BENGALURU, INDIA — After a third and final ground test of its newest cryogenic upper stage engine Feb. 19, India’s Space Research Organisation has said it is confident of launching its heavy-lift rocket this December.

“The most powerful version of ISRO’s Geostationary Launch Vehicle (GSLV Mark-3) will use the new home-made Cryo CE-20 Engine that has been qualified,” ISRO spokesman Deviprasad Karnik told SpaceNews.

The GSLV Mark-3, also known as LVM3, can put into orbit communications satellite weighing 4,000 kilograms — roughly twice the payload that GSLV the Mark-2 and its domestically built CE-7.5-powered upper stage can deliver to geostationary transfer orbit.

The liquid-hydrogen-fueled CE-20 engine that will propel the third stage of GSLV Mark-3 was test fired for 640 seconds at the ISRO Propulsion Complex at Mahendragiri in Tamil Nadu state,about 300 kilometers southeast of Bengaluru. The test was conducted with a Mixture Ratio Controller in closed-loop mode, ISRO said.

Karnik said the CE-20 is the first Indian cryogenic engine to feature a gas-generator cycle. It produces a nominal thrust of 45,000 pounds with a specific impulse of 444 seconds in vacuum. The CE-20 had undergone two short-duration hot-fire tests last year and demonstrated repeatability of engine ignition characteristics and steady state performance, ISRO said.

Karnik said that in the next few months ISRO scientists will test the complete cryogenic stage with CE-20, fuel tank, plumbing and other systems. ISRO chairman A.S. Kiran Kumar told reporters he is confident of “a full launch of GSLV Mark-3 in December.”

“Kudos to ISRO Team for successful ground-testing of its new cryogenic engine CE 20 for 640 seconds,” tweeted Koppillil Radhakrishnan, previous chairman of ISRO. “India is one major step ahead to fly its advanced launcher LVM3 with a Communication Satellite much heavier than that GSLV carries now.

ISRO took up indigenous development of cryogenic stage in 1993 after Russia’s refusal to transfer the technology under pressure from the United States.