Gauss rifle or Coilgun or Gaussian gun is a type of mass driver that consists of one or more coils being used as electromagnets in the configuration of a linear motor that accelerates a ferromagnetic or conducts a projectile to high velocity. Coils and the gun barrels are arranged around a common axis in almost all coilgun configurations. Coilgun is not a rifle as the barrel is the smooth article. The name “Gauss” referred to Carl Friedrich Gauss. Carl Friedrich Gauss invented and explained the mathematical descriptions for the magnetic-effect that had been used by magnetic- accelerator cannons.
The mass driver is the kind of a coilgun that magnetically accelerates a package having a magnetizable holder having a payload. When its payload has been accelerated, the two separated, and the holder is slowed and recycled for another payload.
Coilguns typically have one or more coils arranged in a pipe called a barrel, therefore the path of the accelerating- projectile is kept along the central axis of the coils. These coils are being switched on and off in an accurately timed sequence, causing the projectile to be quickly accelerated along the tube barrel through magnetic-forces.
Coilguns are different from railguns as they accelerate at right angles to the central axis of the current loop being formed. Also, railguns normally require the use of sliding contacts for passing a large current from the projectile, but the coilguns do not necessarily need sliding-contacts.
History
Norwegian scientist Kristian Birkeland invented the first Coilgun from the university of Kristiana in 1900. In his experiments, Birkeland accelerated a 500 gm projectile with 50 m/s speed (110 mph, 180 km/h, 160 ft/s).
In 1933, Texan inventor Virgil Rigsby, Texan inventor developed a stationary coilgun which was designed as a machine gun in 1933. A large electric motor and generator were used to supply the power in it.
There are mainly two types of setups in Coilgun, i.e. single-stage and multistage. A single-stage coilgun uses only one electromagnet to propel it from the projectile while A multistage coilgun has many electromagnets in succession that progressively increase the projectile-speed.
Ferromagnetic Projectiles
A single-stage coilgun can be formed for ferromagnetic projectiles, by the coil of wire, and an electromagnet along with a ferromagnetic projectile kept at one of its ends. This Coilgun is formed like the solenoid which is used in an electromechanical relay. A large current is applied through the coil of wire, and a strong magnetic field generated that pulls a projectile towards the centre of the coil.
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An illustration of a solenoid
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A single-stage coilgun after electromagnets were used for repeating the same process to progressively accelerate the projectile in a multistage-design.
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A simplified diagram of a multistage coilgun with three coils, a barrel and a ferromagnetic projectiles
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A multistage coilgun
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A simple electromagnet consisting of a coil of wire wrapped around an iron core.
We use a diode to protect the polarity sensitive components from the damage due to inverse-polarity of the voltage after turning-off the coil.
Non-Ferromagnetic Projectiles
Some of the designs for Gauss rifle consist of non-ferromagnetic projectiles, which are made of materials like Aluminium or Copper. In this case, the armature of the projectile acts as an electromagnet with the internal current induced by some pulses of the acceleration coils. Quench gun is an example of Non-ferromagnetic projectiles. It is prepared by successive quenching of adjacent-coaxial conducting coils. It forms a gun barrel and generates a magnetic field gradient to get more desirable speed.
Switching
There is one main obstacle for the coilgun design, which is switching the power through the coils. For switching several common solutions are being used, however, the simplest and probably the least effective one is the spark gap that releases the stored-energy by the coil when the voltage reaches a certain threshold value.
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A spark gap
The second or better option is to use solid-state switches; these include IGBT (Insulated-gate bipolar transistor) or power MOSFET and SCR.
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Silicon controlled rectifier
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MOSFET, showing gate (G), body (B), source (S) and drain (D) terminals.
A quick-and-dirty method for switching is when we use the flash-tube itself as the switch. Prepared by wiring it in series with the coil, it can silently and non-destructively permits more current to pass through in the coil so a large amount of the energy will dissipate as heat and light, and, as the tube being a spark-gap, the tube stops conducting when the voltage across it will drop sufficiently, leaving some charge remaining on the capacitor.
However, in order to reduce the component size, weight, durability, and most importantly, the cost, the magnetic circuit has to be optimized to deliver maximum energy to the projectile for given energy input. It has been addressed to some extent by the use of back iron and end iron.
How to Prepare a Gauss-Rifle?
For making a Gauss Rifle, i.e. a steel ball rolls to a magnetic taped plastic-rail. When the magnet gets hit by the steel ball, another one shoots on the opposite side at a quite higher speed. For the preparation, we require some simple materials as given below:
1. Wooden Ruler
2. Two dowels
3. Copper pipes
4. Clear adhesive tape
5. Glue
6. Strong cylindrical magnets
7. Nine steel balls
Preparation
(a) We place the first magnet at the 2.5-inch mark on the wooden-ruler.
(b) Fix the ruler on the table with the help of a tape so that magnets attach to prevent jumping.
(c) Then we place four magnets on the ruler at the 2.5-inch gap between them.
(d) Place two steel balls on the right-hand side of each magnet, And ensure that the ball doesn’t roll down from the wooden ruler.
(e) Now, we have to fire, so set the ball on the extreme left magnet then push-roll to the magnet.
(f) While the gauss rifle will fire the ball on the right-shoots away from the gun to hit the target with sustainable required force.
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Gauss Rifle
Observation
When we release the first ball to the extreme left magnet, it will hit it with a sufficient amount of force and produces kinetic energy. This energy carried from the ball is transferred to the magnet and then the ball on the right releases. Then the third ball will move with kinetic energy and repeats the process until the last ball shoots with the greater force.