I was intrigued to read about a new tunneling machine that promises to bore through rock using plasma torches, much faster than existing technology.
Unlike conventional boring machines, which typically use massive cutting wheels to slowly excavate tunnels, Earthgrid's robot blasts rocks with high temperatures to break and even vaporize them via a process called spallation.
The machine can run on electricity, meaning it can also be emissions-free, depending on how energy is sourced. Earthgrid also claims that its system, which doesn't need to come into contact with the rocks directly as it excavates, is so fast and cheap it will open up a whole host of possibilities. In other words, projects that were once deemed economically unfeasible will now be possible.
Earthgrid is currently operating on pre-seed funding, and it is developing its "Rapid Burrowing Robot (RBR)", a spallation boring robot with several 48,600 °F (27,000 °C) plasma torches mounted on large discs.
When operational, the RBR will fire up those torches and rotate the discs to blast the rocky surface in its way. The torches on the discs are arranged in a Fibonacci spiral, meaning they widen out away from the center for full coverage. Debris is collected in small pushcarts.
There's more at the link.
It sounds very interesting, but there are two issues that the article doesn't address.
- How hot is the "debris" that the "small pushcarts" will collect? If the plasma is operating at over 48,000 degrees, the "debris" is likely to be just as hot when it flies off the tunnel face - in fact, it'll probably be molten rather than solid. What sort of "small pushcart" will be able to handle temperatures like that? How long will the debris take to cool down, to the point that it's more manageable? How will they stop molten debris from fusing to the pushcart as it cools down?
- In deep rock mining in South Africa, one of the primary problems is methane pockets in the rock. Gold and coal miners have learned to be very, very careful about drilling into them, because the methane can be ignited by any stray spark, leading to a catastrophic explosion. I'd imagine that a superheated plasma torch will be more than enough to produce the same effect, making tunneling through rock more than a little hazardous. How will the machine cope with that issue?
Peter
17 comments:
Depends on the type of rock. Some are susceptible to spallation, some are not. Really hard rock (e.g. granite) spalls well. Limestone or shale, not so much.
The rock isn't really vaporizing, but the temperature differential is so great that the rock thermally fractures.
It's old tech, really. Some granite quarries have used flame jet spallation for years. It was being researched as a good way to drill deep holes for geothermal energy extraction back in the 1980s. One of the members of my graduate research group at MIT did his doctoral thesis on flame jet spallation drilling. He did field tests and compared them to his computational models to predict drilling rates. This was done in cooperation with Los Alamos National Labs.
If they keep the tunnel head oxygen free, maybe just nitrogen they shouldn't have any explosion risk.
Makes repairs to the robot harder but we have a lot of experience in nitrogen atmosphere storage facilities to deal with that.
Interesting to see where this goes...
Burning bars...see the movie "Thief". Used by Chicago burglars in the 60's 70's. Technology taken from underwater work and the mining industry.
The reason why all commodities have decreased in real price, over the long term. We get better at getting them out.
Probably not useful for coal mining.
Jean
Molten rock. Emission-free. Sure.
I can't help but wince when I read things like this:
The machine can run on electricity, meaning it can also be emissions-free, depending on how energy is sourced.
First, no method of generating electricity is emissions-free if you look far enough back. Not just what's being burned, if it does that, but what was used to refine the materials that made the generator. Then ponder if they're saying the rocks aren't going to give off ... anything... when heated to 46,000 F.
Am I the only one who thought of the Horta from Star Trek, the original series?
The type of rock they are boring through with this is not likely to have methane pockets. This is more like for making tunnels through the Alps.
However, definitely not recommended for coal mines.
Vaporware.
And what they'll be dealing with is lava removal.
Let's see them build one that works, and successfully cut a tunnel with it, then we can talk.
The energy requirements much be staggering.
I agree; not only will this take LARGE amounts of energy, but also lots of ventilation to deal with the emissions from super hot rocks and burning debris.
The challenge of building equipment that can take the heat won't be trivial either!
I assume this is a very early stage company, far from any kind of prototype...
Anybody thinking about the prison break scene in Oath of Fealty (Niven/Pournelle) ?
Made me think of the movie Invaders from Mars (1953).
Science Fiction writer T.C. McCarthy has two books (Germline & Exogene) which feature a device called a "Fusion Borer". In his dystopian future, wars are often fought underground and minerals, particularly rare earth elements, are the prize.
He has an interesting background: PhD in Geology, worked for CIA and the US Patent Office. Maybe he knows what's in the works
That will need one heck of an extension cord, but I'm sure they have it.
I thought the conventional tunnel boring machines also ran on electricity, but probably less of it. Running a several-thousand horsepower fuel-burning engine of any kind in a tunnel requires an incredible ventilation system. It's simpler to either have power lines run to the site or set up a motor generator outside the tunnel.
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