago

Nuclear 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.

BorisMelnik• 12 years ago

if they get to the center they will find the gnomes, which won't end well.

gulpahum• 12 years ago

This sounds like a controlled version of the China syndrome. http://en.wikipedia.org/wiki/Nuclear_meltdown#China_Syndrome

entangledqubit• 12 years ago

A patent for a similar device from back in the 60s: http://www.google.com/patents/US3115194

Happened to see it while archiving the inventor's papers. :)

spingsprong• 12 years ago

Would this produce a new volcano?

Or would the magma just freeze as it travels through the relatively cool hole?

dredmorbius2• 12 years ago

My 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• 12 years ago

Why not place the sphere into a pre-made hole so it will make it to the center of the planet faster?

jimmyswimmy• 12 years ago

A 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• 12 years ago

Drop it into a volcano, for example?

msane• 12 years ago

What 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?

A Nuclear Probe to Explore Earth’s Interior

Related Stories