Coilgun Turret ASR Second Semester Project Paper Tinyen Shih I. Abstract: The end goal of this project was to build a remote control coilgun turret capable of firing one-inch slugs of decapitated screws, nails, and magnets of similar sizes while being remotely aimed and fired by a remote control. This was originally going to be a coilgun mounted on a remote control car, but delays caused by finding capacitors and chargers able to produce the amount of power needed from small batteries required the project be downscaled to its present incarnation. The final coilgun is powered by a set of capacitors totaling 1.32 mF at 330V. This provides the coilgun with about 65.3 J of energy discharged over ?? seconds for a peak current of ??. With that in mind, the coilgun can consistently shoot the screw slugs several feet and with enough force to make recoil a problem. The turret itself is constructed out of Lego for several reasons: One, because I couldn’t find a better turntable with gear teeth. Two, I took my project home several times and my lack of access to SolidWorks, a 3D Printer, and time drove me to find alternatives. In the final product, the Arduino can drive with the gears with motors and can rotate the barrel in all directions and elevate it between 10 degrees and 60+ degrees from the horizontal. Tinyen Shih Dr. Dann May 2013 ASR D Block 1 Table of Contents: I. Abstract…………………………………………………………………………...1 II. Introduction…………………………………………………………………..........1 II.I. Applications…………………………………………………………….....3 II.II. Motivation…………………………………………………………………5 II.III. History……………………………………………………………………..5 III. Theory……………………………………………………………………………..6 IV. Design……………………………………………………………………………..8 IV.I. Physical Design……………………………………………………………8 IV.II. Circuit Design……………………………………………………………10 IV.II.I. Coil Circuit……………………………………………………….10 IV.II.II. Motor Circuit……………………………………………………12 IV.II.III.Aggregate Circuit……………………………………………….13 IV.III. Radio Design……………………………………………………………..14 V. Results (incomplete)……………………………………………………………..14 VI. Acknowledgements………………………………………………………………15 VII. Bibliography……………………………………………………………………..15 Appendix A: Parts List……………………………………………………………...……16 Appendix B: Arduino Code…………………………………………………………..….17 Appendix C: Photos+ CAD Drawing: (19) 2 II. Introduction: This second semester project, building a remote control coilgun turret, has two parts; one, it explores the applications of electromagnetism to launch physical objects, and secondly, it delves into radio communications used in remote control toys and combines both into a miniature weapons platform. II.I Applications: Imagine an omni-ammunition gun. One whose specifications allow it to shoot any type of ammunition, from manufactured bullets to refrigerator magnets to broken screws. Imagine a gun more silent than any other, even more quiet than those with silencers. This is the coilgun: silent, deadly, and magnetically appealing to science-fiction writers all across the world as a futuristic weapon of choice. If it makes anyone feel any better, these guns are also naturally semi-automatic, easily made fully automatic while remaining perfectly legal without a permit, easy to build, and nigh-impossible to regulate. On the other hand, the most powerful ones available to civilians right now, such as the one I built barely outclass airsoft guns [7]. Still, the potential of electromagnetic weapons is immense. Theoretically, given the development of superconductors with zero resistance, the only two factors limiting how fast a projectile can be launched are: energy storage in capacitors and relativity as the velocity approaches the speed of light. And when the projectile hits something…well, there’s a reason this is the current focus of Navy research. The fundamental principle behind such principles is that anything in the universe can be destroyed by hitting it really, really hard with something else. A projectile coming in even at some small fraction of the speed of light will still have more damaging power behind it than even nuclear weapons of the same mass. Kinetic weapons are just that powerful. [2] 3 Figure 1: Picture of Navy test. [6] That propellant-like plume? That’s super heated gas turned to plasma from the friction generated by the projectile passing by. The distortion in front? Air build up in front of the projectile. It’s going really, really fast. Now imagine this…in space, where there is no air to superheat or build up. All 2 2 that energy instead going to the forward kinetic energy. Pure ½ mv and no Fair=bv . As a non-player character gunner in the video game Mass Effect 2 once stated about his weapon: “Sir Isaac Newton is the deadliest son-of-a-bitch in space!” [2] The remote control aspect of this project is more benign, yet has some roots in darker applications, such as drones. As a democracy, we care very much for the value of each human life, and the ability to not risk American lives is one of the primary motivation behind the current airborne drone and drone spying programs. Other benefits include being able to switch out pilots easily, reducing stress on soldiers operating these war machines and making the concept of 10+ hour flights that were once common with the U2 spy planes look silly and Spartan in comparison [1]. But such systems demand 4 much of engineers, with much smaller fault tolerances, and I wanted to experience for myself a little of what some of those challenges were. II.II. Motivation: Upon reading aerodynamic engineer Ben Rich’s Skunk Works, describing the design process and testing of the iconic U-2 spy plane still in use today over 50 years since the first deployment, the SR-71 Blackbird that set speed records on its retirement flights, and the Nighthawk F-117 Stealth Fighter that was responsible for 20% of hits in Operation Desert Storm [1], I realized many engineers are employed by the defense industry. As an aspiring engineer myself, this is a very real reality in the job marketplace, and so I wanted to try out making a small-scale weapon to see how it felt. More directly related, however, is that the United States military is also testing numerous electromagnetic weapons systems. One such system of railgun launches hunks of metal at Mach 8 speeds, resulting in damage approximating that of a cruise missile. However, since the projectiles are hunks of metal, they are far cheaper to produce and store allowing battleships to pack a hundred times more firepower using the same capacity as compared to now. [5] I also wanted to incorporate as much as I learned throughout the year in ASR and Physics C last year into this project. Building a coilgun turret hit many of them, such as the electromagnetism used in the motor project, the radio communications used in the weather balloon project, and the Newtonian physics and electricity/magnetism learned last year. I intended this project to be able to follow orders from a remote control to aim right, left, up, down, and fire metal projectiles at reasonable speed, maybe enough to puncture empty soda cans or at least knock them over. The coilgun itself was to be a single stage (one coil) only, with the projectile getting drawn from behind the coil into the coil, where upon the coil is turned off, allowing the projectile to emerge forth. II.III. History In 1819, Hans Christian Orsted of Copenhagnen noticed, much to his confusion, that compass needles were being deflected when there was current traveling through nearby wires. Within two years, Ampere had developed his theory of “electrodynamics” through experimental procedure while Simeon Denis Poisson explored the first 5 approximations of magnetization. Michael Faraday and Joseph Henry each finally discovered electromagnetic induction in 1835 independently, one of the primary principles upon which the coilgun portion of this project depends on. From here, modern electromagnetism was born, forming many of the foundations of the industrialized world such as motors. [3] Coilguns were first made practical in the 1960s, when science research accelerated into overdrive and finally created electrical components capable of handling the large currents involved. [8] On the other hand, automated and remote control systems are not new at all. Greek Mythology has references to a metal automaton, named Talos, who would launch rocks at enemies from the sea much like artillery emplacements, but autonomously, much like this project in remotely launching projectiles. From the view of military planners, purely kinetic weapons such as coilguns are also easier to predict, resulting in less collateral damage and civilian casualties, which is why many American missiles are essentially guided blocks of concrete [2]. As a result, such limitations aren’t stopping the Navy, who plan to equip warships with 64 MJ railguns, which work similarly to coilguns in needing a large amount of current and also using magnetism to launch projectiles or even planes at high speed. [2] These hunks of metal, launched at Mach 8, do about the same amount of damage as a cruise missile, but are lower maintenance than cruise missiles while allowing warships to carry a hundred of them in the space it takes to ship one cruise missile. III. Theory: Coilguns operate by using the principles of electromagnetism. As Hans Christen Orsted discovered, a wire carrying current creates a magnetic field around itself. When the wire is bent into loops, the magnetic field lines then approximate that of a bar magnet when current is running through. Magnets, permanent or created from such configurations of wire, induce magnetism in ferromagnetic materials such as the steel projectiles used in this project. The original magnetic field and the induced one The coil actually accelerating the projectile does so on the principles of electromagnetism. The projectile needs to be ferromagnetic so that when the sudden spike in current from the capacitors happens, the magnetic field produced by the coil, or 6 flux, changes, exerts a force on the projectile, causing it to accelerate toward the center of the coil.