Design and Development of Terminal Velocity Measurement System for Descending Modules 2024-26-0438

Gaganyaan programme is India's prestigious human space exploration endeavour. During the re-entry of the spacecraft, achieving the minimum terminal velocity is paramount to ensure the crew's safety upon landing. Therefore, acquiring accurate in-flight velocity data is essential for comprehensively understanding the landing dynamics and facilitating post-flight data analysis and validation. Moreover, terminal velocity plays a pivotal role in the qualification of parachute systems during platform-drop tests where the objective is to minimize the terminal velocity for safe impact. Terminal velocity also serves as a critical design parameter for the crew seat attenuation system. In addition to terminal velocity, it is equally necessary to characterize the horizontal velocities acting on the decelerating body due to various factors such as parachute sway and wind drift. This data also plays a central role in refining our systems for future enhancements. However, existing methods for calculating terminal and drift velocities are beset with limitations in terms of accuracy, feasibility, and cost-effectiveness. In response to these challenges, the Terminal Velocity Measurement System (TVMS) is developed for accurate and precise computation of tri-axial velocities.TVMS harnesses state-of-the-art Ka-Band Doppler radar technology to provide real-time velocity calculations with a rapid update rate. It primarily consists of a lightweight Doppler radar sensor with an inbuilt antenna for measuring the Doppler shift in transmitter and receiver frequencies due to descend velocity. Doppler frequency outputs are acquired and processed into velocity data through a PIC microcontroller and associated electronic components integrated onto a minitiarized PCB. TVMS's velocity processing card was developed and subjected to rigorous testing using simulated frequencies which produced highly promising results. TVMS offers both analog as well as digital data in RS-485 format, enabling seamless telemetry to ground stations according to mission requirements. This innovative system ensures precise measurement of terminal velocity, thereby enhancing the safety and reliability of crewed missions. TVMS promises to set a benchmark for other velocity measurement methods and offers immense potential for future space exploration endeavors.