Browse Publications Technical Papers 2024-26-0432
2024-06-01

High Frequency Unsteady Pressure Measurement System for Aerodynamic Characterization 2024-26-0432

Unsteady pressure fluctuations in launch vehicles can induce aerodynamic instabilities, potentially resulting in vibration, structural fatigue, and even catastrophic failure. These risks undermine structural integrity and jeopardize payload delivery, threatening mission success and crew safety. Therefore, precise measurements of unsteady pressure are vital for understanding dynamic pressure distribution and flow behaviour caused by phenomena like shock waves, vortices, boundary layer interactions, and flow separation. While ground-based wind tunnel tests have conventionally provided these insights, this paper presents an on-board system designed for real-time unsteady pressure data acquisition. The system addresses the challenge of accurately resolving high-frequency pressure variations over very high base pressure values. It can be integrated into re-entry vehicles and stage recovery experiments, providing confidence in acquiring data for complex geometrical shapes. Moreover, the capability to store and process data as per requirement during flight enhances its utility in practical scenarios. The system incorporates an 8-channel Sigma-Delta Analog to Digital Converter (Σ-Δ ADC) with necessary signal conditioning. A reprogrammable Field Programmable Gate Array (FPGA) handles data acquisition, ADC configuration and required processing for telemetry-based transfer and storage. Post-processing involves a Cascaded Integrator-Comb (CIC) compensation filter to enhance the overall frequency response within the intended bandwidth. This approach promises invaluable insights into launch vehicle dynamics and unsteady flow phenomena, with the system offering an accuracy of about 0.1% of full scale input range and supporting bandwidths up to 8 kHz.

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