On 12 April 2018, a satellite IRNSS 1I is launched by the ISRO. IRNSS is eighth successfully launched satellite of IRNSS constellation. The successful launching of IRNSS - 1I has held on Satish Dhawan Space Center ( SDSC) at 04:04 am. The satellite is launched with the help of PSLV - C41. So let we discuss PSLV in detail.


PSLV stands for Polar Satellite Launch Vehicle. Development of PSLV allow ISRO to launch Indian Remote Sensing (IRS) satellites into sun-synchronous orbits, a service that was, until the advent of the PSLV in 1993, commercially available only from Russia. PSLV used to launch a satellite of up to 1.7 tons in weight into the sun-synchronous polar orbit and to launch the satellite of up to 1.4 tons in weight into the Sub Geosynchronous Transfer Orbit. Various major components are used for the construction of PSLV . Similar components are also used on GSLV. PSLV has gained credence as a small satellite launcher due to its numerous multi-satellite deployment campaigns with auxiliary payloads usually ride sharing along with an Indian primary payload.

Four Stages Of PSLV

As the PSLV contains the four stages, so the vehicle is also known as a four-stage vehicle. Let us go through all the stage of PSLV, these are as follows:-

First Stage

The first stage of PSLV known as PS-1 also called the core stage. Core stage is to be integrated to PSLV uses the rocket motor in the first stage. The height of this stage is 20 meters or 66 ft long and around 138 tons of propellant is used in this stage. The diameter of the first stage of PSLV is 2.8 meter or 9.2 ft. In order to generate the required lift-off thrust, six large strap-on boosters are used in the XL version of PSLV, which are attached to the core stage. The height of each booster attached to core stage is 2 meters long and around 12 tons of solid propellant is used in these.Four boosters are ground-lit and the remaining two ignite 25 seconds after launch. The stage generates a maximum thrust of 4,846.9 kN (1,089,600 lbs) and has a nominal burn time of  110 seconds. Specific impulse noted of the first stage is 237 s (2.32 km/s) at sea level and 269 s (2.64 km/s) under vacuum. HTPB is used in it as fuel. The solid boosters carry 9 t (20,000 lb) or 12 t (26,000 lb) (for PSLV-XL configuration) propellant and produce 510 kN (110,000 lbs) and 719 kN (162,000 lbf) thrust respectively. Two strap-on boosters are equipped with SITVC for additional attitude control.There is no strap-on booster are used in PSLV-CA.

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Second Stage

The second stage of PSLV is stacked above the stage that known as core stage. The second stage of PSLV is known as PS-2. The height of this stage is 12.8 meters or 42 ft long and diameter of this stage is 2.8 m (9.2 ft). Around  42 tons of earth storable liquid propellants are used in this stage. The proven liquid engine which is known as High Thrust Vikash Engine ( HTVE ) is used in the second stage ( PS-2 ) of PSLV. The use of Vikas engine increases its thrust and reliability. PS-2 also contains two liquid propellants of about  41.5 t (91,000 lb). The two liquid propellants that used in PS-2 are:-  ( i )  unsymmetrical dimethylhydrazine (UDMH) used as fuel and nitrogen tetroxide (N2O4 ) as an oxidizer.The PS-2 stage generates the maximum thrust of 803.7 kN (180,700 lbs) and has a burn time of 133 seconds.Specific impulse noted for the second stage is 293 s (2.87 km/s).The engine is hydraulically gimbaled (±4°) to provide pitch and yaw control, while roll control is provided by two hot gas reaction control motors.

Third Stage

The third stage of PSLV is placed over the second stage. The third stage of PSLV is known as the PS-3. The height of this stage is 3.6 meters or 12 ft long and diameter of this stage is 2 meters or 6.6 ft. Around 7.6 tons of solid propellant is used in this stage.The solid rocket motor is used at this stage in order to provide high thrust after crossing atmospheric phase of the launch. The uppermost stage of the vehicle comprises two liquid engines.The PS-3 stage contains Hydroxyl-Terminated Polybutadiene - Based solid propellant ( HTPB ) used as fuel which generates the maximum thrust of 240 kN (54,000 lbs) and has a burn time of 83 seconds. Specific impulse noted for the third stage of PSLV is  295 s (2.89 km/s).This stage has a Kevlar-polyamide fiber case and a submerged nozzle equipped with a flex-bearing-seal gimbaled nozzle (±2°) thrust vector engine for pitch & yaw control. Roll control is provided by the fourth stage reaction control system (RCS).

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 Fourth Stage

The fourth stage of PSLV is known as PS-4. The height of the fourth stage is 3 meters or 9.8 ft long and diameter of this stage is  1.3 m (4.3 ft). Around 2.5 tons of earth-storable liquid propellant is used at this stage. The twin L-2-5 engine is used in the fourth stage.Monomethylhydrazine (MMH) and mixed oxides of nitrogen (MON) are used as fuel. Each engine generates 7.4 kN (1,700 lbf) thrust, hence it generates total 14.8 in thrust and is gimbaled (±3°) to provide pitch, yaw & roll control during powered flight. Coast phase attitude control is provided by RCS. The stage carries 2,500 kg (5,500 lb) of propellant in the PSLV and PSLV-XL and 2,100 kg (4,600 lb) in the PSLV-CA.Burn time for this stage is 425 seconds.Specific impulse is noted for PS-4 is  308 s (3.02 km/s).Payload fairing is attached above the fourth stage. In which the spacecraft is housed.

Variants Of PSLV

ISRO has constructed a number of variants of PSLV to for different mission requirements. There are currently three operational versions of the PSLV. The three variants of PSLV are:-


PSLV - G is the standard version of the PSLV. PSLV - G consist four stages. These four stages using solid and liquid propulsion systems alternately and also uses the six strap-on boosters.PSLV - G is able  to launch 1,678 kg (3,699 lb) to 622 km (386 mi) into sun-synchronous orbit.

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Out of PSLV-CA, CA stands for "Core Alone".The  PSLV - CA does not contain any strap-on booster. Two small roll control modules and two first-stage motor control injection tanks were still attached to the side of the first stage.The fourth stage of the CA variant contains 400 kg (880 lb) of propellant.PSLV - CA is able to launch 1,100 kg (2,400 lb) to 622 km (386 mi) satellite into Sun-synchronous orbit.


PSLV-XL is known as the upgraded version of the standard configuration of PSLV. PSLV-XL boosted by using more powerful stretched strap-on boosters.Weighing 320 t (710,000 lb) at lift-off, the vehicle uses larger strap-on motors (PSOM-XL) to achieve higher payload capability. On 29 December 2005, ISRO successfully tested the improved version of strap-on booster for the PSLV. The first use of PSLV-XL was the launch of Chandrayaan-1 by PSLV C11.

Development Of PSLV

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 and ISRO Inertial System Unit ( IISU ) has a special contribution in the development of PSLV. The inertial navigation systems are developed by ISRO Inertial Systems Unit (IISU) at Thiruvananthapuram. The liquid propulsion stages for the second and fourth stages of PSLV as well as the Reaction control systems (RCS) are developed by the Liquid Propulsion Systems Centre (LPSC) at Mahendragiri near Tirunelveli, Tamil Nadu. The solid propellant motors are processed at Satish Dhawan Space Centre (SHAR) at Sriharikota, Andhra Pradesh which also carries out launch operations.Realising each launch is a herculean and present challenge both technical and logistics in nature. To meet this, ISRO over the year has natured a healthy ecosystem of Indian industries which today play a major role in the realization of the PSLV by manufacturing and supplying various important parts of the rocket.