Geosynchronous Satellite Launch Vehicle abbreviated as GSLV, is an expendable launch system operated by the Indian Space Research Organisation (ISRO). GSLV has been used in ten launches to date, since its first launch in 2001 to the most recent on March 29, 2018 carrying the GSAT-6A communications satellite. Even though Geosynchronous Satellite Launch Vehicle Mark III shares the name it is an entirely different launcher.


The Geosynchronous Satellite Launch Vehicle (GSLV) project was initiated in 1990 with the objective of acquiring an Indian launch capability for geosynchronous satellites.[4][5]

GSLV uses major components that are already proven in the Polar Satellite Launch Vehicle (PSLV) launchers in the form of the S125/S139 solid rocket booster and the liquid-fueled Vikas engine. Due to the thrust required for injecting the satellite in a GTO orbit the third stage was to be powered by a LOX/LH2 Cryogenic engine which at that time India did not possess or had the technology know-how to build one.

The first development flight of the GSLV (Mk.I configuration) was launched on 18 April 2001 was a failure as the payload failed to reach the intended orbit parameters. The launcher was declared operational after the second development flight successfully launched the GSAT-2 satellite. During the initial years from the initial launch to 2014 the launcher had a checkered history with only 2 successful launches out of 7.[6][7]

Cryogenic Engine Controversy

The third stage was to be procured from Russian company Glavcosmos, including transfer of technology and design details of the engine based on an agreement signed in 1991.[5] Russia backed out of the deal after US objected to the deal as in violation of the Missile Technology Control Regime (MTCR) May 1992. As a result ISRO initiated the Cryogenic Upper Stage Project in April 1994 and began developing its own cryogenic engine.[8] A new agreement was signed with Russia for 7 KVD-1 cryogenic stages and 1 ground mock-up stage with no technology transfer, instead of 5 cryogenic stages along with the technology and design as per the earlier agreement.[9]. These engines were used for the initial flights and were named GSLV Mk.1[10]

Vehicle description

The 49 metres (161 ft) tall GSLV, with a lift-off mass of 415 metric tons (915,000 lb), is a three-stage vehicle with solid, liquid and cryogenic stages respectively. The payload fairing, which is 7.8 metres (26 ft) long and 3.4 metres (11 ft) in diameter, protects the vehicle electronics and the spacecraft during its ascent through the atmosphere. It is discarded when the vehicle reaches an altitude of about 115 km.[11]

GSLV employs S-band telemetry and C-band transponders for enabling vehicle performance monitoring, tracking, range safety / flight safety and preliminary orbit determination. The Redundant Strap Down Inertial Navigation System/Inertial Guidance System of GSLV housed in its equipment bay guides the vehicle from lift-off to spacecraft injection. The digital auto-pilot and closed loop guidance scheme ensure the required altitude maneuver and guide injection of the spacecraft to the specified orbit.

The GSLV can place approximately 5,000 kg (11,000 lb) into an easterly Low Earth orbit or 2,500 kg (5,500 lb)(for the Mk. II version) into an 18° geostationary transfer orbit.

Liquid boosters

The first GSLV flight, GSLV-D1 used the L40 engine. Subsequent flights of the GSLV used high pressure engines in the strap-on boosters called the L40H.[12] The GSLV uses four L40H liquid strap-on boosters derived from the L37.5 second stage, which are loaded with 42.6 tons of hypergolic propellants (UDMH & N2O4). The propellants are stored in tandem in two independent tanks 2.1 metres (6 ft 11 in) diameter. The engine is pump-fed and generates 760 kilonewtons (170,000 lbf) of thrust, with a burn time of 150 seconds.

First stage

GSLV-D1 used the S125 stage which contained 125 metric tons (276,000 lb) of solid propellant and had a burn time of 100 seconds. All subsequent launches have used enhanced propellant loaded S139 stage.[12] The S139 stage is 2.8 m in diameter and has a nominal burn time of 109 seconds.[13] The stage generates a maximum thrust of 4700 kN.[14]

Third stage of GSLV Mk II

Second stage

The GS2 stage is powered by the Vikas engine. It has 2.8 metres (9 ft 2 in) diameter.[13]

Third stage

The third stage of the GSLV Mk.II is propelled by either the Russian KVD-1 or the Indian CE-7.5 cryogenic rocket engine. It uses liquid hydrogen (LH2) and liquid oxygen (LOX)[15] The Indian cryogenic engine was built at the Liquid Propulsion Systems Centre [16][17] The engine has a default thrust of 75 kilonewtons (17,000 lbf) but is capable of a maximum thrust of 93.1 kilonewtons (20,900 lbf).


GSLV rockets using the Russian Cryogenic Stage (CS) are designated as the GSLV Mk I while versions using the indigenous Cryogenic Upper Stage (CUS) are designated the GSLV Mk II.[18] All GSLV launches have been conducted from the Satish Dhawan Space Centre in Sriharikota.


The first developmental flight of GSLV Mk I had a 129 tonne (S125) first stage and was capable of launching around 1500 kg into geostationary transfer orbit. The second developmental flight replaced the S125 stage with S139. It used the same solid motor with 138 tonne propellant loading. The chamber pressure in all liquid engines were enhanced, enabling a higher propellant mass and burn time. These improvements allowed GSLV to carry an additional 300 kg of payload.[19][20] The fourth operational flight of GSLV Mk I, GSLV-F06, has a 15 tonne propellant loading in the third stage, called the C-15.[21]


This variant uses an Indian cryogenic engine, the CE-7.5, and is capable of launching 2500 kg into geostationary transfer orbit. Previous GSLV vehicles (GSLV Mk.I) have used Russian cryogenic engines.[22]

For launches from 2018 a 6% increased thrust version of the Vikas engine was developed. It was demonstrated on 29 March 2018 in the GSAT 6A launch second stage. It will be used for the four Vikas engines first stage boosters on future missions.[23]

Launch Statistics

Launch history

Flight № Date / time (UTC) Rocket,
Launch site Payload Payload mass Orbit Customer Launch
D1 18 April 2001
Mk I First India GSAT-1 1540 kg Partial failure[24][25]
Developmental flight, payload placed into lower than planned orbit, and did not have sufficient fuel to reach a usable orbit.[24] ISRO claims the launch to be successful.[26] In a 2014 interview, ISRO Chairman K. Radhakrishnan attributed the failure to incorrect mixture ratio used in the cryogenic upper stage.[27]
D2 8 May 2003
Mk I First India GSAT-2 1825 kg Success
Developmental flight.[28]
F01 20 September 2004
Mk I First India GSAT-3 1950 kg Success
First operational flight.[29]
F02 10 July 2006
Mk I Second India INSAT-4C 2168 kg Failure
Both rocket and satellite had to be destroyed over the Bay of Bengal after the rocket's trajectory veered outside permitted limits.
F04 2 September 2007
Mk I Second India INSAT-4CR 2160 kg Partial failure[30]
Apogee lower and inclination higher than expected, due to an error in the guidance subsystem.[31] Eventually the 2160 kg payload reached the designated geostationary transfer orbit.[32][33] Minor error in orbit inclination corrected by satellite mission operators. Satellite is fully operational and full design life of ten years will be achieved. It completed 6 years in orbit successfully.[34] ISRO claims this GSLV flight to be successful.
D3 15 April 2010
Mk II Second India GSAT-4 2220 kg Failure
First flight test of the ISRO designed and built Cryogenic Upper Stage (CUS). Failed to reach orbit due to malfunction of the Fuel Booster Turbo Pump (FBTP) of the cryogenic upper stage.[35]
F06 25 December 2010
Mk I Second India GSAT-5P 2310 kg Failure
First flight of GSLV Mk.I (c). Destroyed by range safety officer after loss of control over liquid-fueled boosters.[36]
D5 5 January 2014
Mk II Second India GSAT-14 1980 kg Success[37][38]
The flight was scheduled for 19 August 2013, but one hour and 14 minutes before the lift off, a leakage was reported and the launch was halted.[39]

Second flight of GSLV with indigenous cryogenic upper stage (CUS) developed by ISRO's Liquid Propulsion Systems Centre (LPSC) was launched successfully on 5 January 2014.[40][41] It was a launch with precision of 40 metres (130 ft). All the three stages performed successfully.[42][43] This was the first successful flight of the cryogenic stage which was developed indigenously in India.[44]

D6[45][46] 27 August 2015
Mk II Second India GSAT-6 2117 kg Success
GSLV Mk II D6 with an Indigenous Cryogenic Engine (ICE) successfully ferried GSAT-6 payload into Geostationary Transfer Orbit (GTO) with injection parameters of 170 km x 35945 km, 19.96 degree inclination. The cuboid-shaped GSAT-6 satellite includes a technology demonstrator S-Band unfurlable antenna with a diameter of six metre which will provide S-band communication services during its expected mission life of nine years.[47]
F05 8 September 2016
MK II Second India INSAT-3DR 2211  kg Success
First operational flight of GSLV Mk II.

The injection parameters were met with extreme precision. Perigee was within 300m (within 0.18%) of the expected value whereas apogee was within 0.2% (80 km). The difference between expected and actual inclination degree was 0.

INSAT-3DR is an advanced atmospheric weather satellite. as well as the second heaviest satellite placed in orbit by an indigenous cryogenic engine propelled GSLV [48][49][50]

F09 5 May 2017
Mk II[52] Second[51] India GSAT-9 / South Asia Satellite 2230 kg[53] GTO[51] Success[51]
South Asia Satellite was previously named as SAARC Satellite[54]
F08 29 March 2018
Mk II[56] Second[55] India GSAT-6A[55] 2140 kg[57][58] or 2066 kg[59] GTO[56] Success[55]
Used an enhanced version of the Vikas engine called High Thrust Vikas Engine(HTVE) which had a thrust of 848 kN in GS2 stage. Electro-hydraulic Actuation used for gimballing in GS2 stage was replaced by more reliable Electro-Mechanical Actuation.[60] Even though the launch was a success, communication was lost with the satellite 48 hours after launch.[61][62][63]

Planned launches

Date / time (UTC) Rocket,
Launch site Payload Orbit Customer
October 2018[64][65][66] Mk II Second India Chandrayaan 2
F10; 3290 kg[67][68][69][70]
2018[64] Mk II Second India GSAT-7A
2018[64] Mk II Second India GISAT 1
2100 kg[71]
2020[64] Mk II Second India Mangalyaan 2
September 2022[64] Mk II Second United States India NISAR
NASA / ISRO collaboration[73]
2022[64] Mk II Second India Insat 3DS

See also


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External links