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.