There is an air of expectancy at Sriharikota even as the Geo-synchronous Satellite Launch Vehicle (GSLV-D3) stands gleaming in off-white and grey on the beachside launch pad of the island. It was fitted together at the towering Vehicle Assembly Building and moved to the pad on April 7. The vehicle, 49 metres tall and weighing 419 tonnes, was married up with the satellite GSAT-4 earlier. When the vehicle lifts off at 4.27 p.m. on April 15, it will be a major riposte to the United States' technology denial tactics.
“The vehicle has been assembled and is ready for the launch,” Mission Director G. Ravindranath told journalists at the spaceport on Friday. He called it “a crucial mission because we are flying our own cryogenic stage for the first time in this flight.” It was “the most reviewed vehicle” and the result of “our efforts of the last 19 years. We started in 1991 and we have reached this stage despite technology denials.”
The entire flight from lift-off will last 1,022 seconds. Of this duration, the indigenous cryogenic engine alone will fire for 720 seconds. At the end of 1,022 seconds, the cryogenic engine will catapult the communication satellite GSAT-4 into the orbit at a velocity of 10.2 km a second. It will be a geo-synchronous transfer orbit (GTO) with a perigee of 170 km and an apogee of 36,000 km.
The cryogenic stage was built at the Liquid Propulsion Systems Centre (LPSC), Mahendragiri, Tamil Nadu. Cryogenic engines are crucial for putting communication satellites weighing more than two tonnes into a GTO. Cryogenic technology involves the use of liquid oxygen at minus 183 degrees Celsius and liquid hydrogen at minus 253 degrees Celsius.
Mohammed Muslim, Project Director, Cryogenic Upper Stage Project (CUSP), said the cryogenic technology was the most complex one to be developed by the Indian Space Research Organisation (ISRO). “It has taken us 15 years to achieve this. It is normal time for any country and we are the sixth country to acquire this technology [after the U.S., Russia, Europe, Japan and China]. This is a highly guarded technology.” The ISRO had not taken chances with this mission and “the vehicle has been reviewed and checked point by point any number of times,” he said.
The ISRO built the cryogenic engine from scratch after the U.S. pressured Russia in April 1992 and July 1993 into agreeing not to sell cryogenic technology to India. In January 1991, India and the erstwhile Soviet Union had reached an agreement, under which the Soviet space agency, Glavkosmos, would sell cryogenic stages and transfer the cryogenic technology to India.
Goes back on pact
Under U.S. pressure, Russia in July 1993 went back on its agreement to transfer the cryogenic technology. In lieu of the technology, it agreed to sell two additional cryogenic stages to India. The last five flights of the GSLV from Sriharikota were powered by the Russian cryogenic stages. A cryogenic stage includes the engine, propellant tanks, motor casing and wiring.
Mr. Ravindranath said it took the ISRO all these years to develop the cryogenic technology because it had to develop special materials.
(At very low temperatures of liquid hydrogen and liquid oxygen, metals become brittle. The ISRO, therefore, had to develop new alloys, new welding techniques and new types of lubricants).
7-year mission life
Satellite Director M. Nageswara Rao said GSAT-4 would have a mission life of seven years. One of the payloads would help passenger aircraft land accurately despite poor visibility.