New Delhi, January 6. The Indian Space Research Organisation (ISRO) has successfully carried out a static test of an improved third stage of its Small Satellite Launch Vehicle (SSLV), marking a major step towards enhancing the rocket’s performance and readiness for future missions.
The test of the upgraded SS3 stage was conducted on December 30, 2025, at the Solid Motor Static Test Facility of the Satish Dhawan Space Centre in Sriharikota. SSLV is a three-stage, all-solid launch vehicle designed for rapid, on-demand launches and is structured to allow large-scale industrial production with quick turnaround times between missions.
The third stage is a critical component of the SSLV, providing nearly 4 km per second of velocity to the rocket. It uses a monolithic composite motor case and a free-standing nozzle to minimise the stage’s inert mass. In the latest version tested, ISRO has replaced the earlier structure with a carbon-epoxy motor case, significantly reducing the stage’s weight and improving the vehicle’s payload capability by about 90 kg.
The upgraded stage also incorporates a redesigned igniter and nozzle system, making it more efficient and robust. Its nozzle is controlled by a fault-tolerant electro-mechanical actuation system supported by low-power electronics. The high-strength carbon filament–wound motor case was developed at the Composites Entity of the Vikram Sarabhai Space Centre, while the solid motor itself was cast at the production facilities of the Satish Dhawan Space Centre.
During the 108-second test, the motor was monitored using around 233 sensors that measured parameters such as pressure, thrust, temperature, vibration and the performance of control electronics and actuators. ISRO said all readings closely matched predicted values, confirming the reliability of the upgraded design. With this successful firing, the improved SS3 motor has now been cleared for induction into flight missions.
The test comes as ISRO continues to expand the country’s solid motor manufacturing and testing infrastructure. In July 2025, new solid motor production facilities were commissioned at Sriharikota to boost capacity. This was followed in September by the commissioning of a second production line at the Ammonium Perchlorate Plant in Alwaye, doubling the supply of the key oxidiser used in solid propellants. ISRO also inducted an indigenous 10-tonne vertical mixer at Sriharikota this year, the world’s largest solid propellant mixing system.
ISRO’s solid motor production and static testing facilities at Sriharikota have also recently supported India’s private space sector, having built and tested the solid motor used for the first orbital launch of a launch vehicle developed by an Indian space start-up.
