How ISRO developed the indigenous cryogenic engine.This is from last year when GSLV II was launched.
The year was 1987. V Gnanagandhi, head of the cryogenic engine project at the Indian Space Research Organisation (ISRO), wanted to set up a highpressure hydrogen plant in Mahendragiri near Thiruvanathapuram. But an official from the supplier of the machinery, a German company called Messers Grieshem, suddenly threw a spanner in the works.
"There are snakes and elephants on the roads in India," he told them. "How can I come there?" Gnanagandhi reached a compromise with the Grieshem executive. He need come only as far as Mumbai the entire ISRO team would meet him there. He agreed. The German—his name is now forgotten—agreed to sell the machinery, but was also inquisitive. "Why do you need a highpressure hydrogen facility?" he asked.
"We are using it to launch rockets," came the answer. "You cannot just fill an engine tank with highpressure hydrogen," he told the ISRO team. "It will evaporate in no time." The ISRO engineers, thus, learned a thing or two about dealing with hydrogen at high pressure.
A few days ago, Gnanagandhi retired after watching his baby fly on a Geostationary Launch Vehicle (GSLV), marking the culmination of a journey that was shot through with frustrations, technology denials, quiet diplomacy and sheer hard work. After two decades of development, India developed the cryogenic technology, giving it the muchneeded capability to launch mediumsized satellites in a geostationary orbit, and joined an exclusive club of six nations. But on that day in 1987, at their Mumbai Guest House, ISRO engineers, led by Gnanagandhi, were taught a thing or two about hydrogen under pressure by their German guest.
Obtaining The Engine Brought into the nascent cryogenic engine team in 1984, Gnanagandhi had begun his job with clean slate. He had not even heard about the cryogenic engine. He didn't know how to get liquid oxygen or liquid hydrogen, let alone how to use them in an engine. But he learned quickly, set up the facilities, and made a onetonne prototype engine by 1988. It blew up during a test. "We had used liquid nitrogen to clean the nozzle," says Gnanagandhi. "And nitrogen solidifies and clogs the nozzle at liquid oxygen temperatures."
ISRO was led by UR Rao at that time. ISRO had been planning larger rockets. Cryogenic engines were absolutely essential to put satellites in geostationary orbit, but the technology was difficult and a closely guarded secret. India had offers of engines. US firm General Dynamics offered first at a high price, and so did the French. It was then that Russia, which was going through difficult times, offered it at a reasonable price. India signed a deal in 1991 for two engines and the technology.
Everything looked good, but soon wasn't. The Americans pressurised the Russians into reneging on the deal, saying its engines will be used for nuclear missiles. ISRO would get the engines but not the technology. UR Rao went to talk to the Americans, and to tell them something that everybody knew: cryogenic engines cannot be used in a missile. But the US had strong commercial interests in denying India the technology. Rao's meeting with vicepresident Al Gore was futile.
Rao then negotiated with the Russians. "I told them that I had paid them too much money for just two engines," says Rao. "If you are not giving me the technology, give me six more engines." Eventually ISRO got seven engines. However, flying them was not a simple matter as there were no data about their performance. The engines that ISRO got hadn't been flown yet in any rocket. ISRO engineers discovered they had to work hard to make the engines fly in their launch vehicle. "We found that the Russian engines did not perform as well as we expected," says Vishnu Kartha, who now heads the cryogenic project.
If flying the Russian engines was hard, copying the engine design was harder. The Russians had designed these engines in the 1960s but not flown them, probably because they were still not flight ready. Moreover, they used a technology— called stage combustion—that was efficient but difficult. It made the engine a bit heavy but gave the highest efficiencies for a specific amount of propellant. The indigenous engines had to be exactly like the Russian engines: the GSLV has already been planned based on them.
The Indian government gave a formal approval to the Cryogenic Upper Stage (CUS) project in 1994. The budget was Rs 300 crore. ISRO then made a key decision quite in keeping with its tradition: involve the private industry from the beginning. "We didn't want to first develop the technology and then transfer it," says BN Suresh, now Vikram Sarabhai distinguished professor in ISRO.
The two major partners were Godrej and the MTAR Technologies. Godrej set up the rotary vacuum brazing facility in Mumbai. Brazing was a key and difficult technology, and setting up the facility took more than a year. MTAR made the turbo pump and some other components.The sophistication of the cryogenic engine would be obvious from a few simple facts. The liquid hydrogen is kept at 253 degree centigrade. The turbo pump operates at 500 degree centigrade and rotates 40,000 times a minute. The combustion temperature is around 3,000 degree centigrade. The pressure inside the combustion chamber is 60 times the atmospheric pressure. The chamber wall has to withstand the high pressure and temperature. No material can withstand a temperature of 3,000 degree centigrade, and so the combustion chamber wall has to be cooled.
ISRO's cryogenic team made the first 7.5tonne engine in 2000. It blew up while being tested. The hydrogen valve had prematurely closed, affecting the oxygenhydrogen ratio in the combustion chamber. "We became failurehardened," says Mohammed Mulsim, head of the cryogenic project at that time. "After each failure we went back not to the Russian engines but to the drawing board." They succeeded finally in 2002. The indigenous cryogenic engine was qualified in 2003. It took another four years to integrate it with the GSLV.
But the first flight failed in 2010, as the engine shut down three seconds after ignition. ISRO then conducted a thorough review of the entire GSLV project. For the cryogenic engine, special vacuum testing facilities were created at Mahendragiri. By 2013 end, every likely cause of failure was looked into. A few days before the GSLV flew on January 5, ISRO officials conducted a review meeting to clear the vehicle for launch. Such meetings usually take several hours. This one ended in 45 minutes. Every possibility had been analysed, and project leaders were quietly confident.
When it flew, the GSLV put the satellite into orbit with a precision never possible with the Russian engines. "We took a long time to develop the engine," says ISRO chairman K Radhakrishnan, "but all countries took 1015 years to develop cryogenic technology." ISRO now has to develop a more powerful engine, to put a 4 tonne satellite into geosynchronous orbit. The older generation that led the first cryogenic engine development has retired. It has been such a long journey, it gave the younger generation now in command a deep understanding of cryogenic technology. And they have long stints left in ISRO.