Weak Russian component downed Indian rocket: Ex-ISRO chief

April 22nd, 2011 - 2:37 pm ICT by IANS  

ISRO Chennai, April 22 (IANS) The destruction of India’s Geosynchronous Satellite Launch Vehicle (GSLV) in mid air in 2010 was due to an inherent weakness in a component in the Russian supplied cryogenic engine.

“We did several simulation tests to find out why the connectors - the wires that carry command signals from the onboard computers at the top to the rocket’s engines down below - snapped,” former ISRO chief Madhavan Nair told IANS.

Nair, who headed the Failure Analysis Committee, said the 12-member panel submitted its report to ISRO two weeks back.

According to ISRO, the failed component, called shroud, was made of composites and is part of the Russian cryogenic engine. It got deformed due to the flight load.

ISRO’s 418-tonne GSLV rocket (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 a minute after lift-off from Sriharikota in Andhra Pradesh last Christmas day.

As the weakness was inherent in the shroud, Nair said ISRO should have a dialogue with the Russians to see how the component could be strengthened.

Informed sources told IANS that even in the GSLV-F04 rocket launched in 2007, one of the connectors got snapped due to weak shroud.

“The fault was there from the first GSLV that flew with the Russian cryogenic engine in 2001. The weakness in the shroud caught ISRO on December 25 last year,” a source told IANS.

Experts told IANS that the first 15 km of a rocket’s flight was very crucial as it is subjected to heavy atmospheric loads. It is more so when the rocket is escaping the earth’s gravitational pull at 330 metres per second.

The flow of air along the rocket will be turbulent at the transonic speed - when the rocket crosses the speed of sound. At that point the air will attach to the rocket at some places and detach at some spots in a haphazard manner.

Out of the seven cryogenic engines supplied by Russia, India has used six. One remains to be used.

According to Nair, it is Russia’s responsibility to set right the shroud in the remaining cryogenic engine as it is their engine and technology.

“The matter has been discussed with them. But the question of compensation from Russia for the loss does not arise,” he said.

The Russians had earlier pointed their fingers at the rocket’s bigger heat shield (4 metre) as the proximate cause for high atmospheric load on the rocket that broke it.

The 2010 GSLV’s heat shield measured 4 metres in diameter as against 3.4 metre in most earlier GSLV rockets.

A retired ISRO scientist with over two decades of experience with rocket motors told IANS that the GSLV most likely broke due to instability caused by the heavy payload - heavier than what the rocket had lifted in earlier missions.

At 2,310 kg, the GSAT-5P communication satellite was the heaviest payload ever lifted by a GSLV.

It was 180 kg heavier than the INSAT-4CR launched in 2007, 360-kg heavier than Edusat launched in 2003 and about 780 kg heavier than GSAT-1 launched in 2001.

All GSLV’s that flew with Russian cryogenic engine have encountered problems carrying a payload of over 2,000 kg.

In 2006, a GSLV rocket carrying INSAT-4C satellite weighing around 2,168 kg was blown mid air after the rocket became unstable.

In 2007, one of the connecters of the GSLV rocket got snapped and the rocket’s performance was considered as below par. The rocket had carried 2,130 kg INSAT-4CR satellite.

Refuting that GSLV is facing a 2,000 kg jinx, R.V. Perumal, a retired ISRO rocket scientist, told IANS: “The increase in the weight of the satellite is only a fraction of the rocket’s total weight (418 tonne). It is well within the scatter mass of the rocket. Hence the satellite weight is not the reason for the rocket’s instability.”

ISRO officials also discounted the possibility of the rocket becoming unstable because of the two-tonne increase in its overall weight as compared to the April 2010 GSLV rocket that weighed 416 tonnes.

“By the time the problem started, the rocket would have burned around 100 tonnes of first stage fuel. So a mere addition of two tonnes to the rocket’s weight would not make it unstable,” an official said.

(Venkatachari Jagannathan can be contacted at v.jagannathan@ians.in)

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