Preliminary investigation of microwave telemetry on an EML projectile

This paper describes a preliminary experimental investigation to convey acceleration measurements, made on-board an electromagnetic (EM) launched projectile, using microwave telemetry techniques. The focus of the investigation is to extend the Hardened Subminiature Telemetry and Sensor Systems (HSTSS) technology for use in EM launch environments. Many aspects of the HSTSS technology have already been successfully demonstrated in high-G, high-pressure launch environments in conventional gun systems. In addition, microwave transmission in stationary experiments, where the telemetry package was exposed to relatively high magnetic fields and EM transients in a railgun launcher, has been demonstrated. However, microwave telemetry during an EM launch has not been demonstrated until now. In this work, setback acceleration measurements obtained with an on-board accelerometer were processed by HSTSS electronics and transmitted simultaneously during launch via an antenna located in front of the EM launch package. While only the test conducted at 9-kG peak acceleration provided the most useful data, detailed analyses suggest that mechanical problems-rather than the microwave telemetry process itself-were probably responsible for difficulties experienced at higher accelerations. This paper reviews the experimental methodology and discusses the results of the investigation.