GSLV-D6 is the ninth flight of India's Geosynchronous Satellite Launch Vehicle (GSLV). It is also the fifth developmental flight of GSLV. This is the third time the indigenously developed Cryogenic Upper Stage (CUS) is being carried on-board during a GSLV flight. GSLV-D6 flight is significant since it intends to continue the testing of CUS. GSLV is designed to inject 2 ton class of communication satellites into Geosynchronous Transfer Orbit (GTO).
GSLV-D6 will be launched from the Second Launch Pad at Satish Dhawan Space Centre SHAR (SDSC SHAR), Sriharikota.
GSLV-D6 will launch 2117 kg GSAT-6, an advanced communication satellite, into a GTO. GSAT-6 will provide S-band communication services in the country. After reaching GTO, GSAT-6 will use its own propulsion system to reach its final geostationary orbital home and will be stationed 0 at 83 East longitude.
GSLV-D6 vehicle is configured with all its three stages including the CUS similar to the ones successfully flown during the previous GSLV-D5 mission in January 2014. GSLV-D5 successfully placed GSAT-14 satellite carried on-board in the intended GTO very accurately.
The metallic payload fairing of GSLV-D6 has a diameter of 3.4 m. The overall length of GSLV-D6 is 49.1 m with a lift-off mass of 416 t.
The Cryogenic Upper Stage (CUS) being flown in GSLV-D6 is 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 liquifies at -183 deg C and Hydrogen at -253 deg C. 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).