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

Unsteady pressure measurements are crucial for understanding dynamic pressure distribution changes in fluid flow fields and over object surfaces, revealing insights into complex flow phenomena induced by 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 for real-time unsteady pressure data acquisition. The system's main challenge is accurately resolving high-frequency static and dynamic pressure variations over very high base pressure values. To meet this challenge, the paper highlights the importance of sigma-delta Analog-to-Digital Converters (ADCs) due to their high resolution, oversampling techniques, noise filtering capabilities, and wide dynamic range. These ADCs seamlessly integrate with digital systems, ensuring reliable real-time pressure data acquisition during launch and flight operations. The system can be integrated into re-entry vehicles and stage recovery experiments to acquire unsteady pressure data for complex geometrical shapes with confidence. Moreover, the capability to store and process data as per requirement during flight enhances its utility in practical scenarios. This approach promises invaluable insights into the dynamic behaviour of launch vehicles and in the study of unsteady flow phenomena. The system incorporates an 8 channel sigma-delta ADC with necessary signal conditioning. To obtain better measurement resolution, gain may be provided to each channel, which is digitally programmable. A reprogrammable FPGA handles data acquisition, ADC configuration and required processing for telemetry-based transfer and storage. The system offers high-frequency accuracy of 0.1% of full scale input range, supporting bandwidths up to 8kHz. In summary, this paper introduces a comprehensive design for a high-frequency unsteady pressure measurement system that enhances aerodynamic characterization in launch vehicles. By leveraging sigma-delta ADCs, this system offers the potential to improve our understanding of dynamic pressure fluctuations and complex flow behaviors during launch vehicle operations.