GSLV-D6 successfully launched, India gets another eye in the sky

Isro's GSLV-D6

Isro’s GSLV-D6

A moment to be proud of India Launches ISRO’s indigenous cryo engine successfully places GSAT-6 in orbit
Indian Space Research Organization (Isro) on Thursday cleared all doubts on its cryogenic capabilities, successfully launching the Geostationary Satellite Launch Vehicle (GSLV-D6), placing GSAT-6, a 2,117kg communication satellite in orbit.

This marks the second successful GSLV launch using an indigenous cryogenic engine. The first launch, on April 15, 2010 was a failure, followed by the second one on January 5, 2014 which was a success.
India is the 6th nation to develop cryogenic engine

Isro's GSLV-D6

Isro’s GSLV-D6


GSLV-D6 carrying GSAT-6 lifted off from Sriharikota spaceport at 4.52pm as scheduled. This was the ninth flight of the Geostationary Satellite Launch Vehicle.

Around 17 minutes after liftoff, the rocket injected GSAT-6 into a Geosynchronous Transfer Orbit (GTO), making the mission a success.

“We have understood the intricacies of a cryogenic engine. The rocket performed normally. This shows that our January, 2014 success with the cryogenic engine was not a fluke. Only numbers will demonstrate the reliability of the launches. It is up to us to ensure that we do not make any errors. ” said Isro chairman A S Kiran Kumar.

“GSLV will command its own market but for that we need more successful launches. As of now we have sent a two tonne satellite and it has been successful, there is a good market for this. If we keep showing a good success rate, GSLV will be a good candidate for commercial launches. Progressively more and more people are coming to us for commercial launches. It is up to us to improve capacity building,” he said

He said satellite that was launched on Thursday would be used for various government purposes.

Speaking about future plans, the Isro chairman said, “We are targeting a four-tonne payload with the Mark III. As part of cooperation with the US space agency NASA, we will be launching a satellite using GSLV – Mk II in 2021. Isro will also launch four nano satellites from the US as a piggy back luggage for its Astrosat that is to be launched next month using a PSLV.”

Satellite director Prakash Rao said, “GSAT- 6 features an unfurlable antenna. When deployed, it will be the largest on board any satellite. The advantage is that the footprint on the ground is larger and the devices can be more compact.”

GSAT-6 provides communication through five spot beams in S-band and a national beam in C-band for strategic users.

GSLV-D6 vehicle was configured with all its three stages including the cryogenic upper stage (CUS) similar to the ones successfully flown during the previous GSLV-D5 mission in January 2014.

The metallic payload fairing of GSLV-D6 had a diameter of 3.4 m. The overall length of GSLV-D6 was 49.1 mass with a lift-off mass of 416 tonne.

The cryogenic upper stage on GSLV-D6 was designated as CUS-06. A cryogenic rocket stage is more efficient and provides more thrust for every kilogram of propellant it burns compared to solid and earth-storable liquid propellant rocket stages.

The cryogenic stage is technically a very complex system compared to solid or earth-storable liquid propellant stages due to its use of propellants at extremely low temperatures and the associated thermal and structural challenges. Oxygen liquefies at -183-degrees celsius and Hydrogen at -253-degrees celsius. The propellants, at these low temperatures, are to be pumped using turbo pumps running at around 40,000 rpm.

The main engine and two smaller steering engines of CUS together develop a nominal thrust of 73.55 kN in vacuum. During the flight, CUS fires for a nominal duration of 720 seconds. S-band telemetry and C-band transponders enable GSLV-D6 performance monitoring, tracking, range safety/flight safety and preliminary orbit determination (POD).

Key Facts About This launch

S-band communication services

The satellite would be eventually fine tuned into the final geostationary orbit at 83 degree East longitude. GSAT-6 will provide S-band communication services in the country.

“The performance of GSLV D-6 has been normal and the intricacies of the rocket have been understood,” ISRO chairman A.S. Kiran Kumar said soon after the launch, from the Mission Control Room.

The Thursday’s launch could mean that the national space agency was increasingly confident of launching the heavy weight rocket with indigenous cryogenic upper stage, which can lift payloads weighing about 2.2 tonne.

Mission Director Umamaheswaran said that the launch was a “Onam” gift of ISRO to the country.

Largest antenna ISRO has ever made

The 2,117 kg-weighing GSAT-6 communication satellite is aimed at primarily benefiting the country’s strategic users and other specific authorised users. The cuboid-shaped satellite with a mission life of nine years also includes a first-of-its-kind S-Band unfurlable antenna with a diameter of six metre. This is the largest antenna ISRO has ever made for a satellite.

Though the Thursday’s launch is the nine time ISRO was using GSLV rocket, this is the third time the rocket was being launched with indigenous cryogenic upper stage. “GSLV-D6 flight is significant since it intends to continue the testing of CUS,” according to ISRO.

The cryogenic stage was “technically a very complex system” compared to solid or earth-storable liquid propellant stages due to its use of propellants at extremely low temperatures and the associated thermal and structural challenges, ISRO stated.

A cryogenic rocket stage “is more efficient and provides more thrust for every kilogram of propellant it burns” compared to solid and earth-storable liquid propellant rocket stages, it added. The cryogenic stages fires for a nominal duration of 720 seconds during the launch.



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