It was exactly 31 years ago that India emerged as a nation with an independent launch capability. On that occasion, the Indian Space Research Organisation's SLV-3 rocket, which stood just 23 metres high, succeeded in putting a 35-kg Rohini satellite into orbit. Since then, the country's spaceport at the Satish Dhawan Space Centre in Sriharikota has seen 32 more launches of satellite-carrying rockets, six of which ended in failure. On Friday, a Polar Satellite Launch Vehicle (PSLV), which was nearly twice the length and 18 times heavier than the SLV-3, took a 1,400-kg communications satellite into space. With 18 successful launches to its credit, the PSLV has matured into a versatile and reliable launcher. Although this is the first time the rocket carried a communications satellite, the PSLV had flawlessly executed similar missions with the country's first dedicated meteorological satellite, Kalpana-1, and subsequently the Chandrayaan-1 lunar probe. However, the PSLV is a less powerful rocket than its trouble-prone sibling, the Geosynchronous Satellite Launch Vehicle (GSLV), which has seen three of its seven flights turn into failure. The latter, equipped with a cryogenic engine, is capable of carrying communication satellites that are about one tonne heavier.
For communication satellites, size matters. The bigger and heavier the satellite, the more communication capacity it is able to pack and the more economical the cost of such capacity works out to be. Globally such satellites have grown bulkier over the years and these days can often be in the six-tonne class. Launching small communication satellites on the PSLV is not an attractive proposition. Therefore, as a first step, it is essential that problems with the GSLV, which is expected to fly again next year with the indigenous cryogenic stage, are sorted out expeditiously. But even that rocket will not be able to launch a three-tonne satellite like the GSAT-8 that was put into orbit by Europe's Ariane 5 in May 2011. So ISRO also needs to get its next-generation launcher, the GSLV Mark-III, which will be able to carry four-tonne communication satellites, operational as soon as possible. That may be easier said than done. Both the giant solid-propellant booster for the rocket and its liquid-propellant core stage were successfully tested last year. But its new cryogenic engine and stage must also be similarly tested and proven flight-worthy. Development of a semi-cryogenic engine, which will run on liquid oxygen and kerosene, has started; this engine will be used for a more powerful launch vehicle. ISRO's launch vehicle programme has come a long way but faces many difficult challenges in the years ahead.
