Effect of in-bore gas on railgun performance

Rolader, G.E.; Batteh, Jad H.

doi:10.1109/20.101006

Cited by 18 publications

(5 citation statements)

References 3 publications

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“…As a result, the constant parameters for the cable collector in the launch experiment were chosen to be specific values which describe best the measured current waveform and the motion of the armature. The tendency showing a large resistance and friction coefficient for the case of the higher muzzle velocity reflects the massive electrical behavior of the cable collector and the increased contribution of air resistance [5,6]. To improve the calculations of the circuit in the launcher system, the responses of the cable collector to a step-function current should be used.…”

Section: Discussionmentioning

confidence: 99%

“…Though there were many unknown parameters in the circuit equations, the method gave the current waveform more close to the measured one. Further studies through the analysis of the cable collector and the consideration of air resistances [5,6] would describe the current waveform and armature motion more accurately.…”

Section: Discussionmentioning

confidence: 99%

“…The inductive voltage is obtained by the time-derivative of the magnetic flux(6).In general, the pair of rails is characterized to have constant values of resistance per unit length p R and inductance per unit length p L . Since the voltages of the rails are accurately described by using the results(5)and(6), the deviated values of the voltage drops from those obtained using the constant parameters are…”

mentioning

confidence: 99%

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Modeling and circuit analysis of an electromagnetic launcher system for transient current waveforms

Kim

Lee

et al. 2014

2014 17th International Symposium on Electromagnetic Launch Technology

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An electromagnetic launcher with a 4.8 MJ pulsed power supply has been fabricated, and experimental tests were started. Through the experiments and calculations, the effects influencing on the electrical properties and the performance of the launcher have been investigated. The electromagnetic launcher system includes pulse-forming inductors in the power supply and rails in the launcher which are made of massive conductors showing a prominent skin effect for a transient current. For these conductors constant impedance values or those defined per unit length have difficulties in calculating correct voltages appearing between the terminals of them. In addition, the frictional force between the rail and armature could not be ignored for a better estimation of the armature motion. To obtain solutions close to the measured ones, the diffusion of the magnetic flux density or current density was taken into account, and the history of the armature motion was reflected in the electrical modeling of the rails. These effects were implemented as voltage correction terms in the circuit equations with the help of the electromagnetic responses for a step-function current. In the equation of the armature motion a reasonable form of the frictional force was modeled considering the velocity skin effect and the structural analysis. In this paper, the application of the voltage correction method into rails and the calculated result of the modified circuit equations for the constructed electromagnetic launcher system are presented.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Modeling and circuit analysis of an electromagnetic launcher system for transient current waveforms

Kim

Lee

et al. 2014

2014 17th International Symposium on Electromagnetic Launch Technology

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“…where Csd = (7 + l)pod2 (4) where 7 = ratio of specific heats for static gun fill gas po = density of static gun fill gas d = diameter of the square bore gun C,, = viscous drag coefficient of the shocked gas Fpd = plasma viscous drag…”

Section: )mentioning

confidence: 99%

A tool for force model analysis for plasma armature railguns

Cobb¹,

Taconi²,

Heddings³

1993

IEEE Trans. Magn.

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The exact forces and the way they act to accelerate and retard a projectile in a railgun and the correct model to represent the data have been debated for years. This paper demonstrates the use of a well known method (Chapman-Kirk) for identification of force parameters in a relatively simple nonlinear differential equation model of railgun projectile motion. Where other methods of parameter identification failed, this method converged well.The data used to demonstrate the procedure is a limited set of CHECMATE data (three shots at approximately the same conditions) and one shot from another gun. The input data to the procedure is the measured current and B time position data. Although the analysis of the results do not show that the model is adequate and correct over a wide range of operative conditions, the force parameters obtained are reasonable and some are substantiated by other methods.

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“…In the J x B relationship the influence of eddy currents would show up as a reduction, or redistribution of B , but in the ideal force given by (5) they are neglected. Three-dimensional effects could also be a source of error since the ideal relationship assumes that all of the J x B force is in the axial direction [6,7].…”

Section: B Electromagnetic Forcesmentioning

confidence: 99%

Experimental comparison of conventional and trans-augmented railguns

1993

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A 2.4 m long, 1 cm diameter round bore railgun was constructed at UTSI to perform careful experiments which compared the performance of conventional and trans-augmented plasma armature railguns. The gun was constructed with c o p per rails and G-9 insulators and had a single augmenting turn. Two separate 240 kJ capacitor banks and inductors were used to provide current independently to the armature and to the augmenting turn. The barrel was fitted with an array of Bdot probes spaced 10 cm apart to provide good resolution of the plasma armature characteristics. A MAVIS electromagnetic transducer was used to provide accurate measurements of the muzzle velocity. The gun bore was lapped full length from the light gas injector to the muzzle between each shot to provide a uniform, high quality bore surface for each experiment. Conventional railgun experiments were performed over a range of currents to characterize the base performance of the railgun and to provide data for the development of ablation drag and thermal propulsive models. Experiments were then performed for a range of (separately powered) augmentation currents but with railgun currents equal to those used in the conventional experiments. The enhanced performance provided by augmentation was found to be significantly less than predicted by theory, even though the railgun operated without the formation of secondary armatures or restrikes.

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Effect of in-bore gas on railgun performance

Cited by 18 publications

References 3 publications

Modeling and circuit analysis of an electromagnetic launcher system for transient current waveforms

Modeling and circuit analysis of an electromagnetic launcher system for transient current waveforms

A tool for force model analysis for plasma armature railguns

Experimental comparison of conventional and trans-augmented railguns

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