22-05-2025
ISRO's 2025 setbacks mirror 1988 — and that's not bad news
Nearly 37 years ago, in 1988, the Indian Space Research Organisation (ISRO) was reeling under two successive failures of the Augmented Satellite Launch Vehicle (ASLV). Critics had then questioned whether ASLV is capable of flying at all. The Expert Review Committee headed by the then director of the National Aerospace Laboratory at Bangalore, Roddam Narasimha, examined the causes of failure and observed that 'the investigations have not revealed any major technological problems that cannot be handled with the capabilities and skills already available in ISRO…. space projects outside India have gone through similar experiences, but lessons learnt from such failures can establish the basis for future successes'. After two successive failures this year, it might seem like deja vu for ISRO, but these lines from the committee's report will form a silver lining.
Early this week, ISRO's reliable workhorse, Polar Satellite Launch Vehicle (PSLV), failed to launch the Earth Observation Satellite (EOS-09) into sun-synchronous polar orbit. It is only the fourth time that PSLV has failed in 62 launches since 1993. In January this year, GSLV successfully launched NVS-02, a surveillance satellite, but could not place it in the correct geosynchronous orbit. NVS-02 is part of a collection of satellites that will form the backbone of India's positioning system NavIC, a subcontinental answer to the United State's Global Positioning System (GPS). Most likely, having missed its correct position in the sky, NVS-02 will not be part of NavIC.
Even as detailed reports on these failures are awaited, the reasons are not about a lack of mastery over the technology of satellite launches and placement in a desired orbit. In comparison, the failures of ASLV in 1988 – an inadequate digital autopilot system to poor control during the transition from one stage to another — were far more fundamental. Despite rare failures, the PSLV has emerged as a reliable and cost-effective launch platform for small satellites weighing up to 2,000 kg. Since 2015, PSLV has helped ISRO generate about Rs 3,861 crore from satellite launch services. In this segment, India's market share is only about 3 per cent, and this potential remains untapped.
The failures remind us that despite the mastery over technology and repeated successes, space exploration will remain an unforgiving territory where even minor errors will be harshly punished. A mildly unhinged screw in a train might be harmless, but on a rocket it can be a disaster. There are many such instances. In 1988, about 50 seconds after the ASLV-D2 was launched, control over the rocket was lost for only about half a second after the first-stage ignition. This half-second error propagated quickly, and the rocket crashed into the sea. NASA launched the Mars Climate Orbiter in 1998. It failed due to a misunderstanding between two teams that used different units for distance measurement, one using meters and the other using inches. The lunar module that carried Neil Armstrong to the moon in 1969 was luckier. With hardly any fuel left, it landed far from the designated place due to an unexpected extra thrust. Expecting such eventualities, the US President's office had a prepared speech in case the astronauts did not return alive. Fortunately, that speech never had to be used.
With lakhs of components and hundreds of interconnected subsystems, the reasons for rocket failures vary widely. Usually, failure implies that the rocket could not place the satellite in the intended orbit. By this yardstick, in the last two decades, the worldwide rocket launch failure rate is about 5-10 per cent. Nearly 58 per cent of the failures arose from propulsion systems responsible for rocket flight. This week's PSLV-C61 failure belongs to this category. ISRO's initial assessment attributes the failure to a pressure drop in its third-stage engine. Further, 36 per cent of failures are due to incorrect functioning of systems that control the trajectory, altitude, and separation of the rocket. Modern rockets are controlled by computer software, which itself is another point of failure. Since 2000, about 14 per cent of failures could be traced back to software glitches. Failures are a great leveller. They haunt more advanced spacefaring nations, such as the US and Russia, as much as they hurt India. The Vanguard rockets the US employed during the 1950s had only a 27 per cent success rate. Russia's famed Soyuz rockets, too, have failed, most recently in 2018 while carrying astronauts to the International Space Station.
Space exploration is fraught with failures. For ISRO, 2025 has kicked off with challenges but not setbacks. As the Expert Committee spelt out in 1989, research, design and operations must be made rigorous in 'evolving solutions to the complex problems posed by the advanced technologies' in launch vehicle programmes. In the world of space exploration with zero tolerance for errors, this is the only way to recover from failures.
The writer is a professor of Physics at IISER, Pune. Opinions are personal
