Chennai: India’s Polar Satellite Launch Vehicle (PSLV) rocket, is undoubtedly among the most successful and consistent rockets in the world among the sub-1.5ton payload to Low-earth orbit or polar orbits. But one lesser-known facet beyond the enviable success rate of this rocket is its second-stage engine - Vikas.


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While ‘Vikas’ translates to development or progress in Sanskrit, the scientist, Padma Bhushan Nambi Narayanan, who led a team to build the engine had secretly kept in mind that this name would be a tribute to ISRO’s founder, visionary scientist and industrialist Dr Vikram. A Sarabhai.


It was his way of offering a tribute to Dr Sarabhai, whom he considers his Guru and biggest influence in his life. August 12, 2020 also marks the 101st Anniversary of this legendary son of the soil--Dr Vikram A Sarabhai. 


The story of the Vikas (Vikram A Sarabhai) Engine:


In its nascent stage, during the 1960s and 70s, ISRO’s scientists had a difference of opinion on technical grounds - whether to develop solid-fueled engines or liquid-fueled engines. A vast majority of the then Indian Space Research Organization (ISRO) believed in focussing their energies and resources towards solid engines as the technologies linked to it were relatively more achievable. Whereas the pursuit of liquid-fueled engines were considered akin to chasing a chimaera. 


Technically speaking, liquid-fueled engines are more fuel-efficient as they can be switched on and off, they can lift heavier payloads/satellites. Liquid engines also have lesser vibration and can burn for longer durations when compared to their solid counterparts. While a solid engine burns out after use, the liquid engine can be tested, re-used after cleaning and re-assembly. Most advanced rockets in the world are primarily dependent on liquid-fueled engines. If and when solids are used, they are only for the initial thrust (using boosters) at lift-off. 


Eventually, it was Princeton-postgraduate ISRO scientist Nambi Narayanan(now regarded as the Father of Liquid Propulsion engine technology in India), who impressed upon the organization to consider diverting resources to urgently develop liquid-fueled engines, given how they were the future of rocketry and how advanced nations were achieving more with these engines. 


Sarabhai had not only permitted the deputation of the young Nambi to Princeton while he was working at ISRO but also ensured that the bureaucratic rigmarole was cleared smoothly before he left. After Nambi Narayanan completed his course in record-time, when the Americans tried to poach Nambi, by coaxing and showing him the high-end American facilities, it was Sarabhai who advised Nambi. “Leave the nasty guys and take the next flight” Nambi recalls the Father of India’s Space programme having told him. 


It was in 1973 that ISRO had launched an experimental rocket(LP-006) using a 600kg thrust liquid engine. The 600kg thrust engine was minuscule compared to the giant 60ton engines(clustered in four to obtain 240ton thrust) that the Americans and Russians were using. However, the success of this liquid engine in its test flight did steer ISRO in the right direction and led to a deal with the French to co-develop a 60-ton liquid-fuel engine(a 100-time jump when compared to ISRO’s 600kg engine). While the engine was not an all-new model, it was an improvised version of a smaller French engine in the Viking series. 


The French had named their engine Viking, but the Indian-side, led by Nambi Narayanan, that negotiated the contract had decided on an Indian name - Vikas. Vikas means development in Sanskrit, but Nambi saw an adapted anagram - Vikram A Sarabhai. This secret was known only to the late TN Seshan, a top bureaucrat who had later served as the Chief Election Commissioner of India. Nambi kept the real-intended meaning of Vikas a secret, owing to the bureaucratic procedures and approvals that ISRO followed when naming a project or a facility. 


From 1974 to 1980, a team of 100 Indian scientists(in different batches) had learnt to jointly develop the 60-ton thrust Viking-3 Engine, after which they returned to India. But that was just half the story. While the team had learnt how to make an engine, they didn’t have the approval for one such project.


And the engine alone doesn’t make the rocket what it is! Hence, on their own, the team had to master several other components, sub-components that went into a rocket. It would be 1982 before ISRO developed these engines and later got the approval for incorporating the engine into a project - the PSLV.


During the development of the PSLV in the late 80s, it was decided that the 60-ton thrust engine developed with the French would fit into the second stage. PSLV is a 4-stage rocket that is powered by solid-liquid-solid-liquid configuration. 


Finally, it was in 1993 that the PSLV lifted off for the first time, but the mission was a failure, after it encountered an error mid-flight. However, most of the critical systems on-board the rocket were validated despite the failed mission. However, nearly a year later in October 1994, the PSLV lifted off majestically and had proven the rocket’s capability to lift 1000 kg to orbit. 


Since then, the PSLV has flown 50 times. With only 2 missions failing. However, the ‘obstinate Vikas Engine’, which was developed by Nambi Narayanan and his team had flown flawlessly in all 50 flights. A fitting tribute to the great Indian visionary, scientist and industrialist it was named after!