EOS-9 Failure Explained: A technical glitch in the third-stage nozzle led to the failure of ISRO’s PSLV-C61 mission, affecting the deployment of the EOS-09 satellite. ISRO Chairman V. Narayanan confirmed the cause of the EOS-9 failure during the PSLV-C61 mission. He explained that while the first two stages of the rocket performed flawlessly as planned, an anomaly occurred in the third stage. Specifically, the chamber pressure in the third-stage engine was lower than expected, which prevented the rocket from delivering the EOS-09 satellite into its intended orbit. As a result, the mission could not be successfully completed.
The mission was carefully planned with growing concerns about space debris in mind. Scientists ensured that a sufficient amount of fuel was reserved specifically for de-orbiting the EOS-09 satellite once its operational life ends. This would have allowed the satellite to be gradually lowered to a lower orbit, where it would naturally re-enter Earth’s atmosphere and burn up within two years. Such a controlled de-orbiting process is crucial for minimizing space debris, helping to maintain a cleaner and safer space environment for future missions. This approach reflects ISRO’s commitment to responsible space operations and sustainable use of orbital resources.
India Partners with HawkEye 360 for Indo-Pacific Surveillance
EOS-9 Failure
The 44.5-meter-tall PSLV-C61 rocket performed nominally during its first two stages, with the solid-fueled PS1 core and liquid-fueled PS2 stage operating exactly as planned. However, issues arose 203 seconds into the flight during the third stage (PS3) solid motor burn, when telemetry data revealed a sudden drop in chamber pressure. The PS3 stage uses a flexible bearing nozzle system—constructed from layered elastomeric materials called flex nozzles—to precisely steer the rocket by controlling the thrust vector during its 114-second burn. This system eliminates the need for complex hydraulic actuators. A malfunction in this flexible nozzle can cause thrust misalignment, leading to a rapid deviation from the intended flight path. The PS3 stage burns hydroxyl-terminated polybutadiene (HTPB) fuel, generating around 240 kN of thrust under optimal conditions to propel the rocket through the upper atmosphere. The failure of this critical third-stage component was key to the EOS-9 failure, ultimately preventing the satellite’s successful deployment.
ISRO to Launch EOS-9 Aboard PSLV-C61 on May 18 to Enhance Border Surveillance Capabilities