It is not a good time for the Indian Space Research Organisation. Two successive failures, just months apart, of the Geo-Synchronous Satellite Launch Vehicle (GSLV) raise serious questions about this rocket. Only once before has the space agency faced such a situation. That was in the late 1980s when the first two launches of the Augmented Satellite Launch Vehicle (ASLV) were unsuccessful. A thorough analysis of the rocket after its second failure in July 1988 revealed a basic design flaw. Understanding the ASLV problem contributed to the success of its successor, the Polar Satellite Launch Vehicle (PSLV). Shaking off the failure of its first launch in 1993, the PSLV has turned into a rugged workhorse that can launch multiple satellites and undertake a variety of missions. The GSLV uses the giant solid-propellant first stage of the PSLV as well as the latter's second stage equipped with a Vikas engine that runs on liquid propellants. In the GSLV, the top two stages of the PSLV have been replaced with a cryogenic stage and the latter's six solid-propellant strap-ons with four Vikas-engine-based ones. These changes allow the GSLV to carry much heavier payloads into orbit. However, it has thus far turned out to be trouble-prone. In its seven flights, it has notched up three failures and one partial success; by contrast, the PSLV, over 17 launches, has had just one failure and one partial success.

The GSLV launch in April this year was unsuccessful because of problems with the indigenous cryogenic stage, which was being flown for the very first time. According to ISRO officials, Saturday's failure occurred because commands from the rocket's onboard computers were not reaching systems in the first stage that control its orientation. Like the PSLV, the GSLV has two sets of wires that relay electrical commands from its onboard computers so that even if one set does not work for some reason, the other set is available as a backup. On Saturday, connectors on both sets of wires are thought to have snapped. That simply should not have happened and raises questions about what led to such an occurrence. Was it because the vehicle was subjected to unforeseen levels of stress, perhaps as a result of extreme vibrations? If so, what caused such stress in this flight? The failure analysis will doubtless address these and other issues. The space agency has just one more Russian-built cryogenic stage left of the seven that it bought. It is therefore vital that problems with the GSLV, including its indigenous cryogenic stage, are sorted out expeditiously. ISRO chairman K. Radhakrishnan has promised a thorough review of the GSLV programme. That is most certainly needed.


PSLV-C16 puts 3 satellites in orbitApril 20, 2011

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