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The Apollo Gauss Cannon
April 2014

1.  Introduction and overview

The Apollo Gauss cannon is a large, 3000J-rated Gauss cannon, or coilgun, which can fire 350g projectiles to velocities up to 80 km/h (further improvements are planned). The bulk of the device was built during summer 2013. Apollo's firing system consists of an underdamped LC circuit with diode-based protection branches for both the capacitors and the inductor. The whole device feeds on mains power to charge the capacitors through a full-wave rectifier, which is separated from the mains via an isolation transformer. The triggering system is made of a "hockey puck" SCR connected to a small 12V DC supply.

High-resolution pictures of the cannon, including during construction, can be found on this photo album.

Total project cost (estimated) : 1700 €.

Apollo Gauss Cannon Apollo Gauss Cannon Apollo Gauss Cannon

 

Here is a quick review of Apollo's characteristics.

Shot power 2916 J, with an efficiency around 3%
Capacitor rack 16x 1800 µF, 450V-rated electrolytic capacitors.
Total capacitance is 28.8 mF.
Firing coil Wire: Copper, 10 mm2, with 1mm-thick PCV insulation.
Coil: 13cm long, 3 winding layers.
Projectile Steel rod, 351g, 9.7cm long, diameter of 2.9cm.
SCR 33 kA, 800V-rated, ceramic disc ("hockey puck") type.

What these pages are about

In Page 2 we will give a detailed description of theory of operation of coilguns. We'll be starting from the most basic phenomena (such as magnetic induction, magnetic susceptibility, etc), and then move on to the mathematical circuit descriptions of our Gauss cannon. Plots of the numerical solutions of the circuit equation will be given for several variations of the circuit. Page 3 contains all the details regarding the construction of the different parts of Apollo, including schematics and design formulas. Finally, we'll examine the results of our cannon shots in Page 4, with efficiency analysis, perspectives for improvement, and of course, pictures of the unfortunate targets used for testing. Page 5 contains sources and relevant links.

To fully appreciate the content, I recommended that you master the fundamental concepts of electromagnetism and alternating current (All About Circuits is an excellent online resource ; volumes I and II largely span the "engineering" part of the aforementioned perquisites), as well as the basics of differential equations.

Please note that Pages 4 and 5 are not finished yet.