# What would be the best capacitor to use for a railgun that uses a capacitor as the projectile?

I have had a long-time interest and fascination with railgun technology and for a long time I have wanted to build a small-scale, simple railgun as a scientific experiment. This railgun is designed to use a capacitor as the projectile.

I want to point out that I am not an electrical engineer nor do I have a background in working with electronic components nor with building things with electronical components. I do have a self-taught understanding of basic circuit design and how some basic electrical components work, such as batteries, resistors, diodes, and capacitors.

I am seeking design advice on the best type of capacitor that I should buy for this simple railgun. I have recently been doing a lot of online research on capacitors, and at this point, I am rather confused by all the various types, sizes, and specifications.

My goal with this simple railgun is to try to launch a small capacitor that will travel at least six meters in distance. I am planning to use four D-size batteries to charge up the capacitor.

I am thinking that to achieve this goal I will need to use a low-weight capacitor, say one weighing 3 ounces or less, yet one that will produce enough current for a long enough time to accelerate the capacitor to the point that it travels at least six meters in distance.

Below is a conceptual design drawing I made to illustrate the working principle of this simple railgun:

What would be the best capacitor to use for a railgun that uses a capacitor as the projectile?

• Cap as projectile? Why would you expend a charge storage device that has pretty miniscule energy storage? I suggest you read up on the magnetic bits of en.m.wikipedia.org/wiki/Railgun 6 meters should be easy enough with a permanent magnet... a D battery is 1.5V.Capacitor energy is .5*Cap*Volts^2...
– Abel
Commented Sep 12, 2023 at 2:43
• Shiva Star - buts that's how I roll;) "Shiva Star was also used as a dense plasma focus driver in the mid-80s, and as an experimental magnetic driver for conventional projectiles in the late-80s." en.wikipedia.org/wiki/Shiva_Star. Separately, accelerations of 100 billion g were obtained 30 years ago. Not sure where the mark is currently. Commented Sep 13, 2023 at 22:56
• Oh, the fun part is designing the switch that dumps a few megajoule in under a microsecond. Commented Sep 13, 2023 at 22:59
• @PhilSweet, I didn't know about the Shiva Star system. I would love to see a live test firing of that system if it's still in operation. Also, I see a problem with my design.... leaving the capacitor on top of the rails in the charging phase will cause the capacitor to move down the rails. I will have to add in a locking mechanism to keep it locked in place while charging. Commented Sep 14, 2023 at 16:20