A New Kind of Engine for Space
For decades, satellites have navigated space using chemical propulsion. Think of it like a powerful sprinter: it provides strong, quick bursts of thrust by burning liquid fuel to get a satellite into its correct orbit or adjust its position. It’s effective,
but it requires carrying a large amount of heavy fuel, which takes up a significant portion of a satellite’s launch weight. Now, ISRO is mastering a different approach: electric propulsion. This system is more like a marathon runner. It produces a very gentle, but incredibly efficient and continuous, thrust. Instead of burning fuel, it uses electricity, typically generated by the satellite’s solar panels, to energize and accelerate a small amount of inert gas like xenon, pushing the spacecraft forward. The thrust is light—often compared to the force of a piece of paper resting on your hand—but over weeks and months, it can achieve tremendous changes in velocity with astonishingly little fuel.
ISRO's Landmark Achievement
The latest breakthrough comes from ISRO’s Liquid Propulsion Systems Centre (LPSC), which has successfully completed a gruelling 1,000-hour endurance test of its indigenously developed 300-millinewton (mN) Stationary Plasma Thruster. This test is a critical milestone, proving that the hardware is robust and reliable enough for long-duration space missions. What makes this achievement particularly significant is that the entire system is homegrown. While ISRO has experimented with electric propulsion before using imported components, this new thruster is a testament to India's growing self-reliance in creating complex space technologies. By validating the thruster’s performance and durability in a vacuum chamber that mimics the harsh conditions of space, ISRO has cleared a major hurdle before this technology is flown on an actual mission.
Lighter Satellites, Longer Lives
The benefits of this electric propulsion system are transformative. The primary advantage is a massive reduction in propellant mass. According to ISRO, its electric propulsion system has a specific impulse—a measure of efficiency—that is at least six times higher than conventional chemical systems. For a typical communication satellite, the fuel required for orbit-raising and station-keeping manoeuvres can be reduced from several thousand kilograms to just a few hundred. This weight saving means two things. First, ISRO can launch satellites on smaller, more cost-effective rockets. Second, the saved mass can be used to carry more transponders or scientific instruments, increasing the satellite’s capability and revenue-generating potential. Furthermore, a satellite's operational life is often determined by how long it can maintain its correct orbit, a task that requires fuel. With a propulsion system that is vastly more efficient, a satellite can perform these station-keeping manoeuvres for many more years, potentially doubling its operational life and providing a greater return on investment.
The Future of Indian Satellites
This technology is a game-changer for ISRO’s entire satellite programme. It is particularly crucial for large geostationary communication satellites, which need to maintain precise orbital slots for 15 years or more. Lighter, more capable satellites will bolster India's telecommunications infrastructure and enhance its position in the competitive global launch market. The high efficiency of electric propulsion also opens new possibilities for ambitious interplanetary missions. Journeys to Mars, Venus, or asteroids become more feasible, as the spacecraft can travel farther with less fuel. The first in-orbit demonstration of this powerful new system is slated for the upcoming Technology Demonstration Satellite (TDS-01). This mission will validate the technology in space, paving the way for its widespread adoption across ISRO’s future fleet of satellites.
