At the Satish Dhawan Space Centre, India’s sole spaceport in Sriharikota, a hulking metal form looms over the Second Launch Pad. Isro’s newest rocket, the Geosynchronous Satellite Launch Vehicle (GSLV) Mark III, is ready to take to the skies this evening.
Isro officials will be keeping their fingers crossed. The performance of the rocket’s cryogenic stage, running on liquid oxygen and liquid hydrogen, will be of particular concern. Very much on their minds will be the memory of what happened when the Mark III’s older sibling, the GSLV, flew with the first domestically made cryogenic stage in 2010. The cryogenic stage malfunctioned, and the flight ended in failure.
The Mark III uses a very different cryogenic stage than the one on the GSLV, simpler in design and two and a half times more powerful than the latter. So far, this stage and its engine have only been tested on the ground.
In an experimental mission in December 2014, the performance of Mark III’s other stages—a large liquid propellant core stage flanked by two huge solid boosters that are among the largest in the world—were tested in flight. On that occasion, a dummy cryogenic stage was used.
Today will see the rocket’s first developmental flight, with all its stages operational. Onboard is a 3.1-tonne communication satellite, GSAT-19, the heaviest the space agency has attempted to launch from within the country.
A successful flight will be a momentous step forward for the space agency. For one thing, it will now be able to launch communication satellites that were being launched abroad at a considerable cost. In the longer term, the Mark III opens the door for a transition to much more powerful rockets that Isro intends to build. These rockets can carry heavier spacecraft and will allow India to contemplate challenging missions in space exploration and human spaceflight. But looking at the evolving space requirements, the Mark III may soon require a major markup.
The step up
Even after the GSLV first flew in 2001, initially with a Russian cryogenic stage and then with an Indian-made equivalent, a dozen of Isro’s communication and meteorological (met) satellites have been launched on Europe’s Ariane rockets. These satellites need to ultimately reach a specific orbit about 36,000km above the equator, the geostationary orbit.
Just eight such satellites have thus far successfully gone on the GSLV.
The reason is simple. As the graph indicates, the GSLV’s heft has been inadequate for several of the satellites Isro needed to send to space.