The Indian Space Research Organisation (ISRO) experienced a setback on Sunday, May 18, 2025, with the unsuccessful launch of its Polar Satellite Launch Vehicle (PSLV-C61) mission. The mission aimed to deploy the EOS-09 Earth observation satellite into a sun-synchronous polar orbit. While the first two stages of the launch performed nominally, an anomaly occurred during the third stage, leading to the mission’s failure. This incident marks a rare failure for the PSLV, which has otherwise been a highly reliable launch vehicle for India.

Mission Details

• Launch Vehicle: Polar Satellite Launch Vehicle (PSLV-C61), the 63rd flight of the PSLV series and the 27th in its XL configuration.
• Payload: EOS-09 (Earth Observation Satellite), a 1700 kg satellite equipped with a Synthetic Aperture Radar (SAR) for all-weather, day-and-night Earth observation. This satellite was crucial for enhancing India’s surveillance capabilities, border monitoring, and providing vital data for agriculture, disaster management, and infrastructure development.
• Launch Site: Satish Dhawan Space Centre, Sriharikota, India.
• Launch Time: 5:59 AM IST, Sunday, May 18, 2025.
• Intended Orbit: Sun-synchronous polar orbit at an altitude of approximately 597 km.

Sequence of Events and Anomaly

According to ISRO, the launch proceeded as expected through the first two stages. The first stage (PS1), a solid rocket motor augmented by six solid strap-on boosters, and the second stage (PS2), a storable liquid rocket engine known as the Vikas engine, both performed within normal parameters.

The anomaly was observed 203 seconds into the flight during the burn of the third stage (PS3). The PS3 is a solid rocket motor that provides high thrust after the atmospheric phase of the launch. Telemetry data indicated a sudden and significant drop in the chamber pressure of the PS3 motor. ISRO Chairman V. Narayanan confirmed this observation, stating that while the third stage motor ignited perfectly, a problem arose midway through its functioning, leading to the mission’s inability to achieve its intended objective.

Initial analysis suggests a potential failure in the flex nozzle control system of the third stage. The PS3 motor uses a flexible bearing nozzle system to steer the vehicle during its 114-second burn. This system, made of layered elastomeric materials, allows for precise thrust vector control. A malfunction in this critical component could cause a misalignment of thrust, leading to a rapid deviation from the planned trajectory and ultimately the mission failure.

Impact of the Failure

The failure of the PSLV-C61 mission has several implications:

• Loss of EOS-09 Satellite: The primary impact is the loss of the EOS-09 satellite. This satellite was designed to provide crucial all-weather surveillance and high-resolution radar imaging capabilities, which would have significantly enhanced India’s monitoring of its borders and assisted in various developmental activities.
• Setback for India’s Space Program: While ISRO has a strong track record of successful launches, this failure is a setback for its ambitious space program, particularly its Earth observation capabilities. It also delays the planned augmentation of India’s 52-satellite surveillance constellation.
• Second Consecutive Failure in 2025: This is the second launch failure for ISRO in 2025. In January, the mission to deploy the NVS-02 navigation satellite also failed due to a valve malfunction. Two consecutive failures will undoubtedly prompt a thorough review of ISRO’s quality control and launch procedures.
• Impact on PSLV’s Reliability Record: The PSLV has been a workhorse for ISRO, with a high success rate. Prior to this mission, it had only failed twice in its 62 launches (in 1993 and 2017). This recent failure might raise concerns about the vehicle’s reliability, although a detailed analysis is needed to understand if this was an isolated incident or indicative of a systemic issue.

Failure Analysis and Way Forward

ISRO has convened a Failure Analysis Committee (FAC) to investigate the cause of the PSLV-C61 mission failure. This committee will meticulously review all available data, including telemetry, manufacturing records, and testing protocols related to the third stage. The FAC will aim to pinpoint the exact reason for the drop in chamber pressure and the suspected flex nozzle malfunction.

The typical process for ISRO after a launch failure involves:

1. Data Review: A comprehensive analysis of the flight data to identify the precise moment and nature of the anomaly.
2. Component Examination: Scrutiny of the components of the failed stage, if recoverable, to look for manufacturing defects or signs of malfunction.
3. Process Review: Evaluation of the assembly, testing, and quality control procedures for the specific components and the overall launch vehicle.
4. Corrective Actions: Based on the findings, ISRO will implement corrective measures to prevent similar failures in future missions. This could involve changes in design, materials, manufacturing processes, or testing protocols.

Former ISRO Chairman S. Somanath emphasized that failures are a part of the learning process in space exploration and that ISRO will bounce back stronger after a thorough analysis and implementation of corrective actions.