GSAT-9 heralds cost-saving electric propulsion

This week’s space mission, GSAT-9 or the South Asia Satellite, will carry a new feature that will eventually make advanced Indian spacecraft far lighter. It will even lower the cost of launches tangibly in the near future. The 2,195-kg GSAT-9, due to take off on a GSLV rocket on May 5, carries an electric propulsion or EP system. The hardware is a first on an Indian spacecraft. Dr M Annadurai, Director of the ISRO Satellite Centre, Bengaluru, explained its immediate and potential benefits: the satellite will be flying with around 80 kg of chemical fuel – or just about 25% of what it would have otherwise carried. Managing it for more than a decade in orbit will become cost efficient. In the long run, with the crucial weight factor coming down later even for sophisticated satellites, Indian Space Research Organisation can launch them on its upcoming heavy rockets instead of sending them to space on costly foreign boosters. Shortly, its own vehicle GSLV MkIII is due for its full test flight. Dr.  Annadurai told The Hindu that GSAT-9′s EPS would be used to keep its functions going when it reaches its final slot – which is roughly about two weeks after launch – and throughout its lifetime. Normally the 2,000-kg class INSAT/GSAT communication satellites take 200-300 kg of chemical propellants with them to space. The fuel is needed to keep them working in space, 36,000 km away, for 12 to 15 years. Dr. Annadurai said, “In this mission, we are trying EPS in a small way as a technology demonstrator. Now we have put a xenon-based EP primarily for in-orbit functions of the spacecraft. In the long run, it will be very efficient in correcting the [initial] transfer orbit after launch.” He said that the space agency normally uses up 25-30 kg of fuel on the satellite each year to maintain its functions and orbit position. An EP system would vastly bring this amount down. Next big trend A xenon based EPS can be five to six times more efficient than chemical-based propulsion on spacecraft and has many uses, according to Dr Annadurai, whose centre assembles all Indian spacecraft. A 3,500-kg EPS-based satellite, for example, can do the work of a conventional spacecraft weighing 5,000 kg, but cost far less. “One day, we should be able to launch a 5-tonne equivalent spacecraft – but weighing less than it – on our own GSLV [MkIII.] We are not yet there,” he said. All this is on the way, may be in around three years. GSAT-20 is planned as the first fully EPS-enabled satellite; its features were not immediately available. ISAC and the Kerala-based Liquid Propulsion Systems Centre are lead centres in developing it. A trend that started about four years back, EPS is expected to drive half of all new spacecraft by 2020. For Space-dependent sectors across the globe, the economic benefits of EP systems are said to be immense. Currently government-owned and private space players agencies are said to be scrambling to make space missions 30 per cent cheaper than now – by lowering the per-kg cost of lifting payloads to specific distances.

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