By Shubhranshu Suman and Ujjwal Pandey:
India wrote a new chapter in the journey of space exploration on September 8 when ISRO successfully launched its advanced weather satellite INSAT-3DR onboard with the Geosynchronous Satellite Launch Vehicle (GSLV-F05). This launch was a giant leap forward as it marks the first operational flight of GSLV that’s carrying the indigenous cryogenic upper stage, paving the way for India’s entry into the elite club of countries. This feat, however, was achieved after a long tussle that lasted two decades.
Need And The Struggle
The story of India’s tryst with space programmes began in the early 60s when a handful of enthusiastic engineers transported the first rocket, made in a bishop’s house, on a cycle. It was launched from the single launch pad situated in Thumba, Thiruvananthapuram, amidst a coconut plantation. This humble beginning quickly transformed into a full-fledged space programme. By the 1970s, the country had successfully developed a sounding rockets programme, and by the late 1990s, research had yielded the Polar Satellite Launch Vehicle (PSLV). The PSLV; designed to launch its Indian Remote Sensing satellites into Sun-synchronous orbit; is also capable of positioning small satellites into Geostationary Transfer Orbit (GTO).
However, to place a heavier and sophisticated INSAT class of satellites into GTO, a more powerful rocket was required. Thus the need for a GSLV was identified. Although the core design of GSLV was adopted from PSLV, it still needed an all new and more powerful ‘Cryogenic Engine’.
The term ‘cryogenic‘ comes from the fact that both propellants, hydrogen and oxygen, are kept at extremely low temperatures so that they become liquids. This engine has the greatest efficiency in terms of thrust generated, or as rocket science calls it, highest specific impulse. It eventually means that for a given amount of thrust required, the rocket needs to carry a lesser amount of cryogenic propellants, which directly translate into a higher weight of payload it can carry.
Easier said than done; cryogenic technology is generally shrouded in opacity given its intrinsic nature. In fact, only the space agencies of the US, Russia, Europe, China and Japan have been able to master it.
Back to the late 80s, after a long period of indecision, New Delhi decided to acquire cryogenic engines from outside. A long hunt culminated in a deal with Glavkosmos, a Soviet company. This facilitated the sale of two cryogenic flight stages as well as technology transfer to India. But the deal suffered a setback when an upset US government imposed sanctions on both India and Russia and stalled it, citing the violation of the Missile Technology Control Regime.
With all options exhausted, the Indian government decided to go ahead with an indigenous Cryogenic Upper Stage (CUS) project and gave formal approval for the same in 1994. However, the bright side was that before the deal was called off, the Glavkosmos had supplied the ISRO with seven cryogenic engines which were later used in GSLV MkI.
A Turbulent Journey
The journey of cryogenic engine development is no less than a heroic saga of blood, sweat and tears. ISRO’s cryogenic team faced its first major challenge not on the technical front but on a very disturbing scenario of espionage. Top scientists were accused of being spies and our very own intelligence agencies interrogated them.
However, all the charges were later dropped against the scientists as nothing conclusive came out of the inquiry. The hoopla around allegations slowly faded, and development headed back on track. As it proceeded, ISRO started to feel the heat of cryo technology. There were many technical hurdles in the development, but two challenges stood apart: the storage of cryo propellants and the development of turbopump.
While gases are liquefied by cooling them: hydrogen to -253.15 degree Celsius and oxygen to -184.15 degree Celsius, attaining such freezing temperatures is a mammoth task. What further complicates the process is the storage of these propellants. To preserve the propellants at this temperature requires specially insulated tanks and their loading onto the rocket needs extra care.
Once the Cryogenic stage on board GSLV comes into play, the exhaust temperature can easily shoot up to 3000 degree Celsius. With propellant storage tanks merely inches away from the exhaust, the task of maintaining cryo temperature becomes even more daunting.
Equally challenging was the complex design of turbopump. Normal pumps can’t move propellants to the engine’s combustion chamber with the tremendous flow rate required by a cryo engine. A turbopump, however, can do so by rotating at an incredible speed of 40,000 times a minute and sends up to 18 kg of propellants every second into the thrust chamber. With freezing-cold and super-hot gases flowing side by side in the turbopump, its functioning is no less than a ballet of engineering perfection.
After all the painstaking efforts, ISRO’s cryogenic team made the first 7.5 tonne engine in 2000, but it blew while testing. Further development led to the indigenous cryogenic engine being declared flight worthy in 2003. It took another four years to integrate it with GSLV.
At last, the first flight of GSLV MkII was attempted in 2010, but it failed as the cryo engine got cut off three seconds after ignition. Against all the odds, ISRO’s engineers toiled day and night to rectify the error, and as a result, first successful flight of GSLV MkII was executed on January 2014.
The Way Forward
With the first operational launch of GSLV MkII, the prospects of ISRO looks bright. On the one hand, it marks a high point in India’s bid to master cryogenic technology. The scheduled developmental flight of an even bigger version of GSLV (MkIII) will make India self-sufficient in launch capabilities. It will add a whole new dimension, not only to the heavy payload launches into the GTO but will also cater to India’s interplanetary missions, as it employs an even more powerful CE-20 cryo engine.
On the other hand, it will lead to the commercialisation of Indian Space industry and possibility of future Public Private Partnerships. At present, the cost per launch of GSLV Mk-II is $36 million and expected cost of launch of Mk-III is $40 – 95 million.
To put things into perspective, similar launchers like Ariane 5 and Falcon 9 costs around $165 – 220 million and $62 million respectively. This fiercely competitive pricing will go a long way in capturing an untapped market of GSLVs, with foreign governments being prime customers.
The launch of GSLV-F05 reflects that ISRO and its engineers have indeed mastered the intricacies of cryogenic technology which has applications far beyond space. With this, ISRO has not only opened new gateways of space exploration but has also ignited the imagination of Indian astronauts in the space. A successful launch of GSLV MkIII in December will add another dimension to the dawn of cryo era.
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Authors:
Ujjwal Pandey: B.Tech in Mechanical Engineering with specialization in Automotive Engineering from VIT University, Vellore. Currently working at Mahindra Research Valley, Chennai.
Shubhranshu Suman: B.Tech in Mechanical Engineering from NIT Tiruchirappalli. Currently working at Mahindra Research Valley, Chennai.
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