As I write this, the GSLV Mk-III would have commenced its 25.5 hour countdown to launch at 1728 hrs (IST) on June 5, 2017. The 3-stage GSLV Mk-III will carry the 3136 kg GSAT-19 to a geostationary orbit. The satellite carries transponders for communication, a scientific instrument to study the nature of charged particles and effect of space radiation on satellites and among various other technologies an indigenously built Lithium ion battery. This will be the launch vehicle’s debut flight and hence called D1.
The GSLV Mk-III flew last as GSLV Mk-III-X, an experimental flight where it flew with a passive third stage and the CARE payload. The sub-orbital flight was intended to study the launch vehicle configuration and went off successfully. It allowed ISRO to study how the launch vehicle performed in flight. The crew vehicle CARE splashed down in the Bay of Bengal near Andaman and Nicobar islands and was recovered by the Coast Guard.
The GSLV Mk-III is India’s medium lift launch vehicle capable of flying 4 tonnes to Geosynchronous Transfer Orbit and 8 tonnes to Low Earth Orbit. It is intended to place India’s heavier communication satellites in orbit. It has two S200 solid fuel boosters attached to a core stage. The core stage has two clustered L110 Vikas Engines. The third stage Cryogenic Upper Stage C25 is powered by the indigenously developed CE-20 engine. The payload fairing also has a “slanted strap-on nose cone for aerodynamic robustness” added to it after the X flight.
Notice the change in language. It is no longer called as first, second, third and fourth stages as in PSLV and the GSLV. The stages are called as booster, core and upper stage.
This will also be the time when the CE-20 will actually fire and take a payload to orbit. It is different from the cryogenic engine on the GSLV which is called CE-7.5. The GSLV Mk-III-X carried the CE-20 but it did not fire.
I had written about the commercial aspects of the GSLV launches in the Wire in 2015 and think that the same holds for the GSLV Mk-III as well. India has already begun developing satellites which require a launch capability more than that provided by the Mk III. An example is the soon to be launched GSAT-11. GSAT-11 weighs 5725 kg and is going to be launched on board the Ariane-5 in 2017-18 and uses the newly developed I-6K bus. This requires development of heavy lift (launch capability to GTO of more than 10 tonnes) launch vehicles. This development would be pursuant to lessons learnt in the development of the GSLV and the Mk-III.
GSAT-19 is largely a communication satellite. It holds improvements in satellite components such as heat pipe, gyros, accelerometers and an indigenous Lithium ion battery. There is very little information that I could find on GRASP (Geostationary Radiation Spectrometer) besides what it says about studying charged particles and impact of space radiation on satellites.
With so much to write about, I was not happy with the initial reportage in the Indian press looking at India’s human spaceflight program (example). I wish they would ask ISRO to share more information on the payload (the science payload as well improvement in space craft instrumentation) and the improvements in the launch vehicle that the GSLV Mk-III X flight enabled.
I wish ISRO and the GSLV Mk-III team all the best and Godspeed!