Development of a low voltage railgun in the context of a swept lightning stroke on an aircraft.

Abstract

When aircraft are struck by lightning, the aircraft's structural fuselage and components are stressed by electrical and thermo-mechanical constraints, which imposes a need for reliable experimental test benches to design accurate and enhanced lightning protection. In order to reproduce the in-flight conditions of an aircraft in a laboratory, the aim of this work is to design and implement launch equipment able to propel aeronautical test samples at speeds characteristic of an aircraft- from 10m/s for ultra-light gliders to 100m/s for airliners-before striking it with an electric arc within the laboratory dimensions of several meters. After a comparison of several propulsion techniques, the selected solution is an augmented electromagnetic railgun launcher. Since it requires the injection of a high current to be efficient and a low voltage operative point for safety considerations, specific and original electric generator and rail structures have been designed and experimentally implemented. Particular attention has been paid to the experimental problems encountered and mainly the sliding contact, since almost no literature references are available for railgun equipment at this level of performance. Then, based on different experimental implementations, a dynamic and ballistic model of the projectile has been developed to evaluate and characterize friction forces with the aim of predicting launcher performances with different inputs. This serves to control the speed of the material test sample during the lightning strike. Finally, the railgun equipment has been coupled to a lightning generator to reproduce the lightning strike of an aircraft respecting in-flight conditions.