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Old 06-14-2019, 11:13 PM   #51
lwcamp
 
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Default Re: (Ultra Tech) How realistic are Electrolasers?

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Originally Posted by Johnny1A.2 View Post
There's always been something about the electrolaser concept that 'feels' impractical to me.

For one thing, local conditions seem like they'd affect these things more than they would most weapons. Rain, humidity, etc. What would happen if you fired one in a blizzard? Would thick fog do anything?
When I went through the math, realistically humid or wet weather would increase the rate of ion recombination and thus increasing the electrical resistance of the plasma channels and decreasing the range. Wet weather would also lower the resistance of the target, making the discharge more effective if you could get it to them.

The rules in Ultra-Tech for adverse weather don't seem particularly realistic.

As for a blizzard or fog, what are you doing shooting at something you can't see?

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Originally Posted by Johnny1A.2 View Post
What happens if the user's aim is a little off and the ionized path intersects something electrical with some serious juice in it? Or something that is more flammable than it looks?
I would certainly not recommend shooting at thunderclouds or high voltage electrical transmission lines. However, it might not be as bad as all that. In my analysis with an example system of 0.1 J UV laser pulse delivered over a 3 cm wide beam and a duration of 0.1 ms, the resistance per meter of beam length near the aperture is about 20 kOhm/m, and it increases with distance so that at 10 meters the resistance is about 285 kOhm. Lets call it 300 kOhm for round numbers. A human body is about 100 kOhm for a total resistance of about 400 kOhm assuming the current just runs down one ion channel through the body to ground. (If it ran down both channels, you get a total resistance of 250 kOhm. If it needed to run down one channel and back down the other, it would be more like 700 kOhm - except that in that case the current would just go through the gun instead of through its user).

A typical industrial power main will be about 500 V. Municipal power distribution lines run at about 11 kV. Long distance power transmission in the USA runs at about 110 kV.

So if the beam connected to an industrial breaker box or exposed wiring, the channel would carry a current of 1.25 mA for 0.1 ms. Compare this to a Taser which delivers 1.9 mA currents for 0.1 ms.

Electrical contact with a municipal power line would give you 27.5 mA for 0.1 ms. This would cause a painful shock. However, the threshold for lethal current is usually said to be around 100 mA, so the user would probably survive.

Shooting a long distance power distribution line is another story. This produces a current of 275 mA, which could be lethal. Hopefully the electrolaser gun has surge protectors.
EDIT - 275 mA can be lethal for currents applied over a second or two. For the 0.1 ms duration we have here, this is unlikely to kill.

Note that these examples assume a 10 m range. At longer ranges, the current will be lower; at shorter ranges it will be higher. It also assumes no insulation from the gun itself, which would be a major safety violation. Since the gun is probably well insulated (to protect the user from electrical malfunctions from the gun, as per usual electrical equipment certification guidelines), all of these currents will be much lower.

There is one last issue to consider. If you are shooting through a region where the electric field is near or above the threshold for cascade breakdown (plasma formation due to a runaway process where each electron gains enough energy between collisions with air molecules to knock further electrons off), but a spark has not yet been initiated due to a lack of seed charges, the ion channel the electrolaser creates could be just the thing to kick-start this process. This would lead to a highly conductive spark forming - and high conductivity leads to nearly constant voltage along the discharge such that the electric field is concentrated at the tip of the propagating spark and becomes more intense as the spark grows (you keep the same potential difference, but across less distance, so the field in V/m gets stronger). Consequently, under conditions of very high electric field an electrolaser shot might initialize a spark discharge back to the gun and its user. This is probably going to be an unusual situation, except in thunderstorms.

On the other hand, you don't have to worry about ricochets or over-penetration. And even hitting the wrong target is not going to have all that severe of consequences. So this is something where firearms are more 'impractical' than electrolasers.

Quote:
Originally Posted by Johnny1A.2 View Post
What happens if there's an exchange of fire and your ionized paths intersect when they fire? That sounds unlikely, but the perversity of the universe, etc., etc.
If one path of one shot intersects both paths of the other shot, it will short that other shot out across the intersecting path. You can come up with other configurations of intersecting paths, and then break out Kirchhoff's circuit laws to figure out the resulting current flows. Since the gun is likely built with good engineering tolerances it is unlikely to suffer, and because the gun is well insulated the user will probably not be affected.

Luke

Last edited by lwcamp; 06-14-2019 at 11:23 PM.
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Old 06-15-2019, 12:18 AM   #52
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Default Re: (Ultra Tech) How realistic are Electrolasers?

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Originally Posted by lwcamp View Post
There is one last issue to consider. If you are shooting through a region where the electric field is near or above the threshold for cascade breakdown (plasma formation due to a runaway process where each electron gains enough energy between collisions with air molecules to knock further electrons off), but a spark has not yet been initiated due to a lack of seed charges, the ion channel the electrolaser creates could be just the thing to kick-start this process. This would lead to a highly conductive spark forming - and high conductivity leads to nearly constant voltage along the discharge such that the electric field is concentrated at the tip of the propagating spark and becomes more intense as the spark grows (you keep the same potential difference, but across less distance, so the field in V/m gets stronger). Consequently, under conditions of very high electric field an electrolaser shot might initialize a spark discharge back to the gun and its user. This is probably going to be an unusual situation, except in thunderstorms.
You can use this to call down lightning? Can I get one in the shape of a hammer?
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Old 06-15-2019, 01:37 AM   #53
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Default Re: (Ultra Tech) How realistic are Electrolasers?

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You can use this to call down lightning? Can I get one in the shape of a hammer?
People have experimented with laser triggered lightning, though it seems to generally be done with terawatt pulse lasers, not the more diffuse beams discussed in this thread.
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Old 06-15-2019, 10:54 AM   #54
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Default Re: (Ultra Tech) How realistic are Electrolasers?

So in some "parallel reality", electrolasers are banned outright, because some unlucky sod fired one in a storm and got struck by lightning. And the ensuing public went with a paranoid overreaction like it often does.
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