India’s heavy rocket broke up when connectors snapped: ISRO (Lead)

December 31st, 2010 - 10:02 pm ICT by IANS  

ISRO Bangalore/Chennai, Dec 31 (IANS) India’s heavy rocket broke up midair on Christmas day when onboard connectors that transmit signals snapped inadvertently, the space agency said Friday.”The inadvertent snapping of 10 connectors carrying command signals from the onboard computer to the control electronics of the four strap-on motors in the first stage is the primary cause of the rocket failure,” the state-run Indian Space Research Organsiation (ISRO) said in a statement here.

The connectors are located beneath the Russian-made cryogenic engine, which was in the upperhird stage of the 418-tonne geosynchronous satellite launch vehicle (GSLV-F06), carrying the 2.3-tonne GSAT-5P communication satellite.

The onboard computer resides in the equipment bay near the top of the rocket. The connectors were to separate on the issue of a separation command at 292 seconds (4.87 minutes) after the 51-metre tall rocket lifted-off at 4.04 p.m. Saturday.

The premature snapping of the connectors stopped the flow of control commands to the first stage control electronics and led to loss of control and break-up of the vehicle.

“The exact cause of snapping of the connectors, whether due to external forces like vibration, dynamic pressure is to be analysed and pin-pointed,” the space agency noted.

An ISRO official, however, told IANS earlier that the onboard computers relay commands through wires to other equipment in the three stages of the rocket.

“As the three stages separate one after another, it is inadvisable to have long wires connecting computers at the top and the stages located below. Hence we have connectors, sort of plugs and sockets, to relay the commands and peel off smoothly when the stages separate,” the official asserted.

According to former ISRO rocket scientist R.V. Perumal, connectors in a launch vehicle are akin to the vertebrae in a human being.

“Breaking of connectors is like cutting the vertebrae,” Perumal told IANS.

When the Rs.175 crore rocket was disintegrating within a minute after a smooth lift-off from spaceport Sriharikota in Andhra Pradesh, about 80km north-east of Chennai, a destruct command was given by the mission control centre to avoid its debris falling on the land though it was 8 km in sky and 2.5 km from the coastline over the Bay of Bengal.

“A destruct command was issued at 64 seconds after lift-off as per the range safety norms and the flight was terminated in the first stage itself,” the findings noted.

Soon after the mission failure, the space agency constituted a preliminary failure analysis team headed by former ISRO chairman G. Madhavan Nair to analyse the flight data.

The team included members of the launch authorization board, mission readiness review committee and senior project functionaries of the project.

The initial analysis found that though the rocket’s performance was normal up to 47.5 seconds from lift-off, it started developing problems in its orientation (attitude) leading to higher structural loads and breaking up six seconds later.

The Rs.125-crore heavy satellite onboard, with a payload of 36 transponders, including 24 in C-band and 12 in extended C-band, was intended to replace the ageing Insat-2E satellite that was launched in 1999, for communications, telecasting, weather and other related services.

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