Analysis of Influencing Factors of Electromagnetic Torque Fluctuation in Round Bore Railgun

The consistency of projectile rotation speed is an important factor affecting flight stability in repeated launching. In this paper, it is found for the first time that the electromagnetic torque fluctuates sharply due to a slight change of the structural parameters of the round bore railgun, and it is verified by experiments that the torque fluctuation will cause the rapid degradation of the projectile's rotary launch performance. Firstly, the variation law of electromagnetic force with structural parameters of a railgun with a larger bore is analyzed. It is found that when the bore of the launcher is 90mm, the electromagnetic thrust changes monotonously with structural parameters, but a slight change of structural parameters will lead to a violent fluctuation of the electromagnetic torque. Secondly, the fluctuation law and influencing factors of the electromagnetic torque with structural parameters are studied. The results show that the increase of the caliber is an important influencing factor for torque fluctuation, and the change of contact position will also cause severe torque fluctuation, which will affect the consistency of projectile rotation speed. Finally, the changes of the rotary launch performance are verified by the railgun with 15mm caliber and 90mm caliber, respectively. The test results show that the monotonic change of the torque is beneficial to improve and regulate the rotary launch of the projectile, and the sharp fluctuation of the torque will cause the rapid degradation of the rotary launch performance and even cause the projectile to stop rotating.