Isro Tests Upgraded SSLV Third Stage Successfully

The Indian Space Research Organisation marked a major milestone in its small satellite launch programme with the successful ground test of an upgraded third stage of the Small Satellite Launch Vehicle. The test, conducted on December 30, 2025, clears the enhanced stage for induction into upcoming SSLV flight missions and strengthens India’s launch-on-demand capability.

Successful Static Firing at Sriharikota

According to “Indian Space Research Organisation”, the static ground test of the improved SS3 motor was carried out at the Solid Motor Static Test Facility of the “Satish Dhawan Space Centre”. The motor was fired for 108 seconds, with all performance parameters closely matching pre-test predictions. The SS3 stage is the uppermost solid stage of SSLV and is critical for imparting the required velocity to place satellites into orbit.

Key Design Upgrades and Payload Gain

A major enhancement in the upgraded SS3 motor is the introduction of a carbon-epoxy composite motor case, replacing the earlier configuration. This redesign has significantly reduced the inert mass of the stage, resulting in a payload gain of about 90 kg for the SSLV. The third stage alone delivers velocities of up to 4 km per second. Additional improvements have been made to the igniter and nozzle systems to enhance efficiency, robustness, and overall performance margins while retaining reliability.

Advanced Control and Monitoring Systems

During the test, the SS3 motor was instrumented with around 233 sensors to monitor pressure, thrust, temperature, vibration, and the behaviour of control electronics and actuators. Nozzle control is achieved through a fault-tolerant electro-mechanical actuation system supported by low-power control electronics. Isro stated that these upgrades collectively strengthen operational efficiency and mission assurance for future SSLV launches.

Imporatnt Facts for Exams

• SSLV is a three-stage, all-solid launch vehicle designed for rapid launch readiness.
• The SS3 is the uppermost stage and provides up to 4 km/s velocity.
• Carbon-epoxy composite motor cases reduce inert mass and increase payload.
• Sriharikota hosts India’s primary launch and solid motor test facilities.

Boost to Indigenous Manufacturing and Capacity

The high-strength carbon filament-wound motor case was developed at the Composites Entity of the “Vikram Sarabhai Space Centre”, while casting of the solid motor was carried out at SDSC facilities. The test follows Isro’s recent expansion of solid motor production infrastructure, including new facilities at Sriharikota, a second ammonium perchlorate production line at Alwaye, and commissioning of an indigenous 10-tonne vertical mixer. These developments reinforce India’s capacity for large-scale, reliable solid motor production and support both national missions and private space start-ups.