Water could propel future Indian satellites

Water could propel future Indian satellitesPlasma with water as propellent (Middle) - Electric Thruster

An Indian start-up foraying into space technology is coming up with a propulsion system for satellites known as Microwave Thruster, designed to run on water as fuel medium. The promising technology has zero erosion characteristics, thus increasing the on-orbit lifespan required for a propulsion system.

"Microwave Thruster produces more thrust per kilowatt of power consumed, compared to most other type of electric propulsion," claimed Yashas Karanam, Director and Chief Operating Officer of Bangalore-based Bellatrix Aerospace.

Bellatrix is the recipient of the prestigious Technology Development Board National Award – 2017 for its innovative satellite propulsion design, for which it holds a patent.

"Electric propulsion is different field that offers up to 10 times higher specific impulse than chemical propulsion systems for the same amount of fuel. An electrically powered spacecraft propulsion system uses electrical energy to change the velocity of a spacecraft," Yashas told Indian Science Journal. "Using electric propulsion instead of chemical propulsion, manufacturers can reduce the overall satellite mass or otherwise accommodate up to four times more payload with the same satellite mass."

Satellite manufacturers have to pay huge launch costs to take their satellites to space, partially because rockets are expendable in nature. But electric propulsion would bring down the overall cost of satellite mission, said Yashas. However, there are only very few players worldwide working on electric propulsion, he added.

Yashas said, conventional chemical propulsion is not an attractive option for interplanetary missions, because there are no refuelling stations to refill the propellant. For future missions to Moon or Mars missions, electric propulsion is the only road to go.

In a satellite using chemical propulsion, fuel constitutes majority of the satellite mass, thus leaving very little space for useful payload. Most of this fuel is used for orbit raising, i.e., to take the satellite from the parking orbit where the rocket leaves it, to the dedicated orbit of the satellite. For example, communication satellites work in geostationary order of 36,000 kms.

All these factors were the motivation for Yashas and his colleagues to venture into the area of electric propulsion. They are now working to see that electric propulsion systems replace most of the chemical propulsion systems by 2025.

Electric Thruster

Electric propulsion is not a new concept. Work in this area had started in the mid 20th century. Russia has pioneered in Hall Effect Thruster Technology and USA in Gridded Ion Thruster Technology. There are many universities and research institutes across the world working on different types of electric propulsion technology.

The main constraint that has restricted electric propulsion from use in spacecraft was the power availability on spacecraft. Higher power availability can enable the use of high power thrusters for orbit raising. In previous generation spacecraft where power available for propulsion was low, only small electric thrusters with lower thrust output could be used. This would make orbit raising time to go over a year. Since power available now for propulsion systems is higher, satellites can use high power thrusters capable of delivering more thrust. This makes it possible for satellites to reach their orbit in four months, thus making electric propulsion a good choice for satellite propulsion.

With the advances in solar panel technology, solar panels today have achieved great efficiencies and can generate significantly higher power on satellites. Also, power consumption of various satellite sub-systems has reduced due to advances in electronics. This has provided more scope for electric propulsion.

Several starts-up in India have entered the field of space technology, to compliment the pivotal role of state-run Indian Space Research Organisation, ISRO. But "ISRO has been very supportive to us in our journey as a mentor," said Rohan M. Ganapthy, CEO of Bellatrix.

With ISRO privatizing its satellite manufacturing and also the PSLV launch vehicle, it offers a big opportunity for private players to look at space business. Several start-ups are now working on many areas like satellite manufacturing, satellite internet services, satellite data analytics, etc. "All these companies, with support from ISRO are together contributing towards building a better space ecosystem in India," added Rohan.

As of today, there is no institutional regulatory mechanism India for private launch service providers. Since ISRO has started pushing the privatization of PSLV and also satellite manufacturing, it is expected that India will soon have a policy framework for participation of private players in satellite manufacturing and launch industry, said Rohan.

Yashas, Rohan and their young team are now looking to provide an economical alternative by developing its own small satellite launch vehicles. Named 'Chetak', the two-staged, reusable rocket can launch smaller satellites up to low-earth orbit at a fraction of the cost. Besides, they are also working on different types of thrusters - Hall Effect Thrusters (electric propulsion), Nano Thrusters (dedicated propulsion system for nano satellites), Green Monopropellant Thrusters (chemical propulsion, effective alternative to carcinogenic hydrazine monopropellant thrusters).

Image (Top) - Plasma with water as propellent (Middle) - Electric Thruster

Image courtesy: Bellatrix Aerospace

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