ISRO Successfully Tests Upgraded PSLV Third Stage at Sriharikota

The Indian Space Research Organisation (ISRO) has successfully conducted a ground static test of the upgraded third stage (PS3) of the Polar Satellite Launch Vehicle (PSLV) at the Satish Dhawan Space Centre (SDSC SHAR), Sriharikota, on 12 November 2026. The test marks an important milestone in ISRO’s efforts to strengthen the reliability of the PSLV launch vehicle following anomalies encountered during two earlier missions.

The test was conducted at the Static Test Facility at Sriharikota using a revised configuration of the PSLV third-stage solid rocket motor. ISRO confirmed that the modified motor was successfully tested after incorporating improvements to its structural configuration, nozzle design, mechanical interfaces and quality assurance procedures.

Comprehensive Review Following Earlier PSLV Mission Anomalies

The modifications to the PSLV third stage followed anomalies observed during the PSLV-C61/EOS-09 and PSLV-C62/EOS-N1 missions. These developments prompted ISRO to undertake a comprehensive reassessment of the PS3 configuration, covering critical aspects of its design, manufacturing, assembly and testing procedures.

The review examined design safety margins, raw material acceptance criteria, assembly procedures and the quality checks applied during manufacturing and integration. The objective was to strengthen the third-stage configuration by addressing areas identified for improvement during the technical assessment.

The comprehensive review resulted in a revised PS3 configuration incorporating improvements intended to enhance the structural integrity and reliability of the solid rocket motor. These changes were subsequently implemented in the new version of the third stage that underwent the successful ground test.

Improvements to Nozzle Design and Structural Interfaces

One of the principal modifications involved improvements to the nozzle configuration of the PSLV third-stage motor. ISRO revised the nozzle design to improve engineering margins and strengthen the configuration in areas identified during the review.

The mechanical interfaces of the third stage were also reinforced, while redundancy was introduced into the sealing systems. The adequacy of the revised design margins was verified as part of the modification process.

The nozzle is a critical component of a rocket motor, directing the high-temperature exhaust gases generated during combustion to produce thrust. Its structural performance and sealing integrity are therefore important considerations in the operation of a solid propulsion system.

By strengthening mechanical interfaces, improving nozzle design margins and incorporating redundant sealing arrangements, ISRO has introduced significant engineering improvements to the revised PSLV third-stage configuration.

Strengthened Quality Assurance and Non-Destructive Testing

In addition to the structural modifications, ISRO updated the procedures governing raw material acceptance, assembly and quality assurance. These measures were incorporated into the revised manufacturing and integration processes for the third-stage motor.

The updated procedures also include improvements to non-destructive testing during various stages of integration and transportation. Non-destructive testing techniques enable engineers to examine components and identify potential material or structural defects without damaging the components being inspected.

The revised inspection and testing procedures form part of the broader effort to strengthen quality assurance throughout the preparation of the PS3 motor.

The modifications extend beyond the motor’s physical design to include the manufacturing, inspection, assembly and transportation procedures associated with the third stage. This comprehensive approach reflects ISRO’s efforts to address the reliability of the propulsion system through both engineering improvements and strengthened process controls.

Successful Ground Static Test at Sriharikota

Following the completion of the design modifications and associated procedural improvements, ISRO realised the new version of the PS3 solid motor and conducted its ground static test on 12 November 2026.

A ground static test allows engineers to evaluate the operation of a rocket motor while it remains secured to a test facility. Such tests provide technical data required to assess propulsion performance and validate design modifications under controlled conditions.

ISRO confirmed that the upgraded PSLV third-stage motor was successfully tested at the Static Test Facility of SDSC SHAR.

The successful test establishes an important ground-validation milestone for the revised PS3 configuration following the implementation of structural, manufacturing and quality assurance improvements.

However, the completion of this test does not constitute final qualification of the modified stage for flight. ISRO has stated that further tests are planned following detailed analysis and review of the ground-test data.

Significance for India’s PSLV Launch Vehicle Programme

The Polar Satellite Launch Vehicle has played a major role in India’s space transportation programme, supporting the launch of Earth-observation satellites, scientific spacecraft, navigation-related payloads and commercial satellites.

The PSLV uses a four-stage propulsion configuration consisting of alternating solid and liquid propulsion stages. The third stage employs a solid rocket motor that contributes to accelerating the launch vehicle during its ascent after completion of the preceding propulsion stages.

The performance of each stage is essential to the overall functioning of the launch vehicle. The reliability of the third-stage propulsion system is therefore an important consideration in the technical assessment and preparation of future PSLV missions.

The successful ground test of the revised PS3 motor represents progress in ISRO’s efforts to address the anomalies identified during the PSLV-C61 and PSLV-C62 missions. The modifications introduced to the nozzle, mechanical interfaces, sealing arrangements and quality assurance procedures form part of the organisation’s continuing technical evaluation.

Further Tests Planned Following Technical Review

ISRO has confirmed that the data obtained from the successful ground static test will undergo detailed analysis and review before further testing activities are undertaken.

The next stages of the evaluation will be determined following assessment of the test results. The organisation has not announced a specific schedule for completing the remaining tests or returning the revised third-stage configuration to flight operations.

The successful test conducted on 12 November 2026 marks a significant engineering milestone in the continuing validation of the upgraded PSLV third stage. With the revised solid motor configuration successfully tested on the ground, ISRO will proceed with further technical assessments and planned tests as part of its efforts to strengthen the reliability of India’s PSLV launch vehicle.

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