Apart from powering rockets to lift heavier satellites, it will also lower the cost per kilo.

An advanced Indian mega space launcher that can deliver ten-tonne and heavier communication satellites to space and using a semi-cryogenic engine is likely to to power ISRO’s launchers by around 2018.

That is the space agency’s next big space vehicle, having just achieved the GSLV for lifting 2,000-kg payloads. The agency is gearing up for first test flight of the GSLV Mark-III vehicle in December with a 4,000-kg payload.

Currently, the government has approved the development of the semi-cryogenic stage alone.

When fitted suitably into a launch vehicle, it will see India putting satellites of the class of 6,000 to 10,000 kilos — or with some variations, lift even 15,000-kg payloads — to geostationary transfer orbits at 36,000 km. The engine is expected to triple or quadruple ISRO's transportation ability.

Pre-project work on what is called the SCE-200 began about four years back. "We plan to have an [semi-cryogenic] engine and stage capable of flight by the end of 2018 and try it on the GSLV-MkIII.

This would readily boost Mk-III's maximum lifting capability from 4,000 kg to 6,000 kg,” Dr K. Sivan, Director of Vikram Sarabhai Space Centre at Thiruvanthapuram, the lead centre for launch vehicle development, said.

Two years thereafter, around 2020, this will be enhanced to 15,000 kg by putting strap-ons in clusters — the stage where major European and U.S. launch providers already are.

The engine will use space-grade kerosene as fuel and liquid oxygen as oxidiser. The development is going on at the Liquid Propulsion Systems Centre and the ISRO Propulsion Complex at Mahendragiri in Tamil Nadu.

“The semi-cryogenic engine is getting fabricated. Testing of its pump and components has been going on. An engine testing facility is also getting set up at Mahendragiri,” Dr. Sivan said.

Apart from powering rockets to lift heavier satellites, it will also effectively lower the cost per kilogram to reach orbits, which is the goal of all space-faring nations, he said.

The high-power local capability is needed as Indian communication satellites move towards 5,000-plus kg and more from 2017. By then, ISRO plans to build and launch its heaviest 5,700-kg GSAT-11 spacecraft, although on a European Ariane rocket for a big fee. Its present rockets can lift only up to 2,000 kg to this orbit.

Dr. Sivan said, “The GSLV-MkIII that we plan to test in December has a core liquid fuel stage. When the semi-cryogenic engine gets ready, our plan is to replace the liquid stage with the SCE. We straightaway get six-tonne payload capability, two tonnes over what Mark III can give.”

Subsequently the plan is to have a modular vehicle (earlier called the unifield launch vehicle) which allows variations suited to different payloads; this being done with the PSLV with its three versions.

For example, Dr. Sivan said: “We can have a bigger semicryogenic stage with clustered engines, similar to what SpawceX did using nine Merlin engines. We can then get a payload of 15 tonnes in the GTO.”