Sriharikota: Time: 4.58 pm. Date: 8 May 2003. It was a hot day with a clear sky. The second geo-synchronous launch vehicle (GSLV-D2) kissed goodbye to Earth once for all and roared into the sky, with a waft of thick orange flame at its tail.
The 49-metre-tall vehicle weighing 414 tonnes (cost: Rs 150 crore) hurtled upwards relatively slowly at first and picked up momentum rapidly to escape the gravitational pull, while the Satish Dhawan Space Centre, Sriharikota, reverberated with its thrust power.
With its white bulbous heat-shield protecting the satellite gleaming in the evening sun, GSLV D2 went out of sight with a parabolic flight carrying India's as well its space scientists' pride high up into the universe.
Seventeen minutes after the lift-off, GSLV-D2 achieved its karma of birth by slinging the Rs 50-crore experimental, 1,800-kg satellite GSAT2 at an orbit of 180.04-km perigee (the nearest point to Earth) and an apogee of 36,000 kms (farthest to Earth) with an orbital inclination of 19.2 degree with respect to Equator. From this geo-synchronous transfer orbit (GTO), the satellite will be raised to the geo-synchronous orbit (GSO) by firing the onboard motors.
"We hit the bull's eye; it's a textbook launch," says a beaming Dr K Kasturirangan, chairman, Indian Space Research Organisation (ISRO), and secretary, India's Department of Space.
Concurs Dr P S Goel, member, Space Commission, and director, ISRO Satellite Centre: "The perfect launch, in turn, has resulted in a longer life for GSAT2. We think the satellite will function for at least 10 years."
Prior to the perfect launch and satellite delivery the scientists gave GSAT2 a life span of seven years as the onboard fuel had to be expended to manoeuvre it to its orbital path.
With the second test flight ending in a grand success and its complex systems working with clockwise precision, GSLV is all set to join India's launch vehicle workhorse, Polar Satellite Launch Vehicle (PSLV), as a fully-operational vehicle (See '').
ISRO has already lined up several payloads for India's new launch vehicle. To start with, the country's first educational satellite, Edusat (GSAT3), weighing 2 tonnes, will go up in the next GSLV flight this year, carrying five Ku-band transponders to provide coverage through five regional beams with spatial frequency reuse. In addition, two Ku-band and six Extended C-band transponders are included to provide India coverage. GSAT3 will be used for interactive education.
The subsequent GSAT4 will include eight channels each in Ka-band regenerative and bent-pipe payload and navigation payloads using CXL and CXC links. Unfurlable antenna is also planned to be tested on this satellite.
Along with improving the vehicle's payload capability, a 3-tonne Astrosat will be sent up in GSLV sometime mid-2004.
GSLV-D2: A much-improved vehicle
The recent GSLV is an improved version of its elder (GSLV-D1) that went up two years ago. GSLV-D2 carried a heavier payload (1,800 kgs) while its predecessor carried a 1,540-kg satellite (GSAT1). How did this happen?
The improvements are surely from the learning from the first vehicle whose mission could not be termed as a 100-per cent success. Owing to some problem in the cryogenic stage, GSLV D1 was not able to generate sufficient thrust or velocity to sling GSAT1 in its intended orbit. While that could have been corrected by manoeuvring the satellite firing its motors, the two dissimilar fuel tanks on board resulted in fuel wastage and the satellite was not able to reach its orbital path.
This time round, Kasturirangan and his team didn't take any risk. Explaining how improvements came about in GSLV-D2, G Madhavan Nair, director, Vikram Sarabhai Space Centre (VSSC), says: "We [Indian and Russian space scientists] studied the cryogenic stage data and did a series of tests in both the countries. The findings were incorporated in the cryogenic stage. Similarly, the mass of the equipment bay was reduced so that the payload capacity would go up."
Some structural changes and the use of light-weight composite fibre in the place of metal also helped to balance the increased fuel weight. In addition the improved liquid propellant Vikas engine (S139) also helped considerably in developing higher chamber pressure in the four strap-on motors and the core motor.
Further, the vehicle carrying more fuel and burning faster gave the necessary thrust power to go towards the heavens. All mission-related studies and simulations, including trajectory design, payload optimisation, configuration of flame jet preventor, thermal analysis and others, were completed carefully.
But ISRO is not content with the 3-tonne payload mark and is looking beyond. Says R V Perumal, associate director (projects), VSSC: "The initial goal was to build a 2-tonne vehicle. But the country's satellite requirements have outgrown the projects and we have to have a 4-tonner GSLV Mark III (M-III)."
The centre approved development of the advanced version last fiscal but it is expected to take six years to have a 4-tonne launcher ready. Interestingly, the vehicle will be shorter at 42.4 metres (presently it is 49 metres) but will be heavier by 220 tonnes at 629 tonnes. The payload fairing and heat shield will have a diameter of 5 metres (now 3.4 metres) and a payload volume of 100 cubic metres.
According the Department of Space, considerable progress has been achieved in detailed design and analysis of GSLV M-III structural design and optimisation, drawings generation, wind tunnel testing for aerodynamic characterisation and aero-elastic evaluation, thermal protection system and design and analysis of stage separation systems. Navigation, guidance and control systems have been finalised. All major vehicle interfaces have also been finalised.
Augmentation of in-house wind tunnel test facilities, honeycomb sandwich fabrication laboratory and structural testing facility has been undertaken to cater to GSLV M-III requirements.
The three-stage vehicle will have a 110-tonne core liquid propellant stage and a new booster in the two strap-on motors with 200-tonne fuel. (The existing model has four strap-on motors with 42-tonne fuel.) This along with a heavier cryogenic stage with 25-tonne fuel (to be locally made) is expected to do the magic of spitting the 4-tonne satellite into orbit.
The ISRO scientists achieved a major milestone last year by successfully ground-testing the cyrogenic engine for 1,000 seconds. "In a launch the cryogenic engine will function for a lesser time, say 800 seconds," says an official. With the engine ready, the next task is to develop other systems that are connected to the cryogenic stage.
Declining to give the cost of development, Kasturirangan says: "All I can say is that it will be comparable with that of Russian engines." The Russians have supplied all the seven cryogenic engines contracted for. Considering the total cost of GSLV (Rs 150 crore) the cryogenic engine and systems shouldn't cost more than Rs 60 crore.
The second launch pad that would accommodate the heavier GSLV will get ready soon. And Kasturirangan and his team are also raring to go ahead with activities related to the lunar probe.
also see : PSLV: The
workhorse to get ready
mission is not a lunatic mission