Today’s launch of a geostationary communication satellite, GSAT-19, is perhaps ISRO’s most important mission in the last three decades. Bigger, probably, in technological significance than even the hugely popular Chandrayaan or Mangalyaan space missions. Not because of the satellite that is being put in space, though that, in itself, is no less special.
The launch is a giant leap for ISRO because of the rocket it is using. More precisely, because of the engine that is powering this rocket. In fact, it is just the third and uppermost stage of that engine that has made this launch extra-special. The mission happens to be the first “developmental” flight of the next generation Geosynchronous Satellite Launch Vehicle, called GSLV-MkIII with an entirely indigenous cryogenic upper stage that ISRO has been trying to master since the 1990s.
This cryogenic stage, that involves handling fuel at very low temperatures, is crucial to providing the extra thrust required by the rocket to carry heavier satellites deeper into space. GSLV-MkIII is meant to carry payloads up to four to five tons and that was not possible with conventional propellants used by ISRO’s main launch vehicle, called PSLV, which can take satellites only up to 2 tons to orbits and that too until orbits of 600-km altitude from the earth’s surface.
It will not just help ISRO probe deeper into space but will also bring it extra revenue, enabling it to make commercial launches of heavier satellites. “It is definitely the biggest event for ISRO in the last couple of decades. For ISRO’s launch vehicle programme, this probably is the most important day. This is a success in which there has been absolutely no foreign assistance. The GSLV-MkIII is entirely home grown and that is why it is so satisfying,” G Madhavan Nair, former chairman of ISRO, told The Indian Express.
Behind the success of the launch is nearly three decades of hard work in taming cryogenic technology and an interesting history of this technology was denied to ISRO by the United States in the early 1990s, forcing it develop it on its own. Amongst all rocket fuels, hydrogen is known to provide the maximum thrust. But hydrogen, in its natural gaseous form, is difficult to handle, and, therefore, not used in normal engines in rockets like PSLV. However, hydrogen can be used in liquid form.
The problem is hydrogen liquifies at very low temperature, nearly 250 degrees Celsius below zero. To burn this fuel, oxygen also needs to be in liquid form, and that happens at about 90 degrees Celsius below zero. Creating such a low-temperature atmosphere in the rocket is a difficult proposition, because it creates problems for other material used in the rocket. ISRO had planned the development of a cryogenic engine way back in the mid-1980s when just a handful of countries — the United States, the erstwhile USSR, France and Japan — had this technology.
To fast-track its development of next-generation launch vehicles — the GSLV programme had already been envisioned — ISRO had decided to import a few of these engines. It had discussions with Japan, US and France before finally settling for Russian engines. In 1991, ISRO and the Russian space agency, Glavkosmos, had signed an agreement for supply of two of these engines along with transfer of technology so that the Indian scientists could build these on their own in the future.
However, the United States, which had lost out on the engine contract, objected to the Russian sale, citing provisions of Missile Technology Control Regime (MTCR) that neither India nor Russia was a member of. MTCR seeks to control the proliferation of missile technology. Russia, still emerging from the collapse of the USSR, succumbed to US pressure and cancelled the deal in 1993. In an alternative arrangement, Russia was allowed to sell seven, instead of original two, cryogenic engines but could not transfer the technology to India.
These engines supplied by Russia were used in the initial flights of first and second generation GSLVs (Mk-I and Mk-II). The last of these was used in the launch of INSAT-4CR in September 2007. But ever since the cancellation of the original Russian deal, ISRO got down to develop the cryogenic technology on its own at the Liquid Propulsion Systems Centre at Thiruvananthapuram. It took more than a decade to build the engines and success did not come easily.
In 2010, two launches of second generation GSLV rockets, one having the Russian engine and the other indigenously developed, ended in failures. The big success came in December 2014 with the experimental flight of third generation (Mk-III) GSLV containing an indigenous cryogenic similar to the one used today. This mission also carried out an experimental re-entry payload, that ejected after reaching a height of 126 km and landed safely in the Bay of Bengal. After that, there have been three successful launches of second generation GSLV (Mk-II), the latest one, in May, being GSLV-F09 that launched the South Asian satellite.
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