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 10 m/s for ultra-light gliders to 100 m/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.

Arc root dynamics in the context of lightning strikes to aircraft

“…The primary objective of this paper is to investigate the displacement of the arc root during the swept-stroke. In order to recreate the pertinent conditions for an experimental study and establish a database meeting scientific requirements, this study employs a test-bed facility previously developed and detailed in two recent papers: a current-regulated lightning arc generator [22] and an electromagnetic launcher [23]. These devices are integrated to replicate an indoor sweptstroke experiment.…”

Physical properties of the swept arc channel in the context of lightning strikes to aircraft

“…The railgun equipment used in this work is described in Andraud et al [25]. It is able to propel aeronautical test samples of weights between 100 and 250 g to speeds between 40 and 80 m s −1 within 2 m of acceleration.…”

“…The experiments using the railgun to propel aeronautical test samples through an electric arc are referred to as railgun experiments (RGE) in the present paper. More details about the coupling can be found in [27].…”

“…The distance between the test sample and the upper electrode is adjusted to 200 mm in both experiments since the certification document ED-14E [28] recommends a minimum inter-electrode distance of 50 mm. Photos of the two setups can be found in [27].…”

“…To establish a relevant experimental database fulfilling the scientific needs, the present study uses the experimental instruments developed in two recent papers: a DC lightning generator [24] and a railgun electromagnetic launcher [25]. These two instruments are coupled to reproduce a sweptstroke experiment.…”