Though the performance was many orders of magnitude below the theoretical upper limit for EML, the experiment was declared a success. Then Fair came across Richard Marshall. Shortly after his record-setting railgun test in Australia, Marshall, too, had lost his funding. He left the university, moved to the United States, and got a job with Westinghouse in Pittsburgh, where Fair found him in Fair, Marshall, Kolm, and their associates now had to confront the enormous technical problems that electromagnetic guns pose.
First and foremost is the power supply. All railguns and coilguns require a power source that can generate, store, and then emit an enormous burst of current—anywhere from to many millions of amperes in a few milliseconds. Marshall had used a homopolar generator, so named because its magnetic field has the same polarity at every point.
Just like any generator, it converts rotational mechanical energy into electrical energy. Another early railgun experiment called for hooking together thousands of lead-acid car batteries to supply the requisite juice. Dumping that much current so quickly raises other problems. To begin with, you need a very-large-diameter cable to deliver so much current—anything smaller would melt. The switch, too, has to be specially designed to prevent a massive arc that would otherwise destroy the switch the instant it was thrown.
Needless to say, railguns also have a tendency to self-destruct. The high-velocity projectile and armature gouge the rails, and the magnetic fields put a tremendous strain on the rails as they try to force themselves apart.
Even the projectiles are a subject of intense inquiry. They leave the barrel at such high velocity that when they hit the air, they tend to flatten, burn up, or shatter. Interest in the technology was building, but the program was still relatively small by DOD standards. Then, on the evening of 23 March , President Ronald Reagan announced a crash program to build defenses against Soviet intercontinental ballistic missiles. Fair believed using railguns to launch simple kinetic projectiles, which destroy targets by the sheer force of their impact, would be much better suited for knocking down missiles.
Fair was asked to manage its EML component. Lenard, too, was a space enthusiast, and he immediately funded an Air Force study of EM guns to launch missile defense systems into orbit, each of them weighing possibly hundreds of metric tons.
But the heaviest projectiles that had been test-fired up to then weighed only a few kilograms. Not surprisingly, this challenge proved impossible, and so Lenard shifted the focus to EM guns for hurling projectiles at incoming missiles. This goal was reasonable, but as Fair and others later charged, the work emphasized hardware demonstrations to the detriment of test and analysis. In an interview with IEEE Spectrum last spring, Lenard said he felt pressured to demonstrate something dramatic because his program was constantly overshadowed by SDIO efforts on directed-energy technologies such as lasers.
Upon detection of a missile launch, the orbiting system would detonate a nuclear warhead, harnessing the blast to simultaneously power thousands of missile-destroying lasers. News stories at the time quoted Wood as claiming that these lasers could focus so much energy so tightly that just one shuttle launch could put enough of them into orbit to take out the entire Soviet ICBM arsenal. You might learn something.
Railgun teams at Westinghouse and Vought Corp. The machines generate very high current and voltage simultaneously. But the numbers turned out to be grossly exaggerated.
The Lawrence Livermore results, too, had been calculated instead of measured directly. Marshall, Fair, and others thus put little stock in the claims. Later, in , they figured out how to measure the velocity—by photographing the projectile as it emerged from the muzzle, among other things. Worse, the plasmas generated in the gun barrels corroded everything they touched, projectiles gouged the rails, and the extreme magnetic fields warped the rails.
The researchers were constantly rebuilding their guns, usually after just one shot. They included the D-2, designed for launching at incoming warheads within the atmosphere, and LEAP Lightweight ExoAtmospheric Projectile , to be shot from orbiting battle stations.
By , meanwhile, SDIO managers had redirected the program away from laser weapons. In two underground nuclear tests, sensors meant to measure the lasing effect were vaporized.
Lenard figured he had won. He was wrong. If the sensors detected anything not cleared for space travel, the nearest Pebble would smash into it. Sometime later, Navy researchers resurrected LEAP and combined it with its existing Standard Missile technology to create a new version of the Aegis Ballistic Missile Defense System, for defeating short- to intermediate-range missiles.
The proposal never made it past the paper-study phase, though. Brilliant Pebbles was quietly canceled after Bill Clinton became president in Meanwhile, a strong critic of electromagnetic launch had emerged. William C. McCorkle Jr. Projects were abruptly halted midway through, experiments were canceled, and researchers fled the field in droves. In every issue raised, he has been rebutted by real calculations or a more sober statement of facts. McCorkle now acknowledges making mistakes.
The Army has this idea that we should be doing this research for them, not the Chinese. The British program, he argued, was an artifact of an EM gun given to them by the U. Defense Department. With Richard Marshall, he also coauthored two textbooks on the subject. Indeed, Marshall and Fair were both delighted to find like-minded colleagues in China. Today China is arguably the largest center of electromagnetic gun research outside the United States.
One intriguing Chinese project is the coilgun-based armor under development at Harbin Institute of Technology. The DC output voltage from the voltage multiplier charges the capacitor bank through the accelerator coil L1, to a voltage that is determined by IC1, a operational amplifier configured as a comparator.
The Cockcroft-Walton voltage multiplier is an interesting device that was named after Douglas Cockcroft and Ernest Walton. In , the scientists used this voltage multiplier cascade design to power a particle accelerator and perform the first artificial nuclear disintegration in history. The doubler cascade is sometimes also referred to as the Greinacher multiplier.
These capacitors are available at most electronics supply companies. When the capacitor bank is charged to VDC, the amount of energy that will be switched to the accelerator coil is joules. With the capacitor storage bank charged to 1, VDC, the amount of energy is joules. The capacitor bank should only be charged to 1, volts if you have installed an SCR that can handle it.
The operational amplifier IC1 is configured as a voltage comparator and is used to set the amount of voltage charge on the capacitor bank. The reference voltage for the comparator is taken directly from the 12 volt DC source through resistor R The voltage charge accumulating on the capacitor bank is dropped down to a value of approximately through a voltage divider made up of resistors R3, R4, and K potentiometer R11, and is then connected to the comparator.
The potentiometer is used to set the exact voltage level on the capacitor bank when calibrating and using the rifle. Note that the capacitor bank is charged through the accelerator coil. When the desired voltage has been reached, the output of the comparator goes high and turns on transistor Q2 and the fire indicator light emitting diode D6. When Q2 is switched on, the base of Q1 is pulled to ground which stops oscillation of the transformer, turning the charging action off.
If the gun is not fired immediately after fully charging, the voltage level on the capacitor bank will slowly start to decrease due to leakage and the comparator will turn the charging circuit back on to keep the capacitor bank voltage level topped off. You will notice the charge and fire LEDs gradually alternating on and off indicating that the comparator and charging circuit are maintaining the set voltage.
Once the capacitor bank has charged to the set level, a ferrous projectile is inserted into the breech loading device and positioned partially into the coil by the bolt. The bolt of the loading device has a small magnet in the end with enough force to hold the projectile in place if the gun is tilted forward, but not enough to interfere with the operation of it. When fire switch S3 is closed, voltage is applied to the gate of the SCR, switching it on and dumping the charge across the capacitor bank into the accelerator coil L1.
The accelerator coil creates an electromagnetic pulse that launches the projectile down the barrel. Diode D9 is required to prevent the voltage from reversing. The heart of this project is a miniature high frequency transformer wound on a 20 mm x 17 mm x 15 mm bobbin with a ferrite core as shown in Figure 3.
All inductance measurements were taken with the iron cores in place. Transformer parts can be salvaged from an energy saver compact fluorescent bulb. Crack open the lamp at the seam, being careful not to break the glass tube, and remove the circuit board.
Locate the ferrite core transformer and unsolder it from the PCB printed circuit board. Detach the core parts by unwrapping any tape that may be holding them together. Use a knife or saw with a fine blade to cut the glue at the points where the core halves are in contact if the E-cores are glued together. There will probably be an air gap spacer on each side of the cores and in the middle so that the ferric material of each core does not contact.
Remove all of the wire and tape from the bobbin. You should now have a bobbin and E-cores similar to the ones shown in Figure 5-A. Start by numbering the bobbin posts from 1 to 8 in the positions shown in Figure 3. Solder one end of a piece of 26 laminated magnet wire to post number 2 and then wind the primary coil of 10 turns clockwise around the top half of the bobbin as shown in Figure 5-B.
Solder the other end of the primary winding wire to post number 3. Using another piece of 26 magnet wire, solder one end of the wire to post number 1 and then wind the feedback coil of eight turns on the bobbin clockwise below the primary winding as shown in Figure 5-C.
Solder the other end of the feedback winding to post number 4. Next, cover the primary and feedback windings with a layer of electrical tape as depicted in Figure 5-D. On the other side of the bobbin, solder the end of a piece of 34 AWG magnet wire on post number 5 and then wind the secondary coil of turns in even layers. Solder the other end of the secondary winding to post number 8 as shown in Figure 5-E.
Wrap the secondary winding with a layer of transformer tape and then coat the solder connections with silicone rubber or a similar insulating material as shown in Figure 5-F. I use a product called Plasti Dip that is available at most hardware stores. The final step in completing the transformer is to add the E-cores to the bobbin. To prevent the two halves of the cores from touching when they are in place, three air gap spacers need to be constructed.
Cut three pieces of electrical tape to a size that is slightly bigger than the end of each of the three legs of one of the cores and then stick them on. In the miniature combat game Battletech, the Gauss Gun is heavy projectile weapon mounted to some types of Mecha robots. The weapon causes heavy damage but produces very little heat, which heat build up is primary concern to the efficient operation of the Mech. In Wing Commander , the coil gun called a "Mass Driver" in the game, even though the term mass driver implies a much larger object is used as a primary weapon in some fighter spaceships.
Metal Gear REX 's primary weapon in the videogame Metal Gear Solid is identified as a railgun , but the description of its functionality would make it a coilgun. It is intended to launch an uninterceptable, untraceable nuclear weapon as the coilgun would leave no propellant trail or engine flares, unlike an ICBM. The Necrons from Warhammer 40, use weapons called gauss flayers to flay the skin off of their enemies.
These weapons are not coilguns, however. The name is misleading. Half-Life has a usable experimental Gauss gun, or Tau cannon. This also appears in Half-Life 2 , mounted on a drivable dune buggy. Halo 2 introduces a variant of the Warthog with a Gauss rifle mounted on the back.
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. Image to be added soon.
An illustration of a solenoid. A single-stage coilgun after electromagnets were used for repeating the same process to progressively accelerate the projectile in a multistage-design. A simplified diagram of a multistage coilgun with three coils, a barrel and a ferromagnetic projectiles.
A multistage coilgun. 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.
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.
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