Come December 2024, and the Indian Space Research Organisation (ISRO) will make a significant leap forward by launching its first fully electric-propelled satellites, a mission that promises to redefine India’s approach to space exploration. Known as the Technology Demonstrator Satellite (TDS-01), these satellites will highlight India’s ability to create lightweight, but powerful, spacecraft using modern electric propulsion systems. The launch is significant as it demonstrates India’s progress in space technology.
Experts point out that the integration of electric propulsion systems signifies a departure from traditional chemical thrusters and highlights the agency’s drive to enhance satellite efficiency, longevity, and operational flexibility. This move not only demonstrates ISRO’s technological capabilities but also places it in step with leading space agencies and private players, such as SpaceX, OneWeb, and China, all of which have been deploying electric propulsion in their satellite constellations.
Electric propulsion offers several key advantages that make it an attractive choice for ISRO. “It drastically reduces the amount of propellant needed compared to chemical propulsion. Traditional satellites rely on chemical fuel for orbit-raising and station-keeping, consuming a significant portion of their mass in the process. Electric propulsion, by contrast, uses small amounts of propellant, which is accelerated to high speeds using electrical energy, allowing satellites to perform the same tasks with much greater fuel efficiency. This efficiency enables ISRO to reduce the weight of its satellites, allowing more room for payloads or additional instrumentation, ultimately enhancing mission capacity,” remarked Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems.
Moreover, electric propulsion extends the operational life of satellites. With traditional systems, once a satellite runs out of fuel, it becomes inoperable, even if its components are still functional. Electric propulsion, with its efficient use of fuel, allows satellites to stay operational for longer periods, providing better value or money and reducing the need for frequent replacements. This is particularly valuable for communications satellites, which need to maintain precise positions in geostationary orbit for years.
"A ajor critical advantage of electric propulsion is its flexibility in orbital maneuvering. Satellites equipped with electric propulsion can make more precise orbital adjustments, making them suitable for missions that require fine control over satellite positioning, such as remote sensing, navigation, and scientific research missions. This flexibility will allow ISRO to expand its satellite capabilities, opening new possibilities for advanced Earth observation systems and interplanetary missions,” added Kesan.
Interestingly electric propulsion, a technology that dates back to the 1960s with the Soviet Union’s Zond 2 probe, has evolved to become a cornerstone of modern satellite design. The first commercial application of this technology came with PanAmSat’s PAS-5 satellite in 1997, which used an electric thruster for station-keeping, marking the beginning of the transition from chemical to electric propulsion for satellites. In recent years, this technology has gained widespread adoption, thanks to its ability to drastically reduce fuel consumption and extend satellite lifetimes.
The TDS-01 satellite will be the first Indian satellite to feature an electric propulsion system developed entirely indigenously. This system operates by using gases, such as argon, which are ionized (charged) and then powered by solar energy to generate thrust. This method makes the satellite more efficient and reduces the need for large amounts of fuel.
"The satellite’s solar panels capture energy from the Sun and convert sunlight into electricity, which then powers various functions, including the electric propulsion system. This process not only helps the satellite move but also ensures that it uses less fuel, making the spacecraft lighter and more cost-effective. In addition to the electric propulsion system, the satellite will include travelling wave tube amplifiers (TWTAs), devices that are crucial for strengthening the satellite’s communication signals and remote-sensing tasks. TWTAs ensure the signals are powerful enough to reach Earth or other spacecraft. This allows for clear data transmission and reliable communication between the satellite and ground stations,” explained space and aerospace expert Girish Linganna.
All parts of the satellite, including the electric thrusters and TWTAs, have been completely developed in India. This highlights the country’s ability to create advanced satellite technologies on its own. "Electric thrusters are engines used in satellites and spacecraft that generate thrust by using electricity to accelerate charged particles (ions). Unlike traditional rocket engines that burn fuel to create force, electric thrusters use much less fuel and are more efficient over long periods, making them ideal for space missions. The satellite will weigh less than two tons, but have the same power as a traditional satellite that weighs four tons. The electric propulsion system will help the satellite stay in orbit for a longer time, which will extend its overall lifespan,” added Linganna.
Experts point out that since electric propulsion requires less fuel and results in a lighter satellite, it can significantly reduce launch and operational costs. Electric propulsion enables more efficient control of the satellite’s position and movement in orbit. Compared to chemical propulsion, electric systems produce fewer emissions, making them more environment-friendly.
There are challenges too. “Electric propulsion produces less thrust than chemical systems, making it slower for the satellite to reach its final orbit. As said earlier, while chemical thrusters can reach a geostationary orbit in about a week, electric propulsion may take up to three months. Additionally designing and implementing electric propulsion systems is more complex and requires advanced technology and specialized knowledge,” said Linganna.