An Induction Launcher?
First of all this is not a weapon of any kind, it does not fall under the UK's firearms acts as it doesn't have a barrel, it uses magnetic induction to repel objects not gas propellants. If it was to be considered a weapon then it would be in the same classification as slingshots, crossbows and bows. This project is intended for scientific purposes only.
So what is an Induction Launcher?
An induction launcher uses a changing magnetic field to induce a current into a piece of non-magnetic metal, the current induced in this metal creates a magnetic field which repels the first field, which in turn causes it to launch the metal. A very simple induction launcher consists of a pancake coil, a pulse energy source and a switch. The pulse energy source is a capacitor bank of high energy stored to hundreds/thousands of volts, the switch (either mechanical or sparkgap) allows this high voltage and current to flow to the work coil. The work coil is usually a pancake spiral, it is laid flat and covered in resin to stop it moving from the repelling of the magnetic field. The metal placed on the coil is usually an aluminium disk, the launcher can be known as the electromagnetic disk launcher.
At this time I'm currently in the process of building a large capacitor bank for my Z-pinch (look in other projects) which is perfect for an induction launcher. About 2 weeks ago I made a pancake coil which I used for the launcher today(its about 3" diameter), the piece of metal that I'm launching is an old aluminium heat sink, 40 x 70 x 2mm. For this experiment I thought that a maximum power of 1kJ at 900V should be sufficient, any higher and I would vaporise the mechanical switch. So I placed the coil flat, put the aluminium square on top, charged the bank to 900V, pressed the switch and BANG.
It completely destroyed the coil, It was filled with industrial glue so it was extremely strong. The aluminium hit my ceiling embedding a 5mm crater into it, the aluminium buckled. The switch was welded together, I managed to prize one set of contacts apart but the others had completely melted together.
So stupidly I did this indoors, so what do I expect it hitting my ceiling, but I certainly didn't think it would have the amount of kinetic energy that it did. I think that If I'm going to scale this thing up then It will have to be outdoors otherwise I will end up with a hole in my roof. The switch will have to be a lot more heavy duty and may possibly be a trigatron. The coil will require thicker wire and a lot of resin, I'm guessing it will only survive one shot again. This experiment was with an energy of 1kJ, I will have 8kJ available, although I don't think this project will go any further as it will have to be fired in a field and I require a mains supply to charge it.
I have wound another coil that I will fire at a maximum of 2kJ, to be honest I hope it will survive.
It is the same dimensions as coil used earlier but this time it has glue between the windings and is constructed a lot stronger.
I can't believe how long it is since I did anything along these lines. I have been doing a lot of thinking about what else I could use my large capacitor bank for, and it came back to this project. The only problem I have is switching the very large currents, but I think that I may have solved this. Basically I will have eight separate switches meaning that they only have to be capable of 1kJ each, to do this I will use trigatrons. A trigatron is a spark gap that can be controlled, two electrodes are separated by a gap, a third electrode has a high voltage source connected to it which causes arcing, the high voltage arc ionises the air and therefore resistance is greatly decreased. This in turn causes the power between the main electrodes to jump across, although not all of the power in the capacitors will be discharged. At my work we use turning tips that are alloys of tungsten, these just get thrown away when people are done with them, I save mine, these will become the electrodes. I have done a little test of 900V at 200J, it fired first time and discharged the caps down to about 100V, was almighty loud though.
This is one of the oldest pages on my website and it seems to be the one that I've done little with. Over the past week I have been finishing off the construction of my capacitor bank for another project. So when it is complete I will resume to make an 8kJ induction launcher, it will be mounted horizontally so that I can fire it through my chronograph to measure the kinetic energy and then the efficiency of the whole system. This thing doesn't have a barrel either so it does not fall under the firearms act, leaving it in the classification same as bows.
The bank is almost complete so I chose to do a couple of small tests. The first one was with the pankcake coil earlier in the pictures, just using the charging capacitors I launched a silver coil several metres in the air. The second test was to put the power up to 1700J and place a large aluminium heatsink on the coil. The heatsink went flying and the coil exploded, I suppose it was a crude experiment.
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