Watch live: India’s most powerful rocket poised for launch

The second orbital test flight of India’s GSLV Mk.3 launcher is set for Wednesday, when it will hoist a high-throughput communications satellite into orbit to connect the county’s remote population and demonstrate new data relay capabilities.

Boosted by two powerful strap-on solid rocket motors, the nearly 143-foot-tall (43.5-meter) Geosynchronous Satellite Launch Vehicle Mk.3 (GSLV Mk.3) is set for liftoff from the Second Launch Pad at the Satish Dhawan Space Center on India’s east coast at 1138 GMT (6:38 a.m. EST) Wednesday.

The launch is scheduled for 5:08 p.m. local time at the Indian spaceport.

It will be the third test flight of the GSLV Mk.3, India’s most powerful rocket, following a suborbital demonstration in 2014 and an orbital launch in 2017. Both missions were successful, and assuming Wednesday’s launch goes according to plan, the GSLV Mk.3 will be declared operational and Indian officials will approve plans to place the Chandrayaan 2 lunar lander on the rocket’s next flight as soon as January.

Indian space program managers earlier this year moved the Chandrayaan 2 launch from the less capable GSLV Mk.2 rocket to the GSLV Mk.3 to accommodate mass growth on the lunar mission.

“This mission is the second developmental flight of GSLV Mk.3, and this is an important mission for the GSLV Mk.3 program, as after the success of this mission, GSLV Mk.3 will be declared as operational and will join the group of operational vehicles PSLV and GSLV,” said K. Sivan, chairman of the Indian Space Research Organization.

Designated GSLV Mk.3-D2, Wednesday’s test flight will send the GSAT 29 communications satellite into an elliptical geostationary transfer orbit, on the way to a final position in geostationary orbit more than 22,000 miles (nearly 36,000 kilometers) over the equator.

The GSLV Mk.3 launcher is prepared for liftoff from the Second Launch Pad at the Satish Dhawan Space Center on India’s east coast. Credit: ISRO

“The payload for GSLV Mk.3-D2 is the very advanced high-throughput satellite GSAT 29. It is a multi-band, multi-beam communications satellite with a liftoff mass of 3.4 tonnes (about 7,500 pounds),” Sivan said. “GSAT 29 payloads are catered to the communications requirements of users from Jammu and Kashmir and northeastern regions of India. Apart from these operational requirements, the satellite will be demonstrating several new and critical technologies also.”

Sivan told Indian media the satellite will also carry tech demo payloads to investigate laser communications links between two satellites in space. Laser, or optical, data links provide a significantly faster way to relay information than conventional radio communications.

The GSLV Mk.3 rocket will lift off powered by two 86-foot-long (26.2-meter) S200 solid rocket boosters, generating a combined 2.2 million pounds of thrust. A core stage driven by two hydrazine-fueled Vikas engines will ignite at T+plus 1 minute, 50 seconds, followed by burnout and separation of the strap-on boosters at T+plus 2 minutes, 19 seconds, after they each burn through their supply of more than 225 tons (205 metric tons) of pre-packed solid propellants.

The twin Vikas engines will fire until T+plus 5 minutes, 15 seconds, each producing around 190,000 pounds of thrust. The liquid-fueled powerplants are new higher-thrust variants of the Vikas engine, an upgrade that debuted on a GSLV Mk.2 launch in March and is flying on the GSLV Mk.3 for the first time Wednesday.

The GSAT 29 communications satellite. Credit: ISRO

An upper stage engine consuming cryogenic liquid hydrogen and liquid oxygen propellants will ignite at T+plus 5 minutes, 21 seconds, moments after separation of the GSLV Mk.3’s core stage. The upper stage engine will burn until T+plus 16 minutes, 28 seconds, to place the GSAT 29 spacecraft in a transfer orbit with a low point of 118 miles (190 kilometers), a high point of 22,353 miles (35,975 kilometers), and an inclination of 21.5 degrees.

The GSAT 29 satellite, based on ISRO’s I-3K spacecraft design, will use an on-board thruster to circularize its orbit over the equator at 55 degrees east longitude for a 10-year mission.

GSAT 29 carries Ku-band and Ka-band spot beams aimed at remote parts of northwest and northeast India, beaming signals to a large population, particularly in hilly and geographically inaccessible regions, according to ISRO.

The satellite’s technology demonstration function focuses on the testing of a new optical communications capability, a Q-band and V-band communications payload, and a high-resolution camera.

The GSLV Mk.3 rocket can lift up to 4 metric tons — about 8,800 pounds — to a geostationary transfer orbit, the drop-off orbit for most large telecom satellites heading for perches more than 22,000 miles over the equator.

For a mission to low Earth orbit a few hundred miles above the planet, ISRO says the GSLV Mk.3 can carry 10 metric tons, or about 22,000 pounds. The GSLV Mk.3 can haul about twice the payload as the GSLV Mk.2, India’s second-most powerful rocket.

That is more than the lift capability of United Launch Alliance’s basic Atlas 5 rocket configuration without strap-on boosters, but well short of the capacity of the Atlas 5’s more powerful versions, the Ariane 5, and SpaceX’s Falcon 9 rocket.

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