Satellite Launching Vehicles

Satellite Launch Vehicle-3 (SLV-3) was India’s first experimental satellite launch vehicle, which was an all solid, four stage vehicle weighing 17 tonnes with a height of 22m and capable of placing 40 kg class payloads in Low Earth Orbit (LEO).

The first experimental flight of SLV-3, in August 1979, was only partially successful. Apart from the July 1980 launch, there were two more launches held in May 1981 and April 1983, orbiting Rohini satellites carrying remote sensing sensors.

The successful culmination of the SLV-3 project showed the way to advanced launch vehicle projects such as the Augmented Satellite Launch Vehicle (ASLV), Polar Satellite Launch Vehicle (PSLV) and the Geosynchronous Satellite Launch Vehicle (GSLV).


The Augmented Satellite Launch Vehicle (ASLV) Programme was designed to augment the payload capacity to 150 kg, thrice that of SLV-3, for Low Earth Orbits (LEO). While building upon the experience gained from the SLV-3 missions, ASLV proved to be a low cost intermediate vehicle to demonstrate and validate critical technologies that would be needed for the future launch vehicles like strap-on technology, inertial navigation, bulbous heat shield, vertical integration and closed loop guidance.

Polar Satellite Launch Vehicle (PSLV) is the third generation launch vehicle of India. It is the first Indian launch vehicle to be equipped with liquid stages. After its first successful launch in October 1994, PSLV emerged as the reliable and versatile workhorse launch vehicle of India with 39 consecutively successful missions by June 2017. During 1994-2017 period, the vehicle has launched 48 Indian satellites and 209 satellites for customers from abroad.


Polar Satellite Launch Vehicle (PSLV) is the third generation launch vehicle of India. It is the first Indian launch vehicle to be equipped with liquid stages.

  • It is a four stage launch vehicle.
  • A large solid rocket motor forming the first stage,
  • An earth storable liquid stage as the second stage,
  • A high performance solid rocket motor as third stage, and
  • A liquid stage with engines as fourth stage.
  • The vehicle successfully launched two spacecraft – Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013


Vehicle Variants and Launch Capability

    • No. of strap-on motors : Nil
    • Payload capability to SSPO (600 km) : 1019 Kg
  • No. of strap-on motors : Two
  • Payload capability to SSPO (600 km) : 1257 Kg
    • No. of strap-on motors : Four
    • No. of strap-on motors : Six
    • Payload capability to SSPO (600 km) : 1673 Kg
    • Payload capability to sub GTO (284 x 20650 km) : 1425 Kg
    • Payload capability to SSPO (600 km) : 1523 Kg

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


GSLV uses major components that are already proven in the Polar Satellite Launch Vehicle (PSLV) launch vehicles 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 geostationary transfer orbit (GTO) 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.



GSLV rockets using the Russian Cryogenic Stage (CS) are designated as the GSLV Mark I while versions using the indigenous Cryogenic Upper Stage (CUS) are designated the GSLV Mark II.[21] All GSLV launches have been conducted from the Satish Dhawan Space Centre in Sriharikota.


Geosynchronous Satellite Launch Vehicle Mark II (GSLV Mk II) is the largest launch vehicle developed by India, which is currently in operation. This fourth generation launch vehicle is a three stage vehicle with four liquid strap-ons. The indigenously developed cryogenic Upper Stage (CUS), which is flight proven, forms the third stage of GSLV Mk II. From January 2014, the vehicle has achieved four consecutive successes.

GSLV MkIII, chosen to launch Chandrayaan-2 spacecraft, is a three-stage heavy lift launch vehicle developed by ISRO. The vehicle has two solid strap-ons, a core liquid booster and a cryogenic upper stage.


  • GSLV Mk III is designed to carry 4 ton class of satellites into Geosynchronous Transfer Orbit (GTO) or about 10 tons to Low Earth Orbit (LEO), which is about twice the capability of the GSLV Mk II.
  • The first developmental flight of GSLV Mk III, the GSLV-Mk III-D1 successfully placed GSAT-19 satellite to a Geosynchronous Transfer Orbit (GTO) on June 05, 2017 from SDSC SHAR, Sriharikota.
  • GSLV MkIII-D2, the second developmental flight of GSLV MkIII successfully launched GSAT-29, a high throughput communication satellite on November 14, 2018 from Satish Dhawan Space Centre SHAR, Sriharikota
  • GSLV MkIII-M1, successfully injected Chandrayaan-2, India’s second Lunar Mission, in to Earth Parking Orbit on July 22, 2019 from Satish Dhawan Space Centre SHAR, Sriharikota



  • It strengthens INDIA’s soft power diplomacy
  • It reduces our dependency on foreign launch vehicles
  • It has multiplier effect on other innovations like chandrayan 2,human space flights etc
  • It leads to commercial
  • Self reliance


What’s the difference between liquid and solid-fuel rockets?

There are two main types of rockets: liquid-fuel and solid-fuel. Liquid-fuel rockets consist of a fuel and oxygen (or other oxidizer) in liquid state. They are combined in a combustion chamber and ignited. The fuel flow to the engine can be controlled, the amount of thrust produced can be regulated and the engine can be turned off or on as needed. Solid-fuel rockets consist of a fuel and oxidizer that are pre-mixed in a solid form. Once the solid fuel is ignited, the resulting thrust cannot be regulated or turned off. This fuel system is simpler, safer, and cheaper—but less efficient—than that of a liquid-fuel rocket.


Functioning of Engines

Cryogenic Engine:

Rocket engine needs enormous amount of thrust to escape Earth’s gravitational pull. However the chemicals used for engines are Hydrogen and Oxygen (Hydrogen used as a fuel, while Oxygen as a oxidiser) that produces a good thrust, found in Earth in the form of gas. Carrying hydrogen and oxygen in their gaseous form will require a bigger fuel chamber, which not only increase the size but also weight of the rockets and this will mean undertaking of impossible task to send a launch vehicle into space. So the solution is to use hydrogen and oxygen in their liquid form or in a cryogenic form which is easier to transport, as the volume of propellent decrease. As density increases in liquid form, more thrust can be produce in less burning time. Such engines are called Cryogenic engine.

Cryogenic fuel is used in rockets, spaceships or satellites because ordinary fuel can not be used in space due to the absence of an environment that supports combustion. This fuel requires storage at an extremely low temperature (-253 degree Celsius) to maintain them in a liquid state.


Semi-Cryogenic Engine:

Unlike a Cryogenic engine, a Semi Cryogenic engine uses Refined kerosene instead of liquid hydrogen. The liquid oxygen is used as a Oxidiser. That’s the advantage of using a Semi Cryogenic engine as it requires Refined Kerosene which is lighter than liquid fuel and can be stored in a normal temperature. Kerosene combined with liquid oxygen provide a higher thrust to the rocket. Refined Kerosene occupies less space, making it possible to carry more propellant in a Semi Cryogenic engines fuel compartment. A semi cryogenic engine is more powerful, environment friendly and cost effective as compared to a cryogenic engine.




GSLV (Geosynchronous Satellite launch Vehicle) uses a three stage launching system.

First Stage:- It is a solid stage which provides lift off to the rocket.

Second Stage:- It is a Liquid Stage.

Third Stage:- The third stage is the Cryogenic stage. This stage provides  a good amount of thrust so that we can put satellites in a geostationary orbit.


India developed the technology of Cryogenic Engine and to develop it further ISRO required to use a combination of Solid, Semi cryogenic and Cryogenic stage instead of a Combination of Solid, Liquid and Cryogenic stage. That  mean

First Stage:- Solid Stage.

Second Stage:- Semi Cryogenic Stage.

Third Stage:- Cryogenic Stage.

Using a semi cryogenic engine in second stage, GSLV will be able to provide more thrust and carry more weight into the space. India plan to use Semi Cryogenic Engine in GSLV (Geosynchronous Launch Vehicle), ULV (Unified Launch Vehicle) and  RLV (Reusable Launch Vehicle) in future.