Why ISRO's New Engine and Mk III Rocket Are Reasons to Forget 1990 Cryogenic Scandal

Even though the US blocked the transfer of cryogenic technology to India towards the end of the Cold War, ISRO has much to gain today from working closely with the West and with NASA.

The GSLV Mk III ahead of a launch in December 2014. Its third, upper stage was a passive cryogenic engine. Credit: ISRO

The GSLV Mk III ahead of a launch in December 2014. Its third, upper stage was a passive cryogenic engine. Credit: ISRO

The Times of India ran a story on May 22 with the headline: ‘Indian rocket that US once ‘grounded’ will put Isro-Nasa satellite in space’. Those who have followed the story of the Indian Space Research Organisation’s (ISRO’s) GSLV programme will know what this is about. The United States crippled India’s cryogenic engines programme in the late 1980s, just as a deal was about to be completed with Glavkosmos, an official space affairs entity of the former Soviet Union. If it had gone through, ISRO would have received two cryogenic engines, technology transfer and a skill-development programme for only Rs 230 crore. But because it didn’t, the GSLV was not ready to fly until 2010 instead of sometime in the early 1990s. This incident has had a cascading effect on a range of issues since then – from trade deal negotiations to politics – and has reared its head again now that the first developmental flight of the GSLV Mk III has been scheduled for June 5.

In light of this, it is clear what the Times of India has tried to do: inflame old passions with a provocative headline. The US didn’t ground any rockets; ISRO was still allowed to fly them. But to be sure, the untenability of the American position has rested on the fact that it came at India swinging the hammer of the Missile Technology Control Regime (MTCR). The US had contended that the cryogenic engines could be used by India to power military projectiles. This makes no sense because military operations require all available assets to be deployed at very short notice – whereas fuelling a cryogenic engine and then loading it onto a rocket takes days. The eventual outcome was for ISRO to have abandoned its own GSLV development programme (initiated in 1986) in favour of an international partnership, only for that partnership to be paralysed by a third country.

Nonetheless, at the time the Glavkosmos deal fell through, ISRO had still been able to secure two mockup engines, four fully qualified engines and an option to purchase three more for $9 million. However, it did not know how to use them or build its own. This prompted an 18-year-long programme that resulted in three kinds of GSLV rockets. All variants had a solid-fuel first stage and a liquid-fuel second stage. The GSLV Mk I used the Soviet cryogenic engine for the third stage. Its first flight was in April 2001. The GSLV Mk II used the indigenous CE 7.5 cryogenic engine, first flying in April 2010. The GSLV Mk III will use the CE 20 cryogenic engine and is set to fly for the first time on June 5. Without the Glavkosmos engines, it is conceivable that the Mk III might not have materialised until 2020, if not later.

The hydrogen problem

An indigenous cryogenic engine being tested. Source: ISRO

An indigenous cryogenic engine being tested. Source: ISRO

The persistence with cryogenic engines owes itself to a dilemma in propulsion engineering. Liquid fuels are less bulky than solid ones, flow better than gaseous fuels and many of them have sufficient energy density to be considered desirable. For example, the PSLV rocket’s second stage is a Vikas engine fuelled by unsymmetrical dimethylhydrazine (UDMH), which is also not sensitive to shocks and can be stored for a long period of time. However, the highest exhaust velocity provided by any fuel happens to be from a gas: hydrogen. When UDMH burns in the presence of nitrogen tetroxide, the exhaust velocity is 3.42 km/s. When hydrogen burns in the presence of oxygen, it is 4.55 km/s. The problem is that, as a gas, it is more difficult to pump hydrogen through an engine than is UDMH.

The engineer’s solution to this problem is to turn hydrogen into a liquid and then use it. But the resulting engine system isn’t very straightforward. Hydrogen liquifies at 20 kelvin (-253 ºC) and oxygen, at 89 kelvin (-184 ºC) – which means they would have to be stored and transported in special tanks, and fed into engines using special booster and turbo-pumps. Engine components have to be made of high-grade alloys because, at cryogenically low temperatures, normal metals become brittle. And unlike other, conventional rocket fuels, hydrogen has extremely low density and leaks very easily. There are a host of other issues and, all together, cryogenic engines require a level of care more exacting than the spaceflight industry is already accustomed to. But the hydrogen advantage is considered to be worth it.

The CE 7.5 engine uses a staged combustion cycle. Two booster pumps supply cryogenic hydrogen and oxygen to a turbo-pump, which then feeds the engine’s combustion chamber. The turbo-pump supplies fuel and oxidiser. It is powered by a turbine, in turn driven by combusting a small amount of the fuel in a pre-burner. The name of the cycle is derived from the fuel being combusted in two steps; this leads to increased fuel efficiency. The ratio of the mixture is controlled by a regulator. While the main engine provides the thrust, two vernier engines ensure the rocket follows its trajectory by firing smaller pulses.

The first test flight of the CE 7.5 engine was onboard the GSLV D3 on April 15, 2010. It failed 295 seconds after liftoff as the rocket tumbled out of its flight path. While ISRO scientists initially believed that the vernier engines had failed, a detailed report submitted in July 2010 pinpointed the booster pump supplying cryogenic hydrogen to the turbine. The pump started up 294.06 seconds after liftoff and operated normally for 0.9 seconds. However, it shutdown anomalously in the next 0.6 seconds, starving the engine. The tragedy forced ISRO to use its Russian engines for the next GSLV launch.

The next-generation CE 20 engine ISRO has been working on has three significant differences compared to the 7.5 variant, apart from the performance characteristics (thrust, specific impulse, etc.). First, the CE 20 will not require separate vernier engines. Instead, former ISRO chief K. Radhakrishnan has said that its nozzle will be able to make small rotations (i.e. gimbal) to control the rocket’s trajectory. This improvement is in keeping with international trends that have jettisoned vernier engines to reduce complexity and increase control. Second, the CE 20 will be completely indigenous; the CE 7.5 uses Russian technology and is of Soviet heritage (although it sports some differences). Third, the CE 20 will use a gas generator cycle instead of a staged combustion cycle.

Towards full control

In the staged combustion cycle, heat from the turbine (powered by the pre-burner) is channelled to the turbo-pumps while its exhaust is sent to the combustion chamber – i.e. optimal fuel-use. In a gas generator cycle, the only difference is that the turbine exhaust is discarded. While this reduces fuel efficiency, it makes the engine easier to build. This complexity advantage is important for ISRO, an organisation that does not have as much to spend as does NASA and also has a smaller workforce. As Radhakrishnan explained during an interview to Frontline in February 2014:

If you look at the reliability aspects – establishing a reliable system and the time required for that – we can work in parallel. The issue is relevant in the context of GSLV Mk III, for which we were working on the engine and stage elements in parallel. The turbo pump … has already been tested. … We have tested the thrust chamber along with the injector, igniter and the nozzle. … Now, when we have sufficient knowledge about the ignition characteristics, the combustion instability aspects and performance in different regimes of mixture ratio, then we can start with engine test and then the stage test. So the time required from now to qualifying the stage becomes less. This is the main advantage. The flexibility that is available in a gas generator cycle is much more because individual systems can be tested from the input/output point of view and they can be qualified in parallel. In the previous [staged combustion cycle] situation, the stage process was started after the engine qualification.

If ISRO pulls off the June 5 flight, it will be a monumental occasion for the organisation. The Mk III is set to be able to carry 4,000 kg to the geostationary transfer orbit (GTO), the perch of choice for communication satellites. The heaviest satellite ISRO has built till date is the 3.4-tonne GSAT-10, launched in November 2012 by an Ariane 5ECA rocket from the Guiana Space Centre. So when the Mk III enters operation, it will mean ISRO can then build and launch all its satellites and not have to rely on Arianes. Full control, from soup to nuts, including the ability to bring launch costs down further.

The ‘legacy of bitterness’

The CE 20 cryogenic engine. Credit: Wikimedia Commons, CC BY-SA 3.0

The CE 20 cryogenic engine. Credit: Wikimedia Commons, CC BY-SA 3.0

At the same time, the comfort of self-reliance should not come at the cost of bigger ambitions. For example, while the GSAT satellites are unlikely to get much heavier, the Mk III will also be able to carry 8,000 kg to the low-Earth orbit (LEO), where most scientific satellites are. This presents a significant opportunity to build heavier, more sophisticated scientific payloads, which can only arise from closer collaboration with research institutions and the ability to plan ahead. Case in point: the media recently covered ISRO’s invitation to scientists to submit ideas for a probe to Venus in the near future. What did not receive coverage was the oddity of inviting ideas after ISRO had decided to fly a probe and not the other way round, where research goals dictate mission characteristics and feasibility.

In fact, in this and many other ways, ISRO has a way to go before it appears to be in its “corrected fullness”, which brings us back to India-US relations apropos space. As the Times of India article quoted in the first line states, “Leaving the past behind, Isro and Nasa are busy building the 2,200-kg NISAR satellite, which will provide a detailed view of the earth by using advanced radar imaging” (emphasis added). The italicised part is not correct.

In 2006, negotiations for a Commercial Space Launch Agreement (CSLA) between India and the US were hampered by negotiators being aware of a “legacy of bitterness”, especially among Indians resentful of the American threat of sanctions in 1990. This was a political complication. However, ISRO had helped extend a satellite-aided search-and-rescue service initiated (among others) by NASA to the Indian Ocean using a payload installed on the INSAT-2 satellite series starting from 1992 itself. Effectively, ISRO-NASA relations had little “leaving the past behind” to do – and they have also helped ease India-US relations vis a vis space.

But generally, rekindling any latent resentment now would be counterproductive. Apart from having been a blessing in disguise for setting India on the path to self-reliance, India has need for US support more than many might be willing to acknowledge if ISRO is to become a more important player. Two successes that ISRO’s fans have been fond of trumpeting – Chandrayaan 1 and the Mars Orbiter Mission (MOM) – would not have accrued the significance they have without American help. Some payloads onboard Chandrayaan 1 involved in discovering water-ice on the Moon were the result of the India-US Joint Working Group on Civil Space Cooperation. As for MOM: ISRO would not have been able to ‘talk’ to it (half the time) without the Deep Space Network. We also benefit from the Mars Working Group that organises joint explorations of the red planet. Indian and American scientists regularly collaborate on research and Indian scientists – most famously, A.P.J. Abdul Kalam – regularly train at American facilities. Moreover, and pursuant to the “leaving behind” statement as well, many private American companies have had their satellites launched onboard PSLV rockets thanks to ‘one-time’ waivers from the US government (to move around the unsigned CSLA). Between September 2015 and February 2017, commercial American payloads had flown on nine ISRO missions to launch 115 satellites.

Help from politics

George W. Bush and Manmohan Singh, 2006, when they sighed the India-US Civil Nuclear Agreement. Credit: Wikimedia Commons

George W. Bush and Manmohan Singh, 2006, when they sighed the India-US Civil Nuclear Agreement. Credit: Wikimedia Commons

Not surprisingly, better political ties have also eased India’s rise as a space power. As Vidya Sagar Reddy writes in the book Space India 2.0: Commerce, Policy, Security and Governance Perspectives (2017):

In 2004, India and the US sought to amend their stagnant relationship to respond effectively to emerging geopolitical dynamics in the Asia-Pacific region. The Next Steps in Strategic Partnership (NSSP) was devised, requiring both countries to undertake a series of reciprocal steps in the trinity areas. By the end of that year, ISRO headquarters was removed from the US Department of Commerce ‘Entity List’ followed by removal of Vikram Sarabhai Space Centre, Liquid Propulsion Systems Centre and Satish Dhawan Space Centres. This set the stage for greater cooperation between ISRO and NASA.

Victoria Samson writes in the same book:

A joint statement released in June 2016 noted that “the U.S.-India defence relationship can be an anchor of stability, and given the increasingly strengthened cooperation in defence, the United States hereby recognises India as a Major Defence Partner.” This announcement also acknowledged that India and the United States had “reached an understanding under which India would receive license-free access to a wide range of dual-use technologies in conjunction with steps that India has committed to take to advance its export control objectives.” But even this statement kept the space cooperation to the civil side, identifying “earth observation, Mars exploration, space education and manned spaceflight” as areas for future cooperative efforts.

She adds that other areas of cooperation include global positioning systems, space situational awareness, maritime domain awareness, peaceful uses of outer space and, of course, the CSLA.

Today, we are less than two weeks away from the Mk III D1 flight. It will attempt to launch the GSAT-19 satellite. The S200 and L110 engines are already in Sriharikota. The CE 20 engine has completed over 200 tests and is among the most powerful of its kind. And while there is no place for jingoism, the engine’s provenance is unquestionable. At this point, there is little doubt that comparisons are going to fly, especially with the RS-25 cryogenic engines used by the former Space Shuttle programme, in an effort to highlight ‘how far India has come without US help’. As always, they are going to be meaningless. For one, RS-25 were first-stage engines while the CE 20 is a third-stage engine. But there is another more important reason – ISRO’s trajectory is very different from NASA’s even as the post-Cold-War world order has pushed India and the US closer together. NASA is facing significant budget cuts going ahead even as it plans manned cislunar and Mars missions. ISRO, to further cement its independence as well as take a bigger bite into commercial spaceflight, is en route to building two even-bigger launch vehicles. There is no longer any room for bitterness.