Liquid Stages of PSLV

PSLV is a 44.4 m high and 2.8 m diameter launch vehicle with a lift-off weight of 320 tonnes. The vehicle is configured in four stages; the second (PS2) and fourth (PS4) Stages are powered by Liquid Engines.
LPSC is responsible for the delivery of Control Power Plants for the first stage booster (PS1), earth storeable liquid stages such as second stage (PS2) and fourth stage (PS4).

Second Stage of PSLV (PS2 Stage)

This stage is powered by a turbo pump fed, radiation cooled liquid engine (Vikas engine) using Nitrogen Tetroxide (N₂O₄) and Unsymmetrical Di-Methyl Hydrazine (UDMH) with 25% Hydrazine hydrate (This combination is referred as UH25) as propellants. During PSLV flight, this Stage gets ignited at an altitude of 50 km and boosts the rest of the PSLV stages and the satellite.

Specifications :		PS2 Stage
Thrust	799 kN
Burn Duration	150 s
Propellants	N2O4 / UH25
Propellant Loading	42 t
Stage Diameter	2.8 m
Stage Height	12 m
PS2 Stage consists of subsystems like Vikas engine, tankage with common bulk head, thrust frame and inter-stages, pressurisation systems, command system, fill and drain system, feed purge and flush system, pogo suppressor command system, gimbal control system, hot gas roll control system, pneumatic umbilical system, slosh baffles etc.

GSLV is capable of launching 2200 kg class communication satellites into the Geo Transfer Orbit (GTO). GSLV is a three Stage vehicle. LPSC is responsible for the realisation and delivery of four L40 strap-on Stages, liquid second Stage and the Cryogenic Upper Stage of the GSLV.

Second Stage of GSLV (GS2 Stage)

Strap-on Stages of GSLV (L40 Stages)

Cryo Stage systems comprise of insulated propellant tanks, booster pumps, inter-Stage structures, fill and drain systems, pressurization systems, gas bottles, command block, igniters, pyro valves and cold gas orientation and stabilisation systems.
Indigenous cryogenic upper stage was successfully flight tested in GSLV D5 mission on 5^th January, 2014.

This new generation launch vehicle developed by ISRO can place 4000 kg class satellites in the GTO. LPSC is responsible for design, development and realization of Earth storable liquid core Stage (L110 Stage) and a powerful Cryogenic Upper Stage (C25 Stage).

L110 Stage

L110 Stage is the largest liquid Stage realized by ISRO. It is the core Stage of GSLV-Mk III which uses two high thrust Vikas engines to generate a combined thrust of 1692 kN for a burn duration of 194 s during the flight. The subsystems of the Stage include pressurization modules, command system module, remote fill and drain system, sit on umbilical system etc. Development Stage hot tests were successfully carried out for a duration of 200 s.

CE20 engine uses independent turbo pumps delivering high pressure propellants to the regeneratively cooled thrust chamber. Small quantities of propellants from the pumps are diverted to Gas Generator where the propellants are ignited and the hot gases produced are used to drive the turbines. The Stage systems include propellant tanks, structures, flow control components, feed lines, mixture ratio control, Pogo control, engine gimbal control etc.
The engines are hot tested in ground including simulation of high altitude condition as part of development.

Small Satellite Launch Vehicle (SSLV) is a three stage Launch Vehicle capable of launching ~500 kg satellite into 500 km planar orbit from First Launch pad (FLP), SDSC/SHAR. SSLV is configured with three solid propulsion stages and liquid propulsion based Velocity Trimming Module (VTM) as terminal stage for precise satellite injection. This vehicle provides low-cost access to Space, offers low turn-around time and flexibility in accommodating multiple satellites, and demands minimal launch infrastructure. SSLV is 2 m in diameter and 34 m in length with liftoff weight of ~120 tons.
VTM is planned for precise injection of satellite injection taking into account the performance deviations from the lower stages. It is also planned for roll control during the 1st stage as well as SS2 and SS3 thrusting phase. It is required for pitch/yaw and roll control during coasting phase between stages and during VTM phase. VTM is configured as blowdown bi-propellant system with 55 kg of MMH & MON-3.

LPSC delivers the mono-propellant propulsion systems for IRS satellites. The IRS propulsion package consists of two types of mono-propellant catalytic thrusters for minor orbital corrections and station keeping/ attitude control, associated propellant tanks, feedlines and flow control components. Twelve AOCS thrusters with four 1 N and two 11 N thrusters in one chain with a corresponding configuration in another chain as redundant are assembled.

ISRO undertakes scientific missions for research in areas like astronomy, astrophysics, planetary and earth sciences, atmospheric sciences and theoretical physics. The Liquid Propulsion Systems Centre (LPSC) is integral to the success of ISRO's major missions, providing cutting-edge propulsion technologies essential for mission-critical manoeuvres. Specializing in the development of liquid propulsion systems, LPSC designs, realizes and tests, engines and stages that power launch vehicles and spacecraft. In missions like Chandrayaan-1, 2 & 3, Mars Orbiter Mission, and Aditya L1, LPSC's propulsion systems enable precise orbital insertions, attitude control, and trajectory corrections. The center's advancements in cryogenic engines, bi-propellant engines, and electric propulsion are pivotal in enhancing ISRO's capability to undertake complex interplanetary missions and sustained exploration, reflecting LPSC's critical role in advancing India's space endeavours.

Chandrayaan-1 Mission:

Chandrayaan-1, India's first mission to Moon, was launched successfully on 22^nd October, 2008 in PSLV C11. The spacecraft orbitted around the Moon at a height of 100 km from the lunar surface for chemical, mineralogical and photo-geologic mapping of the Moon.

The PSLV C11 placed the Chandrayaan-1 spacecraft precisely into geostationary transfer orbit (GTO) with an apogee of 22,860 km and a perigee of 255 km. LPSC delivered PS2 & PS4 Stages and five Control Power Plants (PS1 RCS x 2 Nos., PS1 SITVC, PS0 SITVC x 2 Nos.) for the PSLV C11. The details of above deliverables are:

• PS2 Stage: The Stage is powered by Vikas Engine producing a thrust of 80t and has a propellant loading of 42t. The PS2 Stage operated for about 150s in this mission.
• PS4 Stage: It is powered by two PS4 engines each 0.73t thrust and 2.5t propellant loading.

The control power plants provide the necessary control of the Vehicle (viz. Pitch, Yaw and Roll) during the PS1 regime. Two numbers of Roll Control System Packages, 2 Strap on SITVC (Side Injection Thrust Vector Control) systems and one PS1 SITVC system were used in this mission.

Bipropellant propulsion system of eight nos. of 22 N AOCS thrusters and one LAM engine were delivered and integrated by LPSC for Chandrayaan-1. LAM was fired successfully for ten times for a cumulative duration of 4589 s in this Mission.

Mars Orbiter Mission (MOM):

Mars Orbiter Mission (MOM), India's first interplanetary mission to planet Mars was launched on board PSLV C25 on 5^th November, 2013. ISRO has become the fourth space agency to successfully send a spacecraft to Mars orbit.

The PSLV C25 placed the Mars Orbiter Mission spacecraft precisely into a highly elliptical Earth orbit with a perigee (nearest point to Earth) of 250 km and an apogee (farthest point to Earth) of 23,500 km with an inclination of 19.2 degree with respect to the equator. LPSC delivered PS2 & PS4 Stages and five Control Power Plants (PS1 RCS x 2 Nos., PS1 SITVC, PS0 SITVC x 2 Nos.) for the PSLV C25. The details of above deliverables are:

• PS2 Stage: The Stage is powered by Vikas Engine producing a thrust of 80t and has a propellant loading of 42t. The PS2 Stage operated for about 150s in this mission.
• PS4 Stage: It is powered by two PS4 engines each 0.73t thrust and 2.5t propellant loading.

The control power plants provide the necessary control of the Vehicle (viz. Pitch, Yaw and Roll) during the PS1 regime. Two numbers of Roll Control System Packages, 2 Strap on SITVC (Side Injection Thrust Vector Control) systems and one PS1 SITVC system were used in this mission.

Astrosat Mission:

AstroSat is India's first dedicated Space Astronomy Observatory launched by PSLV-C30 (XL). It carries a total of five scientific payloads enabling imaging, studying temporal and spectral properties of galactic and extra- galactic cosmic sources in a wide range of wavelengths on a common platform.

The PSLV C30 placed the Astrosat spacecraft precisely into a 650 km orbit of 6 deg inclination to the equator. LPSC delivered PS2 & PS4 Stages and five Control Power Plants (PS1 RCS x 2 Nos., PS1 SITVC, PS0 SITVC x 2 Nos.) for the PSLV C30. The details of above deliverables are:

• PS2 Stage: The Stage is powered by Vikas Engine producing a thrust of 80t and has a propellant loading of 42t. The PS2 Stage operated for about 150s in this mission.
• PS4 Stage:It is powered by two PS4 engines each 0.73t thrust and 2.5t propellant loading.

The control power plants provide the necessary control of the Vehicle (viz. Pitch, Yaw and Roll) during the PS1 regime. Two numbers of Roll Control System Packages, 2 Strap on SITVC (Side Injection Thrust Vector Control) systems and one PS1 SITVC system were used in this mission.

Eight Nos. of 11 N monopropellant AOCS thrusters-based propulsion system for the Astrosat spacecraft was delivered and integrated for this mission by LPSC.

Chandrayaan-2 mission:

India's Geosynchronous Satellite Launch Vehicle, LVM3-M1, successfully launched Chandrayaan-2 spacecraft on 22^nd July, 2019 into its planned orbit with a perigee of 169.7 km and an apogee of 45,475 km. This mission was a highly complex mission, which represents a significant technological leap compared to the previous missions of ISRO, which brought together an Orbiter, Lander and Rover with the goal of exploring south pole of the Moon.

• L110 Stage: The core liquid stage for LVM3-M1 was designed, developed and realized by LPSC. This Stage is loaded with ~ 114t of Earth Storable propellants (N₂O₄ and UH25) and powered by twin Vikas Engines.
• C25 Stage:The terminal stage of LVM3 was also designed, developed and realized by LPSC. This Stage is loaded with 28.5t of Cryogenic Propellants viz. Liquid Hydrogen and Liquid Oxygen, which are stored in the propellant tank at 77K and 20K respectively.
• Fluid Control Components: Fluid control components and modules for S200 Solid Stage's Flex Nozzle Control (FNC) system and sit-on umbilicals used for servicing the S200 FNC system etc. were designed & realised by LPSC.
• Orbiter Module propulsion system: Chandrayaaan-3 Propulsion Module with one 440N LAM engine and eight 22N thrusters was configured by LPSC with Propellant tanks and flow control components. The LAM engine in the Orbiter was successfully fired 11 times for a cumulative duration of 10171 s. Chandrayaan-2 orbiter and lander propulsion systems were delivered by LPSC. The Orbiter has a life of in excess of 7 years due to excellent performance of liquid propulsion systems.
• Lander Module Propulsion system: The bipropellant throttleable lander propulsion system for Chandrayaan-2 mission included Four 800 N throttleable engine, one 800N thrust central engine, eight nos. of 58 N thrusters. The Lander propulsion system also include the throttleable Engine Flow Control Valve (TFCV) and Throttleable Engine Control Electronic Module (TECEM), which was designed and developed by LPSC. Extensive testing of the engines along with the TFCV & TECEM was carried out for qualification of these systems.
  

Chandrayaan-2 mission is a highly complex mission, which represents a significant technological leap compared to the previous missions of ISRO. It comprised an Orbiter, Lander and Rover to explore the unexplored South Pole of the Moon. After the injection of Chandrayaan-2, a series of maneuvers were carried out to raise its orbit and on 14^th August, 2019, following Trans Lunar Insertion (TLI) maneuver, the spacecraft escaped from orbiting the earth and followed a path that took it to the vicinity of the Moon. On 20^th August, 2019, Chandrayaan-2 was successfully inserted into lunar orbit. While orbiting the moon in a 100 km lunar polar orbit, on 2^nd September, 2019, Vikram Lander was separated from the Orbiter in preparation for landing. Subsequently, two de-orbit maneuvers were performed on Vikram Lander so as to change its orbit and begin circling the moon in a 100 km x 35 km orbit. Vikram Lander descent was as planned and normal performance was observed upto an altitude of 2.1 km. Subsequently communication from lander to the ground stations was lost.

In addition, Vikram Lander underwent a hop experiment. On command, it fired the engines, elevated itself by about 40 cm and landed safely at a distance of 30-40 cm away. In another unique experiment, the Propulsion Module of Chandrayaan-3 was moved from an orbit around Moon to an orbit around Earth.

• Bipropellant based Spacecraft Propulsion system: The Spacecraft Propulsion System consisting of primarily one LAM engine, 8 numbers of 22N, 4 numbers of 10N thrusters and associated propulsion elements like 390L propellant tanks, precision control components etc.
  
• In addition, the Centre had also delivered 220 numbers of critical sensors which were used in both Launch Vehicle and Spacecraft.

• Spacecraft propulsion system performance was as expected during the successful four Earth-bound manoeuvres for cumulative duration of 2715.3s followed by Trans-Lagrangean point1 (L1) Insertion for a duration of 590.5s.
• A Trajectory Correction Maneuver (TCM) was performed on 5^th October, 2023 to ensure that the spacecraft is on its intended path towards the Halo orbit insertion around L1. Final insertion to Halo Orbit planned on 7^th January, 2024. Thus India's first solar observatory is in its journey to the destination of Sun-Earth L1 point (1.5 million km away from Earth, directed towards the Sun, which is about 1% of the Earth-Sun distance) using the Spacecraft propulsion system delivered by LPSC.

• PS2 Stage: The Stage is powered by Vikas Engine producing a thrust of 80t and has a propellant loading of 42t. The PS2 Stage operated for about 150s in this mission.
• PS4 Stage: It is powered by two PS4 engines each 0.73t thrust and 2.5t propellant loading. After injection of XPOSAT, the PS4 stage was re-started twice to reduce the orbit into 350 km circular orbit to maintain in 3-axis stabilized mode for Orbital Platform (OP) experiments. LPSC also delivered and integrated the Orbital Platform Attitude Control thrusters (OPACS) also for this mission. The PSLV Orbital Experimental Module-3 (POEM-3) experiment was executed meeting the objective of 10 identified payloads, delivered and integrated by ISRO and IN-SPACe.
• Control Power Plants (CPP): The control power plants provide the necessary control of the Vehicle (viz. Pitch, Yaw and Roll) during the PS1 regime. Two numbers of Roll Control System Packages, 2 Strap on SITVC (Side Injection Thrust Vector Control) systems and one PS1 SITVC system were used in this mission.
• Spacecraft Propulsion system: Eight Nos. of 1N monopropellant AOCS thrusters-based propulsion system for the XPoSat spacecraft was delivered and integrated for this mission by LPSC.