Tracee Howard Jameson McGhee John Thomas Daniel Jenkins

1. Coil Gun-TM 81 Tracee HowardJameson McGheeJohn Thomas Daniel Jenkins

2. Our Objective • The purpose of our project is three fold. • First, and most importantly, we are going to use all of our education and experience gained from our time at ITT Technical Institute. • Secondly, we will be trying to work outside of our comfort zone to create a new way of successfully firing this coil gun. • Lastly, the purpose of this project is not only to fire the coil gun, but do so with the most efficiencypossible (Projected goal is 1%).

3. A coil gun, also known as a mass driver, consists of a coil of wire with a projectile placed at one of its ends. A large current is pulsed through the coil and a strong magnetic field forms, pulling the projectile to the center of the coil. When the projectile nears this point, the coil is switched off and a next coil can be switched on, progressively accelerating the projectile down successive stages. In common coil gun designs, the "barrel" of the gun is made up of a track that the projectile rides on, with the driver coils around the track. Power is supplied to the coils from some sort of fast discharge storage device, typically a battery or high-capacity high voltage capacitors designed for fast energy discharge. Coilgun

4. Picking the Wire • What American Wire Gauge size of wire is most adequate for our purposes? • What is the time constant for the current we plan to use on American Wire Gauge standard wire we are using? Calculations concluded that 20 Gauge wire can handle 1500 Amps for approximately 7 milliseconds.

5. Coil Size • How many turns? • 250 turns • How long? • 50 turns (3 inches) What we are looking to for in the size of the coil are the lowest resistance and the lowest inductance that allows for optimal power transfer.

6. Coil design • Initial Design • Continuous wraps of 250 turns in increments of 50 • Secondary Design 50 wraps run in parallel for 5 layers = 250 • Reduces resistance • Greater current • More power /magnetic force

7. Framework of Coil gun • The design of the framework allowed for easy assembly or disassembly if necessary.

8. Coil Gun Design • We initially planned to build this gun using 27 coils or stages. • However, with efficiency being our largest goal, we decided that a 14 stage gun would be better.

9. Fire/Timing and Speedometer Circuits • Using operational amplifiers and infrared sensing sets we were able to calculate the speed/acceleration of our projectile at any point in the gun. • Using the same concept, we built another circuit that is able to time when the and in what sequence the coils need to be fired.

10. Flux Timer • The purpose of our Flux Timer is to determine precisely how long that the current of 30 amps is travelling through the rails to the coils. • The reason that we needed to do this is to determine efficiency of the coil gun. • It does this by detecting the magnetic flux field surrounding the power rails, which starts/stops a timer.

11. Bullet (Projectile) • Composition • 9% nickel, 90% copper,1% trace elements • Dimensions • .230”O.D., 1.67” length, .180”I.D. • Description • Slotted down entire length • Width of slot .05” Slotting the projectile restricts the ability of the eddy currents to flow in the material. The direction of the slotting should be axial since we are more interested in stopping circumferential eddy currents.

12. Smart Bullet Concept • Our second choice for a bullet is a concept based around the knowledge of step-down transformers. • When the eddy currents from the coil reach the outer coil of the bullet it will induce a current flowing into the inner coil. The inner coil creates (over time) a tremendous magnetic field which allows for even faster speed. • pix

13. Switch Types: • 3055 • SCR • Vacuum tubes • Relays Because of price and current capabilities, we went with the relays.

14. Timing the coils using pulses. • We initially thought about using the 555 timer as way of pulsing the coils, but this proved to be problematic due to amount of chips and inconsistencies. • We settled on using micro pulses using the circuit designs (previously mentioned) and an 8051 microprocessor. Doing this we were able to more accurately time the pulses and convert data input.

15. Microprocessor Programming • We wrote our own timing /firing and speedometer programs in assembly language for the 8051.

16. Power • Multiple Car Batteries • In our coil gun project we are using 40 Amps from two car batteries that are rated to produce 1,200 Amps. • We are using batteries instead of a capacitor because of the LRC time constant. This time constant would have slowed our charge time.

17. Discharging • Discharging the current thru 10kΩ resistor. • The reason for this is because it allows for a discharge rate in the picoseconds range. • The really cool fact about doing this is what Ohm’s Law tells us. For the time duration of the current on the resistor, the resistor has a voltage spike of approximately 400,000 volts! That’s 16,000,000 watts! This is something that we considered, but we did not have to do!

18. In conclusion, using all the knowledge obtained in our 2 years at ITT Tech (as well as obtained elsewhere), we were able to successfully fire the gun at a velocity of 50mph coming out of the gun with an overall efficiency of 1.97%. Conclusion

19. Potential of the Coil Gun In this graph it shows how the gun was speeding up and slowing down internally. Between coils 1 and 3 we had measured speeds of 216 mph. That is 216 mph in a distance of approximately 9”, or 0 – 216mph in 29 milliseconds. However, at coil 4, the projectile begins to slow. At coil 7 it begins to speed back up again. This continues the entire length of the gun. This is because of switching with the relays, they simply were not fast enough to keep up with bullet. Unfortunately, we were unable to resolve this issue due to the fact that any faster alternative to the relays was far to expensive. If we could have had access to 14 SCR’s, the potential of this gun is simply staggering.

20. We would like to thank everyone for their help and for all the support from our classmates. • Tracee Howard • Jameson McGhee • John Thomas • Daniel Jenkins Thanks