Sciencemadness Discussion Board

Rock blasting with HV capacitor

jock88 - 27-4-2015 at 08:25


Has anyone any views on blasting rocks with a high voltage capacitor.
Are they successful?

Patent uses some energetic material along with the capacitor 'blast'.

Big beast of a homemade capacitor would do the job. A read danger no doubt

Book on the subject here

There's nothing like a bit of green rock blasting!

[Edited on 27-4-2015 by jock88]

Fenir - 27-4-2015 at 16:17

Take my advice with a whole shaker full of salt because I have only basic knowledge of HV capacitors. I think discharging a high current cap through a thin wire, fed through a rock, could vaporize the wire and blow the rock apart.

diddi - 27-4-2015 at 17:06

capacitors act like a battery, except the energy in a capacitor is stored electrostatically rather than chemically. so the energy can be retrieved from a capacitor in an instant. the amount of energy stored is affected by 2 variables; the voltage of the electricity used to charge the capacitor and the total amount of electricity stored (the charge).

The capacitor is composed of two plates (charged oppositely). the size of the plates limits the overall amount of charge stored. the plates are insulated by a material known as a dielectric. the thickness and type of material used in this insulator is the limiting factor for the voltage of the electricity stored. All capacitors will thus have two values quoted on the package. a voltage and a capacitance measured in Farads (usually micro- or pico-).

To produce a substantial discharge, a combination of high capacitance and high voltage is best, since each stored electron will have a lot of energy and there will be many electrons available. The notion of melting a rock using a capacitor imho is ridiculous for two reasons. capacitor discharge requires a short unobstructed path for the spark to arc across, much as a "stick" welder will not arc if the metal is a bit greasy etc. Also the amount of charge required to be effective would be enormous and impractical to store in a capacitor.

That said, the use of a capacitor as a detonator is quite feasible. I simple timing circuit could be used to unleash the spark. I have seen vision of a capacitor spark so fierce that it blew the claw off a claw hammer when the hammer was used as the path to "short" the terminals of the capacitor. There is no way you could split rocks without the use of EMs within the context of the OP

Hennig Brand - 27-4-2015 at 18:01

The charge stored in the capacitor is just meant to provide the energy to ignite the fuel/oxidizer mixture which then does the heavy lifting of fracturing and moving rock. Basically a high powered igniter for a relatively insensitive fuel/oxidizer type explosive.

jock88 - 28-4-2015 at 03:06

Something like this perhaps.
I guess you would still have to drill holes etc. The rock in the vid is a 'sitting duck' not quite like a large smooth packed rock face.
The addition of some explosives/metal powers-in-gels would no doubt help

Hennig Brand - 28-4-2015 at 17:38

Interesting, that does appear to be rock blasting using only electrical power. The big problem is likely delivery, even EBWs which are low power in comparison to what would be needed for practical rock blasting require electrical power that is difficult to deliver to the target from any significant distance.

Here is a little something for comparison purposes (hopefully I haven't messed up the numbers):

Take TNT as an example, which is actually only a moderately powerful explosive. If we take 1kg of TNT in the shape of a sphere it will have a radius of about 0.05246m (V=4/3*pi*r^3). It takes about 7.602*10^-6s (ca. 7.6 microseconds) for the shock zone to travel from the center to the outer edge of the sphere of TNT (t=D/V=0.05246m/6900m/s). The energy content of TNT is given as 4.7MJ/kg (Wiki). The power produced by the 1kg sphere of TNT during detonation, (P=E/t), is more than 618 GigaWatts or 618*10^9 Watts! For the powerful grades of dynamite and the more powerful military explosives the power would be even higher. Larger explosive charges will of course be more powerful too, doubling the radius means the shock zone takes twice as long to traverse the charge, but the volume and therefore mass has increased by eight times which means the charge produces 4X the average power. Very hard to compete with chemical explosives especially since they can normally be placed exactly where they can work most efficiently.

[Edited on 29-4-2015 by Hennig Brand]