With the successful launch of Geosynchronous Satellite Launch Vehicle (GSLV) D6 from India’s premier rocket launching station at Sriharikota on Aug. 27, Indian space scientists have undoubtedly reached yet another important milestone and achieved a new momentum in the country’s long quest for perfecting indigenously developed cryogenic technology, which involves the use of rocket propellants at extremely low temperatures in flight.
Indeed, it has been an arduous journey for Indian rocket engineers and scientists as the bold attempt to master the art of delivering heavy payloads to outer space has not been easy. International sanctions were imposed on Indian Space Research Organization (ISRO) so that it cannot acquire dual-use technologies from the Russians.
Clearly, an influential lobby benefitting from commercial use of space technology was not comfortable with the idea of a new player entering the select grouping that possesses the capability to launch heavy communication satellites at one go. Since rocket engines need to produce large amount of thrust to neutralize earth’s gravitational pull, a combination of liquid oxygen and liquid hydrogen offers the highest energy efficiency in such a scenario. However, oxygen, being volatile, remains in liquid state only at temperatures below minus 183 degree Celsius and hydrogen at below minus 253 degree Celsius.
America was the pioneer in developing cryogenic rocket engines. The Centaur, a rocket stage designed for use in space launch vehicles, with RL-10 engines registered its first-ever successful flight in 1963 and is still in use on NASA’s Atlas V rocket. And American space scientists’ phenomenal success in cryogenic technology eventually paved the way for introduction of sophisticated J-2 engine, which powered the upper stages of the historic Saturn V rocket that sent humans to the Moon. The Japanese followed suit by developing the LE-5 pump-fed engine, possessing a thrust of 10 ton in vacuum, in 1977 for its H-1 launch vehicle.
France’s HM-7 cryogenic propellant rocket engine with unique regenerative cooling technology took Ariane-1 to space in December 1979 and the Chinese broke the barrier for the second time in Asia with their YF-73 gimballed cryogenic engine, which was used to lift Changzheng-3 orbital carrier in mid-1980s.
That mastering the art of cryogenic science is no child’s play can be ascertained from the fact that the erstwhile Soviet Union, despite being the first country on earth to put a satellite and later a human being in space, managed to successfully launch a rocket with a cryogenic engine only in 1987. But then, India was in desperate need of graduating into the exclusive cryogenic club as a rocket stage based on a cryogenic engine offered the most potent way of revolutionizing the process of placing indigenously built heavy satellite into earth’s outer orbit.
Cryogenic engineering was that magical medium, which would effectively enable Indian scientists to lift the country’s most successful Polar rocket launch system (PSLV), capable of placing comparatively lighter earth-viewing satellites in geostationary transfer orbit, to a far more powerful GSLV stage for transporting manned space-flight and heavier spacecraft into the orbit from Indian soil in the near future.
Besides, in comparison to PSLV’s four stages that alternate between solid and liquid fuels, GSLV has three stages, with only the first stage depending on solid fuel. Most importantly, while PSLV is designed mainly to deliver payloads to Sun-synchronous low earth circular polar orbits of 600-900 kilometers altitude apart from launching satellites of lower lift-off mass of up to about 1400 kilogram to the elliptical geosynchronous transfer orbit (GTO), the GSLV can exclusively deliver large communication satellites to the highly elliptical 250 x 36000 kilometer GTO.
The payload once placed in GTO successfully by the launch vehicle is thereafter raised to its final geo-synchronous earth orbit destination of maximum 36,000 kilometer altitude by firing the in-built engines on board.
And after the Russians backed out of a deal to supply two cryogenic flight stages as well as transfer of technology for manufacturing in India due to sustained international pressure, ISRO finally launched the cryogenic upper stage project in April 1994. Though, skeptics claim that the India-produced GSLV cryogenic engine is a product obtained by reverse engineering of the Russian made KVD-1 cryogenic engine — a modified version of 11D56 engine that was originally developed for one of the upper stages of the scrapped N1 lunar project — the truth is somewhat different.
The Russian design involved a complicated staged combustion cycle for increasing the engine efficiency by partially burning Hydrogen with a little oxygen in a gas generator.
The hot gases in return drive a turbo-pump and are then injected at high pressure into the thrust chamber where the rest of oxygen is introduced and full combustion takes place. Whereas the Indian version of the cryogenic engine model operates on gas generator cycle and has been conceived, configured and realized by ISRO’s scientists exclusively.
As the design of the launch vehicle and the working of the cryogenic engine have been validated by two successful launches, ISRO should now not only gear up for the next technology leap in space cryogenics and explore new commercial opportunities, but also work on actualizing ex-President Abdul Kalam’s dream reusable launch vehicle project to make the global cost of launching affordable for relatively poorer nations.
