India plans to loft the heaviest variant of its Geosynchronous Satellite Launch Vehicle (GSLV), the Mk. 3, in 2014, even as the country’s space agency prepares for another mission with an earlier GSLV variant in July of this year, a senior space scientist says.

The GSLV Mk. 3, an advanced version of the GSLV that will weigh 640 tons at liftoff, is designed to launch communications satellites weighing more than 4 metric tons (8,800 lb.) once it begins orbital flights next year, Indian Space Research Organization (ISRO) Chairman K. Radhakrishnan says.

“We are targeting an experimental flight of the GSLV Mk. 3 in January,” he says. The rocket will fall into the sea after reaching a height of 120 km (75 mi.), Radhakrishnan says. “Further development will happen after that.”

GSLV Mk. 3 also could be used for launching future Indian astronauts, the ISRO official says.

S. Somnath, the GSLV Mk 3’s project director, says simulation of the flight is being performed. But “there are certain tests that cannot be performed on the ground. So an experimental launch is required.” Space agency engineers have plans to take some 2,000 measurements during the flight.

ISRO scientists claim the new rocket will offer the cheapest launch option in the space market. “We will test the rocket in a cost-effective manner,” Somnath adds.

Meanwhile, ISRO is planning to make a fresh attempt at launching the GSLV in July. The rocket is being built with an Indian cryogenic third stage, which ISRO developed to replace the Russian hydrogen-fueled engine used on the GSLV Mk. 1 model, the rocket’s early variant.

The latest announcement comes in the wake of successive failures of the GSLV — four of its 10 attempted flights have ended in disappointment in recent years.

The GSLV is a three-stage vehicle and stands 49 meters (160 ft.) tall, with a 414-ton liftoff weight. It has a maximum diameter of 3.4 meters at the payload fairing.

GSLV-Mark 1 and 2 are capable of placing the Insat-II class of satellites (2,000-2,500 kg) into geosynchronous transfer orbit.

“GSLV is an excellent vehicle, a beautiful vehicle. As compared to the PSLV [Polar Satellite Launch Vehicle], it is much less complex, except for one stage. It is far simpler to handle, though it has a large number of control components,” Radhakrishnan says.

The GSLV is the second satellite launch vehicle developed by ISRO, after the PSLV, which has successfully completed 22 launches in a row.

GSLV photo: ISRO