The 29-hour countdown for tomorrow's launch of a homegrown rocket GSLV-D3 powered for the first time by indigenous cryogenic technology ticked today without any hitches and a successful mission will put India in an elite five-nation group.

Nearly 18 years after Indian scientists began working to develop the complex cryogenic engines, it will be for the first time that ISRO will be flight-testing the strategic technology, which is crucial to put communication satellites weighing more than two tonnes into geosynchronous transfer orbit (GTO). Geosynchronous orbit is 36,000 km above earth.

The 29-hour countdown began at 11.27 am and "things were progressing as per countdown", an Indian Space Research Organisation spokesperson said.

The 50-metre tall GSLV-D3 with the country's latest communication satellite GSAT-4 on board is scheduled to blast off from the Satish Dhawan Space Centre at 4.27 pm tomorrow. The 2,220 kgs GSAT-4 satellite has a seven-year mission life.

It took nearly two decades for Indian scientists to go in for a home-made cryogenic technology after its bid to acquire cryogenic propellant from Russia in 1992 failed in the face of US opposition. US, Russia, Japan, France and China are the only countries to have developed this complex technology.

The development of the cryogenic technology did not materialise for long due to strong US opposition and "technology denial regime of big powers", Director of Satish Dhawan Space Centre M C Dathan said.

"Often in the past, we have purchased completed cryogenic engines from Russia and five of them had been used for our GSLV missions. But we felt that it was important to develop indigenous capability as cryogenic technology is crucial to take our space programme to new heights," he said.

"It was a 'milestone' for Indian space programme in many ways and proved 'our capabilities and reflects our scientists' determination to take up any challenge," he said.

Apart from the first time use of indigenously made cryogenic technology, the launch also involve one of the heaviest satellites ever put in space by Indian satellite launch vehicles.

The successful launch of the GSAT-4 will elevate India's growing status as a space faring nation putting it in the league of a handful of nations that can launch satellites weighing above two tonnes in the geo synchronous orbit.

ISRO had used Russian cryogenic stages for the last five GSLV flights.

According to an ISRO spokesperson, GSAT-4 is India's 19th geostationary satellite built by the space agency and the fourth in GSAT series. The previous GSAT series were launched by GSLV vehicles in 2001, 2003 and 2004.

After its commissioning, GSAT-4 will join the group of India's 11 operational geostationary satellites, the spokesperson said.

G Ravindranath, Project Director, GSLV-D3, was quoted in an official statement as saying that reaching the testing of the indigenously developed cryogenic stage was a "big struggle."

Former Chairman of ISRO, Dr G Madhavan Nair, who has been involved in the project said that India managed to achieve its goals on developing indigenous cryogenic technology without anybody's assistance.

"We have set our goals and worked for it and we have achieved it. (It's) Not to show about our strength and things like that," he said.

Nair said development of cryogenic technology was a challenging job. "Our engineers and scientists have toiled and they have really mastered the technology. This is the highest levels of technology in rocket," he added.

"So, that way we are mastering that. I think we are becoming one of the world leaders in rocketry," he said.

The 'desi' version of the technology has given India the coveted status of total self-reliance in launch vehicle technology and would help ISRO in its future GSLV missions to carry heavier payloads, Dathan said.

There has been a growing demand for communication satellites in India and abroad.

The greatest advantage of cryogenic propellant will be the greater energy, thrust and velocity to the launch vehicles as compared to the conventional solid or liquid propellants.

"The technology has already come through a lot of ground tests and faults found during the process have been corrected.

It has also been evaluated by national-level experts. What is going to happen tomorrow is its flight worthiness test," Dathan said.

The development of cryogenic engines involves mastering several complex disciplines such as materials technology, operating rotary pumps and turbines that run at 42,000 rpm at cryogenic temperatures.

"This flight is going to be very critical since we are going to demonstrate a major technology. So we have had no stone unturned to ensure it as a success," he said.