Chennai: The second development geosynchronous satellite launch vehicle (GSLV D2) is all set to roar up on 8 May 2003 from Satish Dhawan Space Centre, Sriharikota.

The launch vehicle will carry GSAT-2 weighing 1,800 kg to place it in a geosynchronous transfer orbit (GTO) of 180 km perigee (nearest point to earth) and 36,000 km apogee (farthest point to earth).

Indian Space Research Organisation (ISRO) ventured into GSLV project to acquire launch capability for geosynchronous satellites. The first test launch was made on 18 April 2001 when it placed the experimental satellite GSAT-1 in a geosynchronous transfer orbit (GTO) (See '').

With the 49-metre-long GSLV D2, India moves one step forward towards enhancing its commercial exploitation of satellite launch capabilities. What is interesting is that there are quite a few differences between GSLV D2 that is going up on 8 May 2003 and the one that went up two years ago.

First the speed, GSLV D2 will deliver its payload faster than its predecessor. As per plans the launch vehicle will sling its payload GSAT 2 997 seconds after the lift-off. GSLV D1 did that after 1,040 seconds after the lift-off. For instance, the payload GSLV D2 will carry GSAT2 weighing 1,800 kg. On the other hand the first test flight placed GSAT1 weighing 1,540 kg.

According to ISRO, the higher payload in GSLV D2 has been achieved by incorporating:
1. Enhanced propellant loading in core solid motor
2. High-pressure engines in liquid propellant strap on motors in the first stage and also in the second stage. (GSLV D2 is a three-stage launch vehicle. The first stage, apart from the engine in the main vehicle, also has four motors strapped to give additional power.)
3. Optimisation of structural elements.

Similarly GSLV D2 will be weighing 414 tonnes as against its elder version that weighed 13 tonnes less. While GSLV D2 will be carrying little more fuel in all the three stages (the four S139 strap on motors in the first stage carries more fuel), interestingly the burn time is less. For instance, each of the four strap on motors will carry 42-tonne fuel and will burn for 149 seconds while GSLV D1's S125 strap on motors carried 40-tonne fuel that burnt for 160 seconds.

Similar is the case with the rocket's second and third stages. Differences are also there in the payload carried by the two launch vehicles (See the comparison table). GSLV as a launch vehicle will be declared operational if the second test flight is successful.

Comparison table

GSAT