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The road to India's Cryogenic Engine
Armies tend to herald their victories with the blowing of bugles. The Indian Space Research Organisation (ISRO) chose to announce its entry into the exclusive club of nations capable of building cryogenic engines with a thunderous sound of a rocket test that lasted 12 long minutes.
The sound, equivalent to that of 10 Jumbo jets taking off simultaneously, reverberated across the Mahendragiri hills in Tamil Nadu where Indias ultra-modern liquid engine test facility is located.
It signalled the culmination of ISROs 13-year quest to build engines using cryogenic fuels that are super-cooled to around minus 250 degrees. (Cryo originates from the Greek word Kryos which literally means ice-cold.)
The quest began in 1993 when Russia, under pressure from the US, reneged from an agreement to supply India with the technology to build such engines. The Americans successfully argued that it would give India the capability to launch Intercontinental Ballistic Missiles (ICBMs).
ISRO needed cryogenic engines to power the upper stages of its Geo-Synchronous Launch Vehicle (GSLV) which is capable of putting two-tonne INSAT-class communications satellite into a geo-synchronous orbit at 36,000 km above the earth.
Cryogenic engines that use a mixture of super-cooled liquid hydrogen and oxygen as propellants are highly efficient providing more bounce per ounce of fuel.
The thrust these engines generate is usually 50 per cent more than that provided either by liquid or solid rockets for the same weight of fuel (see graphic). In doing so, it gives a space-faring nation the flexibility to put heavier satellites or other payloads into space.
So as not to delay its GSLV programme, ISRO renegotiated the agreement with Russia for outright purchase of two cryogenic engines.
It simultaneously began designing and building an indigenous cryogenic engine similar to the Russian one for future flights. ISRO had hoped to complete the indigenous project within five years but the sheer complexity of building such an engine frustrated scientists for many years.
Barring the performance designs given by the Russians, the fully assembled engines purchased by them were, as one scientist put it, like a blackbox.
That meant that ISRO had to do everything from scratch. Given that the rocket has to withstand extremely hostile temperatures that vary from super-cooled temperatures before ignition to superhot ones when it fires, metallurgy was a key hurdle that had to be overcome.
The right alloys had to be developed that could take these massive temperature fluctuations and also keep the weight of the engine down.
There were other complications. The problem with liquid hydrogen is that it has a tendency to return to its gaseous form rapidly and is highly inflammable.
Cryogenic engine under testIt ignites spontaneously when it comes in contact with atmosphere. So the temperature has to be tightly monitored and the pipelines and pumps through which liquid hydrogen is fed have to be totally leak proof. This meant that joints had to be welded rather than screwed tight.
The cryogenic engines project director Mohammed Muslim says, There is absolutely no margin for error. Other major hurdles were developing the thrust chamber, which required intricate grooves to be machined, and the high speed turbo pumps.
Initial efforts by ISRO engineers met with little success. The first test that took place in 1999 ended in abject failure when one of the gas generators blew on the test stand.
With delays inevitable, in 2001 ISRO negotiated with the Russians to supply five more cryogenic engines to power its GSLV flights at a cost of $5 million (Rs 20 crore) each.
It was only in 2006 that the ISRO team felt it had, to an extent, mastered the range of technologies needed for the test. The first firing of the engine in October 2006 went off smoothly for the planned 50-second duration.
Emboldened, the scientists tried for a longer duration in January 2007 but had to abort it within 30 seconds as an extraneous fire occurred in one of the pipelines. More recently in August this year, the system fired smoothly for 500 seconds but because of a technical glitch, it had to be aborted before completion.
After identifying the problem, the scientists felt that it was a minor issue and so scheduled another test for mid-November. They waited anxiously at the Mahendragiri test stand to watch as the countdown began for the engine. This time the test was flawless.
ISRO Chairman Madhavan Nair, who was there too, told India Today: For ISRO, it is the culmination of the development of rocket technologywe are now totally self-reliant in the entire range of rocketry whether solid, liquid or cryogenic.
Nair points out that the development was critical not just because of the foreign exchange it saves but also because getting cryogenic engines from the international market is proving increasingly difficult.
He says, Not only were other nations asking for the moon in terms of price but they were also not available for the next five years. He denies that India took Russian help to develop the engine as alleged by some scientists and points out that ISRO not only indigenously developed a host of new materials needed for the engine but also the various critical components for it.
Much more though needs to be done. The research organisation is in the process of building the more powerful GSLV Mark III launch vehicle capable of putting a four-tonne INSAT class satellite in orbit, almost twice the weight of its current capacity.
For this, an all new heavy cryogenic engine is being developed. The first test is being planned next year. Even the recently tested cryogenic engine has to be modified if it has to fly for a future mission to carry slightly heavier satellites than the existing two-tonne class.
More importantly, the proof of ISROs capability would be demonstrated only when the cryogenic engine that it has developed flies on the GSLV and performs perfectly. Till then, ISRO scientists can take the much deserved credit while keeping their fingers firmly crossed.
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Russian tech assistance to India has been outstanding - no wonder India is loath to damage such ties over Gorshkov's - though we'll have to wait and see....
