Observation and simulation of armature contact performance in the cannon-caliber electromagnetic gun

Zielinski, A.E.; Hildenbrand, D.J.

doi:10.1109/20.559935

Cited by 11 publications

(3 citation statements)

References 5 publications

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“…In previous work, an analysis of the measured breech and muzzle voltage and its relation to the armature function was documented. 6 The measured breech and muzzle voltages are indicative of the electrical performance of the armature contacts. The voltages associated with the augmented launcher are much larger than those measured in a regular (i.e., single turn) railgun, and the additional voltage contributions are attributable to the augmenting turn.…”

Section: Methodsmentioning

confidence: 99%

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Electromagnetic and Aeromechanical Analysis of Sabot Discard for Railgun Projectiles

Zielinski

Weinacht

Bennett

2000

Journal of Spacecraft and Rockets

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Experimental and engineering modeling techniques were applied to examine the role that electromagnetics plays during the sabot discard process in a solid-armature railgun. Current and magnetic eld diffusion in the conducting armature and sabot produce residual forces that tend to clamp the sabot petals during in-bore acceleration and after launch. The effect of this force on sabot discard was investigated. The experimental portion of this work used the measured downrange magnetic elds to quantify the effect on subprojectile performance. The time rate of change of launcher and switch currents and launcher voltages were measured. In addition, the time rate of change of the armature magnetic eld was measured downrange from the launcher. Electrical parameters that characterize the magnetic elds were used to calculate the residual current owing in the armature after exit. An engineering model that includes both aeromechanicaland electromagnetic forces was developed to predict the sabot discard process. The model for the magnetic clamping force used the inferred current from the magnetic elds measured downrange. The results from the sabot discard analysis are in good agreement with the measured sabot trajectory data, particularly when the sabot petals are in close proximity. The analysis shows that the aerodynamic moment acting on the sabot is relatively small following launch, and small magnetic clamping forces could delay sabot separation. NomenclatureA pocket = horizontal area of sabot petal pocket a, b = downrange and transverse current loop dimensions, respectively C m a = slope of the pitching moment coef cient with angle of attack d = downrange distance from muzzle dl 0 = incremental arc-length vector along current loop F aero = sabot petal lifting force F EM = electromagnetic clamping force F pocket = sabot petal pocket force F x-react = sabot petal reaction force in horizontal direction F z-react = sabot petal reaction force in vertical direction H = magnetic eld vector H x = downrange component of magnetic eld H y = orthogonal component of magnetic eld I = local inferred loop current in armature I o = average inferred loop current at muzzle exit I t = projectile transverse moment of inertia l aero = moment arm of sabot petal lifting force l EM = moment arm of electromagnetic clamping force l pocket = moment arm of sabot petal pocket force M 1 = freestream Mach number m = projectile mass P t2= stagnation pressure behind normal shock wave P 2 = static pressure behind normal shock wave P 1 = freestream static pressure p = separation distance between current loops in adjacent sabot petals r = local position vector r 0 = position vector along current loop S = planform area of sabot petal

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Section: Methodsmentioning

confidence: 99%

“…A peak current of 950 kA was estimated 6 to drive the 140-g launch package to 2500 m/s. The armature current at exit I o was calculated from the inferred current presented in the preceding section and scaled by the ratio of the peak in-bore currents.…”

Section: Sabot Discard Modelmentioning

confidence: 99%

Electromagnetic and Aeromechanical Analysis of Sabot Discard for Railgun Projectiles

Zielinski

Weinacht

Bennett

2000

Journal of Spacecraft and Rockets

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“…The voltage data and previous analysis indicate that the rear armature contact transitioned. [5] While this certainly plays an important role in ILP performance, the entire jump test was conducted with a transitioned rear contact.…”

Section: Methodsmentioning

confidence: 99%

Improved integrated launch package ballistic performance

Zielinski

Weinacht²

1999

IEEE Trans. Magn.

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A detailed experimental investigation of the launch and flight performance of a kinetic energy fin-stabilized penetrator has been performed. The Integrated Launch Package (ILP) consists of the subprojectile and mid-riding armature. The armature front contact is electrically insulated from the rails. This configuration has shown potential for effectively managing the launch disturbances. To evaluate the transitional ballistics, aeroballistics, and jump characteristics, single-shot firings with an exit velocity of 1,350 m/s were conducted at the ARL Transonic Experimental Facility, APG, MD. The impact data show larger variability in the vertical direction than in the horizontal direction. Results from the j u m p survey indicate that effects of the deviation from the launcher centerline (i.e., straightness) contribute significantly to the target impact dispersion. Substantial contributions from the linear and angular rates at the muzzle are evident in the vertical direction. The contribution attributable to sabot discard in either plane is minimal. When possible, comparisons are made to our earlier investigation which examined the ballistic behavior of a similar ILP with a conducting front contact.

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