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The ‘naughty boy’ of space tamed Shriharikota, January 5 The GSLV hasn’t been behaving too well and of its previous seven flights only three were successful. So when the GSLV-D5, as today’s mission was labelled, functioned with immaculate precision, its proud Mission Director K. Sivan said, “The naughty boy has become obedient and meticulous.”
The difference between the GSLV and its younger sister, the Polar Satellite Launch Vehicle (PSLV) is that it is designed to put heavier communication satellites weighing between 2 and 4 tonnes into a geo-synchronous orbit 36,000 km in space. The PSLV, which has become the workhorse of ISRO’s rocketry because of its reliability, can put satellites weighting 1 to 2 tonnes, mainly for remote sensing, into a polar orbit of around 1,000 km. Unlike the PSLV, which relies on solid and liquid propellants to power its rocket motors, the GSLV in addition uses the advanced cryogenic or super-cooled engines to thrust heavier weighing satellites into space. Ever since Russia, under US pressure reneged from a deal to supply cryogenic technology to India in 1992, ISRO has struggled to build an indigenous version of the engine to power the GSLV. That’s because cryogenic rockets are extremely complex to make. The propellants have be stored in super-cool temperatures varying from minus 180 degrees centigrade to minus 250 degrees centigrade. Yet when the engine is fired, temperatures can soar to as much as 800 degrees C. Mastering the metals and their interaction with the propellants became a key technology to develop. To tide over the delay in developing the technology, India bought six cryogenic engines from Russia but three of the six GSLV flights in which these engines were mounted failed. In 2001, the first mission labelled GSLV-D1, which used a Russian-built cryogenic upper stage, underperformed resulting in the satellite it injected barely lasting two months. The second and third missions of the GSLV flown in 2003 and 2004 were, however, successful and they launched the GSAT-2 and EDUSAT satellites, respectively.The success though was short-lived. In 2006, during the launch of the GSLV-F02 a lower stage strap-on motor malfunctioned resulting in the vehicle spinning out of control. A year later in 2007, the GSLV-F04 also underperformed resulting in the life of the satellite it launched being considerably reduced. But as Radhakrishnan points out, “Neither of these though had anything to do with the cryogenic engines or the GSLV configuration but was a result of component failures in the other stages.” All these five flights used the Russian cryogenic engines for its upper stage. In April 2010, for the first time an Indian built cryogenic engine was flown on the GSLV-D3. But while the cryogenic ignited after 800 milliseconds the fuel-booster turbo pump stopped working and the mission had to be aborted. That year proved disastrous for in December the GSLV-F06 flight using a Russian cryogenic stage failed because communication wires snapped resulting in total loss of control. Radhakrishnan recalls gratefully that Prime Minister Manmohan Singh called him up and comforted the scientists telling them, “Don’t be disheartened — the nation is backing you.” So India’s space scientists went back to the drawing board and did a thorough failure review of the indigenously built cryogenic engine. They found that the fuel-booster turbo pump that malfunctioned hadn’t been tested under extreme temperatures. They also deduced that because of the extreme temperature various contractions on the different metals and bearings and casings would vary considerably and cause stress. They also looked at possible contaminants in the fuel. They then took measures to correct these possible flaws through extensive testing and came back with a flight test on August 19, 2013. But that flight had to be aborted because of a leak in liquid fuel engine an hour before the blast-off. They fixed it in record three months and were back by January to give the country a wonderful New Year gift. As Mission Director Sivan put it, “It took us 1,000 hours to fix the GSLV after the first failure. And the 1,000 seconds it took to prove itself today made all the struggle worth the effort.”
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