Snappping of connectors caused launch failure: Scientist

The Indian Space Research Organisation (ISRO) scientist denied that Saturday's failure was caused by the 90-kg increase in the satellite's weight or the marginal increase in the overall rocket's weight.

Speaking to IANS on the condition of anonymity as he was not authorised to speak to the media, the official said: "It seems some heavy load had come at the place where the connectors were located, between the third and second stage, for them to snap. A detailed study will throw more light on the matter."

According to ISRO officials, commands from the on-board computers to other equipments - including the three stages/engines - are relayed through wires.

"As the three stages would separate after their work one after another, it is inadvisable to have long wires connecting the 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 said.

"Connectors in a rocket are akin to the vertebrae of a human being.  Breaking of connectors is like cutting the vertebrae," added R.V. Perumal, a retired ISRO rocket scientist.

"We do not find any pattern in GSLV failures as the reasons are different," another official said.

On Christmas day, a GSLV rocket (weight 418 tonnes, cost Rs.175 crore) carrying advanced communication satellite GSAT-5P (weight 2,310 kg, cost Rs.150 crore) veered off its flight path and began disintegrating within one minute after lift-off from Sriharikota in Andhra Pradesh.

Speaking about the disaster, ISRO chairman K. Radhakrishnan had said that control over the rocket was lost 47 seconds after lift-off as the four connectors to the strap-on motors got snapped.

Recalling the flight sequence, an ISRO source told IANS: "The rocket lifted off smoothly and the flight was normal till the 47th second.

"Problems stared between the 47th and 50th seconds. A total of 10 connectors located between the second and third/cryogenic stage separated, leading to the rocket going out of control."

He said the cryogenic engine, the heat shield capsule-housing the equipment bay and the satellite broke away first. Then the strap-on motors part of the first stage started breaking.

In order to avoid the remaining rocket turning rogue, Range Safety Officer Vinod Kumar Srivastava blew the rocket mid-air.

A retired ISRO official had told IANS that the cable snapping was the effect of the GSLV breaking. He contended that the GSLV most likely broke due to instability caused by the heavy payload.

Dismissing the contention, an ISRO official said: "The increase in GSAT-5P's weight is just 90 kg as compared to the GSLV rocket that carried the GSAT-4, weighing 2,220 kg, in April. Such marginal increase in weight will make no difference."

He discounted the possibility of the rocket becoming unstable because of the two-tonne increase in its overall weight as compared to the April GSLV rocket that weighed 416 tonnes.

"On Saturday, the rocket would have burned around 100 tonnes of first stage fuel by the time the problem started. So a mere addition of two tonnes to the rocket's weight would not make it unstable," he added.

"Further, when the rocket configuration changes, necessary calibrations will be carried out in the rocket's navigational systems, control dynamics and aerodynamics to make the mission successful," Perumal told IANS.

ISRO officials say the rocket's capability will be improved continuously so as to arrive at its optimum capability.

The GSLV rocket that flew in April 2010, powered by an indigenous cryogenic engine, stood 50 metres tall and had a lift-off weight of 416 tonnes. That mission failed as there was a problem in the cryogenic stage built by the  ISRO.

The standard configuration for GSLV is a height of 49 metres and 414 tonnes in weight at lift-off whereas the rocket that went up in flames was taller by two metres and heavier by four tonnes.