The Indian Space Research Organisation (ISRO) Thursday took a big step towards realising its second Moon mission this year with a fifth consecutive success in the use of an indigenous cryogenic engine to fire an improved version of its heavy-lift GSLV Mk II rocket to launch a satellite into space from the Satish Dhawan Space Centre at Sriharikota.
The GSLV F08, a fully operational version of ISRO’s GSLV Mk II rocket series, launched the GSAT 6A communication satellite into its orbit. “The major phases of the flight occurred as intended. About seventeen and a half minutes after lift-off, GSAT-6A was successfully placed in GTO,” ISRO said in an official post-launch statement.
“Soon after separation from GSLV, the two solar arrays of GSAT-6A were automatically deployed in quick succession and the Master Control Facility (MCF) at Hassan in Karnataka assumed control of the satellite,” the statement said.
The launch was the 12th satellite launched on board the GSLV rocket and the fifth consecutive success for a GSLV equipped with an indigenously developed Cryogenic Upper Stage engine.
The liquid stage 2 Vikas engines on the GSLV F08 were significantly souped up for power when compared to the standard Vikas engines used on previous flights. Thursday’s GSLV-F08 flight was also the first GSLV flight under the stewardship of new ISRO Chairman K Sivan.
The GSLV — specifically the GSLV F10 — is the designated rocket to fly India’s second mission to the Moon, the Chandrayaan 2, weighing around 3,290 kg, at the end of the year.
The GSAT-6A built by ISRO is intended to provide mobile communication services through multibeam coverage. The satellite is equipped with S- and C-band transponders. The GSAT 6A was originally intended to be launched for the private firm Devas Multimedia to provide communication services in India, but the deal was scrapped by the UPA government in 2011 after it came under scrutiny for irregularities. Under the deal, ISRO was to build and launch the GSAT 6 and 6A at a cost of Rs 766 crore. The GSAT 6, weighing 2,117 kg and very similar to the GSAT 6A, was ultimately launched on the GSLV D6 in August 2015.
The indigenous cryogenic stage on the GSLV is the third stage, and uses liquid hydrogen as fuel and liquid oxygen as oxidiser. Cryogenic stage is a highly efficient rocket stage that provides more thrust for every kg of propellant it burns compared to solid and earth-storable liquid propellant stages. The impulse achievable with cryo fluids is 450 seconds compared with 300 seconds for other fuels.
According to space scientists, cryogenic engines provide unprecedented thrust to GSLV rockets in their final stages while keeping fuel loads relatively low. Nearly 50% of the power for GSLV rockets as they push into space comes from the cryogenic stage. India had first ventured on the path of obtaining cryogenic technology in 1992 with a two-pronged strategy of purchasing cryogenic engines from Russia, and acquiring the technology from the US. But following the 1998 nuclear tests and the sanctions that followed, the US denied India cryogenic technology.
ISRO used seven cryogenic engines sold by Russia for the early phase of its GSLV programme that began in 2001, while parallely developing an indigenous technology. GSLV launches with Russian engines, including early operational flights, had mixed results, with only two flights going perfectly to plan. The first GSLV flight with an indigenous cryogenic upper stage failed on April 15, 2010.
In the absence of heavy-lift rocket technology, India has been relying on France for launching its communication satellites. India is among six nations — along with the US, Russia, France, Japan and China — to possess cryogenic engine technology, a key frontier in rocket science.
While ISRO has brought the GSLV Mk II to an operational phase, it is still in the process of developing a fully operational GSLV Mk III rocket, which can carry satellites weighing more than four tonnes to space. The GSLV Mk III D1 flight delivered a 3,136 kg GSAT-19 satellite — the heaviest launched from Indian soil — to a geosynchronous transfer orbit in June 2017.
The cryogenic upper stage in the GSLV Mk III rocket, called the C25 engine, is an improvement on C20 cryogenic engines used in the GSLV Mk II rockets which entered the operational phase after over 25 years of development, in September 2016, following the successful flight of the GSLV F05 with a 2,211 kg INSAT-3DR weather satellite. A GSLV Mk III D2 rocket is scheduled to fly a GSAT 29 communication satellite to space in its second mission which is scheduled for the first half of 2018 by ISRO.