GSAT-9 launch: With South Asia Satellite Isro moves into heavyweight category
By focusing on GSLVs powered by semi-cryogenic engines Isro is preparing itself for the global space market where the advantage will be with countries owning heavy lift boosters and cheap launching costsopinion Updated: May 05, 2017 17:25 IST
The Geosynchronous Satellite Launch Vehicle (GSLV) Mk II has launched from Sriharikota carrying India’s GSAT-9 (rechristened “the South Asia Satellite”) into orbit 36,000 km above Earth.
While media attention is focused on the political significance of the satellite — New Delhi is keen to showcase the GSAT-9 as a ‘gift’ to South Asian countries — Indian Space Research Organisation (Isro) scientists are more interested in the launch vehicle’s performance. And with good reason, too, as the success of the mission depends wholly on the rocket performing flawlessly.
In fact, hardly the countdown to the launch ended when another began, this time for the launch of India’s heaviest rocket, GSLV Mk III. “We hope the GSLV Mk II has a good launch,” S Somnath, director of Isro’s Liquid Propulsion Systems Centre, told this correspondent in a telephonic interview. “For that’ll lead into the GSLV Mk III’s flight towards the end of May or beginning of June.”
Unlike the Polar Satellite Launch Vehicle (PSLV), the development of the GSLV has been plagued by so many setbacks that observers have nicknamed it ‘Isro’s Naughty Boy’.
Since its prototype first test-flew in 2001, the GSLV has had an unflattering four failures in seven launches. The launcher’s first stage comprises a solid rocket motor (proven on the PSLV), while liquid propellants make up the second stage; the all-important cryogenic upper stage (CUS) completes its three-stage configuration.
The CUS uses cryogenic fuel (gases liquefied and stored at extremely low temperatures) that mixes liquid oxygen and liquid hydrogen to produce maximum energy efficiency for the engine. Since oxygen remains a liquid only at temperatures below minus 196 Celsius and hydrogen at below minus 253 Celsius, they can only be stored in special tanks fitted with multi-layered insulation. Scientists have to overcome such enormous technological challenges in thermal and structural engineering before a cryogenic engine could be built. Few countries have mastered cryogenic technology and it remains a most zealously guarded preserve. Nasa’s Apollo Moonshots, for instance, would not have been possible without the cryogenic engines used in the Saturn V launcher.
India’s cryogenic pursuit began more than a quarter century ago when Isro sealed a deal with Russia on transfer of cryogenic technology. But the United States, fearing India might use its space launch capabilities for military purposes, pressured Moscow to renege on the deal, leaving New Delhi with the Hobson’s choice of eventually buying off-the-shelf cryogenic engines from Russia. For Isro, however, this turned out to be a blessing in disguise as it spurred its space engineers to develop cryogenic technology on their own. In 1994, the CUS project was launched to build a cryogenic engine and stage based on the Russian design.
“After the Russian supply of the upper stage of the GSLV Mk II ended, we were ready with our indigenously developed cryogenic engine,” explains Somnath. “We’ve already developed the CUS on GSLV Mk II. Its first flight was a failure, but since then it has flown three times successfully. This will be its fourth flight.” But the CUS used in the GSLV Mk III is a totally different engine. “It is the one which we have developed from scratch ourselves and is double the size and capacity of the one GSLV Mk II uses,” says Somnath. “The Mk III cryogenic engine, called C25, has a 20-ton thrust and (consumes) 25 tons of propellants.” Isro’s confidence in the C25 received a boost in February when the engine was tested for a flight duration equivalent of 640 seconds at the propulsion complex at Mahendragiri in Tamil Nadu.
Considering that the global space market’s future will be defined by heavy lift boosters, it is imperative for Isro to develop the GSLV’s advanced avatars as soon as possible. The international launch scene is changing rapidly with newer launchers constantly pushing the bar higher on payload capability.
Isro scientists seem ready for the challenge and have set their sights on leapfrogging to GSLVs powered by semi-cryogenic engines. Fuelled by kerosene and liquid oxygen, these engines would be capable of lofting ten-ton satellites into space, cutting launch costs dramatically. “We expect to test the prototype of a semi-cryogenic engine in a year’s time,” says Somnath. “And we may fly it by 2021. Engine development takes a very long time, at least 10 years for realisation.” But for the moment, all eyes are on the GSLV Mk II as it gets ready to scorch ether.
Prakash Chandra is a science writer
The views expressed are personal