ISRO mission fails due to rocket motor glitch, officials begin investigation

The Indian Space Research Organisation’s (ISRO) 63rd mission using the Polar Satellite Launch Vehicle (PSLV) ended in failure after encountering an issue in the rocket’s third stage, preventing the successful deployment of the Earth Observation Satellite-9 (EOS-9).

The launch, which took place from Sriharikota, experienced a malfunction six minutes into its flight, as the rocket descended over the Indian Ocean.

EOS-9 was intended to enhance India’s all-weather and night-time surveillance capabilities through its Synthetic Aperture Radar (SAR). Designed to provide critical remote sensing data for sectors such as agriculture, forestry, urban planning, disaster management, and national security, the satellite's loss is considered a significant setback.

Its replacement could take several years to develop.

ISRO Chairman V Narayanan confirmed the disruption, saying, “Today, we targeted the 101st launch from Sriharikota, the PSLVC6-1 EOS-09 mission. The PSLV is a four-stage vehicle and up to the second stage, the performance was normal. The third stage motor started perfectly, but during the functioning, we are seeing an observation and the mission could not be accomplished.” He further added that there was a “fall in the chamber pressure of the motor case.”

Traveling at over 20,000 km/h, the PSLV-C61 had just ignited its third stage when the issue surfaced, roughly 888 km from the launch site. Though the rocket continued its trajectory and even appeared to ignite the fourth stage, it eventually lost altitude and plunged into the ocean. The satellite and debris are now believed to be lying deep under the Indian Ocean, making recovery and investigation more challenging.

Experts suspect the failure may have been caused by hot gases leaking into sensitive areas of the rocket motor, potentially due to vulnerabilities in the nozzle or Kevlar casing. Hydroxyl-terminated polybutadiene (HTPB), the solid fuel used, may have contributed to the motor’s “misbehaviour.”

Former ISRO Chairman Dr G Madhavan Nair expressed his surprise: “I was shocked and surprised that the solid-fuelled rocket motor with an enviable record of 62 successive launches failed like this.” He suggested a “possible rupture in the fibre casing” and raised concerns over a potential lapse in quality control.

EOS-9’s failure comes at a time of heightened focus on regional surveillance, following recent India-Pakistan tensions. Despite this setback, ISRO continues to operate four radar satellites and eight Cartosats, maintaining its surveillance capabilities.

Historically, the PSLV has had a strong success rate, failing only four times in 63 missions. The last two launches in December 2024 – SpaDex and ESA’s Proba-3 – were executed with precision. A robust internal failure analysis committee has now been formed to determine the root cause of the anomaly. On occasion, the government may also assign an external committee with independent experts to review such incidents.

Dr Abhay A. Pashilkar of the National Aerospace Laboratories noted, “ISRO always does thorough failure investigation and fixes the problems.” The current ISRO Chairman, known for leading the investigation into the Chandrayaan-2 lander failure, successfully spearheaded improvements that led to the Chandrayaan-3 success.

Although recent committee reports have not been made public, ISRO remains a transparent and technically rigorous organisation, where even junior engineers can question top leadership on technical matters.

The failed mission could delay six upcoming PSLV launches, including the first privately manufactured PSLV by a consortium of L&T and Hindustan Aeronautics Limited (HAL), reported NDTV.

Nevertheless, ISRO remains undeterred.

Former Chairman Dr. S Somanath voiced confidence in the organisation’s resilience: “I am aware of the formidable challenges we faced during the development of the third-stage solid motor — an endeavour marked by multiple failures. It is indeed unusual to witness such anomalies resurfacing at this stage. Nevertheless, I have complete confidence that the team will identify the root cause both swiftly and effectively.”

He concluded with a message of optimism: “Over the years, such challenges have only strengthened our conviction that failure is never defeat, but rather a formidable tutor. Every towering success of ISRO has been forged in the crucible of adversity — shaped by lessons deeply learnt and courageously applied.”