GSLV Mk. II Launch Vehicle - spaceflight101.comGSLV performed as planned and successfully delivered the GSAT-2 payload to Geosynchronous Transfer Orbit. The next GSLV launch came in

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GSLV Mk. II Launch Vehicle

The Geosynchronous Satellite Launch Vehicle,

better known by its abbreviation GSLV, is an Indian

expendable launch system that was developed and

is operated by the Indian Space Research

Organization.

The GSLV project was initiated back in the 1990s

when India determined that it needed its own

launch capability for Geosynchronous Satellites to

become independent from other launch providers.

At the time, India was relying on Russian/Soviet

launch vehicles for heavy satellite launches. With

the emergence of commercial launch providers,

such as Arianespace, India shifted its GSO Satellites

to those while GSLV was being developed.

The launch system uses a large number of heritage

components already employed on the Polar

Satellite Launch Vehicle that first flew in 1993. The

three-stage GSLV has an improved performance

over four-stage PSLV with the addition of strap-on

liquid-fueled boosters and a cryogenic upper stage.

GSLV uses a combination of solid fueled, liquid-fueled and cryogenic stages. The vehicle weighs 414,000

Kilograms at liftoff standing 49 meters tall with a core diameter of 2.8 meters.

The first stage is the S139 solid-fueled

stage that is also used on PSLV. Around the

core, four strap-on liquid-fueled boosters

are mounted each featuring a Vikas engine

using storable propellants. The second

stage is also a storable propellant stage

using a single modified Vikas engine while

the third stage is a cryogenic stage using

liquid Oxygen and liquid Hydrogen that is

consumed by an ICE engine. The vehicle

can deploy payloads of up to 2,500

Kilograms to a Geosynchronous Transfer

Orbit, Low Earth Orbit Capability is

5,000kg. GSLV is operated from the Satish Dhawan Space Center. Photos: ISRO



Over the course of its development, GSLV flew in various

configurations being designated Mk I a, b and c, and Mk II

with Mk III being the successor to the first generation of GSLV

launchers scheduled to make its first flight in 2014.

In the Mk Ia configuration, the most basic version of the

launcher that is now retired, GSLV used a 125-ton Core Stage

and a Russian-built Cryogenic Upper Stage since the Indian-

developed cryogenic stage required more time to be designed

and built. Mk Ia flew its first development flight on April 18,

2001 marking the first launch of the GSLV class vehicle. The

flight was only a partial success as the launcher delivered its

payload, the GSAT-1 Communications Satellite, to a lower-

than planned orbit due to a shortfall in performance either

caused by the vehicle’s guidance system or a premature

shutdown of the third stage. GSAT-1 ended up in a lower orbit

and due to a design flaw in its propulsion system, was unable

to reach Geostationary Orbit rendering its useless for its

original purpose.

In May 2003, Mk Ia flew for the second time. On that mission,

GSLV performed as planned and successfully delivered the

GSAT-2 payload to Geosynchronous Transfer Orbit. The next GSLV launch came in September 2004 and was the

first flight of the Mk Ib configuration that still used the Russian upper stage, but featured the 139-ton first

stage. The flight was a success and delivered the GSAT-3 spacecraft to its intended orbit to serve as

experimental communications satellite.

On its next flight in July 2006, GSLV suffered another

failure. Shortly after launch, the vehicle had to be

destroyed by Range Safety Personnel because it veered

off its pre-planned course due to the failure of one of

the boosters. Remains of the rocket and the INSAT-4C

payload fell into the Bay of Bengal.

GSLV Mk Ib flew again in September 2007 – successfully

reaching orbit, but placing the INSAT-4CR satellite into a

lower-than-planned orbit at a higher inclination due to a

guidance system issue. The spacecraft reached its orbit

using its own propulsion system and became fully

operational, making this mission a partial success.

Photos: ISRO



The sixth flight of the GSLV marked the first flight

of the Mk II variant that uses the Indian-built

cryogenic upper stage. The flight test was not

successful as the rocket encountered a

malfunction of the Fuel Booster Turbo Pump on

its third stage causing the loss of the vehicle and

GSAT-4 satellite. Flight 2 of the Mk II version was

attempted in 2010 and marked another failure as

the vehicle was destroyed by the Range Safety

Officer after a loss of control that was the result

of a structural failure.

After that, the GSLV launch system underwent a thorough review and improvements were made to its

Guidance System and Upper Stage to increase its reliability. The GSLV Return to Flight Mission was successfully

performed in 2014.

GSLV Specifications

The Geosynchronous Satellite Launch Vehicle in its Mk II configuration stands 49 meters tall, with a Core

Diameter of 2.8 meters and a liftoff mass of about 414,000 Kilograms.

The vehicle features three stages plus an optional fourth stage. The first stage is a solid-fueled stage holding

138,000kg of propellant.

Around the Core Stage, four strap-on, liquid-fueled boosters are installed. One of the oddities about GSLV is

that the four boosters burn longer than the Core Stage does. The second stage of the vehicle is liquid-fueled

and uses storable propellants.

The upper stage is a cryogenic stage that uses LOX and LH2 as propellants. Photo: ISRO

Type GSLV

Height 49m

Diameter 2.8m

Span 6.9m

Launch Mass 414,000kg

Stage 1 S139

Boosters 4 x L40

Stage 2 GS2

Stage 3 GS3

Mass to LEO 5,000kg

Mass to GTO 2,500kg



First Stage

The Core Stage of the GSLV is called S139 and is derived

from the PS1 Core Stage of the Polar Satellite Launch

Vehicle.

The only change is the removal of the Secondary Injection

Thrust Vector Control System that is needed on PSLV. On

GSLV, the Boosters are used to control the vehicle during

first stage flight, thus eliminating the need for a Thrust

Vector Control System on the core stage. Adding SITVC

onto the GSLV is optional and was only performed on its

very first flight.

The S139 has an inert mass of 28,300kg and holds

138,000kg of HTPB-based (Hydroxyl-terminated

polybutadiene) solid propellant.

The stage is 20.1 meters long and 2.8 meters in diameter

featuring a maraging steel case. It has a vacuum thrust of 4,860 Kilonewtons (495,600kg) and burns for 107

seconds.

The stage separates with the four boosters once

they are reaching depletion. Staging between S139

and GS2 (Stage 2) is accomplished in hot-staging

mode – the second stage ignites 1.6 seconds

ahead of Booster Shutdown.

When the boosters have shut down, the two

stages are separated by flexible linear shaped

charges that pyrotechnically separate the two

stages allowing the spent first stage and boosters

to be pushed away by the second stage.

This maneuver comes at the cost of propellant and

performance but minimizes propellant unsettling

that occurs when igniting in coast mode.

Photo: First Stage Nozzle-End Segment (ISRO)

Type S139

Inert Mass 28,300kg


Diameter 2.8m

Length 20.13m

Case Material Maraging Steel

Propellant Solid – HTPB Based

Propellant Mass 138,000kg

Guidance From Upper Stage

Propulsion S139 Solid Rocket Motor

Thrust (Vacuum) 4,860kN

Impulse 105sec

Burn Time 106.9sec

Attitude Control via Boosters, SITVC (Optional)

Stage Separation Flexible Linear Shaped Charge

Hot Staging



Boosters

Four liquid-fueled boosters are clustered around the

Core Stage of the vehicle. Each is 2.1 meters in

diameter and 19.7 meters long facilitating two

Aluminum propellant tanks that can hold about 42,000

Kilograms of Nitrogen Tetroxide Oxidizer and UH25

fuel – a mixture of 75% Unsymmetrical

Dimethylhydrazine and 25% Hydrazine Hydrate. (UH

25 prevents combustion instability)

Each Booster is equipped with a single Vikas 2 engine which is a Viking engine that was used aboard the

European Ariane 1 launcher and is now manufactured under license in India. The Vikas engine used on GSLV is

a lightly modified Viking 2 engine. It is 2.87 meters long and 0.99m in diameter and weighs 900 Kilograms. The

engine operates at a Chamber Pressure of 58.5 bar and uses an Oxidizer to Fuel Ratio of 1.7. Vikas 2 delivers a

thrust of 763 Kilonewtons (77,800kg). The four boosters have a burn time of 148 seconds.

The Vikas engines on each booster can be gimbaled in a single plane allowing three-axis control during first

stage flight.

The four boosters ignite 4.6 seconds prior to the first stage to allow the Vikas engines to reach operational

conditions before the Core Stage is ignited and the rocket blasts off. In flight, the four boosters continue to

burn after first stage shutdown and are separated from the vehicle with the first stage. The advantage of this

simpler design is that a Booster Separation event is avoided, but it comes at the cost of performance because

the four boosters have to propel the first stage once it has burned out which represents nearly 30 tonnes of

dead weight.

Photo: ISRO

# Boosters 4

Type LH40

Length 19.7m

Diameter 2.1m

Inert Mass ~5,600kg


Tank Material Aluminum Alloy

Fuel UH25 – 75% UMDH, 25% Diazane

Oxidizer Nitrogen Tetroxide

Propulsion 1 Vikas 2

Thrust 763kN

Impulse 293 sec

Engine Dry Weight 900kg

Engine Length 2.87m

Engine Diameter 0.99m

Burn Time 148sec

Chamber Pressure 58.5bar

Mixture Ratio 1.7 (Ox/Fuel)

Attitude Control Single-Plane Engine Gimbaling

Stage Separation With Core Stage



Second Stage

The second stage of the GSLV launcher, designated

GS2, also uses hypergolic propellants – NTO and UH25.

It has a launch mass of 44,900kg being 11.6m long and

2.8m in diameter.

The tanks are made of Aluminum alloy and hold

39,400kg of storable propellants that are being

consumed by a single Vikas 4 engine. The engine is based on the Viking 4 of the Ariane 1 launcher and also

features slight modifications. It is optimized for operation in vacuum conditions with an extended nozzle that

has an area ratio of 31.

Vikas 4 is 3.51m long and 1.7m in diameter, weighing about 900kg and generating 799 Kilonewtons of vacuum

thrust (81,500 Kilograms) over the course of its 158-second burn. It operates at an Ox. to Fuel Ratio of 1.7 that

can be optimized by the Flight Control System.

Vehicle Control during the second stage burn its provided by gimbaling the main engine by up to 4 degrees for

pitch and yaw. Roll Control is provided by a Cold Gas Thruster System. The second and third stage again

separate in a hot-staging mode – the second stage shuts down and at the same time, the ignition of the third

stage and the stage separation mechanism, a Merman Band Sep System, are initiated. Photo: ISRO

Type GS2 – L37.5H

Inert Mass ~5,500kg


Length 11.56m

Diameter 2.8m


Fuel UH25 – 75% UMDH, 25% Diazane

Oxidizer Nitrogen Tetroxide


Guidance From Upper Stage

Propulsion 1 Vikas 4

Thrust (Vacuum) 799kN

Impulse 293s


Engine Length 3.51m


Burn Time 158sec

Chamber Pressure 58.5bar

Mixture Ratio 1.7 (Ox/Fuel) – MR Optimization

Area Ratio 31

Prop Flow Rate 278.04kg/s

Attitude Control Main Engine Gimbaling, Roll RCS

Stage Separation Merman Band



Third Stage

The third stage or GS3 of the GSLV Mk II is an Indian-built cryogenic upper stage. It is 8.7 meters long and 2.8

meters in diameter featuring two Aluminum Alloy Tanks that hold about 12,800 Kilograms of Liquid Hydrogen

and Liquid Oxygen. The inert mass of the third stage is about 2,500kg.

It is powered by a single ICE (Indian Cryogenic Engine) or CE-7.5. The engine is a staged combustion type

engine. Some of the propellant is used to power the turbopump of the engine before being injected into the

main combustion chamber along with the rest of the propellant. The turbopump spins at about 42,000 rpm.

The engine weighs 445 Kilograms and is 2.14 meters long and 1.56 meters in diameter operating at a chamber

pressure of 58bar. It provides a nominal thrust of 73.5 Kilonewtons (7,500kg), but can be throttled up to

93.1kN (9,500kg).

Usually, the engine operates at a higher thrust level for the first 300 seconds of its burn before throttling down

to nominal thrust for the remainder of its firing that can be up to 1,000 seconds in duration. Vehicle control is

provided by two vernier jets that can be swiveled in all directions to provide three-axis control.

Each vernier provides 2kN (204kg) of thrust. During Coast Phases, a cold gas reaction control system is used for

vehicle stabilization and re-orientations. Photo: ISRO

Type GS3 – C15

Inert Mass ~2,500kg

Launch Mass ~15,300kg

Length 8.7m

Diameter 2.8m


Fuel Liquid Hydrogen

Oxidizer Liquid Oxygen


Guidance Inertial Platform, Closed-Loop

Propulsion 1 ICE (CE-7.5)

Cycle Staged Combustion

Thrust (Vacuum) 73.5 to 93.1kN

Impulse 454sec


Engine Length 2.14m


Burn Time Up to 1,000sec

Chamber Pressure 58bar

Attitude Control 2 Vernier Jets, each 2kN

RCS for Coast Phases

Stage Separation Merman Band, Hot Staging



The third stage can be re-ignited in flight. The spacecraft is separated by

spring thrusters mounted at the separation interface with the third

stage. The third stage of the launch vehicle also houses the flight

computers and the inertial guidance platform of the GSLV.

The control system was developed and built in India. GSLV uses a

Redundant Strap Down Inertial Navigation System/Inertial Guidance

System that is housed in the equipment bay of the third stage. The

digital control system of the launcher uses closed-loop guidance

throughout the flight to ensure accurate injections into the target orbit.

Also mounted on the third stage is the communications system of the

launch vehicle consisting of an S-Band system for telemetry downlink

and a C-Band transponder that allows radar tracking and preliminary

orbit determination. The communications link is also used for range

safety / flight termination that uses a dedicated system that is located on

all stages of the vehicle and features separate avionics.

Payload Fairing

The Payload Fairing, or “Heat Shield” as ISRO refers to it, is positioned on

top of the stacked vehicle and its integrated Payload. It protects the

spacecraft against aerodynamic, thermal and acoustic environments that

the vehicle experiences during atmospheric flight. When the launcher has

left the atmosphere, the fairing is jettisoned by pyrotechnical initiated

systems. Separating the fairing as early as possible increases launcher performance.

The fairing of the GSLV is 3.4 meters in

diameter and 7.8 meters in length

offering enough space for a variety of

payloads that are in the weight-category

of GSLV. The fairing is made of Aluminum

Alloy featuring acoustic absorption

blankets.

The fairing is separated at an altitude of

115 Kilometers. Separation is

accomplished by a linear piston cylinder

separation and jettisoning mechanism

(zip cord) running along the full length of

the PLF and a clamp and joint at the base of the fairing. Both systems are pyrotechnically initiated. The gas

pressure generated by the zip cord expands a rubber bellow that pushes that piston and cylinder apart, pushing

the fairing halves laterally away from the launcher. Photos: ISRO

Diameter 3.4m

Length 7.8m

Construction Aluminum Alloy

Sep Altitude 115km



Optional Fourth Stage

The GSLV launcher can be outfitted with a fourth stage that could serve as apogee module to boost a satellite

or spacecraft into its final orbit or trajectory. Usually, satellites and spacecraft are equipped with their own

propulsion systems that are capable of performing apogee maneuvers so that the fourth stage is not required.

A possible fourth stage design for GSLV closely resembles the fourth stage of the PSLV launcher that uses

storable propellants to provide precise injection capability.

Photo: ISRO

Documents

GSLV Mk. II Launch Vehicle - spaceflight101.comGSLV performed as planned and successfully delivered the GSAT-2 payload to Geosynchronous Transfer Orbit. The next GSLV launch came in