The Indian Space Research Organisation (ISRO) has achieved a significant milestone in its small satellite launch program. The space agency has successfully conducted a static test of an upgraded third stage for its Small Satellite Launch Vehicle (SSLV). The test was performed at the Solid Motor Static Test Facility within the Satish Dhawan Space Centre (SDSC) in Sriharikota, Andhra Pradesh, on Tuesday, December 31.
Key Enhancements in the Upgraded Stage
The static firing validated a host of improvements in the SSLV's third stage, designated SS3. The most notable upgrade is the adoption of a carbon-epoxy motor case, manufactured by the Composites Entity of the Vikram Sarabhai Space Centre. This high-strength, filament-wound case has significantly reduced the mass of the stage. According to ISRO, this weight reduction directly translates to an impressive increase in payload performance by 90 kilograms.
Furthermore, the stage incorporates an enhanced design for its igniter and nozzle system, making the propulsion mechanism more efficient and robust. The nozzle is now controlled by a fault-tolerant electro-mechanical actuation system paired with low-power control electronics, improving reliability. The solid propellant for the motor was cast at SDSC's own production facilities.
Test Results and Qualification for Flight
The critical test lasted for 108 seconds, during which all measured parameters closely matched pre-flight predictions. With this successful outcome, ISRO has officially qualified the improved SS3 motor for induction into future flights. The third stage is crucial as it provides the final velocity boost, delivering up to 4 kilometres per second to the launch vehicle.
Boosting India's Solid Motor Production Capacity
This test is part of a broader push by ISRO to enhance domestic capacity for solid motor production, a cornerstone of its launch vehicle program. In 2025, several key facilities were commissioned across the country:
- New Solid Motor production facilities were activated at Sriharikota in July 2025 to augment manufacturing capacity.
- A second production line at the Ammonium Perchlorate Plant in Alwaye was commissioned in September 2025, doubling the output of this vital propellant ingredient.
- An indigenous 10-tonne vertical mixer, claimed to be the world's largest solid propellant mixing equipment, was installed at SDSC.
The enhanced infrastructure is already proving its worth. The SDSC facilities have also produced and static tested the solid motor for the maiden orbital launch attempt of a launch vehicle developed by an Indian space startup, showcasing the ecosystem's growing capabilities.
The SSLV is ISRO's dedicated, three-stage, all-solid launch vehicle designed for the commercial small satellite market. It is built for quick turnaround and launch-on-demand flexibility, making it amenable to high-volume industrial production. The successful test of the upgraded third stage marks a vital step in optimizing the vehicle's performance and competitiveness.
