GSLV Gyan: Why Experts Think the Mk III Is a Big Deal for ISRO and India

It is not often that a single rocket inspires conversations across history, politics, astronomy, engineering, communications and business at once.

The GSLV Mk III at the Satish Dhawan Space Centre, Sriharikota. Credit: ISRO

Update: ISRO successfully launched the GSLV Mk III on Monday, June 5.

At 5:28 pm on June 5, the Indian Space Research Organisation (ISRO) will attempt to launch the Mk III variant of its Geosynchronous Satellite Launch Vehicle (GSLV). It will be an historic occasion for the country’s space programme. The Mk III is ISRO’s most muscular launch vehicle to date, being able to lift 4,000 kg of payloads to the geostationary transfer orbit (GTO) and 10,000 kg to the low-Earth orbit. These capacities have been enabled by a third stage powered by an indigenous cryogenic engine, the development of which has engaged ISRO’s best for over two decades. Naturally, the success of this rocket will mean a lot for India, in a variety of ways that can be difficult to assimilate.

So The Wire asked five experts – in space policy, space science, commercial spaceflight, geopolitics and journalism – to chip in. Their comments, edited for clarity, are presented below.

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Rajeshwari Rajagopalan Pillai, Senior fellow and Head, Nuclear & Space Policy Initiative, Observer Research Foundation, New Delhi

The GSLV Mk III launch slated for early June, which will showcase ISRO’s fully indigenous cryogenic upper stage, is a major achievement for India. So far, India has relied on the French Ariane 5 rocket to launch its heavy satellites and it has remained an important component of India-France space cooperation. Two decades ago, this technology was denied to India by the Soviet Union under pressure from the US. Export controls on strategic technologies were used to prevent India from developing missile or nuclear technology. Today, the equations have changed and India is on the other side of the table.

Since the early 2000s, the rationale of technology export control regimes and its dynamics have undergone some change. Despite technology controls, the West, and the US in particular, had to recognise the new reality, that they could not entirely control the spread of technology. But more importantly, changing global political dynamics, especially the rise of China, provided new impetus to the US to change these regimes to include others, such as India, with which there was common interest regarding China.  

At a practical level, India’s development of the GSLV Mk III, capable of launching four-tonne satellites into geostationary orbit, relieves India of dependency on foreign players to launch its heavy satellites. This has been an expensive proposition: the launch cost of heavy payloads is estimated to cost upwards of Rs 400 crore. A successful GSLV Mk III test can make India somewhat self-reliant in launching heavier communication satellites. Some of the other launchers in the market, such as Ariane 5 and the Delta IV Heavy, can launch even heavier payloads, of course.

India’s capability to launch heavy satellites also has significant positive commercial spin-offs. This will make India an important player in the multibillion-dollar global satellite launch market, making India a cost effective and reliable partner for heavy satellite launches, generating additional revenue for ISRO. Given that the future satellite launch market will have a big focus on heavy communication satellites, India has a strong incentive to master this launch vehicle, as it has done with its PSLV. The heavy launcher has the potential also to be used in a future Indian human space programme, even though it is not clear that a political decision on whether India wants to do one or not has been taken yet. Lastly, the enhanced launch capability builds up India’s potential to undertake deep space exploration more seriously.


Rajaram Nagappa, Visiting professor, National Institute of Advanced Studies, Bengaluru

On the heels of the successful launch of the South Asia Satellite on May 5, 2017, ISRO is gearing up for the maiden flight of its four-tonne class GSLV Mk III vehicle in early June. The vehicle will launch the 3,200-kg GSAT 19 satellite, which will carry communication, scientific and experimental payloads. The launch will bring to fruition the efforts put in by the scientists and engineers of ISRO in realising the GSLV Mk III. Having said that, the vehicle development has been substantially delayed from the initial estimate. The first launch of GSLV Mk III was expected to happen in the 2011-2012 timeframe as per the Department of Space Annual Report of 2009-2010.

The GSLV Mk III lower stages are derived from proven technologies of PSLV and GSLV. The cryogenic third stage, C25, however, uses elements of technology different from the cryogenic upper stage (CUS) of the GSLV Mk II. The CUS employs a staged combustion cycle. The C25 on the other hand employs a gas generator cycle. The gas generator cycle has a lower specific impulse (of the order of 4%) but is less complicated and provides a certain level of flexibility in testing. The lower performance with lesser complexity of the stage engineering seems to be a conscious trade-off. The GTO capability of the launcher is now pegged at four tonnes.

It is seen from newspaper reports that integration of the vehicle has commenced. The GSLV Mk III D1 launcher [that will be launched on June 5] will carry the 3,200-kg GSAT-19 satellite (with Ku and Ka band payloads), scientific experiments and an indigenous lithium-ion battery. Knowing the ISRO culture of documentation, strict adherence to laid out processes and the rigour of design/flight readiness reviews, one can expect a successful mission outcome.

However, there is still a gap between transponder requirement and availability. To bridge the gap, heavier satellites carrying more number of transponders as well as increase in launch frequency will be called for. S. Chandrashekar has studied the international communication satellites launched during 2005-2015. His findings indicate that 12% of the satellites fall in the <2,500-kg category; 30% in the 2,500-4,200-kg category; 27% in the 4,200-5,400-kg category; and 31% in the very heavy 5,400+ kg category. This trend is witnessed in ISRO satellites as well. Of the twelve GSATs flown since 2010, five are in 3,000+ kg category. The GSAT-11 under assembly at the ISRO Satellite Centre weighs 5,700 kg and is beyond the GSLV Mk III’s capability. The following suggestions are pertinent in this regard: