On 29 March 2018 GSAT 6A Communication satellite launched by ISRO with the help of GSLV F08. but unfortunately, ISRO lost the link with GSAT 6A soon after the successful launch of GSAT 6A. After hard work, ISRO's team figured out the where GSAT 6A satellite is in the space. Now, lets we discuss the GSLV which lift off the GSAT 6A on the back of it.

Geosynchronous Satellite Launch Vehicle

GSLV stands for the Geosynchronous Satellite Launch Vehicle. The construction of GSLV vehicle is to launch 2-tonne square loaded satellites in Geosynchronous orbit.
GSLV project was started in 1990 which aims to achieve Indian launch capability for geosynchronous satellites. GSLV also uses the major components similar to Polar Satellite Launch Vehicle . On 12 April 2018 ISRO launched IRNSS - 1I with the help of PSLV - C41 . S-Band telemeter and C - Band transponders are used in GSLV that enables the operations such as performance monitoring, tracking, range safety/flight safety and preliminary orbit determination.The Redundant Strap Down Inertial Navigation System / GSLV's inertial guidance system places its equipment in the bay, driving the vehicle from lift-off to spacecraft injection. Digital auto-pilot and closed-loop guidance plan ensure speed and guidance injection of the required height of the spacecraft for a specific orbit.

Three Stages Of GSLV

As GSLV contains three stages so it it is known as a three-stage vehicle. The three stages of GSLV are:-

First Stage Of GSLV

The first stage of GSLV is a solid core that contains 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. The S139 stage is 2.8 m in diameter and has a nominal burn time of 109 seconds. The stage generates a maximum thrust of 4700 kN.The first stage also contains four straps on motors fitted on it. The strap on motors contains UDMH + N2O4 as fuel. Its maximum thrust is 680 KN and burn time of 160 seconds.The four liquid engine strap-ons used in GSLV are heavier derivatives of PSLV's PS2 and use one Vikas engine each.

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Second Stage GSLV

 The High Thrust Vikas Engine ( HTVE ) is fitted in the second stage. The High Thrust Vikas Engine ( HTVE ) increases the functionality of GSLV. By using the Vikas engine thrust of GSLV increased by 6%, thereby enhancing payload capability by 50%. Vikas engine also increases the reliability of GSLV. HTVE has 2.8 meters (9 ft 2 in) diameter.

Third Stage Of GSLV

The third stage of GSLV is a Cryogenic Upper Stage ( CUB ) . In this stage,Cryogenic Upper Stage contains cryogenic propellants. Two cryogenic propellants are filled in the upper stage. These two liquid propellants are Liquid Hydrogen and Liquid Oxygen used as fuel. These two fuels are filled in two tanks separately. Liquid Oxygen i.e. LOX is used as the liquid oxidizer. Liquid Oxygen is stored at - 183 ℃. Liquid hydrogen i.e. LH - 2 is stored at - 253 ℃.The Indian cryogenic engine was built at the Liquid Propulsion Systems Centre.The engine has a default thrust of 75 kilonewtons (17,000 lbs) but is capable of a maximum thrust of 93.1 kilonewtons (20,900 lbf).

Capacity, Length, Diameter Etc. Of GSLV

The complete length of GSLV is about 49 meters (161 ft) and 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 meters (26 ft) long and 3.4 meters (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.

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Payload To Geostationary Transfer Orbit: 2,500 kg

 GSLV's main charter is an INSAT-class communications satellite operating in geosynchronous orbit. Therefore, these satellites are transferred to geosynchronous orbit.

Payload To Low Earth Orbit: 5,000kg

 Apart from this, the capacity to set up 5 tons of low-Earth orbit is achieved by GSLV. May be able to launch many smaller satellites from heavily on.

Development Of GSLV

The Vikram Sarabhai Space Centre located at Thiruvananthapuram and the Liquid Propulsion Systems Centre (LPSC) located at Valiamala, in Thiruvananthapuram of Kerala, and Bengaluru of Karnataka has a special contribution in the development of GSLV. GSLV is assembled after testing in the ISRO Propulsion Complex ( IPRC ) located in Mahendragiri. Propulsion system and its various stages were fitted here. All the testes of all stages and engines of ISRO's vehicles are perform here.

Variants Of GSLV 

Russian cryogenic stage (CS) is carried by GSLV designated Rockets as the GSLV Mk I while the native named GSLV Mk II versions using Cryogenic Upper Stage (CUS). All GSLV launches have been organized at Satish Dhawan Space Center in Sriharikota.


Flight of first development of GSLV Mk was the first phase of 129 tons (S 125) and it was able to launch about 1,500 kilograms into a Geosynchronous transfer orbit. The level of S 125 with the second development flight S139 has been changed. They used the same solid motor with 138-ton propeller loading. The pressure of the chamber has increased in all liquid engines, thereby causing high reproductive matter and burn time. In these reforms, GSLV was allowed to issue an extra 300 kg payload. In the fourth phase of the GSLV MKI, GSLV-F0, 15 tonnes of reproduction is being loaded in the third phase, which is called C-15.


 GSLV Mk II version uses an Indian cryogenic engine, CE -7.5, and able to launch 258 kilograms of it into Geostationary Transfer Orbit. The previous GSLV vehicle (GSLV Mk I) used the Russian cryogenic engine. The GSLV Mk II also use High Thrust Vikas Engine that increased its thrust by 6% to launch from 2018, it was shown on 29 March 2018 in the second phase of the GSAT 6A launch. It will be used for the first step booster for four Vikas engines on future missions.

Launches By GSLV

During the launch of GSAT 6A it was the twelfth flight of GSLV and with Cryogenic Upper stage, it was the sixth flight of the GSLV . The twelve launches by GSLV are :-
Launches By GSLV
S No.TitleLaunch DateRocket Type OrbitPayloadRemarks
4GSLV-F02 / INSAT-4CJul 10, 2006GSLV-MK-IIGTOINSAT-4CMission Unsuccessful
6GSLV-D3 / GSAT-4Apr 15, 2010GSLV-MK-IIGSAT-4Mission Unsuccessful
7GSLV-F06 / GSAT-5PDec 25, 2010GSLV-MK-IIGTOGSAT-5PMission Unsuccessful
11GSLV-F09 / GSAT-9May 05, 2017GSLVGSOGSAT-9
12GSLV-F08/GSAT-6A MissionMar 29, 2018GSLVGSOGSAT-6A