May 08, 2003


The Geosynchronous Satellite Launch Vehicle (GSLV) project has the objective of acquiring launch capability for Geo-synchronous satellites. The first flight test of the vehicle, GSLV-D1, was conducted successfully on April 18, 2001 when the 1,540 kg experimental satellite, GSAT-1, was placed in a Geo-synchronous Transfer Orbit (GTO).

GSLV-D2 is the second developmental test flight of the vehicle. In this flight of GSLV placed a heavier satellite - the 1,800 kg GSAT-2 -- into Geo- synchronous Transfer Orbit of 180 km perigee (nearest point to earth) and 36,000 km apogee (farthest point to earth). The higher payload capability has been achieved by incorporating:

  • enhanced propellant loading in core solid motor
  • high pressure engine in liquid propellant strap-ons and second stage and
  • optimisation of structural elements

In its present configuration, GSLV was 49 m tall three-stage vehicle weighing about 414 tonne at lift-off. The first stage comprises a solid propellant motor (S139) and four liquid propellant strap-on motors (L40H). S139 stage was 20.1 m long and 2.8 m in diameter and it carried 138 tonne of Hydroxyl Terminated Poly Butadiene (HTPB) based solid propellant. The stage developed about 4736 kilo Newton thrust and burnt for 107 seconds.

The four strap-on (L40H) stages are 19.70 m long and 2.1 m in diameter. Each of them is filled with 42 tonne of hypergolic propellants (UH25) and Nitrogen Tetroxide (N2O4). Each produced 765 kilo Newton thrust and burnt for 149 sec.

The second stage of GSLV is 11.6 m long and 2.8 m diameter. It is filled with 39.3 tonne hypergolic propellants (UH25) and Nitrogen Tetroxide (N2O4). It produced a thrust of 804 kilo Newton. The stage burnst for about 136 seconds.

The third stage of GSLV used a Cryogenic Stage (CS) procured from Russia. The stage was 8.7 m long and 2.9 m in diameter and carried 12.6 tonne of liquid hydrogen and liquid oxygen and burnt for a duration of about 705 second producing a nominal thrust of 73.5 kilo Newton.

The Payload Fairing, which was 7.8 m long and 3.4 m in diameter, protected the vehicle electronics and the spacecraft during its ascent through the atmosphere. It is discarded once the vehicle has reached an altitude of about 115 km.

Inter-stage structures, which connect different stages of GSLV, house the avionics and control systems. The vehicle equipment bay housing electronic systems like processors, navigation system, control system, guidance system, telemetry system, telecommand system, etc, is mounted above the cryogenic stage.

The spacecraft, which is mounted above the equipment bay through a payload adapter, is separated by a Merman clamp-band joint and spring mechanism that provides the required separation velocity.

The launch of GSLV is conducted from Satish Dhawan Space Centre - SHAR (SDSC- SHAR), Sriharikota, about 100 km north of Chennai.