Travelling to outer space had been our wet dream and we finally landed on the moon. The dream was fulfilled, but it has now been extended to Mars. However, we are far from it and might not see that happening even in the next decade. Chemical rocket systems have a huge fuel requirement and take up a majority of the weight of the rocket. This propulsion system is mostly used for rocket launch vehicles but we’ll be focussing on satellite propulsion systems in this story.
Satellites don’t require high thrust. Hence, electrothermal and ion thrusters become the standing candidates. Research is still going on to improve the efficiency of these existing systems. A space company in India thinks otherwise. Bellatrix Aerospace, a private company in India, is experimenting with microwave electrothermal thrusters (MET) that uses water as its fuel.
What is Bellatrix Aerospace?
Bellatrix Aerospace primarily deals with satellite propulsion systems including microwave electrothermal thrusters, Hall Effect thrusters and nano thrusters. Their main focus is their Microwave Electrothermal Thruster (patent pending) for satellites that will run on water as a propellant. Back in 2011, Rohan Ganapathy, an aeronautical engineer from Hindustan College of Engineering and Technology, Coimbatore, was busy researching the MET thruster technology. With some progress, Yashas Karanam, an electrical engineer from Sri Jayachamarajendra College of Engineering, Mysore, also joined him. Both of them had a vision of turning the forgotten propulsion system into reality. After receiving a grant of Rs. 20 lakhs from JSW in 2013, they finally came out with a proof of concept by the end of the year 2015.
The company was incubated at the Indian Institute of Science (IISc) in Bengaluru. All the lab facilities and faculty support have been provided by the institute. Apart from working on satellite propulsion systems, the other vertical of Bellatrix includes launch vehicles.
For now, they are focussing on the microwave electrothermal thruster project for which they have already received an order from ISRO for their future satellite missions. Bellatrix Aerospace claims to be the only private company in India working on satellite propulsion systems. They are funded by angel investment and they are actively seeking to raise funding on a much bigger scale for their ambitious future projects.
Efficient propulsion system
Before considering the microwave electrothermal thruster, the duo was working on magnetoplasmadynamic thrusters. However, that was short-lived because this particular system required a huge amount of power, which can’t be generated onboard a satellite.
Let’s briefly understand how the MET thruster works. The basic idea here is to inject microwave energy into a cavity containing plasma where the microwave energy will be absorbed and dissipated in the form of thermal energy. An electromagnetic resonant cavity creates an alternating electromagnetic field where free-floating plasma is created and sustained. Along with the microwave energy and propellant gas, all the free electrons and heavy particles start colliding with each other. This increases the temperature of the propellant and accelerates it through the nozzle to generate thrust. In Bellatrix’s design, they were able to build this system and successfully run it using water vapour as a propellant. Water is easy to store, transport, and easily available. Hence, the application of this thruster in satellites can be a huge deal. A patent for this, applied in late 2016, is yet to be granted.
Bellatrix’s MET thruster design is supposed to be highly scalable starting from nanosatellites to microsatellites. According to them, it should be able to generate between a few micronewton of thrust to 200 millinewton of thrust. This system can be used for both orbit raising and orbital station-keeping. Another advantage is the higher thrust-to-power ratio achieved in this system compared to others. When the microwave energy is injected into the cavity, the plasma generated doesn’t touch the walls of the thruster. The resonant cavity design ensures the plasma freely floats inside without touching the walls. The same applies to the nozzle. Essentially, the thruster gets higher durability.
As mentioned earlier, Bellatrix hasn’t invented a new propulsion system. They have simply worked out all the specifications and created a physical system that proves the technology works. Since these propulsion systems aren’t bulky, the prototypes were built to actual scale. Yashas recalls that their prototype would simply lay idle and there wouldn’t be any plasma formation. At its early stages, the same procedure was being used but it would fail. Different configurations let to different problems such as the water corroding the thruster. Sometimes the plasma wouldn’t be stable enough and not work for a long period.
All these experiments were conducted inside their own lab. Before moving in, the prototyping was conducted with support from Hindustan College of Engineering and Technology, Coimbatore. They built their own vacuum chamber facility to test the prototype thruster. After those numerous trials and changes in configurations, the team was able to successfully generate thrust using water in 2015. The water didn’t need special storage conditions and it was at room temperature as well. Yashas claims that no one else in the world was able to achieve thrust using water as a propellant before using their type of propulsion system.
The team hasn’t finished building and testing all the components of the engine yet. So, there’s still time until they can test the MET in its full glory. However, simulations have been successfully carried out for the entire system.
Working with ISRO
On a global scale, the Indian Space Research Organisation (ISRO) has already impressed everyone with its potential in space research. Hence, it was only natural for the team from Bellatrix Aerospace to seek opportunities at ISRO. As college students, they weren’t able to figure out the correct approach to get in touch with ISRO. Fortunately, former ISRO chairman, Mr A. S. Kiran Kumar was the guest of honour at their convocation ceremony. They got the opportunity to present their work to him and were told to expect a call later. Mr A S Kiran Kumar escalated the project at ISRO and they were contacted after a few months. Both the co-founders were delighted and surprised on being taken seriously by the government’s space body so early in their journey. And ISRO has been actively following up with their project. After their collaboration with ISRO kicked off, Yashas attributed a lot of support to Dr P. S. Goel and Dr B. N. Suresh, especially suggestions for design improvements and also guiding other projects.
Already having delivered a working prototype, the company was able to bag a contract with ISRO. The space agency wanted them to build the microwave electrothermal thruster according to specific configurations and requirements of their satellites.
Generally, any company that receives a tender from ISRO has to pay a certain security deposit and provide a performance bank guarantee, among other clauses. As a startup, Bellatrix didn’t really possess the required funds and hence, they couldn’t think of going ahead with the offer. Fortunately, according to Yashas, ISRO had an internal policy change and they accepted Bellatrix’s request of waiving off the clauses. The company got the contract. Yashas mentioned that ISRO has provided incredible support to the company in terms of technical knowledge. Every time they visit the space centre to test their thruster, they are always learning new things from the bright minds working there.
Apart from ISRO, Bellatrix also received an order from the Bengaluru division of Liquid Propulsion System Centre (LPSC). Collaboration with LPSC gave them knowledge on how ISRO validates all the technologies. Bellatrix wants to learn and incorporate a similar level of validation techniques into their own projects.
There are quite a few things that Bellatrix Aerospace is working on for the future. In launch vehicles, one of their focus areas, they’ve developed a couple of designs, Chetak and Garuda, that can carry a payload of 500kg and 1010kg respectively. They’re also working on a Green Monopropellant Thruster (HAN blend), which is a cleaner alternative to Monopropellant Hydrazine Thrusters, a toxic chemical used in chemical propulsion systems. The company is also developing Hall Thrusters, a type of ion thruster, with specific improvements to extend the expected life of these kinds of thrusters.