An Indian rocket with over two tonne communication satellite GSAT-6, which has several strategic applications, blasted off from Andhra Pradesh's Sriharikota spaceport on Thursday.

The Geosynchronous Satellite Launch Vehicle D6 (GSLV D6) rose from the second launch pad at Satish Dhawan Space Centre at 4.52 pm.

The 49.1 metre tall rocket weighing 416 tonnes would sling the 2,117 kg GSAT-6 communication satellite in the geosynchronous transfer orbit (GTO) around 17 minutes into the flight.

Indian Space Research Organisation (Isro) scientists at the mission control centre in Sriharikota watched their monitors intently to see the rocket's progress.

One of the crucial rocket engines is the cryogenic engine, more efficient as it provides more thrust for every kilogram of propellant burnt, designed and developed by Isro.

This is the GSLV rocket with domestically-built cryogenic engine that is flown after nearly a year, in its second mission during the last five years after two such rockets failed in 2010.

One of the failed GSLV rockets flew with an Indian cryogenic engine and the other with a Russian engine.

The GSLV is a three-stage/engine rocket. The core of first stage is fired with solid fuel while the four strap-on motors by liquid fuel. The second is the liquid fuel and the third is the cryogenic engine.

For the country, Isro perfecting the cryogenic engine technology is crucial as precious foreign exchange can be saved by launching communication satellites on its own.

Currently Isro flies its heavy communication satellites by European space agency Ariane.

India pays around Rs 500 crore as launch fee for sending up a 3.5 tonne communication satellite. The satellite cost is separate.

The Isro can send smaller communication satellites - weighing around two tonnes - till such time it gets ready an advanced GSLV variant-GSLV-Mark III that can lug satellites weighing around four tonnes.