Indian Startup Plans to Build Ultra-Low Orbit Satellite

Satellites with extremely low-orbits could lower launch costs and improve sensing and communication capabilities. Indian start-up Bellatrix Aerospace has unveiled plans for a spacecraft that will orbit at altitudes below 200 kilometers, and the company says it aims to launch its first satellite by 2026.

Anything below 1,200 kilometers is considered a low Earth orbit (LEO), but satellites that can fly even closer to Earth’s surface have a host of benefits, says Rohan Ganapathy, CEO of Bengaluru-based Bellatrix. For starters, ultra-LEO satellites can achieve comparatively higher resolution imaging for Earth observation applications such as climate modeling, agriculture, and mapping. Low orbits also reduce the latency of communication with ground stations, which Ganapathy says could make them attractive for supporting 6G telecom networks.

At these altitudes, satellites also experience significant atmospheric drag. So their orbits are “self-cleaning,” meaning they rapidly fall back to Earth at the end of their lifetimes, reducing the problem of space debris. On the other hand, keeping ultra-LEO satellites aloft is much harder than conventional satellites. Fighting drag entails carrying large amounts of propellant to power the spacecraft’s engines, which can increase the bulk and weight of the vehicle and can seriously limit how long they can operate.

Air-Breathing Propulsion—in Space

Bellatrix says they have resolved this challenge by developing a novel air-intake electric propulsion system, which collects air particles from the upper atmosphere and uses them as propellant. The company recently displayed the technology at the Space Expo 2024 in Bengaluru following successful ground testing. “It’s like an airplane with an unlimited supply of fuel, you can sustain as long as you want,” says Ganapathy. “This is going to open up a lot of new opportunities, especially for 6G, Internet of Things and hyperspectral imaging.”

Bellatrix, founded in 2015, specializes in developing propulsion systems for satellites and earlier this year completed space qualification of two of its engines. The Arka 200 is a Hall-effect thruster, which uses electric fields to turn a propellant into an ionized plasma before accelerating it to provide thrust. And the company’s Rudra engine replaces the toxic hydrazine normally used in satellite propulsion systems with a proprietary, environmentally-friendly propellant.

But Ganapathy says the company’s long-term goal has always been to develop an ultra-low-earth orbit satellite, and they’ve been working on this project since the company’s inception. “We wanted to do satellites from before we were building engines,” he says. “But we didn’t want to enter an already crowded segment where there are a lot of players building satellites for higher altitudes.”

The vehicle the company is developing will be roughly 2 meters long and can carry a payload of between 50 and 70 kilograms. It will produce more than 1 kilowatt of power from a solar panel array and is designed to operate between 180 km and 200 km. Flying at such low orbits requires the resolution of two interrelated challenges, though, says Ganapathy–how to use air as a propellant and how to gather enough of it in the rarefied atmosphere found at those altitudes.

Hall thrusters normally use gases like xenon as a propellant, because it’s easy to ionize as well as chemically inert and capable of being stored at high densities and pressures. By contrast, using nitrogen and oxygen in air as propellant requires significantly more energy to ionize into a plasma than xenon. So, Ganapathy says, the company has created a hybrid engine that uses radio waves to ionize the gas before a Hall-effect thruster accelerates it.

The Innovations Required for Air Propulsion

Collecting—and then compressing and storing—substantial enough amounts of nitrogen and oxygen propellant from the upper atmosphere required some innovations, Ganapathy says. Collecting more nitrogen and oxygen generally means increasing the size of the intake on the satellite. But a larger intake also increases the satellite’s drag, and higher drag adds to satellite’s overall fuel requirements. So the company had to carefully optimize the size and shape of the satellite and its intake to balance these competing tensions.

Although Ganapathy says the company’s exact resolution of the optimization problem is a trade secret, he did note that part of the secret was using a combination of passive and active compression.

The company has carried out ground tests of the engine, demonstrating that it can efficiently ionize air and provide sufficient thrust for a satellite in orbit. But testing the compression system is more complicated, says Ganapathy, due to the scarcity of data on the density of the upper atmosphere.

So, next year, the company is planning a demonstration mission with a scaled-down version of their satellite. As well as testing out a prototype of the engine and compression system, the mission will carry various probes to collect data on the atmospheric conditions at 200 km. The company is also building a dedicated testing facility that will simulate particles flying into the intake at orbital velocities, which Ganapathy says will be crucial for validating their simulations.

While the engine is validated, there is still work to be done on the spacecraft itself. One of the main outstanding challenges is developing an inertial navigation system capable of dealing with the increased jitter caused by atmospheric drag—a particular concern for imaging applications. “You want the satellite to be as stable as possible, so it poses a lot of challenges on your guidance, navigation and control system” to accomplish that, says Ganapathy.

Bellatrix is aiming for a full-scale demonstration in 2026, the CEO says, but it isn’t the only company targeting this emerging segment in the space industry. Florida-based Redwire Space, California-based Skeyeon, and New Orbit in the UK are all actively developing satellites that also aim to operate at very low orbits.