India’s GSLV rocket successfully launches GSAT-9

by William Graham

India launched its GSAT-9 communications satellite via a Geosynchronous Satellite Launch Vehicle (GSLV) rocket Friday. The Indian Space Research Organisation (ISRO) launch is aimed at supporting international partnerships in South Asia. The launch, which wasn’t shown live by ISRO, occurred at 16:57 local time (11:27 UTC).

GSLV Launch:

GSAT-9, also known as the South Asia Satellite, is a Ku-band broadcasting and telecommunications spacecraft which India has developed to provide services to members of the South Asian Association for Regional Cooperation (SAARC).

The GSAT-9 spacecraft is a 2,230-kilogram (4,920 lb) satellite based on ISRO’s I-2K bus. With a design life of twelve years, the satellite is expected to support education, medical, disaster management and communications initiatives as well as international cooperation between the member states. It is equipped with twelve Ku-band transponders.

The South Asia Satellite program is a partnership between India and most of the other member nations of SAARC: Bangladesh, Bhutan, the Maldives, Nepal and Sri Lanka. Afghanistan has not yet signed up to the program but is expected to, while Pakistan has opted not to be involved.

South Asia Satellite was proposed by India’s Prime Minister, Narendra Modi, in line with his foreign policy objective of strengthening India’s relations and cooperation with neighboring countries. India has funded the development and launch of the spacecraft, at a total value of around 4.5 billion rupees (70 million US dollars). Modi described the satellite as a “gift” to the region.

The Indian Space Research Organisation (ISRO) constructed GSAT-9 and launched the spacecraft via its Geosynchronous Satellite Launch Vehicle (GSLV) rocket. A three-stage rocket designed to carry satellites into geostationary transfer orbit, the GSLV will be making its eleventh flight across the Mark I and Mark II versions of the rocket.

Friday’s launch, designated GSLV F09, was the fifth flight of the Mark II GSLV which debuted in April 2010. This replaced the Mark I, which first flew in 2001 and made its final flight at the end of 2010, introducing an Indian-developed third stage engine instead of a Russian-built engine flown on the Mark I. With this new cryogenic propulsion system, the GSLV Mk.II is a fully indigenous vehicle.

The GSLV’s service has been marred by concerns over its reliability – to date only half of its flights have been successful – however last September’s launch of INSAT-3DR saw it achieve three consecutive successes for the first time.

The first of the GSLV’s failures came on the rocket’s maiden flight in April 2001; with the third stage cutting off earlier than planned, leaving GSAT-1 in a lower than planned orbit. Although ISRO attempted to use the spacecraft’s own propulsion to rescue the mission, a design flaw with the satellite prevented it from raising its orbit sufficiently.

Two years after the failure, GSLV posted its first success with the launch of GSAT-2 in May 2003. This was followed up with a successful third flight, the first operational mission, orbiting GSAT-3 in September 2004. This would be the rocket’s last successful launch for almost ten years.

In July 2006, a GSLV lifted off with the INSAT-4C communications satellite. One of the vehicle’s four liquid booster rockets suffered an engine failure at liftoff, which resulted in the rocket deviating from its planned course fifty-six seconds later when the asymmetric thrust overwhelmed the flight control system.

The GSLV’s return to flight in September 2007 carried a replacement satellite, INSAT-4CR. This was deployed into a lower-than-planned orbit after the rocket underperformed, however the spacecraft was able to correct its own orbit using its onboard propulsion systems.

The next launch for the GSLV was the maiden flight of the Mark II configuration. This proceeded nominally up until ignition of the new upper stage engine, which shut down two seconds into its burn leaving the rocket unable to reach orbit. The failure was traced to a turbopump malfunction which starved the engine of propellant.

In December 2010 the final Mark I GSLV was destroyed by range safety after going out of control 48 seconds after launch. After this fourth consecutive anomaly, the GSLV returned to flight in January 2014; a Mark II vehicle successfully deploying GSAT-14. Subsequent launches have placed GSAT-6 and INSAT-3DR into orbit.

GSLV launches take place from the Satish Dhawan Space Centre, Sriharikota. While the GSLV is able to launch from either of the center’s First or Second Launch Pads, all of its launches since the completion of the Second pad have occurred from that complex.

The Second Launch Pad allows for the rocket to be assembled vertically in an integration building away from the launch pad. The integrated GSLV is them transported to the launch pad atop a mobile launch platform.

Derived from the less powerful Polar Satellite Launch Vehicle (PSLV), the GSLV’s first stage is unique in that it consists of a solid core stage with liquid strap-on boosters. The GS-1 core stage’s S-139 motor is augmented by four L-40H boosters, propelled by Vikas engines.

The boosters burn UH-25, a mixture of three parts unsymmetrical dimethylhydrazine and one part hydrazine hydrate, oxidized by dinitrogen tetroxide. Their Vikas engines are license-built derivatives of the Viking engines used on earlier members of Europe’s family of Ariane rockets.

The boosters ignited 4.8 seconds before the GSLV was due to lift off, with the S-139 igniting at the zero mark in the countdown. The GSLV lifted off and begin its ascent towards orbit. The core stage burned for the first 106 seconds of flight.

After first stage burnout, the stage remained attached as the strap-on boosters were burning. These did not cut off until 149 seconds into the flight. Half a second after booster shutdown, the second stage ignited. Stage separation did not occur until a second and a half after stage two ignition.

The GSLV’s second stage is a GS-2, or L-37.5H. Like the boosters, this is powered by a Vikas engine burning UH-25 and dinitrogen tetroxide. It powered the vehicle for about two minutes and twenty seconds. Around eighty seconds into the second stage burn the payload fairing separated from around GSAT-9 at the nose of the rocket.

When the second stage completed its burn, four minutes and 49 seconds after liftoff, the spent stage remained attached for four seconds before separation. The third stage ignited one second after staging, beginning a twelve-minute burn.

The third stage of the GSLV Mark II is India’s Cryogenic Upper Stage (CUS). This is fuelled by liquid hydrogen and liquid oxygen and provided the final thrust to inject GSAT-9 into its planned geosynchronous transfer orbit. Spacecraft separation occurred a little over seventeen minutes after launch.

From this initial transfer orbit, GSAT-9 will maneuver into geostationary orbit under its own power. The satellite is equipped with a liquid apogee motor and – in a first of an Indian-built spacecraft – electric ion propulsion.

The launch of GSAT-9 was the second of the year for India, after February’s PSLV launch of Cartosat-2D: an imaging satellite for the country’s military. ISRO’s next launch is scheduled for late May or early June, with a PSLV scheduled to deploy another Cartosat spacecraft, Cartosat-2E.

Friday’s launch clears the way for assembly of an LVM3 – or GSLV Mark III – vehicle at the Second Launch Pad, ahead of its first orbital launch attempt which is currently scheduled for June. This launch will carry the GSAT-19 satellite. The next GSLV Mk.II launch is slated for September with GSAT-6A.

(Images via ISRO)

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