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The mantle - the layer under earth's crust is 1000C hot rock
in of a fuggy texture, not melting due to the pressure at
those depths (14 km into the crust and 2,900 km thick).
Since there is always a gradient in heat between the crust
and the mantle, the energy difference could be used to
and maintain a technologically working vehicle,
which may treat the pressure in the way deep submarines
are able to contain the pressure and heat (or cold) of the
deep sea, while providing surface pressure and heat inside.
Because this is an unmanned vehicle, the heat and pressure
inside could be above what humans would withstand, and
there exist many materials for the external surface that do
not melt at 1000C.
I presume that electronic communication could work
underground, but even if not, a trailing line of carbon-
steel or cupro-nickel wire could be used.
Journeys to the Center of the Earth
Discover magazine article. [Loris, Mar 10 2015]
Mission to Earth's core a modest proposal
Original paper in Nature (paywall - abstract free) [Loris, Mar 10 2015]
Mission to Earths core a modest proposal
Free pdf [xaviergisz, Mar 12 2015]
||Something like this could only sample its immediate environs. Although that is not hugely different from an extraplanetary rover.
||Will you lay out how the heat differential could be used to power the digger? Would it be via the towed cable? Because this is now converging on a drill. I would think that changes in temperature in a conductive material like rock occur over sizeable distances. At any given rover sized area there would be one ambient temperature.
||But maybe I am wrong. Water bodies have thermoclines. Is there a chthonic equivalent?
||A scientifically rigorous proposal has previously been made to send a probe to the Earth's core, using a nuclear bomb and 110,000 tons of molten iron.
||[bungston] 3.5°K / 100 meters, average over normal drilling
||//3.5°K / 100 meters, average over normal drilling
||Which would put the centre of the Earth
at...223,000°K. Unprobable and inlikely, if you ask
||Since the linked Nature article is paywalled, I cannot
resist quoting the first paragraph of the Introduction:
||"We live on the Earth's surface, which divides what is
above from what is below (Fig. 1). The part above us
(the rest of the Universe) is mostly empty, mostly
unknown and about 10^57 times larger by volume.
The part below is crammed with interesting stuff and
is also mostly unknown, despite its much greater
proximity to us."
||This has to be one of my favourite opening
paragraphs of all time. I also quite like, from a little
further into the paper:
||"The Earth's interior is opaque to electromagnetic
signals with periods of less than the mission
timescale, and neutrinos are difficult to use, so
acoustic communication would be best."
||I found that paper hard to read - the smug was dripping off the page and it had a unsettling mixture of excessive detail on some aspects and no detail on others. Interesting idea though.