Cryogenics is the study of substances at very low temperature - at minus 150 degrees Celsius and less, in which gases like oxygen, hydrogen and nitrogen turn liquid. Cryogenic engines are called so because they use liquid oxygen and liquid hydrogen as fuel. The extremely cold temperatures make these liquids tricky to operate.

ISRO has taken 20 years to develop this complex technology after Russia denied cryogenic engine technology to India under US pressure. The cryogenic rocket project had been launched in 1994.

The 25-ton cryogenic engine will power India's most powerful rocket, the GSLV Mark III, which is expected to place 4-ton satellites in orbit.

The C-25 cryogenic engine will also be able to push spaceships that could carry Indian astronauts someday.

The first test flight of the GSLV MK-III is expected in the next few weeks.

The full stage of the C-25 engine was tested for a 50-second duration at the ISRO Propulsion Complex at Mahendragiri in south India late on yesterday evening.

On April 28, 2015, the ISRO had successfully conducted the ground test of the engine.

The GSLV MK II (Geo-synchronous Satellite Launch Vehicle) nicknamed "Naughty Boy", had its first operational launch last September, when it launched an advanced weather satellite into orbit.

In about a year, the GSLV MK II is expected to launch India's second moon mission - the Chandrayaan-2. It will also smooth the nation's path to the multi-billion dollar commercial space launcher market.