I recently played Killzone 2, and the only thing that particularly stood out to me was the gun that shoots lightning. Besides being the only unusual weapon in the KZ2 arsenal, it was extremely well-realized, and actually looked like it would be functional. Would a gun that shoots lightning actually be possible? And would lightning in general make an effective weapon?
Possible? Maybe. Effective? Well, you could probably get it to maim/kill people. Practical? Absolutely not.
There’s nothing particularly exotic about lightning. Air within a cloud circulates through electric fields, causing the water within it to pick up electric charge and thus causing electric charge to build up within the cloud. The cloud is separated from the ground by a body of air with a given dielectric strength (read: resistance to having electrical shit travel through it). Once the electrical charge of the cloud is great enough to overcome the dielectric strength of the air beneath it an interesting thing happens: the insulating properties of the air not only fail, they break down entirely, resulting in the formation of an electrically conductive path of ionised air between the ground and the cloud called a leader. Through this leader there can either be an electrical discharge from the ground (which is also highly charged at this point) to the cloud, or the cloud to the ground – either way you get lightning strokes.
This is a really simplified version since the exact mechanisms behind lightning generation in clouds aren’t really understood that well, but in general you need two things to make lightning: a relatively large quantity of charge and a path of least resistance for it to travel through to whatever you want to hit with that charge. The basic mechanism can be reproduced by using a van de Graff accelerator to build up a large static charge and then allowing it to discharge through something moved close to the sphere – a negatively charged rod, your finger etc. etc. It’s the same principle, except the amount of charge you’d need to kill somebody is fairly large, and having to trick somebody into moving close enough to your charge source for it to discharge naturally wouldn’t make it a very good weapon.
So really what’s needed here is a way of creating a path of least resistance between you and your target, and at this point you say something along the lines of “Well, lightning looks pretty but if I wasn’t too bothered with having the actual lightning effect why the hell wouldn’t I just use a pair of wires?” And lo, you have invented the taser. Sure, you could try and gin up some way of creating an ionised stream of air like a lightning cloud does, but the problem here is that you can’t control where that stream goes – the lightning bolt could hit the target, it could hit somebody standing next to the target, it could decide to try and earth itself through your shoes, the list is endless. If your objective is to pass a current through somebody to hurt or kill them then the taser setup is infinitely more practical; if your objective is simply to hurt or kill somebody I recommend using a regular bullet-firing gun, since this would be much more effective even if you could tell the lightning where to go. Lightning is an unpredictable natural phenomenon that can only be induced, not controlled, and this makes it a very poor weapon.