[HN Gopher] Systems and Cost Analysis for Nuclear Subterrene Tun...
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Systems and Cost Analysis for Nuclear Subterrene Tunneling Machine
(1973) [pdf]
Author : benbreen
Score : 25 points
Date : 2022-09-05 16:47 UTC (1 days ago)
(HTM) web link (www.osti.gov)
(TXT) w3m dump (www.osti.gov)
| CSMastermind wrote:
| Skeptoid recently covered this topic in the context of the
| conspiracy theory that the soviets were weaponizing such
| technology: https://skeptoid.com/episodes/4845
| gene-h wrote:
| The soviets did something of almost the same level of sanity,
| they used rockets to dig holes rapidly.[0]
|
| An underground rocket is basically a specialized rocket nozzle
| pointed straight at the ground, the hot fast moving exhaust
| gases are able to excavate soil and rock. Speed up to 100 m/s
| through soil and 5 m/s through solid rock have been claimed.
| Here's a video of a missile being repurposed to do this[1].
|
| I've read, although I forget where, that there were concerns
| the soviets could use this technique to quickly place a nuclear
| weapon under west germany as part of a nuclear first strike. I
| suspect these concerns were quite short lived
|
| [0]https://en.wikipedia.org/wiki/Underground_rocket
| [1]https://www.youtube.com/watch?v=e7_tRmSIIEo
| wcoenen wrote:
| > 100 m/s through soil and 5 m/s through solid rock
|
| The Wikipedia article says meter/minute where it mentions
| those numbers, not meter/second.
| ceejayoz wrote:
| Same engineers that designed the firefighting tank with two
| MiG engines?
|
| https://www.caranddriver.com/features/a15138374/stilling-
| the...
| nickhalfasleep wrote:
| Imagine if all the national labs just designed tools like this to
| be built for the betterment of humanity instead of weapons.
| Humans are so silly.
| gene-h wrote:
| A far more 'sensible' approach to rapid tunnel construction was
| experimentally tested in the 70s. The Rapid Excavation And
| Mining(REAM) project showed how high speed kinetic projectiles
| could be used to to rapidly fracture rock to dig a tunnel.
|
| This is a fancy way of saying that someone dug a tunnel through
| rock by repeatedly shooting at it with a tank.[0] This was found
| to be impractical due to the cost of gun powder.
|
| However, a company has proposed a supersonic ramjet accelerator
| instead of a conventional gun to accomplish this. SCRAM
| accelerators use a specially shaped projectile that acts as a
| SCRAM jet when it's inside a tube full of fuel/oxidizer, which
| may be much cheaper than gun powder.[1] They have started to
| demonstrate fracturing rock walls with this approach.
|
| [0]https://apps.dtic.mil/sti/pdfs/AD0757116.pdf
|
| [1]https://www.hypersciences.com/applications/
| janef0421 wrote:
| Using an electromagnetically accelerated projectile, such as
| one from a rail or coil gun, could reduce the cost even
| further, since no fuel would be required. Has that been
| considered?
| lven wrote:
| Main problem is the rock melting temperature ~ 1500 to 2000 degC.
| Even the best performing nuclear fuels can only reach 1600degC in
| the fuel (TRISO Particle or FCM fuel) for limited periods of
| time, meaning 1000degC of heat delivered due to major limitations
| in the steels and heat transfer. They realized this early on in
| the Subterrene project at Los Alamos, and transitioned to
| electrically heated electrodes like graphite and tungsten. They
| even did field tests near Bandelier National Monument, digging a
| large diameter door sized hole using 100s of small diameter holes
| to form the perimeter. Even then, there are material degradation
| problems especially in the presence of air and water, that make
| rock melting pretty challenging. More recently, an MIT spinoff
| (Quaize or Quarkz or something like that) is using microwave
| emitters to vaporize the rock - which reduces material and
| mechanical challenges. But it's not ideal for large diameter
| holes - mostly for geothermal, fossil, or utility boring.
|
| It's not clear to me that melting is less energy intensive than
| digging (and all it's related machinery and material movement).
| nickpinkston wrote:
| I think it's pretty clear from an energy perspective that
| melting/vaporizing or even pulverizing the rock is waaaaay more
| energy intensive as the force to shear rock is orders of
| magnitude less than melting it.
|
| One way to think of this is to just imagine the chemical bonds
| holding the rock together. Tricone drills and TBMs both just
| sheer the rock, the latter on a massive scale, which is only
| has to expend that localized bond energy, whereas melting all
| of it is massively inefficient even with good heat recovery.
|
| One thing I've wondered is if a focused energy beam could just
| locally break the bonds in a way that'd produce pieces
| optimized (size, shape, etc.) for transport back through the
| tunnel. In this way the minimum of energy needs to be expended
| by reducing the linear distance of cutting.
|
| However, energy beams still have to heat up the rock a lot to
| vaporize it, so this would still locally be less efficient than
| cold sheering that current methods use, so when you think about
| it, TBMs, etc. are actually doing pretty good.
| saddlerustle wrote:
| Why does efficiency matter at all? Tunneling costs thousands
| of times more than the energy cost.
| peteradio wrote:
| Could you use a nuclear element to directly create pressure
| waves against the material? Something like: nuclear fuel,
| graphene drum head, water injectors to drive the drum
| expansion.
| iancmceachern wrote:
| I think this problem may be one if the classic solid state is
| not actually better than the old-school mechanical solution.
|
| As an experiment, it would be fun to architect 2 designs. One
| that has a fancy microwave or thermal rock melting setup, one
| that has a traditional rock drilling approach, both powered by
| a nuclear power source. Add up the cost of ownership for both,
| and I'd bet the mechanical solution comes out on top.
| nickpinkston wrote:
| Fully agree
| prox wrote:
| This sounds like an ideal candidate for nuclear. It's underground
| functioning would make it relatively safe? And it wouldn't cost a
| lot of fuel.
| klabb3 wrote:
| It would be fun if it ran a random walk guidance system of a
| roomba, and you could just let it go on its own. When will it
| visit your city? Oops, a high pressure magma pool, better turn
| around.
|
| Like a cursed Thomas the tank engine.
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