Download Laboratory Project 1 - Electromagnetic Projectile Launcher | ECE 2260 and more Lab Reports Electrical and Electronics Engineering in PDF only on Docsity!
LABORATORY PROJECT NO. 1
ELECTROMAGNETIC PROJECTILE LAUNCHER
1. Introduction
350 scientists and engineers from the United States and 60 other countries attended
the 1992 Symposium on Electromagnetic Launch Technology at the University of Texas at
Austin. This symposium was the sixth in the biennial series initiated in 1980 to provide a
forum for presentation and discussion of research on critical technologies for accelerating
macroscopic objects or projectiles to hypervelocities using electromagnetic (EM) or
electrothermochemical launchers. Over 150 papers were presented at this symposium (see
the January 1993 issue of the IEEE Transactions on Magnetics for more information).
The two main kinds of EM launchers are called rail guns and coil guns. In rail
guns, a conducting projectile is placed between two parallel rails and a short high-current
pulse is applied between the rails. The resulting magnetic field forces move the projectile
along the rails, launching it with a very high velocity. A coil gun consists of a series of coils
(solenoids) with the projectile placed inside. Applying a short high-current pulse to the
coils produces magnetic field forces that move the projectile through the coils and launch it
with a very high velocity. In both rail guns and coil guns the short high-current pulses are
produced by charging banks of capacitors and then discharging them into the rails or the
coils. In rail guns, current flows through the projectile and an arc occurs between the rails
and the projectile, while in coil guns, there is no electrical contact between the coils and the
projectile.
Conventional propulsion systems can produce launch velocities up to about 1.
km/s. Rail guns have accelerated gram-size projectiles to almost 6 km/s. Researchers at
the Sandia National Laboratories in Albuquerque, New Mexico (R. J. Kaye, et al., "Design
and performance of Sandia's contactless coilgun for 50 mm projectiles," IEEE Transactions
on Magnetics , vol. 29. January 1993, pp. 680-685) are designing a coil gun expected to
produce velocities of 3 km/s in 50 mm diameter, 200 - 400 gram projectiles. These much
higher velocities are called hypervelocities. The Sandia launcher presently being tested
consists of 40 stages. Each stage consists of a 30 μH coil, a 176 μF capacitor, a switch,
and a cable. A laser-ranger tracks the location of the projectile in the launcher and switches
each capacitor to discharge at the proper time to accelerate the projectile. The capacitors are
charged by a 15 kV voltage source to store 20 kJ of energy. The Sandia researchers hope
eventually to achieve velocities in the range of 4-6 km/s, which is sufficient to launch
payloads into low earth orbit at reasonable cost. A 960-m long coil-gun launcher consisting
of 9,000 coils could accelerate a 1200-kg launch package to deliver a 100-kg payload into
low orbit.
Applications of EM launchers include a broad range of military applications, the
launch of aircraft into flight, the launch of objects directly into space, and the acceleration of
materials to extremely high velocities, either for ultrahigh-pressure or impact physics
research or for the acceleration of fusile material to achieve impact fusion. An EM cannon
could have a range of about 200 km, which means that 10 tanks with EM cannons properly
deployed could cover an entire country of 450,000 square kilometers. Eventually, EM
launchers might be used to launch toxic wastes into space. Spin-off of EM launcher
research might lead to interplanetary vehicles using rail-gun-like plasma thrusters to eject
hydrogen plasma at 100 km/s that could travel to Mars in two weeks with payload fractions
similar to commercial aircraft, and hybrid gasoline-electric automobiles with acceleration
like sports cars, but with lower fuel consumption, lower emissions, greater safety, and lower
cost (M. R. Palmer, "Midterm to far term applications of electromagnetic guns and
associated power technology," IEEE Transactions on Magnetics , vol. 29. January 1993, pp.
345-350). Although great progress has been made in developing EM launchers, the overall
cost, weight and volume of power sources is still too great for many applications of the
technology.
In this project, you will construct and test an EM launcher similar in many respects
to the coil guns described above, but to avoid the time, expense, and danger involved in
materials necessary for construction of the coil are available for purchase in the electrical
engineering stockroom.
1.5 cm
2.5 cm
.1 cm
TYP
0 .4 cm
TYP
Fig. 1. Configuration of the coil.
2.2 Component value measurement. Measure the inductance and series
resistance of the coil. For use in the circuit of Section 5, procure the following:
1 100 mH inductor
1 30 nF capacitor (C 1 )
1 10 nF capacitor (C 2 )
1 300 Ω resistor (R 1 )
1 10 kΩ resistor (R 2 )
1 5.1 kΩ resistor (R 3 )
Measure the values of these components and record them for use in the analysis of
Section 5.
3. Analysis of Launcher Circuit
Analyze the launcher circuit shown in Fig. 2 by two methods (classical time-domain
solution, and MATLAB ode solver) and compare the results.
3.1 Classical time-domain solution. Write the second-order differential
equation for the current i , determine the appropriate initial conditions, solve the equation,
and use MATLAB to plot i versus time for C = 2,000 μF and for C = 2,000 nF, using the
values of L and Rs that you measured for your coil.
30 V dc
t = 0 L^ R s
i
C
Fig. 2. Circuit diagram for the EM launcher.
3.2 MATLAB ode solver. Write two coupled first-order differential equations for
the state variables (voltage across the capacitance and current through the inductance) for the
circuit of Fig. 2, and determine the initial conditions for the state variables. Write a
MATLAB program using the ode45 function to solve the differential equations and plot i
versus time for C = 2,000 μF and for C = 2,000 nF, using the values of L and Rs that you
measured for your coil.
5.3 Comparison. Compare calculated and measured values of v 2 by plotting them
on the same set of axes. Give reasons for differences.
R
L i
v (t) g
C
v 2
v 1
C
R
R
2 L 1
Fig. 3. Circuit diagram of the third-order system.
6. Formal Report
Write a formal report describing your work on this project. See instructions in
"Course Procedures" about how to write the report. Include at least the following in your
report:
- A short introduction. You may attach this handout to the report and refer to it so
that you don't have to copy the information in it.
- A careful description of the work that you did in Sections 2 through 5 above.
a. Give clear derivations of the mathematical expressions. Include consistency
checks.
b. Explain all measurements carefully and include data appropriately in clearly
labeled tables (some of them might be placed in appendices).
c. Include a listing and explanation (may be in the form of comment statements)
of computer programs in an appendix.
e. Give a clear comparison of measured and calculated values by plotting
calculated and measured values on the same set of axes (see Section 5.3).
Explain why calculated and measured values are not the same.
- Conclusions, including:
a. A discussion of the validity of the models used for the devices.
b. A discussion of the effectiveness of your procedures for analyzing and
designing pulse circuits.
7. Your Grade
Your report will be graded according to the following:
Category Points
Communications 30
- System Components 10
- Analysis of Launcher Circuit 20
- Construction and Testing of Launcher 10
- Third-Order System 25
Conclusions 5
Total 100
