A GIANT LEAP
On June 5, the Indian Space Research Organisation (ISRO) crossed a significant milestone—the flawless launch of the heaviest rocket it has ever employed, partially powered by an indigenously designed cryogenic engine. The rocket, GSLV Mk. III, weighs 640 tonnes, and is capable of carrying a maximum pay-
load of 4,000 kg into orbit. The most significant feature of the launch was that the engine performed flawlessly before ejecting the satellite. It is the most powerful upper stage developed by ISRO, and uses a combination of liquid oxygen and liquid hydrogen, loaded in two independent tanks, as a propellant combination. The development of a cryogenic stage has unique design challenges, with liquid hydrogen and oxygen stored in its tanks at (-)253 degree Celsius and (-)195 degree, respectively. To store these cryogenic fluids at these extreme temperatures, a special multi-layer insulation is provided for the tanks and other structures.
Independence apart, an indigenous vehicle means lower costs of putting spacecraft into orbit, says K. Sivan of the Sarabhai facility
The Mk. III, says ISRO chairman A.S. Kiran, will “increase our capability to launch satellites manifold. The payload will increase in future flights”. It could also be the launch vehicle used to send “Indians into space, from Indian soil, using Indian rockets”.
The engine, designated CE-20, was developed at the ISRO liquid propulsion complex at Mahendragiri, and is capable of generating about 20 tonnes of thrust. “No technological element was borrowed or adapted from any other space organisation,” emphasises S. Somanath, director of the liquid propulsion systems centre. The technological challenge in developing such an engine is daunting—hydrogen, for instance, must be cooled to below (-)250 degrees centigrade before it becomes a liquid, which puts significant strain on the engine itself. “Independence apart, an indigenous launch vehicle means lower costs of putting spacecraft into orbit,” adds K. Sivan, director of the rocket design facility, Vikram Sarabhai Space Centre, Thiruvananthapuram.