Loss of thrust in one of four liquid-propellant strap-on stages immediately after lift-off caused the 10 July failure of the Indian Space Research Organisation's (ISRO) Geosynchronous Satellite Launch Vehicle (GSLV) 56.4s into its ascent.
The fault saw the loss of India's Insat-4C direct-broadcast satellite, which would have gone into geosynchronous orbit. ISRO's failure analysis committee (FAC) found that due to a manufacturing error, instead of stabilising at 5.85MPa (850lb/in²), combustion chamber pressure in the strap-on stage reached 7.11MPa leading to its failure 5.2s after ignition.
"With only three strap-on stages working there was a significant reduction in the control capability," the report by the 15-member FAC says.
Tests simulating possible failure modes were conducted to identify the cause. Vehicle attitude could be controlled until about 50s into the flight. "[When] the vehicle reached the transonic region of flight [attitude error increased and] the aerodynamic load exceeded design limits, leading to the break up of the vehicle," it says.
ISRO is instigating new inspection methods to detect strap-on engine faults in future, and a critical review has been put in place for the next flight of the four-stage Polar Satellite Launch Vehicle, expected during the fourth quarter. The failed launch cost ISRO around Rs2.5 billion ($54 million) for the lost satellite. The next launch of a GSLV will take place in June 2007.
The GSLV was declared operational after its two developmental flights in April 2001 and May 2003 were successful. The 10 July mission, designated F02, followed three earlier post-qualification missions - D1, D2, F01 - which were all successful.
Source: Flight International
