by S. Prasad Ganti
GSLV-D6 on the Launch Pad Credit: ISRO
Indian Space Research Organization launched a communication satellite. On the surface of it, it may not be a big piece of news. But since I have been following the space news from ISRO as much as I do from NASA or SpaceX, there are some baby steps leading to something bigger.
The two-ton satellite called GSAT-6 is well on its way to geostationary orbit. It stays in the same place above the Indian subcontinent providing communication services to the country. Launched aboard GSLV-D6 (Geostationary Satellite Launch Vehicle), the satellite was placed in a geostationary transfer orbit or GTO. The satellite will then use its own propulsion to reach the final orbit about 36,000 kms above the Earth where it will be parked in a fixed slot for rest of its life.
About 60% of the two-ton satellite is fuel to propel it into the higher geostationary orbit. Afterwards the fuel is burnt to operate the communications equipment to provide services to the country for nine years.
India has developed complex satellites before and attained a level of maturity in building satellites, but the launch capability was lagging behind. Some of the earlier satellites were launched using foreign launch vehicles like European Space Agency’s Ariane. Lifting a two-ton satellite into a GTO requires more power and complexity. The current launch vehicle GSLV uses three stages to give the payload a heavy boost.
The first stage is powered by solid fuel. Like the first relay runner, a solid stage provides a massive push. The solid stage cannot be stopped once ignited. It cannot be controlled easily. After a big push during the first few seconds of a rocket launch, its job is done, and it falls back to the Earth. The second stage is powered by liquid fuels. A liquid fuel and an oxidizer are stored in separate tanks and are pumped into a combustion chamber to generate the thrust. The liquid stage is controllable since the pumps can be slowed down or turned off. These two stages were mastered in the earlier phases of India’s space program.
The third stage is powered by cryogenic engines. Cryogenics means dealing with super cooled matter close to absolute zero of -273 degrees Kelvin. The super cooled fuel and oxidizer give lot of punch per unit of weight. These propellants are difficult to handle and tame in an engine. The technology is so complex that very few countries in the world have this capability. The first two Indian attempts in 2010 led to failures. In 2014, the first successful launch with cryogenic engines took place. This is the second successful launch and augurs well for the Indian space program.
Next in line is the launch of newer generation of GSLV called Mark 3, which is very likely to happen in next couple of years. Each succeeding generation of space vehicles leads to more lifting capabilities, and more mastery over space launches. Whether it is SpaceX, NASA, ISRO, ESA or JSA, it only bodes well for humanity’s future in space.
Amateur Astronomers Association of Princeton 