The Indian Space Research Organisation (ISRO) crossed an important milestone with the successful launch of weather satellite INSAT-3DR using a Geosynchronous Satellite Launch Vehicle equipped with the indigenous cryogenic upper stage. The successful launch marks a departure from the long history of failures with the GSLV; except for the first, every launch of the Polar Satellite Launch Vehicle (PSLV), the workhorse of ISRO, has been a success. That September 8 launch marks the third consecutive success; the fact that it is the first operational flight by the GSLV carrying the indigenous cryogenic upper stage is confirmation that India now belongs to the elite club of countries that have mastered the cryogenic technology. Maintaining structural and thermal integrity of the engine at very high temperatures during combustion just a few centimetres away from – 250° C, a temperature at which materials behave very differently, is a huge challenge. Likewise, igniting a cryogenic fuel and sustaining the combustion for a prolonged period is a daunting task. The Thursday launch had fully utilised the maximum payload carrying capacity of the GSLV-Mk II by carrying the heaviest satellite (2,211 kg) ever from Indian soil. This became possible only because the cryogenic upper stage was used. Unlike solid and liquid propellants, the specific impulse or thrust provided by a cryogenic rocket stage is much higher and is therefore more efficient to carry heavier payloads.
Unlike in the case of the PSLV where industry participation is around 80 per cent, it is only about half in the case of the GSLV. ISRO is a research and development organisation and not a production organisation, but the lack of greater industry participation has resulted in it being unable to launch more satellites in a year using the GSLV. However, efforts are under way to change this and ISRO has set a target of two GSLV launches in a year by 2018-2019. Even as the GSLV-Mk II has completed its first operational flight, ISRO is busy preparing for a ground qualification test of a more powerful GSLV-Mk III launch vehicle in about two months. The first experimental flight using the GSLV-Mk III is scheduled to take place by the end of this year and will use a new cryogenic engine. With an ability to provide double the thrust compared with the current cryogenic technology, the vehicle would be able to carry payloads up to four tonnes. This would mean that the GSLV-Mk III, when fully operational after three-four launches, will make ISRO truly independent by not having to rely on facilities abroad for launching heavier payloads. Besides independence, the country would stand to gain tremendously through cheaper launches.