Why the third stage in ISRO rockets is tricky

ISRO's PSLV missions faced back-to-back failures in the third stage, but the overall track record remains strong despite these anomalies.

In back-to-back failures, two of ISRO’s PSLV missions have malfunctioned during the third of four stages. In May last year, PSLV-61 experienced a drop in pressure in the propulsion chamber during the third stage, leading to a deviation from the intended course. And last week, PSLV-62 too deviated off course towards the end of the same stage.

ISRO's PSLV-C62 carrying the EOS-N1 lifts off from the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh last Monday, (PTI)

The third stage can be challenging because it uses a solid propellant, which does not allow the precise control that liquid propellants provide