Yes I have and I will give you the reason why I decided against using them!
Super capacitors are excellent for storing large amounts of energy via a very large capacitance value. While this is great for many applications, it is actually not the best for use in fast discharge systems like railguns. Although I said in one of my comments below that I was going to add a series inductor to "slow" the current down a bit, the timescale of this slowdown is still on the order of singular milliseconds. Super capacitors typically cannot discharge the majority of their electrical energy in the time-frame required so for that reason they are not well suited for the task.
Another major factor in not using super capacitors is that they have low operating voltages. The trade-off in having a very high capacitance is that their is much less space between the plates, or graphene sheets in most super capacitors, so there is less of a potential gap meaning a lower breakdown voltage. Having a higher operating voltage for railguns is desired for a few reasons:
1) Ohm's law tells us that Voltage = Current X Resistance. Doing a little bit of rearranging you get Current = Voltage / Resistance. From this we can see that the lower the voltage, the lower the current and therefore, the lower the pushing force on the railgun projectile. Additionally, the power stored in a capacitor is: Power = (1/2) X Capacitance X (Voltage^2). As you can see from this, you get a lot more power from higher voltage than higher capacitance(linear vs quadratic rates).
2) All capacitors are non-ideal in the sense that they have parasitic inductance, especially electrolytic ones. The bigger the capacitor, the large this value typically is. This means that it will take a lot longer for the discharge to reach its peak "steady state" current value. I say "steady state" because on the time scale of the inductor effect, the current is essentially steady. Increasing the voltage increases the current through the inductor.
3) Putting a bunch of smaller capacitors in parallel allows you to have a larger current pulse than what the equivalent singular one would. This is due to the above mentioned parasitic inductance.
There are a few other smaller factors as well, but these 3 are the major ones why I did not use super capacitors. These ones were also a good deal on Ebay:)
Yes I have and I will give you the reason why I decided against using them!
Super capacitors are excellent for storing large amounts of energy via a very large capacitance value. While this is great for many applications, it is actually not the best for use in fast discharge systems like railguns. Although I said in one of my comments below that I was going to add a series inductor to "slow" the current down a bit, the timescale of this slowdown is still on the order of singular milliseconds. Super capacitors typically cannot discharge the majority of their electrical energy in the time-frame required so for that reason they are not well suited for the task.
Another major factor in not using super capacitors is that they have low operating voltages. The trade-off in having a very high capacitance is that their is much less space between the plates, or graphene sheets in most super capacitors, so there is less of a potential gap meaning a lower breakdown voltage. Having a higher operating voltage for railguns is desired for a few reasons:
1) Ohm's law tells us that Voltage = Current X Resistance. Doing a little bit of rearranging you get Current = Voltage / Resistance. From this we can see that the lower the voltage, the lower the current and therefore, the lower the pushing force on the railgun projectile. Additionally, the power stored in a capacitor is: Power = (1/2) X Capacitance X (Voltage^2). As you can see from this, you get a lot more power from higher voltage than higher capacitance(linear vs quadratic rates).
2) All capacitors are non-ideal in the sense that they have parasitic inductance, especially electrolytic ones. The bigger the capacitor, the large this value typically is. This means that it will take a lot longer for the discharge to reach its peak "steady state" current value. I say "steady state" because on the time scale of the inductor effect, the current is essentially steady. Increasing the voltage increases the current through the inductor.
3) Putting a bunch of smaller capacitors in parallel allows you to have a larger current pulse than what the equivalent singular one would. This is due to the above mentioned parasitic inductance.
There are a few other smaller factors as well, but these 3 are the major ones why I did not use super capacitors. These ones were also a good deal on Ebay:)