Space

Cryogenic success

Print edition : October 02, 2015

The GSLV-D6 launch from Sriharikota on August 27. Photo: S.R. Raghunathan

A picture taken from the video of the GSLV-D6 launch show the separation of the first stage with strap-ons. Photo: Courtesy: ISRO

The inter-stage separation. Photo: Courtesy: ISRO

The cryogenic upper stage zooming away in a magnificent blaze after the ignition of the indigenous cryogenic engine. Photo: Courtesy: ISRO

K. Sivan, Director, Vikram Sarabhai Space Centre, and R. Umamaheswaran, Mission Director, GSLV-D6. Photo: M. Karunakaran

If there was any doubt about India mastering cryogenic technology for its space endeavours, the flight of the Geosynchronous Satellite Launch Vehicle (GSLV-D6) from Sriharikota (or SHAR) on August 27 dispelled it. The 17-minute flight was smooth and “clean” all the way. The indigenous cryogenic engine in the third, topmost stage fired flawlessly for 12 minutes, to put the 2,117-kilogram communication satellite GSAT-6 into its initial orbit.

An important feature of GSAT-6 is its six-metre diameter unfurlable antenna which will help Indian armed forces personnel communicate with each other on secure lines using compact handheld devices.

The GSLV-D6 was a crucial flight, for it would prove that the success on January 5, 2014, of GSLV-D5 was no fluke (Frontline, February 7, 2014). That was the Indian Space Research Organisation’s (ISRO) first success with an indigenously developed cryogenic stage, and it needed two consecutive triumphs so that the vehicle, belonging to the GSLV-Mark II generation, could be declared operational.

ISRO’s maiden attempt with a home-grown cryogenic upper stage, flying the GSLV-D3 on April 15, 2010, ended in heartbreak. The fuel booster turbo-pump in the cryogenic engine ignited but the ignition failed to sustain, plunging the rocket into the Bay of Bengal.

With ISRO proving again the robustness of the GSLV-Mk II equipped with an indigenous cryogenic engine, it can be declared an operational vehicle. ISRO need not depend on the European Space Agency to put its communication satellites, weighing more than two tonnes, into a geostationary transfer orbit. This means an enormous saving of money because foreign space agencies charge anywhere between $22,000 and $25,000 a kg to put a satellite into orbit.

ISRO Chairman A.S. Kiran Kumar said: “For GSLV-Mk II, we are getting requests. We will be launching one of ISRO-NASA [National Aeronautics and Space Administration] satellites on that.”

He asserted that the GSLV-Mk II’s second success in a row “demonstrated that what happened on January 5, 2014, was not a flash in the pan.... This means we understand the intricacies of the cryogenic system.” He added: “More and more you repeat and succeed, you can say you have a reliable system. Our efforts will be to show that we are not complacent and that we do not make errors.”

K. Sivan, Director, Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, pointed out that ISRO need not go abroad now to launch its home-built GSAT-9, GSAT-7A and INSAT-3DR, which were two-tonne class satellites. “We can launch them from India now,” Sivan said.

Furthermore, GSLV-Mk II can now put Chandrayaan-II, which weighs 2,018 kg, into orbit. Work is proceeding apace at the ISRO Satellite Centre and the ISRO Satellite Integration and Test Establishment, Bengaluru, to build the orbiter, the lander and the rover. It will be a totally indigenous mission and is scheduled for 2017/2018.

That ISRO’s launch vehicle engineers were gaining more and more confidence with GSLV-Mk II was apparent when the three-stage GSLV-D6, weighing 416 tonnes and standing 49.1 metres tall, was assembled in just 33 days at the Satish Dhawan Space Centre (SDSC), Sriharikota. R. Umamaheswaran, Mission Director, GSLV-D6; P. Kunhikrishnan, Director, SDSC; and S. Somanath, Director, Liquid Propulsion Systems Centre, Valiamala, near Thiruvananthapuram, all highlighted the speed with which the massive vehicle was assembled.

While it normally takes more than 100 days to assemble a GSLV-D6, it took only “33 days of dedicated work at SHAR” to integrate the three-stages of the GSLV, Umamaheswaran said.

Besides, compared with GSLV-D5, which put GSAT-14 weighing 1,982 kg into orbit, the latest mission heaved the 2,117-kg GSAT-6 into orbit. This demonstrates that there were no issues at all with the indigenous engine. Umamaheswaran said: “Our effort is to prove that our launch technology has improved. This vehicle can carry 2.2 tonnes to 2.5 tonnes into orbit. Commercial requirements are there for putting satellites weighing from 2.15 tonnes to 2.3 tonnes into orbit. We will go ahead with the improvements in the vehicle so that we can reach 2.5 tonnes in three years.”

S. Ramakrishnan, former Director, VSSC, called the GSLV-Mk II’s cryogenic engine an “indigenised Russian engine”. GSLV-Mk II’s cryogenic engines are “indigenously manufactured and tested”, he said. (GSLV-Mk I rockets, launched from Sriharikota, used Russian cryogenic engines. Out of six flights that used Russian cryogenic engines, four failed).

ISRO is looking forward to the lift-off of its gigantic GSLV-Mk III with a massive indigenously developed cryogenic stage in December 2016. The 600-tonne GSLV-Mk III’s cryogenic engine will develop a thrust of 20 tonnes. It will have liquid oxygen and liquid hydrogen, together weighing 25 tonnes.

The GSLV-Mk III can put a four-tonne satellite into a geostationary transfer orbit. Ramakrishnan said: “We started from scratch to develop the cryogenic engine for GSLV-Mk III. It is a fully indigenously developed engine from the drawing stage. It has no reference to foreign technology. We recently successfully tested it for its full flight duration of 800 seconds.”

T.S. Subramanian

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