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Snapped connectors led to Indian rocket failure

Posted: December 31, 2010

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Investigators have traced the cause of Saturday's Indian rocket failure to snapped cable connectors, which disrupted critical control commands and precipitated a fiery end to the launch of a communications satellite.


The Geosynchronous Satellite Launch Vehicle tumbled out of control and broke apart in a dramatic fireball less than a minute after liftoff Dec. 25. The failure destroyed an Indian communications satellite named GSAT 5P.

A preliminary failure analysis team concluded the primary cause of the mishap was the "untimely and inadvertent snapping of a group of 10 connectors," the Indian Space Research Organization announced Friday.

The connectors are located near the bottom of the Russian cryogenic third stage and route command signals from a computer near the top of the GSLV to electronics of the vehicle's four L40 strap-on boosters on the first stage, according to ISRO.

"The premature snapping of these connectors has led to stoppage of continuous flow of control commands to the first stage control electronics, consequently leading to loss of control and break-up of the vehicle," ISRO said in a statement. "The exact cause of snapping of the set of connectors, whether due to external forces like vibration, dynamic pressure is to be analysed further and pinpointed."

The preliminary failure analysis team was led by G. Madhavan Nair, the former chairman of ISRO.

The GSLV's first stage is powered by a single solid-fueled core motor and four L40 strap-on boosters.

The liquid-fueled L40 boosters are each powered by a single engine producing about 170,000 pounds of thrust. The engines burn hydrazine and their nozzles pivot to steer the rocket during the first two-and-a-half minutes of flight.

Unable to receive steering commands from the GSLV's computer, the rocket veered off course and spun out of control. High structural loads tore the 167-foot-tall launcher apart as it was engulfed in a cloud of fire, debris and rocket fuel.

Indian officials say the flight, codenamed GSLV F06, was normal for the first 47.5 seconds. The events leading to the failure began 47.8 seconds after liftoff, ISRO reported Friday.

"Soon, the vehicle started developing larger errors in its orientation leading to build-up of higher angle of attack and higher structural loads, and consequently [the] vehicle broke up at 53.8 seconds from liftoff (as seen visually as well as from the radars)," the ISRO statement said.

The GSLV poised for launch. Credit: ISRO
Safety officials issued a destruct command from the ground 64 seconds after liftoff, terminating the flight.

ISRO has established a failure analysis committee to further review data from the launch and determine why the connectors snapped. Also chaired by G. Madhavan Nair, the 11-member analysis board will recommend corrective actions for future GSLV flights.

A program review and strategy committee is studying the future of the GSLV program and its readiness to launch Indian communications satellites and Chandrayaan 2, a joint lunar orbiter, lander and rover mission between India and Russia. Chandrayaan 2 is scheduled for launch on a GSLV mission in 2013.

Both review boards are expected to submit their reports by the end of January, according to ISRO.

Four of the GSLV's seven flights have been failures. The first launch of an indigenous Indian cryogenic upper stage was brought down by a turbopump anomaly in April.

India purchased seven readymade upper stages from Russia, but just one of the hydrogen-fueled engines is left in ISRO's inventory. India is still tweaking the design of its own upper stage after the failure in April.

Officials planned another test flight of the Indian third stage in 2011, but that schedule was announced prior to Saturday's launch accident. ISRO calls the second-generation all-Indian rocket the GSLV Mk.2.