Sridhar NarayananJun 02, 2017

India enters the big league with new, powerful rocket

GSLV-MK3's first fully operational flight scheduled for June 5

The countdown has begun for the first fully operational flight of the Indian Space Research Organization’s most powerful rocket to date: The Geostationary Launch Vehicle Mark 3, or GSLV-MK3.

Liftoff is scheduled for Monday, June 5 at 7:58 a.m. EDT (11:58 UTC, 17:28 local time in India). The rocket will launch from the second launch pad at the Satish Dhawan Space Center at Sriharikota on the southeastern coast of India. 

The GSLV-MK3 can haul about 8 metric tons to low-Earth orbit and 4 metric tons to geostationary transfer orbit, putting its capacity just shy of the no-booster version of United Launch Alliance’s stalwart Atlas V.

It is also the first new launcher for ISRO in more than a decade. The GSLV-MK3 uses a completely new design from the ground up, with little resemblance to India’s workhorse Polar Satellite Launch Vehicle (PSLV) and its variants, or the GSLV-MK1 and GSLV-MK2 vehicles that evolved from the PSLV design.

GSLV-MK3 launcher
GSLV-MK3 launcher Fully assembled GSLV-MK3 launcher on its launch pad at the Satish Dhawan Space Center. ISRO

A short history of the Indian Space Research Organization

The Indian Space Research Organization (ISRO) traces its origins to 1962, when its predecessor, the Indian National Committee for Space Research, was established. It set up the first rocket launch station at the southern tip of the Indian peninsula at Thumba, from where a NASA suborbital sounding rocket, the Nike Apache, was launched in 1963. This site served as an active launch station for sounding rockets from NASA, the French space organization CNES, the Russian space agency, and also India’s indigenously developed Rohini-series sounding rockets for upper atmosphere research.

ISOR rocket component transportation
ISOR rocket component transportation Rocket component being transported on a bicycle in the early days of the Indian Space Program. ISRO

In 1969, the Department of Space and ISRO were formed, and a program to develop an orbital launcher was initiated soon thereafter, along with programs for developing satellites and their applications. This led to the first test of the all-solid four stage SLV-3 launcher in 1979, which was unsuccessful, but quickly followed by a successful test in 1980. After two other tests of this launcher, ISRO developed a follow-on launcher called the Augmented Satellite Launch Vehicle, or ASLV.

SLV-3 launch vehicle lifting off
SLV-3 launch vehicle lifting off ISRO

The ASLV rocket added two strap-on solid-fueled boosters to the SLV-3 and used a slightly enlarged payload fairing to accommodate bigger payloads. Both the SLV-3 and ASLV were technology demonstrator vehicles that could place 40 and 150 kilograms, respectively into low-Earth orbit.

Fully assembled ASLV on its launch pedestal
Fully assembled ASLV on its launch pedestal ISRO

The PSLV, India’s first operational launcher, arrives

The first operational launcher from the ISRO stable was the Polar Satellite Launch Vehicle (PSLV), which debuted in 1993. While the first test of this launcher was not successful, it has had a remarkably successful run of 37 flawless launches since then, with only a single launch termed a partial success.

The PSLV was developed to place a payload of 1 metric tons into an 800-kilometer-high polar, sun-synchronous orbit, which is ideal for Earth observation satellites. The rocket’s original configuration was a four-stage vehicle with two solid stages and two hypergolic liquid stages, as well as solid-fueled strap-on boosters. Since its debut, the PSLV has evolved to have three variants with varying configurations to achieve different payload capacities. The most powerful PSLV-XL version has launched geostationary communications and weather satellites, satellites for India’s own regional version of the Global Positioning System (GPS), an orbiter around the Moon, and even a Mars orbiter, in addition to the Earth observation and scientific satellites it was originally designed to launch.

PSLV-XL lifting off from the Satish Dhawan Space Center
PSLV-XL lifting off from the Satish Dhawan Space Center ISRO

Developing cryogenic engine technology: the GSLV

The follow-on launcher to the PSLV was the Geostationary Launch Vehicle, or GSLV. This vehicle retained the two lower stages of the PSLV and replaced its two upper stages with a more powerful cryogenic stage, and also replaced the solid strap-on boosters with more powerful hypergolic liquid boosters. This launcher, designed to place 2 metric tons into geostationary transfer orbit (GTO), has had a more checkered history. The project was delayed due to international pressure on Russia, which was contracted to transfer cryogenic engine technology for the GSLV’s upper stage to ISRO. Due to this pressure, Russia backed out of the contract and instead supplied India with seven, off-the-shelf cryogenic engines without transfer of technology. These were used for the GSLV-MK1 rocket, the first of which was launched in 2001. Six of these vehicles were launched, but only two were complete successes. Two launches were partial failures, where the launcher (and specifically its cryogenic stage) underperformed and placed the satellites in lower orbits than planned. Two other flights were failures with the complete destruction of the vehicles.

GSLV-MK2 just after lift-off from Satish Dhawan Space Center
GSLV-MK2 just after lift-off from Satish Dhawan Space Center ISRO

Simultaneously with the GSLV-MK1 program, ISRO initiated development of its own cryogenic engine that, like the Russian-supplied engines, used liquid hydrogen and oxygen for propellant. This stage powered the GLSV-MK2 launcher, a slightly more powerful version of the GSLV-MK1, with the capability to launch 2.2 metric tons to GTO. 

After an initial failed test in 2010, the launcher has had four consecutive successes, and has been declared an operational vehicle. In addition to launching communications satellites to geostationary orbit, it is scheduled to launch the Chandrayaan-2 orbiter/lander/rover mission to the moon.

Bigger and more powerful: The GSLV-MK3

The original ISRO plan was to have a two-launcher family—the PSLV and GSLV—to launch Earth observation and communications satellites of the 1 and 2 metric ton class, respectively. But as the sizes of satellites—particularly, communications satellites—grew, and as ISRO expanded into other areas of space research including planetary exploration, the need for a more powerful launcher increased. 

This led to the development of the GSLV-MK3 launcher. Despite bearing the nomenclature of its predecessors, the new rocket has little resemblance to the earlier vehicles. Unlike the solid/liquid/cryogenic stages of the GSLV-MK1 and GSLV-MK2, with liquid strap-on boosters, the GSLV-MK3 has two powerful solid booster engines, a clustered hypergolic liquid core stage and a more powerful liquid hydrogen/liquid oxygen cryogenic upper stage than the GSLV-MK2. This vehicle is designed to place satellites weighing 4 metric tons into geostationary transfer orbit, or 8-metric-ton payloads into low-Earth orbit.

The GSLV-MK3 vehicle has two S-200 solid booster engines with 200 metric tons of hydroxyl-terminated polybutadiene (HTPB) as propellant in each, and providing over 5 mega-newtons thrust in each of the two engines. This engine is one of the most powerful solid-fueled rocket engines ever developed.

The core stage of the launcher has a two-engine cluster of ISRO’s Vikas liquid engine. The Vikas, derived from the French Viking engine developed for the Ariane program, powers various stages in all the variants of the PSLV and GSLV. This stage, referred to as the L-110 stage, carries 110 metric tons of hypergolic propellant, which burns spontaneously when the fuel, unsymmetrical dimethylhydrazine (UDMH) and oxidizer, dinitrogen tetroxide (N2O4) are mixed together. This core stage provides an additional 1.5 mega-newtons of thrust.

The GSLV-MK3’s C-25 upper stage has a liquid hydrogen/liquid oxygen CE-20 cryogenic engine that carries 25 metric tons of propellant and generates 200 kilo-newtons of thrust. Cryogenic engines have the highest specific impulse (efficiency of propellant) of all types of engines and are frequently employed in heavy lift launch vehicles. They are also the most complicated of all the kinds of engines used in rocketry, with only a handful of players in the U.S., Russia, Europe, China, Japan and now India possessing the closely guarded technology.

While the GSLV-MK3 cryogenic engine is not the first cryogenic engine developed by ISRO (the GSLV-MK2 employs a smaller cryogenic engine), it is a new design, using a different combustion cycle. This upcoming launch will be the first time this engine is flight-tested. The C-25 cryogenic upper stage is crucial for the vehicle since about half of the 10-kilometers-per-second final velocity imparted to the payload at the time of injection into orbit is provided by this stage.

GSLV-MK3 upper stage
GSLV-MK3 upper stage The C-25 cryogenic upper stage of the GSLV-MK3, awaiting integration into the vehicle. ISRO

While this is the first flight test of the GSLV-MK3 launch vehicle in its full configuration, it is not the first test of the vehicle itself. The vehicle was flight tested with a dummy cryogenic upper stage, but live solid boosters and liquid core stage, in December 2014. This was a suborbital test, with the vehicle taking its payload up to an altitude of about 125 kilometers and a velocity of about 5 kilometers per second, insufficient to inject it into orbit. The payload was a prototype of a proposed future crew vehicle that could be used for a future, yet-to-be-approved human spaceflight program for which ISRO has been steadily developing and testing enabling technologies. 

The 2014 test qualified the booster and core stages and allowed the organization to study the performance of the launcher in its crucial low-atmospheric phase, when the vehicle is subject to the greatest stresses due to denser atmosphere. It also tested the atmospheric re-entry and braking systems of the crew vehicle, which splashed down into the sea and was recovered. For the upcoming test on June 5th, the launch vehicle has been slightly modified to improve its aerodynamics, with an ogive payload fairing instead of the conventional shape used by ISRO so far, and new nose cones for the two S-200 solid boosters, amongst other changes.

GSLV-MK3 CARE Liftoff of the GSLV-MK3 crew module atmospheric reentry (CARE) experimental flight. ISRO

Future applications

Speaking of enabling technologies for future crewed missions, the GSLV-MK3 itself is one of the crucial enabling technologies. ISRO proposes to human-qualify the vehicle. A launch vehicle carrying a human crew should not just have high level of redundancies built in to ensure the lowest possible probability of failure; it needs to be designed to have low enough G-forces to ensure crew safety and comfort. Additionally, technologies will have to be developed for crew escape at various stages of launch to allow the crew to bail out in case of a failure.

The design of the GSLV-MK3, with a payload capacity of 8 metric tons to low-Earth orbit, and an over 100-cubic-meter payload fairing volume with a large 5-meter diameter makes it the most suitable of all ISRO launchers for future crewed missions.

In addition to crewed missions, the launcher will enable ISRO to greatly expand the scope of its space science missions. ISRO’s initial focus was on developing satellites and applications to serve the people of India, along with the launchers to place these payloads into orbit. While it launched several space science satellites and payloads over the last several decades—including the sounding rockets that initiated the space program—the exploration of the solar system and beyond has been added as an area of focus for the organization in recent years. The Chandrayaan-1 Moon orbiter, the Mars Observer Mission to Mars, and the Astrosat X-ray telescope satellite are examples of such missions.

All of these missions have been launched using the PSLV launcher, with its payload capacity of about 1300 kilograms to GTO (lower for interplanetary missions), thereby limiting the size and scope of the space vehicles launched. The follow-on Chandrayaan-2 orbiter/lander/rover mission to the Moon plans to use the GSLV-MK2 launcher with its somewhat greater payload capacity, but the GSLV-MK3 will greatly expand the size and scope of future interplanetary missions of ISRO. Three such missions currently in the planning stage are a follow-on mission to Mars, a mission to Venus, and a satellite proposed to be placed in the L1 Lagrangian orbit to study the Sun. 

Crewed missions and planetary science apart, the main reason for the development of the GSLV-MK3 is to launch heavier commercial satellites to geostationary orbit. ISRO’s heaviest communications satellites are already in the 3 metric ton weight range, and the organization currently lacks the capability to launch them using its own launchers, relying on Arianespace instead. With the qualification of GSLV-MK3, ISRO will finally succeed in its quest to develop, build and launch its own payloads into space without relying on other organizations. In addition to its own missions, the rocket also provides ISRO greater options in the competitive commercial satellite launch market, where it could only offer its services for small satellites so far—mostly Earth-observation and experimental/research satellites. With the GSLV-MK3, ISRO can offer launch services for heavy communications satellites.

The June 5 test of the GSLV-MK3 will carry GSAT-19, an experimental communications satellite with Ka/Ku band high-throughput transponders, an instrument to study the effects of space radiation on satellites in geostationary orbit, and several other experimental technologies to be tested for use in future operational satellites. The satellite, with a liftoff mass of 3136 kilograms, uses the same I-3K satellite bus as ISRO’s operational large commercial satellites. Subsequent launches of GSLV-MK3 propose to place operational communications satellites of ISRO into orbit.

Moving GSLV-MK3
Moving GSLV-MK3 GSLV-MK3 being moved to the launch pad from the Vehicle Assembly Building in the background. ISRO

Next steps

If the test launch on June 5 is successful, ISRO will conduct a series of development flights of the launcher over the next two to three years before declaring it operational. As is the general practice in the space industry, the envelope of the launcher’s capabilities will be gradually expanded over time. Its payload capacity will be expanded and different flight profiles tested, including to other orbits and potentially interplanetary trajectories. The proposed payload capability of about 4 metric tons to GTO will be realized in future missions.

The launcher has significant growth potential and is proposed to evolve into a new family of launch vehicles, sometimes referred to by ISRO as the Unified Modular Launch Vehicle (UMLV), or simply the Unified Launch Vehicle (ULV) family. A new engine under development for converting the GSLV-MK3 into the ULV family is the SCE-200 semi-cryogenic engine using kerosene and liquid oxygen as fuel and oxidizer, respectively, and generating 2 mega-newtons of thrust. This high-thrust engine, likely in a clustered configuration with two or more engines in the core stage would potentially replace the L-110 core liquid stage of the GSLV-MK3. Coupled with enhancements to the booster stages and the cryogenic upper stage, the upgraded core stage could significantly enhance the payload capability of the launcher to 6 metric tons to GTO and beyond —placing it among the most powerful rockets currently available. While the configurations of future launchers are yet to be finalized, the vision of the ULV proposal is to provide a family of launchers with a range of capabilities, while sharing common components, including engines and stages, to take advantage of economies of scale and to simplify the development process. If developed, the ULV family of launchers derived from the GSLV-MK3 could replace the PSLV and its derivatives such as the GSLV-MK2 as the set of ISRO workhorse launchers.

June 5 is a very important date for ISRO, since it heralds the coming of age of the organization, and its emergence on the world stage as a significant player in space transportation. Coupled with the new opportunities in commercial and space exploration missions for which the new launcher opens the doors, this date could be hugely consequential—not just in the history of ISRO and India, but through its potential to add India to the list of significant space faring nations, in the history of space exploration itself.

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