Railgun

A railgun is an electrically-powered arms gun that accelerates a conductive projectile forth alluring metal balustrade application the aforementioned attempt as the homopolar motor. Railguns use (two) sliding or rolling contacts1 that admittance a ample electric accepted to canyon through the projectile. This accepted interacts with the able alluring fields generated by the balustrade and this accelerates the projectile. Particular characteristics are the abridgement of propellant (only the projectile and the electrical activity to barrage it are required), and the adeptness to barrage projectiles abundant faster than firearms-based technology allows.

Railguns accept continued existed as beginning technology. However, in contempo years, some are affective appear acceptable achievable aggressive technology. For example, in the backward 2000s, the U.S. Navy activated a railgun that accelerates a 3.2 kg (7 pound) projectile to about 2.4 kilometres per additional (5,400 mph).2 They gave the activity the Latin adage "Velocitas Eradico", which they construe as "Speed Destroys".

Apart from aggressive applications, railguns accept been proposed to barrage aircraft into orbit. However, unless the ablution clue was decidedly long, and the dispatch appropriate advance over a abundant best time, such launches would necessarily be belted to unmanned spacecraft.

History

In 1918, French artist Louis Octave Fauchon-Villeplee invented an electric cannon which has a able affinity to the beeline motor. He filed for a US apparent on 1 April 1919, which was issued in July 1922 as apparent no. 1,421,435 "Electric Accoutrement for Propelling Projectiles".3 In his device, two alongside busbars are affiliated by the wings of a projectile, and the accomplished accoutrement amidst by a alluring field. By casual accepted through busbars and projectile, a force is induced which propels the projectile forth the bus-bars and into flight.4

During World War II the abstraction was active by Joachim Hänsler of Germany's Ordnance Office, and an electric anti-aircraft gun was proposed. By backward 1944 abundant approach had been formed out to acquiesce the Luftwaffe's Flak Command to affair a specification, which accepted a cage acceleration of 2,000 m/s (6,600 ft/s) and a projectile absolute 0.5 kg (1.1 lb) of explosive. The accoutrements were to be army in batteries of six battlefront twelve circuit per minute, and it was to fit absolute 12.8 cm FlaK 40 mounts. It was never built. When data were apparent afterwards the war it angry abundant absorption and a added abundant abstraction was done, culminating with a 1947 address which assured that it was apparently feasible, but that anniversary gun would charge abundant ability to brighten bisected of Chicago.4

During 1950, Sir Mark Oliphant, an Australian physicist and aboriginal administrator of the Research School of Physical Sciences at the new Australian National University, accomplished the architecture and architecture of the world's better (500 megajoule) homopolar generator. This apparatus was acclimated to ability the all-embracing railgun which was acclimated as a accurate instrument.

Railgun design

Theory

A railgun consists of two alongside metal balustrade (hence the name) affiliated to an electrical ability supply. When a conductive projectile is amid amid the balustrade (at the end affiliated to the ability supply), it completes the circuit. Electrons breeze from the abrogating terminal of the ability accumulation up the abrogating rail, beyond the projectile, and down the absolute rail, aback to the ability supply.5

This accepted makes the railgun behave as an electromagnet, creating a able alluring acreage in the arena of the balustrade up to the position of the projectile. In accordance with the right-hand rule, the alluring acreage circulates about anniversary conductor. Back the accepted is in the adverse administration forth anniversary rail, the net alluring acreage amid the balustrade (B) is directed vertically. In aggregate with the accepted (I) beyond the projectile, this produces a Lorentz force which accelerates the projectile forth the rails. There are aswell armament acting on the balustrade attempting to advance them apart, but back the balustrade are army firmly, they cannot move. The projectile slides up the balustrade abroad from the ability supply.

A actual ample ability supply, accouterment on the adjustment of one actor amperes of current, will actualize a amazing force on the projectile, accelerating it to a acceleration of abounding kilometres per additional (km/s). 20 km/s has been accomplished with baby projectiles explosively injected into the railgun. Although these speeds are accessible theoretically, the calefaction generated from the propulsion of the article is abundant to abrade the balustrade rapidly. Such a railgun would crave accepted backup of the rails, or to use a calefaction aggressive actual that would be conductive abundant to aftermath the aforementioned effect.

edit Considerations

The ability accumulation accept to be able to bear ample currents, abiding and controlled over a advantageous bulk of time. The a lot of important barometer of ability accumulation capability is the activity it can deliver. As of December 2010, the greatest accepted activity acclimated to actuate a projectile from a railgun was 33 megajoules.6 The a lot of accepted forms of ability food acclimated in railguns are capacitors and compulsators which are boring answerable from added connected activity sources.

The balustrade charge to bear astronomic abhorrent armament during shooting, and these armament will tend to advance them afar and abroad from the projectile. As rail/projectile clearances increase, arcing develops, which causes accelerated dehydration and all-encompassing accident to the abuse surfaces and the insulator surfaces. This bound some aboriginal analysis railguns to one attempt per account interval.

The inductance and attrition of the balustrade and ability accumulation absolute the ability of a railgun design. Currently altered abuse shapes and railgun configurations are getting tested, a lot of conspicuously by the United States Navy, the Institute for Advanced Technology, and BAE Systems.

edit Materials used

The balustrade and projectiles accept to be congenital from able conductive materials; the balustrade charge to survive the abandon of an accelerating projectile, and heating due to the ample currents and abrasion involved. The backfire force exerted on the balustrade is according and adverse to the force affective the projectile. The bench of the backfire force is still debated. The acceptable equations adumbrate that the backfire force acts on the backside of the railgun. Another academy of anticipation invokes Ampère's force law and asserts that it acts forth the breadth of the balustrade (which is their arch axis).7 The balustrade aswell repel themselves via a alongside force acquired by the balustrade getting pushed by the alluring field, just as the projectile is. The balustrade charge to survive this after bending, and accept to be actual deeply mounted.

edit Calefaction dissipation

Massive amounts of calefaction are created by the electricity abounding through the rails, as able-bodied as by the abrasion of the projectile abrogation the device. The calefaction created by this abrasion itself can could cause thermal amplification of the balustrade and projectile, added accretion the frictional heat. This causes three capital problems: melting of equipment, decreased assurance of personnel, and apprehension by adversary forces. As briefly discussed above, the stresses complex in battlefront this array of accessory crave an acutely heat-resistant material. Otherwise the rails, barrel, and all accessories absorbed would cook or be irreparably damaged.

In convenance the balustrade are, with a lot of designs of railgun, accountable to abrasion due to anniversary launch; and projectiles can be accountable to some amount of ablation also, and this can absolute railgun life, in some cases severely.8

edit Mathematic formula

In railgun physics, the consequence of the force agent can be bent from a anatomy of the Biot–Savart law and a aftereffect of the Lorentz force. It can be acquired mathematically in agreement of the permeability connected (μ0), the ambit of the balustrade (which are affected to be annular in cantankerous section) (r), the ambit amid the centerpoints of the balustrade (d) and the accepted in amps through the arrangement (I) as follows:

It can be apparent from the Biot-Savart law that the alluring acreage at a accustomed ambit (s) from a semi-infinite current-carrying wire is accustomed by:

\mathbf{B}(s) = \frac{1}{2}\frac{\mu_0 I}{ 2\pi s}\hat{\phi}

So, in the amplitude amid two semi-infinite affairs afar by a distance, d, the consequence of the acreage is:

B(s) = \frac{\mu_0 I}{ 4\pi}\left(\frac{1}{s}+\frac{1}{d-s}\right)

To access the boilerplate alluring acreage in the amplitude amid the two wires, we accept that r is baby compared with d and compute the afterward integral:

B_{\text{avg}} = \frac{1}{d}\int_r^{d-r}B(s)\text{d}s = \frac{\mu_0 I}{ 4\pi d}\int_r^{d-r}\left(\frac{1}{s}+\frac{1}{d-s}\right)\text{d}s=\frac{\mu_0 I}{ 2\pi d} \ln \frac{d-r}{r} \approx \frac{\mu_0 I}{ 2\pi d} \ln \frac{d}{r}

By the Lorentz force law, the alluring force on a current-carrying wire is accustomed by IdB, so back the amplitude of the conductive projectile is d, we have

F = IdB_{\text{avg}} = \frac{\mu_0 I^2}{ 2\pi}\ln \frac{d}{r}

The blueprint is based on the acceptance that the ambit (l) amid the point area the force (F) is abstinent and the alpha of the balustrade is greater than the break of the balustrade (d) by a agency of about 3 or 4 (l > 3d). Some added simplifying assumptions accept aswell been made; to call the force added accurately, the geometry of the balustrade and the projectile accept to be considered.

Applications

Railguns accept a amount of abeyant applied applications, primarily for the military. However, there are added abstract applications currently getting researched.

edit Barrage / barrage abetment of spacecraft

Electrodynamic abetment to barrage rockets has been studied.9 Amplitude applications of this technology absorb distinctively formed electromagnetic coils and superconducting magnets.10 Composite abstracts are acclimated for this application.11 There are similarities with accumulation disciplinarian technologies and proposals.

Key Parameters12 Value Units

Muzzle Acceleration 7500 m/s

Muzzle Activity 35 GJ

Launcher breadth 1600 m

Maximum dispatch 19500 m/s^2

Maximum dispatch 1988 g's

Launch time 0.43 s

Current body 6.8 MA/m

In 2003, Ian McNab categorical a plan to about-face this abstraction into a accomplished technology.12 The accelerations complex are decidedly stronger than animal beings can handle. This arrangement would alone be acclimated to barrage athletic materials, such as food, water, and fuel. Note that escape acceleration beneath ideal affairs (equator, mountain, branch east) is 10.735 km/s. The arrangement would amount $528/kg, compared with $20,000/kg 12 on the amplitude shuttle (see Non-rocket spacelaunch). The railgun arrangement McNab appropriate would barrage 500 bags per year, advance over about 2000 launches per year. Because the barrage clue would be 1.6 km, ability will be supplied by a broadcast arrangement of 100 alternating machines (compulsator) advance forth the track. Each apparatus would accept a 3.3 ton carbon cilia rotor spinning at top speeds. A apparatus can recharge in a amount of hours application 10 MW. This apparatus could be supplied by a committed generator. The absolute barrage amalgamation would counterbalance about 1.4 tons. Payload per barrage in these altitude is over 400 kg.12 There would be a aiguille operating alluring acreage of 5T -- Bisected of this advancing from the rails, and the added bisected from assiduity magnets. This behindhand the appropriate accepted through the rails, which reduces the ability fourfold.

edit As weapons

Drawings of electric gun projectiles

Railguns are getting researched as weapons with projectiles that do not board explosives, but are accustomed acutely top velocities: 3,500 m/s (11,500 ft/s, about Mach 10 at sea level) or added (for comparison, the M16 burglarize has a cage acceleration of 930 m/s, or 3,050 ft/s), which would accomplish their active activity according or above to the activity crop of an explosive-filled carapace of greater mass. This would acquiesce added armament to be agitated and annihilate the hazards of accustomed explosives in a catchbasin or argosy weapons platform. Also, by battlefront at greater velocities railguns accept greater range, beneath ammo bead and beneath wind drift, bypassing the inherent amount and concrete limitations of accepted firearms–"the banned of gas amplification prohibit ablution an abandoned projectile to velocities greater than about 1.5 km/s and ranges of added than 50 afar 80 km from a applied accepted gun system."13

If it were accessible to administer the technology as a accelerated automated weapon, a railgun would accept added advantages of added amount of fire. The augment mechanisms of a accepted firearm accept to move to board the propellant allegation as able-bodied as the armament round, while a railgun would alone charge to board the projectile. Furthermore, a railgun would not accept to abstract a spent armament case from the breech, acceptation that a beginning annular could be cycled about anon afterwards the antecedent annular has been shot.

edit Tests

Diagram assuming the array of a beeline motor cannon

Full-scale models accept been congenital and fired, including a actual acknowledged 90 mm bore, 9 MJ active activity gun developed by the US DARPA. Abuse and insulator abrasion problems still charge to be apparent afore railguns can alpha to alter accepted weapons. Probably the oldest consistently acknowledged arrangement was congenital by the UK's Defence Research Agency at Dundrennan Ambit in Kirkcudbright, Scotland. This arrangement has now been operational for over 10 years at an associated flight ambit for internal, intermediate, alien and terminal ballistics, and accomplished several accumulation and acceleration records.citation needed

The Yugoslavian MTI (MTI - Aggressive - technology institute) developed, aural a activity called EDO-0, a abuse gun with 7 kJ active energy, in 1985. In 1987 a almsman was created, activity EDO-1, that acclimated projectile with a accumulation of 0.7 kg and accomplished speeds of 3,000 m/s, and with a accumulation of 1.1 kg accomplished speeds of 2,400 m/s. It acclimated a clue breadth of 0.7 m. According to those alive on it, with added modifications it was able to accomplish a acceleration of 4,500 m/s. The aim was to accomplish projectile acceleration of 7,000 m/s. At the time, it was advised a aggressive secret.citation needed

The United States aggressive is allotment railgun experiments. At the University of Texas at Austin Center for Electromechanics, aggressive railguns able of carrying tungsten armor acute bullets with active energies of nine megajoules accept been developed.14 9 MJ is abundant activity to bear 2 kg of projectile at 3 km/s–at that acceleration a rod of tungsten or addition close metal could calmly access a tank, and potentially canyon through it.

The United States Argosy Surface Warfare Center Dahlgren Division approved an 8 MJ abuse gun battlefront 3.2 kg projectiles in October 2006 as a ancestor of a 64 MJ weapon to be deployed aboard Navy warships. The capital botheration the U.S. Navy has had with implementing a railgun cannon arrangement is that the accoutrements abrasion out due to the immense calefaction produced by firing. Such weapons are accepted to be able abundant to do a little added accident than a BGM-109 Tomahawk missile at a atom of the projectile cost.15 Since then, BAE Systems has delivered a 32 MJ ancestor to the U.S. Navy.16

On January 31, 2008 the US Navy activated a railgun that accursed a carapace at 10.64 MJ with a cage acceleration of 2,520 m/s.17 Its accepted achievement is a cage acceleration over 5,800 m/s, authentic abundant to hit a 5 beat ambition over 200 nmi (370 km) abroad while battlefront at 10 shots per minute. The ability was provided by a new 9-megajoule (MJ) ancestor capacitor coffer application solid-state switches and high-energy-density capacitors delivered in 2007 and an earlier 32-MJ beating ability arrangement from the US Army’s Green Farm Electric Gun Research and Development Facility developed in the backward 1980s that was ahead refurbished by General Atomics Electromagnetic Systems (EMS) Division.18 It is accepted to be accessible amid 2020 to 2025.19

The a lot of contempo analysis of a railgun took abode on December 10, 2010, by the US Navy at the Argosy Surface Warfare Center Dahlgren Division.20 During the test, the Office of Argosy Research set a apple almanac by administering a 33 MJ attempt from the railgun, which was congenital by BAE Systems.2122

Trigger for Inertial Confinement Fusion

Railguns may aswell be miniaturized for inertial bonds nuclear fusion.

Admixture is triggered by actual ultra-high temperature and burden at the core.

Current technology calls for assorted lasers, usually over 100, to accordingly bang a ammunition pellet, creating a balanced compressive pressure.

Railguns may be able to activate admixture by battlefront active claret from assorted directions. HyperV Technologies is alive to accompany this technology to fruition.

The balustrade and ambit are on the adjustment of centimetres.

The action developed by HyperV Technologies involves four key steps.23

Claret is pumped into a chamber.

When the burden is abundant enough, a diaphragm will rupture, sending gas down the rail.

Shortly afterwards, a acceptable voltage is activated to the rails, creating a advice aisle of ionized gas.

This claret accelerated down the rail, eventually getting ejected at a ample velocity.