PSLV’s third stage, a solid motor with about 7.6 tonnes of propellant, burned for 108 to 122.5 seconds on earlier flights.(Image Courtesy: X/@RT_India)
SRIHARIKOTA: The Indian Space Research Organisation on 12 November 2026 successfully fired an upgraded third-stage motor for the Polar Satellite Launch Vehicle. The test took place at the Static Test Facility of the Satish Dhawan Space Centre. Notably, it is the first public hardware milestone in the effort to return PSLV to flight after two consecutive third-stage failures.
What ISRO tested
ISRO says it revisited the PS3 configuration comprehensively and strengthened it. The nozzle configuration was modified to widen design margins. Mechanical interfaces now carry redundant sealing. Furthermore, raw-material acceptance criteria and quality checks were tightened, and assembly procedures were updated. Non-destructive testing now runs across integration and transportation. Consequently, the changes cover design, procurement and handling. ISRO reports that the firing verified the adequacy of design margins. It adds that further tests are planned after a detailed review of the data.
Two setbacks, one stage
PSLV made its first launch on 20 September 1993 and its first orbital success in October 1994. Its record stood above 90% success, according to Union Minister Dr Jitendra Singh. Then PSLV-C61 flew on 18 May 2025 with the 1,696 kg EOS-09 radar imaging satellite. ISRO Chairman V. Narayanan said a drop in combustion chamber pressure in the third stage led to loss of thrust. Subsequently, PSLV-C62 flew on 12 January 2026 with the DRDO’s EOS-N1 and 15 co-passenger satellites. Narayanan said performance was as expected until close to the end of PS3, when roll-rate disturbances and a flight-path deviation occurred. All 16 satellites were lost. The government ruled out sabotage and set up a National Level Expert Committee, with external appraisal of ISRO’s reviews. By June, Dr Singh said investigators had identified the cause of the C62 anomaly, though the findings were not made public.
Why the third stage leaves no room
PS3 is a solid motor holding roughly 7.6 tonnes of HTPB-based propellant in a polyaramide-fibre case. Earlier flights recorded burn times of 108 to 122.5 seconds. Unlike the liquid stages, a solid motor cannot be throttled or shut down once lit, so any flaw plays out across the whole burn. Moreover, PS3 steers in pitch and yaw through a flex nozzle, while roll control comes from the fourth stage’s reaction control system. Pressure loss and roll disturbance typically trace back to the pressure boundary, seals or nozzle. The disclosed fixes address those areas, though ISRO has not published root-cause findings or named nozzle materials. Encouragingly, the response spans process as well as hardware, because inspection through transportation closes a gap between factory and launch pad.
Why PSLV still matters
The failures cost India two sovereign Earth observation satellites. Carnegie Endowment estimates that replacing such spacecraft takes two to three years, which raises the value of a dependable launcher. PSLV costs about $21 million to $31 million a launch by the same estimates, well below the heavier GSLV at about $47 million. Its multi-orbit rideshare capability serves Indian start-ups and foreign institutions, while Falcon 9 enforces a 50 kg minimum order. Dr Singh said in February that no commercial customer had cancelled, across 18 planned launches for 2026 and three major international contracts for 2027. Likewise, industrial plans continue. A HAL and L&T consortium holds an ₹860 crore NSIL contract for five PSLV-XL rockets, and reports say ISRO aims to move half of PSLV production to industry. Standardising stronger margins and checks before serial production helps carry the lessons into private assembly lines.
What to watch
Several answers will decide timing. First, ISRO has not said how many follow-on tests are planned or when they will finish. Second, it has not released telemetry such as chamber pressure, thrust and burn duration from the 12 November firing. Likewise, no return-to-flight date or launch order has been announced. Meanwhile, the PSLV-C63 technology demonstrator, carrying electric propulsion and quantum key distribution hardware, awaits clearance. Furthermore, it is unclear whether motors built before the redesign will be retrofitted, and the failure analysis reports remain unpublished. More detail would help commercial customers and insurers, since none of the seven Indian entities aboard C62 had insured payloads, according to Carnegie.
Even so, the direction is constructive. ISRO has tested the fix on the ground before flying it, widened margins and tightened inspection at each stage. Encouragingly, the investigation has stayed broad, with external review of ISRO’s own findings. If follow-on tests confirm the margins, a vehicle flying since 1993 could return as a more rigorously verified workhorse for India’s space plans.
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