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The Next Generation of Railway, EM Rails
The Railway of Tomorrow
1996 Science Fair Project
By: Kyle Doerksen
Send comments, questions and suggestions to [email protected]
Note: Some footnotes, and other formating may have been lost in translation.
Special Thanks:
------------------------------------------------------------------------
There were many people who helped make this project possible. I would like to thank
Larry Dyck of the University of Calgary for his help with formulae and theories. Also, I
would like to thank Keith Chrystall of the Alberta Research Council for his help with the
location of suppliers. Without their help, this project would not have been possible.
Of course, I would also like to thank my parents for their ongoing moral and emotional
support
Abstract:
------------------------------------------------------------------------
This is an ongoing study of the design of electromagnetic railguns. I have drawn up plans,
and then calculated their characteristics by use of computer programs. The project
explores Lenz's law, the left-hand rule, and the Biot-Savart law. Also, this project includes
a comparison of existing railguns at military facilities in the United States. My research has
culminated in the construction of a prototype railgun
Introduction:
------------------------------------------------------------------------
Deep inside a hollowed out mountain in Nevada, technicians are busily working on a
space age weapon.
The bullet hums as it spins in the barrel, hiss of an airlock, hum turns into a whine, as the
bullet spools up to thousands of R.P.M. There is a tremendous bang, and the bullet is
gone. It speeds through the atmosphere at several kilometres per second. In a few
moments, there is a sonic boom, and then there is no sign of the bullet.
You have just experienced a trial launch of an Electromagnetic rail gun. This is not science
fiction, but science fact. It occured at the Cheyenne Mountain Space Command Facility.
There are a number of groups racing to develop Electromagnetic rail guns, all of which are
under the umbrella of the military. Railguns are devices which use electromagnetic energy
to propel objects at tremendous speeds. Proponents of the Strategic Defense Initiative
(SDI) are very interested in rail guns as a method to destroy in-coming cruise missiles.
President Reagen realized the need for a missile defense system, and rail guns would be a
very important part of this system. Although the Americans are actively pursuing rail gun
technology, the Soviets are thought to be at least a decade ahead in rail gun research. With
the Clinton Administration, the SDI program has been scrapped, but various parts of the
program still exist, and are under different names.
Rail guns could not only shoot down satellites, but presumably could also launch them
into orbit. This idea has been raised in many science fiction books, including Rendezvous
With Rama by Arthur C. Clarke. A device capable of launching a large projectile at a
speed of several kilometres per second could give a satellite enough kinetic energy to
reach orbit. This could, conceivably provide a `railway' to the stars
Objective:
------------------------------------------------------------------------
The example which I used at the beginning of this report was what interested me in rail
gun research. I was reading through a book on The Star Wars Project, or SDI, and found
a small paragraph devoted to rail guns. Although very little information is available to the
public regarding electromagnetic railguns, they are scientificaly interesting, and utilizing as
they do, physical principles. They are a direct application of Lenz's law and the left-hand
rule.
It strikes me as odd that other amateur scientists have not attempted to build such devices,
nevertheless, I will attempt to design and build a railgun. Railguns do not, however, lend
themselves well to experimentation. Experimentation at the theoretical level is much more
cost-effective than it is at the construction level. Therefore, I have decided not to perform
an experiment. Instead, I have spent a great deal of time trying to design a small railgun
which is inexpensive, and uses only readily available components.
I am very interested in railguns, and building such a device is the logical continuation of
my interest and research.
Background Research:
------------------------------------------------------------------------
Electromagnetic Rail Guns: History
It may seem that railguns are a cold-war weapon, however the theories, and ideas behind
them date back hundreds of years. The idea of using guns to propel objects into space has
been around for more than a century. Jules Verne wrote about huge guns that could be
used to shoot things into space in his book From the Earth to the Moon. He was not
referring to rail guns, but rather large powder-operated cannons. In fact, Verne
successfully calculated escape velocity (see Orbital Velocity and Escape Velocity) to
12000 yards per second, which he mentioned in his stories. The following is Vernes
proposition for an Earth to Moon (ETM) gun:
1st. The cannon ought to be planted in a country situated between 0 and 28 of N. or S. lat. 2nd. It ught to
be pointed directly toward the zenith of [the moon] 3rd. The projectile ought to be propelled with a initial
velocity of 12000 yards per second. 4th It ought to be discharged at 10hrs. 46m. 40sec. of the 1st o
December of the ensuing year.
By the late 1800s, American scientists had placed patents on rail gun technology. Later, in
1929, a Russian theorist proposed to use a rail gun to launch items into space. Rail gun
technology did not progress significantly after that until the beginning of the Star Wars
program in the 1980's.
During the years that Reagan was the president of the United States, a program was
introduced which would develop cutting edge anti-missile and anti-satellite weaponry.
With Russia's huge stockpile of nuclear missiles, the Reagan administration found that it
was necessary to institute such a program. Much of the technology was already being
developed at facilities such as the Los Alamos National Laboratory, the Electric
Armaments Research Centre, and the University of Texas at Austin. The Star Wars
Project simply united such efforts, and put them under the control of the US Military.
Electromagnetic Rail Guns are a major constituent of the hardware that was (and perhaps
still is) involved in the SDI. Rail guns would be used as an anti-ballistic-missile weapon, to
destroy incoming missiles, while they are at their peak altitudes. It was later found that
laser and ElectroMagnetic Pulse technology are better weapons for high altitude targets.
However, electromagnetic rail guns may one day be placed in space, and provide orbiting
gunships to target and destroy missiles, and satellites. President Clinton shut down the
program, and it is basically back to its pre-Reagan form. Although many of the involved
contractors and laboratories are no longer united, many of them still work on rail gun
research.
Although much of the Russians work on rail guns is classified, speculation is that they may
be decades ahead of the US in rail gun technology.
The Left Hand Rule, and Lenz's Law:
Rail guns operate by a well known law of physics called the "left-hand rule". The "left-
hand rule" is a simple method for calculating the interactions between a magnetic field,
and an electric current through a material. With your left hand held in the position shown
in the diagram, it is easy to figure out the direction in which the object will move. With
your thumb pointed in the direction of the magnetic flux, and your index finger pointing in
the direction of the electric current, the middle finger will point in the direction that the
object will move. The formula is as follows:
v=IBl
Where:
v = Velocity
I = Electrical Energy
B = Magnetic Flux
l = Length of projectile (distance between rails)
Thus, this formula can be applied to figure out the design of a rail gun. This propulsive
force which is induced at right angles to both the electric current and the magnetic flux, is
known as the Lorentz Force. This "left-hand rule" can also be applied to the generation of
an electric current by moving the armature. When you move a piece of metal (or other
conductive substance) along the rails (in the direction of your middle finger), an electric
current will be induced in the direction of your index finger.
Electromagnetic Rail Guns: The Physics
Electromagnetic rail guns operate on the principle of the "left-hand rule". The idea of
Electromagnetic Launchers has been around for quite some time in science fiction, and
recently, the dream has become reality. Some science fiction stories talk about giant guns
on the moon which could easily return ore samples and waste. The reason that these guns
would be placed on the moon is that, in the reduced gravity, the escape velocity is
nowhere near as high as it is here on earth.
The physics behind a rail gun are quite simple, but that does not mean that the design of a
railgun is simple. Electricity is run down one rail, through the armature, and back through
the other. This completes the circuit. On the top and bottom are large magnets which
generate a directional magnetic flux. Using the left-hand rule, we can very easily find that
the armature will be propelled perpendicular to the rails. Once constructed, a rail gun only
needs electricity to operate. This energy does not even need to be regulated, and is simply
high amperage DC current. Basically, a rail gun is a simple motor, however, instead of the
armature spinning around it is propelled down the length of the rails. Rail guns also work
in reverse if the projectile is pushed along the rails, an electric current will be induced.
There are many factors that control how fast the rail gun can shoot. These include:
The strength of the top and bottom magnets
The amount of electricity going through the rails
The length of the rails
The size of the projectile
The interaction between these factors is quite complex, so it is best to use a computer to
calculate them. There are also other factors which must be considered in a practical rail
gun (see My Rail Gun Calculation Program).
The "left-hand rule" can also be seen in other electromechanical devices. A motor is
basically a rail gun formed in a circle. Another very interesting application is Magneto-
Hydrodynamic-Propulsion (MHD). In the book, The Hunt for Red October, Tom Clancy
writes about a Russian submarine that uses a "caterpillar" drive. This is just a code name
for the MHD engine. MHD is very closely related to the "left-hand rule". Basically a rail
gun under water, the MHD creates electrified water which is affected by the magnetic
field, and is pushed out the back of the engine.
Orbital Velocity and Escape Velocity:
Orbital velocity is the speed at which an object must be propelled in order to reach and
maintain orbit. This varies depending on the "height" of the orbit, or how far away from
the earth the satellite is to orbit. Escape velocity is simply the speed at which an object
must be propelled in order to break out of orbit. In other words, to get from Earth to
Venus, one must achieve escape velocity in order to escape the earth's gravitational pull.
The formula to calculate escape velocity is:
Where:
G = The Gravitational Constant: 6.672*10-11
Me = Mass of the celestial body: 5.98*104 Kg
R = Radius of the celestial body: 6.37*106 metres
This works out to approximately:
11200m/s on earth
2300m/s on the moon
Therefore, a rail gun located at sea-level here on earth will have to be able to shoot an
object away from the Earth at a speed of 11200m/s if it is to be sent on an interplanetary
journey. (A rail gun located at 10000 feet above sea-level in the Rocky Mountains would
require 21 percent less power than one at sea level ) It is easy to see that it is much more
practical to position rail guns on the moon, and launch things from there. It had been
thought that lunar mining would be a good use for rail guns. Ore that is extracted from the
lunar surface could be shot to Earth by rail gun.
Electromagnetic Rail Guns: Existing Rail Guns
As I have said, many laboratories are developing rail guns. They range from small, 1 metre
long guns, to proposals for 3.2 km long devices built into the Rocky Mountains. I will
briefly outline some of the major projects in the United States .
The University of Texas at Austin:
At the University of Texas's centre for Electromechanics, scientists designed and
built a rail gun which is reported to shoot a one-hundredth of a gram ball of
metallic plasma to a velocity of 143968 km/h, or 39991 m/s. This project was
funded by the Armament Research Development Centre of Dover, New Jersey.
The project cost around $800000, and the ultimate aim is for the gun to achieve a
speed of 179915 km/h or about 50000 m/s. This was, at the time of development,
the world's fastest rail gun. However, this was built in the spring of 1985, and
many refinements may have been made by now. Also, the projectile is extremely
small, so the possibly of launching satellites is completely out of the question.
Quick Facts:
Projectile Size: UNKNOWN
Projectile Weight: 0.01g
Maximum Speed: 50km/s
Electrical Energy: UNKNOWN
Length of Barrel: 3m
IAP Research Inc.:
This gun is being developed at the Air Force Armament Laboratory at Eglin AFB,
Fla. This gun has, from a military standpoint, a major advantage over the gun built
at the University of Texas. This is because it can fire 6 shots in rapid succession.
This would mean that rail guns may eventually be more like machine guns than
rifles. The projectiles reached speeds of 1200 m/s and this was using 700000 amps
of power. The 2 inch projectiles were able to punch through 4 inch armoured
plates. Future tests will involve 1.5 million amps. This rail gun has also achieved
more than 50% efficiency in converting electrical energy to projectile kinetic
energy, a major improvement over other guns.
Quick Facts:
Projectile Size: 5cm
Projectile Weight: UNKNOWN
Maximum Speed: 1.2km/s
Electrical Energy: 700000 amps
Length of Barrel: 3m
General Atomics:
General Atomics has supplied three guns to the Air Force Armaments Test
Laboratory at Eglin AFB Fla. These guns range in size from 1 to 5 metres long.
They also vary in specifications. The unique part of this project is that it uses
14000 car batteries to supply the power for this project. Originally, the designers
were going to use a Homopolar Generator operating at 0.85 mega-amp (Ma).
However, the car batteries supply 1.5 Ma, and saved the project an estimated 25
million to 55 million dollars.
Quick Facts:
Projectile Size: 5cm
Projectile Weight: 150g
Maximum Speed: 1.3-2.7 km/s
Electrical Energy: 1850000 amps
Length of Barrel: 1 - 5m
Sandia National Laboratories
Sandia National Laboratories is one of the most advanced military research labs in
the world. Their project is not actually a rail gun, but an electromagnetic coilgun.
Instead of the rails, there is a series of coils which run along the barrel of the gun.
The coils are turned on in sequence, so that as the projectile moves, the magnetic
field is pushing on it. There are some advantages to using coils; the projectile, does
not touch the gun, but is suspended in the middle. Therefore, friction does not
create an overheating problem within the gun. It is easy to add more coils
(stages), to produce faster speeds. To vary speed, change the speed at which the
stages are fired. However, sophisticated computers are required to sequence the
stages.
A possible spin-off of this device is the WARP 10, a theoretical contactless coil
gun, which would be built into a mountain. It would be 3.2km long, and would be
capable of Earth to Orbit (ETO) applications. Bill Cowan, a scientist at Sandia,
developed a computer program which simulates the WARP 10. With its 3100
stages, the computerized model of the coil gun took 30 hours to calculate on a
Cray super computer. It was calculated that the gun will be able to launch a 450kg
projectile to 4.1km per second. This is the most ambitious EM launcher plan yet.
Los Alamos National Laboratories (LANL)
The laboratory which developed the atomic bomb is building their own rail gun.
The LANL gun is probably the most "scientific" rail gun project currently
underway. They are working to develop a gun which will have very little barrel
erosion, and powerful power-supplies for railgun use. The end result of the
research at LANL will be the construction of the sub-scale Scientific Ultrahigh
Velocity Accelerator (SUVAC), and a larger Thunderbolt rail gun. New materials
will be tested in these guns to try to overcome some of the problems which face
rail gun researchers.
Quick Facts:
Projectile Size: 3cm
Projectile Weight: 10g
Maximum Speed: 5 km/s
Electrical Energy: UNKNOWN
Length of Barrel: 3m
Design:
------------------------------------------------------------------------
There are many factors which must be considered when designing a rail gun. These
include:
The length of the gun:
This determines how long the acceleration caused by Lenz's Law will last. The longer
it lasts, the longer the projectile is under power, and the more velocity it can acheive.
Size/weight of the projectile:
The length of the projectile (the distance between the rails) is one of the key factors in
the left-hand rule equation. The longer it is, the more force that is generated. Also, a
light projectile is beneficial, because the less mass it has, the less inertia it has, so the
easier it can be accelerated.
The electrical current involved:
When large electric currents are involved, the wire/rails involved must be able to
handle the ammount of current that is being pushed through them. Otherwise, they
may overheat, and even melt.
The power source:
The power source is a major consideration. Railguns work best, when operated with
high amperage, low voltage, DC current. Because the projectile does not stay on the
rails very long (it is soon out of the end of the gun), a quick jolt caused by a capacitor
can be used.
The strength of the magnetic field:
Another key factor in the left-hand rule is the strength of the magnetic field. This
depends on the size, and shape of the magnet, as well as the number of turns of wire,
and the strength of the magnets power source.
Barrel erosion:
When dealing with projectiles moving at high speeds, and sliding along metal rails,
friction can cause errosion of the projectile, and the rails. To overcome this, some
railgun researchers use more slippery materials such as graphite which slide easier than
typical metals. Obviously a small railgun that can propell a projectile at only 10m/s will
not be prone to significant barrel erosion.
Cooling:
When dealing with high-current electricity, fast moving projectiles, and
electromagnets, cooling is very important to consider. Some railguns use liquid
nitrogen to stay cool, others use water, and some do not need any cooling at all.
The formation of plasmas:
When moving at very high speeds, any material will turn into a plasma. This can be
very bad for the gun, and the projectile. Plasma gives the gun strange new
characteristics which are undesirable in railgun operation. To prevent formation of
plasmas, some railguns have lubricated rails, and some do not propel the projectile fast
enough for the formation of plasma to occour.
Air resistance:
As well as friction between the rails and the projectile, there is also friction between
the air and the projectile. With tremendous speeds, air resistance can warp even the
strongest metals enough that they are broken apart. A projectile hitting the air at 2
km/s is like a car hitting a brick wall at 1000 miles an hour.
Materials:
After considering all of the above, materials must be chosen wisely. Ceramics are
good, because they can withstand heat. Graphite is good, because it is quite slippery,
and a good conductor. With new materials being developed every day, it is important
for railgun researchers to always be investigating the properties of such new materials,
and test their feasibility for railgun applications.
Some of these factors do not need to be considered when developing small rail guns, but
anything large requires the consideration of all of these points.
Conclusion:
------------------------------------------------------------------------
Although my prototype railgun did not operate as hoped, much can be learned from this
project. Of course, not all devices can operate successfully the first time that they are
tried. For example, it took hundreds of years to develop motorized flying machines, and
decades before the rocket was space-worthy.
I neglected one calculation when designing this railgun, and that was the magnetic strength
in rectangular magnets. Although I calculated field direction in my program, field strength
was not considered, and the values which I used in the speed calculation program were
purely theoretical. The materials which I used were suited for the application, with the
exception of the projectile. Because the projectile is aluminum, gravity does not exert
enough force to make good contact between the rails and the projectile.
The main problem, though, is in the magnets themselves. They produce very little
magnetic strength for the amount of turns of wire in them. A small magnet, with a one
inch core, and the same number of turns, produces much more force than these magnets.
Part of this may be that each coil of wire is 3 feet long. This means that the resistance is
quite high, and current can not be run through them as well as in the smaller magnet. To
rectify this problem, I will need to buy several batteries, and hook them together, so that I
have more than 12 volts. This will allow higher current to be passed through the same
magnets. I have a hypothesis that rectangular magnets do not work as well as cylindrical
magnets, however I have found no proof of this in any books on the subject. Using a well
known formula, I can calculate that there were 4 amps going through the magnets. This is
a lot for the type of wire which I used. I have many questions about my magnet; Are
rectangular electromagnets weaker than cylindrical ones? Does bolting together a core
reduce the strength compared to bonding them securely (welding)? Does the size of a
magnet compared to the number of coils affect its performance? These are all questions
which I must find answers to, if I am to determine why my magnets were not as strong as
they should be. Also, these should be answered before I make another railgun plan.
I would have liked to use capacitors to produce high current for a short period of time.
This would be better than the battery, because it would result in very fast discharge of
energy. This way, the peak current is instantaneous, and the projectile can accelerate very
rapidly. The capacitors which were available to me when I was looking for parts for this
project did not meet the specifications which are required for railgun application. Because
of this, I calculated that a car battery could provide just as much power as the capacitors
which are available to me.
As I mentioned earlier, this project is ongoing, and I hope to wrap it up in a couple of
months. New magnet designs, and other materials, including composites and plastics, will
be some things which I will have to consider. So far, my budget has been very small, and I
have spent about 20 dollars on wire, metal, and wood. I think that I can continue to
contain costs, and may eventually post plans for my railgun on the Internet, so that
amateur scientists around the world can build this space-aged device.
There are few applications for electromagnetic railguns, but these applications are suited
very well for railguns. Satellite launching is the most probable use of electromagnetic
railguns in the near future. Because most guns generate very high speeds, achieving escape
velocity is not out of the question. I hope that the technology is released to NASA, and
other civilian agencies, and does not remain in the government's small group of elite
contractors. Civilian satellite launching is a very good application for railguns, but the
military may decide to hold on to the technology. However, it is possible that other civilian
labs could develop railguns for civilian satellite launching technologies.
Railguns are much better than rockets for launching payloads. They use no fuel, which
conserves the environment, and have no extra bulk for engines, or fuel systems, allowing
for
larger payloads. But there are problems with launching satellites by railgun. They need a
tremendous amount of acceleration hardening to survive the acceleration which may reach
several thousands of g's. Some military electronics are capable of withstanding that kind of
force, and the magnetic fields produced by the railgun, however, they are much more
expensive than standard semiconductors. These Gallium Arsenide semiconductors are
currently used in some artillery shells.
It is obvious that railgun research must continue, and this research must be shared with
everyone. There is an underwhelming amount of information which is available today, but
much exists in the military's closed circles. My research, although the prototype was
inoperative, is important, because it shows that even though little exists, much can be
discovered. The questions which I need to ask number far more than the questions which I
asked at the beginning of this project, and this is true with most science projects. I hope
that I have made my point known that railguns may provide the Railways of Tomorrow.
Bibliography:
------------------------------------------------------------------------
LAMPTON, CHRISTOPHER. Star Wars. New York: Franklin Watts, 1987
TAYLOR, L.B. JR. Space: Battleground of the Future. New York: Franklin Watts, 1983
BARNABY, FRANK. --Space-- Weapons. New York: Gallery Books, 1984
KOLM, HENRY, LAX, BENJAMIN, BITTER, FRANCIS, MILLS, ROBERT. High Magnetic
Fields. The M.I.T. Press, 1961
MIMS, FORREST, M., III. Getting Started in Electronics. United States of America: Radio
Shack Press, 1983
"Electromagnetic Gun" R.N LANGRETH. Popular Science V. 245:32 N `94
"Hyper Weapons: Goodby, Gunpowder?" The Futurist V. 27:55-6 Jl-Ag 93
"Workin' on the Railgun" D. SCOTT. il Add Astra 2:10-14 Je `90
"Electric rockets." T. L. METZGAR. il Discover 10:18+ Mr `89
"General Atomics supplies rail guns for SDI space interceptor research." M.A.
DORNHEIM. il Aviation Week & Space Technology 129:71 Ag 29 `88
"USAF expands rail gun facility to allow open-air firing tests [Eglin AFB]" il Aviation
Week & Space Technology 129:41-2 Ag 22 `88
"SDI research railgun succeeds in rapid repetitive firing." il Aviation Week & Space
Technology 127:29 D 21 `87
"Ground-based hypervelocity guns [SDI program]" il Aviation Week & Space Technology
127:81 N 23 `87
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