Why the INSAT launch failed

Two failures in two days are certainly a setback to India's ambitious space and defence programmes.

ISRO officials say the GSLV-F02 disaster is a pointer to the fact that the apex space agency needs to do a lot more before it goes global with its space programmes.

What went wrong with the GSLV-F02 that would have put in orbit the state-of-the-art communication satellite INSAT-4C?

ISRO Chairman G Madhavan Nair, who along with the space agency's top scientists witnessed the disaster, said the failure was "one of the rarest phenomena."

"The lift-off was normal. But after a few seconds, the vehicle did not follow the designed trajectory. It deviated. After about 60 seconds, some parts of the vehicle broke up," Nair said.

"Our mission team had done an excellent job. Every sub-system was checked. If you look at the launch vehicles' history, failures are not uncommon. The shuttle (of the United States) had failures."

The cost of the launch vehicle was Rs 160 crore (Rs 1.6 billion) and that of the satellite was about Rs 96 crore (Rs 960 million). ISRO will get back much of the money, as the launch vehicle and the satellite were insured.

In the next few days, ISRO technical teams will examine a variety of data to pinpoint what led to the crash.

top ISRO sources put forward three reasons.

First, the mission may have failed because the vehicle was carrying the heaviest satellite -- weighing 414 tonnes -- ever by an ISRO vehicle so far. The 49-metre tall GSLV is a three stage vehicle. The first stage, GS1, comprises a core motor with 138 tonne of solid propellant and four strap-on motors each with 42 tonne of hypergolic liquid propellants.

The second stage has 39 tonnes of the same hypergolic liquid propellants. The third stage is a cryogenic stage with 12.6 tonne of liquid oxygen and liquid hydrogen. The aluminium alloy GSLV payload fairing is 3.4 metres in diameter and is 7.8 metres long.

Second, the launch vehicle veered off course because one of the four strap-on motors did not work. Stabilization of the GSLV is achieved by autonomous control systems provided in each stage. But according to officials, seconds after the launch, pressure in one of these motors dropped to zero, which meant the vehicle was not developing the thrust to go up. The lack of thrust resulted in a deviation of the flight path, forcing the ISRO top brass to instruct the range safety officer at the Satish Dhawan Space Centre in Sriharikota, off the Andhra Pradesh coast, to press the 'destruct' button.

Third, the vehicle was originally scheduled to take off at 4.38 pm. But it was delayed by an hour as a safety valve in one of the pumps did not re-seal when the third stage of the vehicle was being filled with cryogenic propellants. Quickly, a team was sent to repair it and the team reported cent percent clearance to the launch.

Officials now say the vehicle launch should have been postponed as there were "some indications" that things were not in perfect condition after the safety valve did not re-seal.

"But minor issues like these occur before any launch. So we did not expect this disaster," said an ISRO scientist in Bangalore.

He pointed out that the subsystems in a launch vehicle should withstand hostile flight environment, should be lightweight, cost effective and should be realisable within a reasonable time.

"We put years of developmental efforts to test in a few minutes of flight requiring performances with practically no margin for error," the official said.

He said the launch vehicle systems were fully integrated and checked out. INSAT-4C, the latest satellite of the INSAT series, was transported from the ISRO Satellite Centre in Bangalore to Sriharikota in the first week of June 2006 and since then, underwent detailed checks. After propellant filling, the spacecraft was integrated with the GSLV.

Then, ISRO's Mission Readiness Review reviewed the launch on July 6. It was followed by the meeting of Launch Authorisation Board, which cleared the launch.

"In the last four days, a complete checkout of the fully integrated launch vehicle along with the satellite was carried out," the official said.

But the realisation of a satellite launch vehicle involves many branches of science and engineering, sophisticated infrastructure and innovative management techniques. Even today, only a few countries possess the technology to successfully build satellite launch vehicles.

Here is what you need to know about GSLV and INSAT 4-C:

GSLV: On its very first developmental test flight on April 18, 2001, the GSLV succeeded in placing an experimental communication satellite, GSAT-1, into a Geosynchronous Transfer Orbit. It was declared operational after its second successful developmental test flight on May 8, 2003, when it placed the GSAT-2 into its orbit. During its first operational flight (GSLV-F01) on September 20, 2004, GSLV launched the 1,950 kg EDUSAT, India's first exclusive satellite for the educational sector.

INSAT-4C: INSAT-4C is the second satellite in the INSAT-4 series. The first, INSAT-4A, was launched in December 2005. INSAT-4C carries 12 high-power Ku-band transponders designed to provide direct-to-home television services, facilitate video picture transmission and digital satellite news gathering as well as to serve the National Informatics Centre for its VSAT connectivity.

The INSAT system was established in 1983. With nine satellites -- INSAT-2E, INSAT-3A, INSAT-3B, INSAT-3C, INSAT-3E, INSAT-4A, GSAT-2, EDUSAT and KALPANA-1 -- in service with a total of 175 transponders in Ku-band, C-band and Extended C-band besides instruments for meteorological imaging and data relay functions, INSAT is the largest domestic communication satellite system in the Asia-Pacific region.

INSAT-4C would have further augmented the INSAT system capacity.