2009-12-11

Transient Electromagnetic Field Coupling with an Airborne Vehicle in the Presence of its Conducting Exhaust Plume

Dr. Sisir Kumar Nayak, Royal Institute of Technology, Stockholm

14 Dec 2009, 15:30; Location: S2|17-103

Airborne vehicle or and its payload are extremely expensive and their loss as a result of a nearby lightning strike is highly undesirable. Even though one could launch only under ideal weather conditions, the cost involved with long launch delays could be very high. So in this age of all weather usage of airborne launch vehicles, it has become necessary to understand the behavior of an airborne vehicle with its exhaust plume when coupled with strong electromagnetic fields generated by a nearby lightning. When the lightning electromagnetic field gets coupled with the vehicle, current is induced on the skin of the vehicle body. The electromagnetic field generated due to the induced current on the skin of the vehicle may get coupled with the internal circuitry through the apertures on the vehicle body. If the coupled electromagnetic energy is more than the damage threshold level of the sensitive devices of the control circuit, they may fail which may lead to aborting the mission or a possible degradation in the vehicle performance. It has been reported that lightning induced phenomena was the cause of malfunctioning as well as aborting of some of the lunar missions. So in the present work, the induced current on the vehicle in the presence of a highly ionized long trailing plume has been computed.

Theoretical analysis is done to estimate the electrical parameters such as electrical conductivity and permittivity and their distribution in the exhaust plume. The electrical conductivity depends on the distribution of the major ionic and neutral species produced from the combustion of the propellant. In addition it also depends on temperature and pressure distribution of the exhaust plume as well as the generated shock wave. The species concentration and other parameters within the combustion chamber up to the nozzle throat point have been studied using chemical kinetics simulation of the combustion process. Computational Fluid Dynamic (CFD) analysis has been carried out to compute the various parameters such as pressure, temperature, and species concentration within the exhaust plume. From the above parameters the electrical conductivity distribution within the plume has been computed and these are used to compute the induced current on the skin of the vehicle by using FDTD and MoM technique.

The presence of exhaust plume is found to enhance the induced current on the body of vehicle by several times and its enhancement is prominent at the tail of the vehicle. Therefore, the present computational results will be useful to study the electromagnetic interference and compatibility (EMI/EMC) aspects of the electronic devices present in the control circuit of the vehicle.

Category: CE Seminar

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