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Comment by sparker72678 | Hacker News Reader

> In its low-power state, with each torch consuming 500 kW, Helming estimates a total power draw of 40 megawatts. If you need to get cracking, the high-power state would draw as much as a constant 120 MW.

40MW at low power. How in the world do they think they’re going to get that much power at a drill site and stay low cost?

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For me, the keyword from the article was

> developing

meaning they haven't completed the tech yet. This is likely a marketing puff piece designed to drum up investment interest. I'll believe wild claims like

> 98% cheaper

once they actually happen.

How will they cool the tunnel? That's for a 1 meter tunnel. If they're cooling it with air heated by 100 C, the airflow will have to be supersonic.

Hmm, liquid sodium, lead or molten salt cooling?

Edit: 40 MW is just 150 liters per second of water with a 80 °C temperature rise.

> 40 MW is just 150 liters per second of water with a 80 °C temperature rise.

That's already out of spec for even the highest rated fire hydrants, so you better hope you have a river handy.

It will also require big pipes to go into your tunnel since you will have to make do with low pressure pump(s) due to your pipes needing to be elastic.

"just"--that's the municipal water supply of a small town.

40MW isnt that much, water can do it (granted at a serious cost)

I'm not even sure they could get that kind of power into the small tunnels they'd be making.

Seems to me, if they really can plasma cut rock it would be way easier to slice out sections and remove large chunks of solid rock. Or chop it into many smaller "bricks" and move those out.

A truck full of batteries to act as a capacitor? Run it for x minutes, wait a while to recharge, go again. Alternately, being a truck mounted gas turbine generator and plenty of fuel.

Still probably not a great plan.

Monster Cables

Receiving power from where? 40MW is the capacity of a medium sized wind farm. The larger tunnel configuration uses 1.38GW. That’s more than most large scale coal or nuclear plants.

Even if they could obtain the supply from a plant operator the cabling to get to the site of the tunnel cost a fortune

If you had pure copper conductors could you even get enough into a 1 meter space to conduct that much power?

If we're going to need high temperature superconductors and fusion power, this isn't the first thing I'd use it for.

(I can't deny the fun factor of this, though.)

An 1cm-ish thick copper cable can handle about a kiloAmp without melting. At 10kV you'd need 12 of them, so call it a 5cm thick bundle with some kind of cooling for the 1m tunnel that needs 120MW.

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