Until now, the Indian Space Research Organisation (ISRO) has used Russian-made cryogenic engines for putting its satellite launch vehicles into space.

The polar satellite launch vehicle (PSLV) is used for launching remote sensing satellites into polar orbits and geosynchronous satellite launch vehicle (GSLV) for launching communication and meteorological satellites into geosynchronous transfer orbit.

But later this month, if the Indian space agency's attempt to launch its largest rocket, the GSLV-D3 with an indigenous cryogenic engine succeeds, then India will join the elite club of five nations in the world to have successfully developed such technology.

For the country's rocket scientists, the yet-to-be-achieved breakthrough is significant on two fronts--one, they will achieve self reliance and confidence in space technology. Two, India will emerge as a serious player in the $4 billion global satellite launch market.

ISRO spokesperson S Satish says, "An indigenous cryogenic engine will power the GSLV for the first time. This is the maiden flight of a launch vehicle and it will give capability to the country of mastering advanced launch vehicle technology which very few countries have at present."

Till date, the US, France, Japan, Russia and China have developed their own engines for satellite launch vehicles. Confidence levels of ISRO scientists are high as earlier this year, they successfully tested the indigenous cryogenic technology when the engine was tested for the full flight duration of 720 seconds at the liquid propulsion test facility at Mahendragiri, Tamil Nadu. Hour of reckoning is round the corner as the indigenous cryogenic engine now remains to be tested in actual flight.

ISRO's previous GSLV flights carried Russian cryogenic engines procured earlier. In total, seven cryogenic stages were procured from Russia of which five stages have been utilised. The space agency had taken up the indigenous cryogenic engine development programme in 1996 following the technology denial regime in the 1990s. The US had then forced Russia to stop giving India the engine technology.

While the GSLVs with Russian cryogenic engines have been designated as operational rockets after two developmental flights, the one that will go up now is called `developmental flight 3' (GSLV D3) as it will be fired by the ISRO-developed cryogenic engine. The 49-metre-tall rocket will have a lift-off weight of 414 tonne and carry the country's advanced communication satellite GSAT-4. It will carry the communications satellite into the geo-stationary orbit about 36,000 km above the earth.

GSAT-4 will carry a multi-beam Ka-band bent pipe and regenerative transponder and navigation payload in C, L1 and L5 bands. The satellite can guide civil and military aircraft. GSAT4 will also carry a scientific payload, TAUVEX, comprising three ultra violet band telescopes developed by Tel Aviv University and Israel space agency (ELOP) for surveying a large part of the sky .

The cryogenic stage is technically a very complex system compared to solid or earth-storable liquid propellant stages due to the use of propellants at extremely low temperatures and the associated thermal and structural problems. According to ISRO officials, the development of the cryogenic engine involves mastering materials technology, which can work at cryogenic temperature. Such a development takes about 10-15 years, so India initially purchased these from Russia, which were used in the previous flights. Key technological challenges faced during the development stage included development of new materials, composite thermal insulation, new fabrication techniques, handling of cryogenic fluids at cryogenic temperatures, realisation of facilities for assembly , integration and testing and associated safety systems.

Today the country has developed this technology, which will be tried out for the first time for the GSLV . The mission will make the country totally self-reliant in all aspects of launch vehicle technology. At a technical level, a cryogenic stage is the upper stage of a rocket that houses a cryogenic engine within it. Cryogenic technology involves the use of super-cooled liquid fuel to launch heavy rockets like the GSLV with the fuel being a mix of liquid hydrogen and oxygen. If the fuel mix is not in the exact proportions, the rocket could explode in geo-synchronous orbit.

Once in flight, the indigenous cryogenic engine is expected to develop a thrust of 73 kilo Newtons (kN) in vacuum with a specific impulse of 454 seconds and provide a payload capability of 2,200 kg to geosynchronous transfer orbit (GTO) for GSLV . The engine works on `staged combustion cycle' with an integrated turbo-pump running at around 42,000 rotations per minute (rpm). It is also equipped with two steering engines developing a thrust of 2 kN each to enable three-axis control of the launch vehicle during the mission. Another unique feature of this engine is the closed loop control of both thrust and mixture ratio, which ensures optimum propellant utilisation for the mission.

Without any doubt, the success of homegrown cryogenic engine technology will bolster the confidence levels of Indian space scientists and engineers as they brace up to launch an average of 10 satellites per year to meet the rising demand for various space applications, including communications and remote sensing. Beginning 2010-11, the Indian space agency is planning to launch 10 satellites per year and has a series of satellites and launch vehicles at various stages of preparation.

Though ISRO was to launch five satellites in 2009-10, it could launch only three -- Oceansat-2, Risat-2 (radar imaging satellite) in association with Israeli Aerospace Industries, and Anusat, a micro-satellite. Oceansat-2 also carried six nano-satellites of foreign countries as additional payloads. The launch of two satellites--GSAT-4 and Cartosat2B--got delayed due to technical complications, one of them being further flight duration tests of 800 seconds (13.3 minutes) conducted for the indigenous cryogenic engine to be used for the first time in the heavy rocket GSLV-D3 (geosynchronous satellite launch vehicle).

Later this year, ISRO plans to launch the polar satellite launch vehicle (PSLVC15). This will carry Cartosat-2B, an Algerian satellite, and two micro satellites--Youthsat from Canada and Studsat built by college students from Karnataka.

ISRO uses the Indian National Satellite (INSAT) series for telecommunication, television broadcasting and meteorological services and Indian Remote Sensing (IRS) satellites for resources monitoring and management. The space agency is also working on launching a Resourcesat-2, Risat-1 and MegaTropiques in the remote sensing area during the later part of this year. In the communications area, it has lined up three heavy satellites -- GSAT-5 and GSAT-6 from Sriharikota and GSAT8P onboard the Ariane launch vehicle from Korou in French Guayana -- by this year-end or early 2011.

Given that the demand for multiple satellites in communications and remote sensing areas would increase in the coming years, ISRO is currently developing an advanced version of GSLV called GSLV Mark III which is capable of putting a 4 tonne satellite into geostationary transfer orbit. Towards this, ISRO is developing an advanced version of cryogenic engine, which contains 25 tonne of cryogenic fuel.

Nevertheless, it is time of reckoning for India's space scientists as they prepare for their first rendezvous with cryogenic engine technology.