How India's space journey made another landmark flight
With yet another successful mission on August 27 evening, the Indian space agency has moved a step closer to acquiring capability to launch heavier satellites all on its own. The technological expertise gained through the launch will help the agency prepare itself for transporting heavier spacecraft, including manned space flight, from Indian soil in future.
While Indian Space Research Organisation (ISRO) has been launching small to medium sized satellites using its workhorse rocket Polar Satellite Launch Vehicle (PSLV) for several years now, it is yet to perfect launch capability for heavier satellites in 2000 to 5000 kg class. Such satellites need more powerful rockets like GSLV. The advanced communication satellite, GSAT-6, launched today weighs 2117 kg. The launch vehicle was powered by indigenously developed cryogenic engine. This is a major landmark in the space journey of India.
A cryogenic rocket stage is more efficient and provides greater thrust for every kilogram of propellant it burns, compared to solid and liquid propellant rocket stages. The cryogenic engine technology is a key to the success of any robust space programme and is considered strategic. Just a handful of countries possess this critical engine technology. India started with Russian-built cryogenic engines in 2001. In all, six flights of GSLV have used cryogenic engines supplied by Russia since 2001. Two of these GSLV flights were unsuccessful while a third mission was partial success. The agreement with Russia was only for supplying these engines and not for any transfer of technology.
Therefore, along with GSLV flights with Russian cryogenic engine, ISRO has been developing its own cryogenic technology. Two GSLV flights powered by indigenous cryogenic upper stage have been tested so far. The first one in April 2010 failed, while the second developmental flight of GSLV with indigenous cryogenic engine in January 2014 was successful. Today's was the third developmental flight of India-made cryogenic upper stage.
Even after the success today, one can say that ISRO's record with the use of cryogenic technology has been mixed so far. The agency will have to have some more successful flights of GSLV with its own cryogenic engine, before it can declare GSLV-Mark II as an operational rocket like PSLV. As of now, ISRO is planning another launch of GSLV with indigenous cryogenic in April 2016.
The cryogenic stage is complex and technically more challenging than solid or earth-storable liquid propellant stages because of the fact that propellants have to be maintained at extremely low temperatures. Oxygen liquifies at minus 183 degrees C and hydrogen at minus 253 degrees C. The propellants, at these low temperatures, are to be pumped using turbo pumps running at around 40,000 rpm.
The space agency has simultaneously been developing next-generation GSLV - called GSLV Mark III - which will be capable of launching satellites weighing 5000 kilos. The experimental flight of GSLV in December 2014 was to test certain parameters of this heavy-duty launch vehicle. When fully developed, it will make India fully self-reliant in the field of launching satellites of any class. As of now, a "man-rated" version of GSLV-Mark III is supposed to be used for human space flight as and when it is approved by the government.
The communication satellite launched on Thursday, GSAT-6, also incorporates several new features. It will provide communication through five spot beams in S-band and a national beam in C-band for strategic users. One of the advanced features of this satellite is its S-Band unfurlable antenna of 6 meter diameter - the largest satellite antenna designed by ISRO till now.