Rail­gun–Weapon of the Fu­ture

the rail­gun made its pub­lic de­but dur­ing the navy s fu­ture force Science and tech­nol­ogy expo held at the Wash­ing­ton con­ven­tion cen­ter in fe­bru­ary 2015. one se­nior navy of­fi­cial ex­plained the im­pact of the pro­jec­tile to a freight train go­ing through the wa

SP's NavalForces - - FRONT PAGE - LT GEN­ERAL NARESH CHAND (RETD)

The Rail­gun made its pub­lic de­but dur­ing the Navy’s Fu­ture Force Science and Tech­nol­ogy Expo held at the Wash­ing­ton Con­ven­tion Cen­ter in Fe­bru­ary 2015. Lt Gen­eral Naresh Chand (Retd)

tHE EM RAIL­GUN USES high-power EM en­ergy in­stead of ex­plo­sive chem­i­cal pro­pel­lants to fire a pro­jec­tile far­ther and faster than any cur­rent gun. When fully weaponised, a rail­gun will de­liver hy­per­ve­loc­ity pro­jec­tiles on tar­gets, at ranges far ex­ceed­ing any of the cur­rent naval guns. it will be able to ef­fec­tively in­ter­cept air threats, par­tic­u­larly anti-ship cruise mis­siles. rail­guns also of­fer much larger am­mu­ni­tion hold­ing ca­pac­ity and lower cost per en­gage­ment as com­pared to mis­siles of sim­i­lar range. they can also be em­ployed to sup­port land op­er­a­tions. in ad­di­tion to mil­i­tary ap­pli­ca­tions, the US na­tional aero­nau­tics and Space ad­min­is­tra­tion ( NASA) has pro­posed to use a rail­gun from a high-al­ti­tude air­craft to fire a small pay­load into or­bit; how­ever, the ex­treme g-forces in­volved would nec­es­sar­ily re­strict the us­age to only the stur­di­est of pay­loads. the ef­fi­cacy will only be seen when the rail­gun is fully weaponised.

How it Works

Ba­si­cally a rail­gun is an elec­tri­cally pow­ered elec­tro­mag­netic pro­jec­tile launcher based on sim­i­lar prin­ci­ple as the ho­mopo­lar motor. The first ho­mopo­lar motor was demon­strated by Michael fara­day dur­ing 1821 in which he used di­rect cur­rent to cause ro­ta­tional move­ment. to un­der­stand the prin­ci­ple be­hind a rail­gun, take a mag­netic com­pass and place an elec­tric wire in north-South di­rec­tion over the com­pass. When you con­nect the wire to a bat­tery, the nee­dle will move a lit­tle. the length of the move­ment will de­pend upon how much cur­rent is flow­ing through the wire. this sim­ple ex­per­i­ment demon­strates that elec­tric cur­rent cre­ates a mag­netic field which in­ter­acts with the nee­dle and makes it move. the force cre­ated is at right an­gles to both di­rec­tion of the cur­rent and the di­rec­tion of the mag­netic field. This sim­ple idea has been trans­lated to de­velop a rail­gun. the build­ing blocks of a rail­gun are a pair of par­al­lel con­duct­ing rails (one acts as pos­i­tive and the other as neg­a­tive con­duc­tor) and a slid­ing ar­ma­ture. When cur­rent flows through the pos­i­tive rail, it cre­ates an elec­tro­mag­netic field due to which the slid­ing ar­ma­ture ac­cel­er­ates and the cur­rent passes through it, the cur­rent then re­turns to the power sup­ply through the neg­a­tive rail. the pro­jec­tile ex­pe­ri­ences a force which is called Lorentz force (after the Dutch physi­cist hen­drik a. Lorentz). the Lorentz force is di­rected per­pen­dic­u­larly to the mag­netic field and to the di­rec­tion of the cur­rent flow­ing across the ar­ma­ture. this phenomenon is being re­searched and de­vel­oped to pro­duce a su­per gun which does not use a pro­pel­lant or ex­plo­sive but a very high de­gree of ki­netic en­ergy. the power of the en­ergy will de­pend on the length of the rail or in­tense cur­rent but as long length of the rails pose prob­lems of space; thus to have an ef­fec­tive rail­gun, a very high level of cur­rent is re­quired. Most rail­guns thus use a strong cur­rent to the de­gree of a mil­lion amps for gen­er­at­ing the re­quired force. When this force is ap­plied to a pro­jec­tile, it ac­cel­er­ates to the end of the rails, op­po­site to the di­rec­tion of the power sup­ply and leaves through an aper­ture. at this point the cir­cuit is bro­ken which ends the flow of cur­rent. An­ti­tank pro­jec­tiles like ar­mour-pierc­ing fin­sta­bilised dis­card­ing-sabot can achieve a muz­zle ve­loc­ity (MV) of about Mach 5 but rail guns can achieve a MV of Mach 7-10. Such a high de­gree of MV makes pro­jec­tiles fired from a Rail­gun more pen­e­trat­ing against hard tar­gets and achieve a much longer range of about 160 km.

De­vel­op­ment

the US navy is vig­or­ously pur­su­ing the de­vel­op­ment of rail­gun for air de­fence role. Dur­ing March 2006, Bae Sys­tems re­ceived a con­tract for de­sign and pro­duc­tion of the 32 mega­joules (MJ) Lab­o­ra­tory Launcher for the US navy. Dur­ing fe­bru­ary 2012, as part of Phase 1 of the navys in­no­va­tive naval Pro­to­type (INP) pro­gramme, en­gi­neers at the naval Sur­face War­fare cen­ter suc­cess­fully fired BAE Sys­tems’ EM Rail­gun pro­to­type at tac­ti­cal en­ergy lev­els. the gun fired a 32 MJ half-power pro­to­type (the navy com­pares one MJ of en­ergy to a one­tonne ve­hi­cle mov­ing at about 160 kmph. the full-scale sys­tem is ex­pected to be 64 MJ. chris hughes, the then Vice Pres­i­dent and Gen­eral Man­ager of Weapon Sys­tems at Bae Sys­tems stated that, Were com­mit­ted to de­vel­op­ing this in­no­va­tive and game chang­ing tech­nol­ogy that will rev­o­lu­tion­ize naval war­fare. the rail­guns abil­ity to de­fend against en­emy threats from dis­tances greater than ever be­fore im­proves the ca­pa­bil­i­ties of our armed forces.

Bae Sys­tems was again awarded a $34.5-mil­lion con­tract by the Of­fice of naval re­search ( onr) for the de­vel­op­ment of the rail­gun un­der Phase 2 of the navys inP pro­gramme. the aim of the Phase 2 was to ma­ture the tech­nol­ogy and de­sign of the launcher and pulsed power from a sin­gle-shot to multi-shot ca­pa­bil­ity. this would also in­volve de­vel­op­ing and in­cor­po­rat­ing a auto-load­ing and ther­mal man­age­ment sys­tems. faster rate of fire is es­sen­tial for achiev­ing a higher kill prob­a­bil­ity at the tar­get end. Phase 2 was to be com­pleted by 2014. it was re­ported that tests were held dur­ing au­gust 2014 how­ever tests are a con­tin­u­ous process and will carry on dur­ing the de­vel­op­ment phase of the gun. the rail­gun is likely to be de­liv­ered by 2020-25.

Pub­lic de­but. the rail­gun made its pub­lic de­but dur­ing the navys fu­ture force Science and tech­nol­ogy expo held at the Wash­ing­ton con­ven­tion cen­ter in Fe­bru­ary 2015. One se­nior navy of­fi­cial ex­plained the im­pact of the pro­jec­tile to a freight train go­ing through the wall at a hun­dred miles an hour. he added that the lack of gun­pow­der and ex­plo­sive war­heads elim­i­nates some sig­nif­i­cant safety haz­ards for navy crews.

Par­al­lel de­vel­op­ment. Gen­eral atomics is de­vel­op­ing a rail­gun called the Bl­itzer Sys­tem. the elec­tro­mag­netic Sys­tems Group of Gen­eral atomics (Ga-eMS) is ac­tively work­ing to bring rail­gun tech­nol­ogy to the Depart­ment of De­fense for mul­ti­ple mis­sions to in­clude in­te­grated air and mis­sile de­fence, sur­face fire sup­port and anti-sur­face war­fare. Ga-eMSs ex­per­tise in eM stems from Gas long his­tory in high power elec­tri­cal sys­tems, from de­vel­op­ing and build­ing both fis­sion and fu­sion re­ac­tors, through the Navy’s first EM launch and re­cov­ery equip­ment for air­craft car­ri­ers. Ga-eMS has de­vel­oped, built and suc­cess­fully tested two rail­guns, the in­ter­nally funded the Bl­itzerª 3 MJ sys­tem and a 32 MJ launcher for the onr. Ga-eMS also de­signed and built the pulse power sup­ply for both guns and is de­vel­op­ing pro­jec­tiles for air and mis­sile de­fence and pre­ci­sion strike. Ga-eMS is con­tin­u­ing the Bl­itzer fam­ily of rail­guns with a 10 MJ sys­tem de­signed for mo­bile and fixed land-based ap­pli­ca­tions. Ga-eMS has an­nounced in Jan­uary this year that the pro­jec­tiles un­der­go­ing fir­ing, not only sur­vived and op­er­ated un­der the 30,000 g-force and multi-tesla mag­netic field launch con­di­tions.

Cen­tre for Strate­gic and Bud­getary As­sess­ment (CSBA) Pa­per. Dur­ing novem­ber 2014, cSBa re­leased a pa­per on com­mand­ing the Seas: a Plan to rein­vig­o­rate uS navy Sur­face War­fare. in which they made wide rang­ing rec­om­men­da­tions on ca­pac­ity build­ing, mod­erni­sa­tion and a de novo ap­proach for medium-range air de­fence for which, cSBa took a lay­ered ap­proach. The first layer is within the 30

nau­ti­cal miles (about 55.5 km) zone which will be de­fended by 32 MJ rail­guns cou­pled with raytheons riM-162 eSSM (evolved Sea Spar­row) mis­siles which has a range of 50 km and a speed of Mach 4+. the logic for not us­ing the long range of the rail­gun was due to its lim­ited ma­noeu­vra­bil­ity but com­pen­sated by its higher MV and less ma­noeu­vring time avail­able to the in­com­ing su­per­sonic mis­sile at close ranges. in the 5 to 15 nau­ti­cal miles (about 9.2 to 27.6 km) zone, a com­bi­na­tion of laser weapon based de­fences (also un­der de­vel­op­ment) and raytheons raM (rolling air­frame Mis­siles) were to be de­ployed. Such an ap­proach would also re­lease ver­ti­cal launch cells for long-range of­fen­sive sur­face at­tack and air-de­nial weapons.

GA-EMS has de­vel­oped, built and suc­cess­fully tested two Rail­guns, the in­ter­nally funded the Bl­itzer ™ 3 MJ sys­tem and a 32 MJ launcher for the ONR. GA-EMS also de­signed and built the pulse power sup­ply for both guns and is de­vel­op­ing pro­jec­tiles for air and mis­sile de­fence and pre­ci­sion strike.

Chal­lenges

Power sup­ply. Both the rail­gun and the laser-based weapons, re­quire power sup­ply which must de­liver large val­ues of sus­tained and sta­ble cur­rents. the most com­mon com­po­nents used for rail­guns are ca­pac­i­tors and com­pul­sators (an amal­gam of the term com­pen­sated Pulsed al­ter­na­tor-orig­i­nally con­ceived for elec­trome­chan­ics to power laser flash-lamps for nu­clear fu­sion re­search but since then found ap­pli­ca­tions for pow­er­ing ex­per­i­men­tal eM launch­ers). this poses a chal­lenge for uSaÕs cG-47 cruis­ers and DDG-51 de­stroy­ers which have low power gen­er­a­tion. even a 32 MJ rail­gun re­quires at least 15-30 MW of power on­board power gen­er­a­tion, which is much more than th­ese class of ships gen­er­ate. 64 MJ rail­guns, would re­quire 40-50 MW ca­pac­ity. this as­pect will be­come one of the key fac­tors of fu­ture de­sign of ships hav­ing rail­guns and laser-based weapons on board. in an­tic­i­pa­tion of the power de­mand from th­ese weapons, the navys brand-new Zumwalt class de­stroyer can gen­er­ate up to 78 MW of power, of which it only needs 20 to op­er­ate. that means it can have lasers and rail­guns that draw up to 58 MW of power. Prob­a­bly in an­tic­i­pa­tion many coun­tries are de­sign­ing their ships based on all-elec- tric con­fig­u­ra­tions, which is why smaller Span­ish and aus­tralian aegis frigates have a ca­pac­ity of 40+ MW.

Re­coil force. the rails need to with­stand enor­mous re­coil force (due to very high MV) dur­ing fir­ing. This force will tend to push the pro­jec­tile and rails apart and as gap in­creases, arc­ing de­vel­ops which causes rapid va­por­i­sa­tion and ex­ten­sive dam­age to the rail sur­faces and the in­su­la­tor sur­faces. Thus early re­search was based on fir­ing of one pro­jec­tile at a time. re­search is on to de­velop more suit­able ma­te­ri­als.

Type of ma­te­ri­als. the rails and the pro­jec­tiles must be built from strong con­ducive ma­te­ri­als to with­stand a very strong re­coil force, force of the ac­cel­er­at­ing pro­jec­tile and heat­ing due to large cur­rents and fric­tion. this re­quires ma­jor de­vel­op­ments in ma­te­rial science.

Heat dis­si­pa­tion. in the present con­fig­u­ra­tion of the Rail­gun, mas­sive amounts of heat is gen­er­ated due to value of the cur­rent re­coil force and the fric­tion of the pro­jec­tile leav­ing the sys­tem. the heat can cause ther­mal ex­pan­sion of the rails and pro­jec­tile, fur­ther in­creas­ing the fric­tional heat. this re­sults in the melt­ing of the equip­ment, re­duced safety of the crew and easy de­tec­tion by the en­emy due to in­creased in­frared sig­na­ture. thus the equip­ment used in a rail­gun has to be higly heat re­sis­tance.

Other fac­tors. there is an ero­sion of the rails after each fir­ing and a de­gree of ab­la­tion (re­moval of ma­te­rial from the sur- face of an ob­ject by va­por­i­sa­tion, chip­ping or other ero­sive) of the pro­jec­tile; both of which can be over­come by bet­ter ma­te­rial and de­sign.

Rail­guns ver­sus Coil Guns

a coil gun (or Gauss gun) is an eM gun that has a se­ries cop­per coils in­stead of a bar­rel. th­ese coils are en­er­gised se­quen­tially, cre­at­ing a mov­ing mag­netic field which at­tracts a fer­ro­mag­netic pro­jec­tile down the bar­rel. Since the pro­jec­tile of a coil gun floats on the mag­netic field with­out touch­ing any sur­face thus it causes less wear and tear, less heat and are com­pletely noise­less. coil guns have been demon­strated to pro­pel pro­jec­tiles at su­per­sonic speeds but they are not as ef­fi­cient or as ca­pa­ble as rail­guns.

Rail­gun in Fic­tion

The Moon is a Harsh Mistress is a 1966 science fic­tion novel by Robert Hein­lein in which lu­nar colonists, in his in­de­pen­dence strug­gle from earth, uses an eM launcher to fire iron con­tain­ers filled with rocks at earth. in the movie Eraser, arnold Sch­warzeneg­ger stars as a Wit­ness Pro­tec­tion Pro­gramme agent who has by chance come across a se­cret gov­ern­ment plot to sell rail­guns to ter­ror­ists. Bat­tlestar Galac­tica, the mu­seum-era war­ship, is armed with rail­guns that use both eM and con­ven­tional tech­nolo­gies. rail­guns are also fea­tured in video games like, quake, Metal Gear Sol­i­dand red fac­tion.

(Top) A pro­to­type of BAE Sys­tems’ elec­tro­mag­netic Rail­gun on dis­play aboard joint high speed ves­sel USS Millinocket; (above) GA-EMS is on the fore­front of ma­tur­ing Rail­gun weapons sys­tems to sup­port air and mis­sile de­fence, counter bat­tery fire, and pre­ci­sion in­di­rect fire.

PHO­TO­GRAPHS: US Navy

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