The results of high-pressure tests of four railgun designs and four projectile types are presented. All tests were conducted at the Los Alamos explosive magnetic-flux compression facility in Ancho Canyon. The data suggest that the high-strength projectiles have lower resistance to acceleration than the low-strength projectiles, which expand against the bore during acceleration. The railguns were powered by explosive magnetic-flux compression generators. Calculations to predict railgun and power supply performance were performed

Adams, D. F.

Cummings, C. E.

Fowler, C. M.

Kerrisk, J. F.

Marsh, S. P.

Parker, J. V.

Peterson, D. R.

UNT Digital Library

A mayx purpose Of the I eChnl-cal Information Center is to providethe broadest dissemination possi-ble of hformation contained inDOE’S Research and DevelopmentReports to ‘ ‘siriess, industry, theacademic co,, mmity, and federal,state and local governments.Although a small portion of thisreport is not reproducible, it isbeing made available to expeditethe availability of information on theresearch discussed herein.LA-UR--83-2717~~84 001202TITLE:AUTHOR(S).SUBMITTED TODESIGN AND TESTING OF HIGH-PRESSURE RAILGUM ANO PROJECTILESD. R. Peterson, C. M. Fowler, C. E. Cunvnlngs,J. F. Kerrisk,J. V. Parker, S. P. Narsh NOTICEPOIJRTIONSOFTlllS REPORT ARE ILLEGIBLE.—.It has been reprodnwed frofa the b8mi watiable copy to permit the broadestpossible ●uailabtiity.Second International Conference on Electromagnetic Launchers,October 14s16, 1983, Boston, MassachusettsThismportwaspropmd a~anmountofwork rponaorodbyanapncyofthelJnltdStataGovernment.NoMmrthcUnWSt~tos@vornment noranyagencythoraof,aocaoyoftiemployoa,makesan)warranty,exprouorimplied, wum44 my J@ I&billtyorraped.bilityfmtb~ur~, -~te-, wumful- tianylnf-atk, a~t~~m-d~~wt~mpn~thatttsuw-~ MMringe@vstolyovmod~ R*.ancohorsinto●nyspocifiicomrnord product,promo,w Borvtwby tti ~ ~manufmcturor,orotborwimdoa notnocowarilyconstitutew Implyit4mdormMo~ ~mandatbn,or korln~ by IhoUnitedS(sIoaOovornrnontor●ny apcy tbord.T’ba~A 0pMon9 of●uthr,.ftexpraoodJmrdn do notnoco4mrilyftator mflaot bond th,UnitedStatesOovornnmtor●ny qoncy thoroofPaM*Ma4----------DESIGN AND TESTING OF HIGH-PRESSURERAILGUNS AND PROJECTILESD. R. Peterson, C. M. Fowler, C. E. Cummings,J. F. Kerrisk, J. V. Parker, and S. P. MarshLos Alanos National La~oriitoryP. O. Box 1663LOS Alamos, NM 87545D. F. AdamsConposite Materials ResearchUniversity of WyomingLaramie, MY R2070GroupM!!!!KYThe results of high-pressuretests of four rail-gun designs and four projectile types are presented.All tests were conductedat the Los Alamos explosivemagnetic-fluxcompressionfacility in Ancho Canyon.The data suggest that the high-strengthprojectileshave lower resistance to accelerationthan the low-strength projectiles,which expand against the boreduring acceleration.The railgun$ were power d by explosive magnetic-flux co~ression generators.f,2 Calculations topredict railgun and p wer supply performance wereperfornw by Kerrisk.!Test NesultsThe cross sectionsof the raiilgunsused in thetests are illustr~tedin Fig. 1 and described inTable I. Table 11 shows a sunssmryof projectiledescriptions ,>ndthe results of selected tests.The theoreticalprojectile accelerat’rallgun is‘2%-%- ‘where v is gro.jectilevelocity. t is ttmaon in a(1)L’ iSthe railqun’in&ctance gredie;~, m is the projectilemass, and I is the armaturecurrent, SO thkt -(2)(3)(4)where x is projectilep]:~tlon, P is average pressureof the plasma armature and A is the rallgun cross-SeCtiOIMl ma. (All railgun tests described tn thispaper wer~ plasma arma~ure driven.) Projectile posi-tion maasur~nts were made by magnetic probes and byin-f1ight and in-boreradiogra~hsModel F. The Model F rallgun was fabricated by~n~ a 25-avn-thickstructural shell onto a rai\-Insulator assembly 38Inm in dtam. The tnsulatormatarial is polycarbonate. F{qur@ 2 shows that thecurrent dcliv~red to the railgun rose from 0.4 MA to1,1 MA in 500 us, The projecttlo acc~leratednormallyat low pressure, as indicatedin the radio raph of!the railgun taken dur~ng oper~tion (Fig. 3 , 300 usafter the start Of current flow. This radiographtndtcatesthat the rail separation,driven by the~t!ternalmag)leticpressure,has increased-1 nsnfromthe breech to the oro.iectile. We , ducted onlv o,etest on the Model F r;ilgun. Model was eventuallysuper!;ededby Model K (descrioed in Table I), whichis more resistant to St.rilcturaldeforfnationpost-shot inspection If the railgu,~ sl19qe~t.~that (isthe operating pressure rose, the railqunstructural shell flexw, from a circular cross sectionto an oval cross section, causinq an interferencebetwel!n the railgun and the projectile (FIq. 4). Thisgun was damaged beyond repair illflrinq.Model ~, We conducted s~veral t~~stson th~ MmlIJl J7E@l . Figure 5 shows data from a tyDica! test. !I~each Case, the pnl;:?rhon,lte SIII] WI< lallnch~,lint.](~,as confirmkd by in-fliqht radioqrauh and the Droiec-@alJ‘lid‘\...\‘\,WE!kmMorelr&MoorL a“-4-”TABLE IDESCRIPTIONOF RAILGUNS TESTEDEoreGun Diameter Length Calculated Inductance~ (lull) (cm) Gradienta (uH/m)F 16 0.3913b 1% 0.35; 16 60 0.45K 16 60 :.3&c.~nductan e gradients calculatedby the method ofKerrisk.ibsquare bore.clhe inductancegradient of railgun Kll, withouta steel sleeve is 0.39 ~H/m; of K21, with a100-m-i. d. steel sleeve, It Is 0.34 vHlm.TABLE IISUPMARY OF TEST RESULTSMuzzle Peak ProjectileVeloclty Current mass ?rojecti1eTest (km/f’) (w) .~. TypeGll 1.3 0.7 17.2G21 3.4 0.7 5.3 11:Kll 2.4 18.5 IVK21 2.2 ::: 17.2 IvProjectileDescription1. 14-nsn-dismiron $ph@re cast Into a polycarbonatecylinder 16 WJIIin dim and i9 m long.11. 13+wn-square,19+n-long polycarbonatvslug.111. 6-@m+diun iron sphere cast into a polycarbonatecylinder 16 m In diun, and 19 mn long.Iv. i4-m.diun, 19-!m-1on9Ti-6Al-4V slug WaPPQdwith a 0.8+wn-thickfiberglass-epoxycoat. Acorundum disk, 16 IMIin dian and 3 m thick, iscemanted to the back of the titanium \lug. AIt-m-dim, 3+m+thick polycarbonategas saal isattached to the back of the corund’umdisk.sa9●1a,aoo#6 w uFig. 2, Measured current, Test f11.confined in the bor~. Also in ccch case, the t@er-ating pr~ssure d~clined substantiallybefore theprojecti1s ●xited the gunAccelerationdata suggest that below *.4 GPa,accelwat ion of PolycarbonateprojectI}CS Is -60Stheoretical. Above *.4 Wt. the acrcls?rationcfpolycarbonateprojectiles is substantf~llylCSS thantho~rotical. Ffguro6 shows the in-flfghtradiograph-.;. ... ... . . -,.* .,**?.*, - . .. -,! ,. - r. .* 1...... .. . ““?f:..z-~~ ‘:’”.: “q.:,....4Fig. 3. Wbore,redlogmph of an acceleratingrallgun pro~tf’ie, Test F1l. The upperImege fs ? static radiograph taken beforethe start of currnnt flow.- “Fi9. 4. Sclmatic illustrationof theapparent mechmlsmfw bore-projectlle ~nterfcrence,Test F1l.3_—3- “8-aFig. 5. kasursd current, Test J12.r.Fig. 6. In flight radiographsof projectileJ12.of projectileJ12. The wedge-shapedappearance 1sbelIeved to be the result of wear caused by thepressure of the projectlle ●gainst the bore. Metheorize that at high pressure, the plastic expansionof the projectile against the bore results, 1n effeet,In the accelerationof an oversized projectile.In some of the tests, we observed d-ge to theIntertorcomponentsof the gun, apparentlybecause ofthe rebound of the rails as tha megnetlc pressuredecayed. We dld not, howevw, observe any d~ge tothe Kevlar shells. We found that the guns could bereftred by enlarglng the bores with a broach to ramovearcdw~. Post-shot tnspect~onrevealed the accum-ulationo sooty meterlal from the plasma atmatures Inthe seams of ttm guns. Butt joints exposed to thebore are espec~a!lyvulnerable. In some c~ses, thedata suggest that a fraction of the curren$ dellveredto the gun was shunted from the armature I to aspurious path wlthtn the seams of the gun.~ Themeasurementof plasma armature lengths and of breechand muzzle voltage is described In Ref. 6.Model G. Figure 7 shows data from the two tests of_el+ design. This model was fabricated bypressing an assembly of matching polycarbonatehemt-cylinderswfth hbedded rails fnto a steel tube.The accelerationof a heavy projectile vers;lsthat of a llght projactlle provides an intere%ttncontrast. The heavy prod !.;lle acceleratednorms lyat low pressure. Post-shot In.pecttonof the gunsuggests that &t high pressure, an interferencedeveloped between the projectile and the rails of thetype illustratedIn Fig. 8. The llght projectileapparentlyachiavad sufficientveloclty during low-pre$sure accelerationto avoid the interferencethat.o~curr~ fr~ the fncrcasin pressure. The ~n-f~lght!radiographof projectileG2 Is shown in Fig. 9.In Test G21, the polycarbonatehemlcyllnderssufferad surprlsln~lyl~ttle mechanical damage fromthe magnetfc pressure age{nst the re~ls. Arc demegcto the polycarbonatewas Il!sltedto the htgh-currentregion near the muzzle. The ratls were not reusablebeceuse they suffared●xtenslve arc dusage and curranthat fng.Fig. 7. Matsured current, Tests Gll and G21.#Fig. 8. Sch~tlc lllustrat~onof the apparent .mechanism of bore-projectileinterference,Test 611.Fig. 9. In-fllghtradiographof projectileG21.The 6 m dt~ iron sphere, ~rlginally inthe front of the sabot, has sunk to therear of tha sabot during acceleration.Model K. Figure 10 shows data from two tests of the- design. Rallgun Kll was fabricatedwith a50-nswthlckKevlar-wound structural shell and no steel%tructural shell. Railgun K21 had a 25-nsn-thtckKevlar-woundstructural rhell. The gun was pressedInto a 100-m-i.d. steel tube that appared to gfvethe gun more reslstaficeto rtll deflection butreduced the inductancegradient from O.39 IK1l) to0.34 uH/m (K21).fhmparlson of the acceleration08 the tltanlumand pol)arbonate projectl;es suggests that thetftanlum projactlles are subject to less $n-borerms~stance to acceleration.The rad~ographs of projectileKll In fllghtreveal that approximatelySW of the tltan~un slugwas eroded. The fn-fllghtrad{o!kph of projactlle!K21, Ffg. 11, thows no eroston o the tltantum slug.We do not know tfthe erostonof project~le Kll Isthe result of the high pressure of test Kll or tfprojectfltK21 was protected by more careful bonrlfngof the corundw disk to the tftanlum slug,ml— —..—● vsr I IU 06’ iuImE @nJiliFip. 10. Measured current, Tests Kll and K21.Fig. 11. In-fllgktradl~rsph, projectileK21.We fourd that the Model K rallguns could berefhd by ramIlng the bores to remove arc damage.As with the Model J postshot Inspectionrevealad theaccumulationof soot IIIthe rallgun seams. Tne nuntwof shots that could be fired before the accumulationof soot In the seams affected raflgun performancewasnot determined.Conclus~onsExperimentalevidence suggests that, at highpressure, the low-strengthprojectiles have moreresistanceto accelerationthan the high-strengthprojectiles. Hhlle conflnad In the bore, poly-carbon.steproject~lescan be subjected to Jressuresas high as 1.3 6Pa without shatterlri.!At highpressure and at low projectileveloc ty, interferencesbetween here and projectilemay occur. In multfshotrailguns, It Is necessary to prevent the accumulationof sooty material from the plasma armature In rallgunscans, wh~ch can provide a ipurlous current path.Kevlar structuralshells are capable of operating atvery high pressure, but appear to allow largs rafldeflections. A steel structural shell with a Kevlarsleeve appears to lessen structuraldeflections.&knowledgm ntsThfs research%:s supported by the 9epartmantofEnergy, the Defense Advanced Research Projects Agency,the US Army Armament Resecrch and DevelopmentCrwand,. . .,the National Aeronautics and Space A&dnlstratlon,and the Ballistlc Missile Defense Advanced TechnologyCenter.1.2.3.4.5.6.ReferencesC. M. Fouler, 0. R. Peterson, R. S. Calrd,Cl.J. Erickson, B. L. Freeman, andJ. C. King,“ExplosiveFlux C~resslon generators for RailgunPower sources,’ presented et the 1980 Conferenceon ElectromagnatlcGuns and Launchers, NovemberM, 1980, San Diego, California. IEEE Trans-actions onllagnetlcs (18), 82 (1982).C. M. Fouler, O. R. Peterson, J. F. Kerrlsk,R. S. Caird, O. J. Erickson, B. L. Freeaan, andJ. H. 6oforth, “ExplosiveFI’QxC~resslon StripGenerators,”presented at thelhlrd InternationalConference on 14egagauss!4s ●tlc Fleld6enerationrand Related Topics. June 1 17, 1983, Novosibirsk.J. F. Kerrlsk, “Electricaland Themal Modeltngof Rallguns,- to be presented at the SecondInternationalConference on Elacttwagnetlf.Launchers,October 14-16, 1983, Boston.Kdssachusetts.J. F. Ke#~$k, wCu~t OlstrfbutionandInductanceCalculationsfor Raflgun Conductors,”h$os;~-s Natfot,llLaboratory report LA-9092-14S●J. F. Kerr sk, C. ?4.Fouler, and O. R. Peterson,“Naasur-ts and Calculation of Ma netlc Flald~!Associated with Raflgun Currents, I EE Conferenceen Plasma Sciences, May 23-25, 1983, S@n Olego,California. LOS AISMOS Natfonal Laboratory reportLA-UR-83-345 (1983).J, V. Parker, O. R. Peterson, C. E. Cumlngs, andC. M. Fouler, %asuraent of Rallgun ArcCharacterlstlcs,”APS Plasma Physics Maettng,Novtir 1-5. 1982. New Orleans, Loujslana.Los Al-s N~tlonal Laboratory reportLA-UR-82-2177 (1982).

Design and Testing of High-Pressure Railguns and Projectiles

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Design and Testing of High-Pressure Railguns and Projectiles

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