ISRO Successfully Tests Upgraded SSLV Third Stage SS3 Motor

Indian Space Research Organisation (ISRO) achieved a major milestone in its small satellite launch programme with the successful ground test of the upgraded third stage (SS3) of the Small Satellite Launch Vehicle (SSLV).

The test was conducted on December 30, 2025, and clears the upgraded SS3 stage for induction into upcoming SSLV missions, strengthening India’s launch-on-demand capability.

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ISRO Successfully Tests Upgraded SSLV Third Stage SS3 Motor

Successful Static Firing at Sriharikota

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.

Key test details:

• Motor firing duration: 108 seconds
• All performance parameters closely matched pre-test predictions
• The SS3 stage is the uppermost solid stage of SSLV
• It plays a critical role in imparting velocity to place satellites into orbit

Key Design Upgrades and Payload Gain

A major upgrade in the SS3 motor is the use of a carbon-epoxy composite motor case, replacing the earlier configuration. This redesign has led to:

• Significant reduction in inert mass
• Payload gain of about 90 kg for SSLV missions
• Velocity delivery of up to 4 km per second by the third stage

Additional improvements were made to the igniter and nozzle systems to enhance efficiency, robustness, and performance margins while maintaining high reliability.

Advanced Control and Monitoring Systems

During the static test, the SS3 motor was instrumented with around 233 sensors to monitor:

• Pressure
• Thrust
• Temperature
• Vibration
• Control electronics and actuator behaviour

Nozzle control is achieved using a fault-tolerant electro-mechanical actuation system supported by low-power control electronics, significantly improving mission assurance for future SSLV flights.

Boost to Indigenous Manufacturing and Capacity

The carbon filament-wound motor case was developed at the Composites Entity of the Vikram Sarabhai Space Centre, while solid motor casting was carried out at SDSC facilities.

This test follows ISRO’s recent expansion of solid motor infrastructure, including:

• New facilities at Sriharikota
• A second ammonium perchlorate production line at Alwaye
• Commissioning of an indigenous 10-tonne vertical mixer

These developments strengthen India’s self-reliance in solid propulsion systems and support national missions as well as private space start-ups.

Exam-Oriented Key Facts

• SSLV is a three-stage, all-solid launch vehicle
• SS3 is the uppermost stage of SSLV
• SS3 delivers velocities of up to 4 km/s
• Carbon-epoxy motor case increases payload by about 90 kg
• Test conducted at Satish Dhawan Space Centre, Sriharikota
• Static test duration was 108 seconds

Question & Answer

Q1. Which organisation conducted the successful ground test of the upgraded SS3 stage of SSLV?
(a) DRDO
(b) ISRO
(c) HAL
(d) IN-SPACe
Answer: ISRO

Q2. The SS3 stage is part of which launch vehicle?
(a) Gaganyaan
(b) PSLV
(c) GSLV
(d) SSLV
Answer: SSLV

Q3. What major material upgrade was introduced in the SS3 motor case?
(a) Aluminium alloy
(b) Titanium composite
(c) Carbon-epoxy composite
(d) Steel casing
Answer: Carbon-epoxy composite

Q4. What is the approximate payload gain achieved due to the upgraded SS3 stage?
(a) 40 kg
(b) 60 kg
(c) 75 kg
(d) 90 kg
Answer: 90 kg

Q5. Where was the static ground test of the SS3 motor conducted?
(a) Thiruvananthapuram
(b) Alwaye
(c) Sriharikota
(d) Bengaluru
Answer: Sriharikota

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