Why didn't the cryogenic engine ignite?

The GSLV-D3, which lifted off from Sriharikota on Thursday, later plunged into the sea as the indigenous cryogenic engine failed to ignite. Photo: V. Ganesan

The non-ignition of the cryogenic engine on board the Geo-Synchronous Satellite Launch Vehicle (GSLV-D3) led to the failure of the mission on Thursday (April 15), the Indian Space Research Organisation (ISRO) has more or less concluded. “The cryogenic engine has not ignited, that is for sure. Why it has not ignited, the reasons have to be found out,” said S. Satish, ISRO spokesman, on Friday.

All the telemetry data had come in by 1 p.m. on Friday and the ISRO top-brass was studying them line by line. The GSLV-D3 is a three-stage rocket and it was flying with an indigenous cryogenic engine for the first time.

A cryogenic engine uses liquid hydrogen at minus 253 degrees Celsius as fuel and liquid oxygen at minus 183 degrees as oxidiser. The vehicle lifted off as planned at 4.27 p.m. and its performance was normal up to the end of its second stage till 293 seconds from the lift-off. But the vehicle developed problems when the cryogenic upper stage should have ignited 304 seconds after the lift-off, and it fell into the sea.

An authoritative former ISRO official said: “It is very clear that the cryogenic engine did not ignite when you look at the curve [of the vehicle's trajectory], everything was normal up to the GS2 [second stage] shutdown. Then you can see clearly that there is no increment in the vehicle's velocity. The velocity is the same. It started losing its altitude also.”

The ISRO rocket engineers are puzzled why the cryogenic engine did not fire at all. On April 9, they had repeatedly told reporters at Sriharikota that the GSLV-D3 was “the most reviewed vehicle” because it was flying an indigenous cryogenic engine for the first time.

A national panel consisting of former ISRO chairmen, specialists in cryogenic technology and academicians had reviewed the vehicle several times and signalled the go-ahead. But for these repeated reviews, the flight would have taken place in December 2009, they had said.

Besides, the indigenous cryogenic engine was tested on the ground cumulatively for 7,767 seconds, while it would fire for only 720 seconds in flight.

Post-flight, ISRO Chairman K. Radhakrishnan said the entire cryogenic stage, including its engine, passed the qualification test on November 15, 2007 when it fired for 720 seconds. “In the last three years, we have been working on the flight-engine,” he said. But he pointed to one big difficulty — the ignition of the cryogenic engine taking place in the vacuum of space [which cannot be simulated on the ground].

S. Ramakrishnan, Director (Projects), Vikram Sarabhai Space Centre, Thiruvananthapuram, also noted, “Ignition in vacuum of the cryogenic engine could be done only in flight.”