THIRUVANANTHAPURAM: A big engine for a big rocket. When the hefty GSLV Mk-III (Geosynchronous Satellite Launch Vehicle Mk-III), India’s most powerful rocket to date, takes to the skies in the first week of June, all eyes will be on its upper stage. Scientists here at ISRO’s Liquid Propulsion Systems Centre (LPSC), especially, are keeping their fingers crossed as the CE-20 cryogenic engine - which powers the upper stage - is about to be flight-tested for the first time.
LPSC was responsible for designing and developing the CE-20. LPSC director S Somanath calls the CE-20 a fully made-in-India engine. “We are happy that work on the engine has been completed successfully. The engine has undergone around 200 tests at the system, sub-system levels alone. The completed engine has been tested around seven times, and two tests have been conducted in flight configuration at the ISRO Propulsion Complex (IPRC) Mahendragiri,’’ he said.
ISRO has been working on developing the CE-20 engine ever since the GSLV Mk-III project was approved by the Centre in 2002. In between, LPSC had built the CE-7.5, a smaller cryogenic engine for the conventional GSLV Mk-II rocket. Until then, India had been using the Russian-made KVD-1 cryos to power the GSLV. Like the CE-7.5, CE-20 also uses liquid hydrogen as fuel and liquid oxygen as oxidiser. But there the resemblance ends.
CE-20 gives a thrust of about 20 tonnes, way more than its smaller cousin. The CE-7.5 was more or less a copy of the Russian engine, but calling the CE-20 a mere scaled-up version of the CE-7.5 would be wrong, he said. ‘’The fundamentals of the two engines are quite different. The thermodynamic cycles are different. The CE-7.5 follows a staged combustion cycle, and the CE-20 a gas-generated cycle. A gas generated cycle is less riskier to develop,’’ Somanath said. ISRO has placed orders for 12 CE-20 engines with LPSC, he added.
GSLV Mk-III can put satellites weighing four tonnes in the geostationary transfer orbit (GTO), making India self-sufficient in this respect. The Mk-III rocket has three stages, with the cryo-powered stage being the uppermost. In December 2014, ISRO had flight-tested the GSLV Mk-III for the first time.
It was a success, but the cryogenic stage was kept ‘passive’ on that mission, as the idea was validate the launch vehicle.