Earth’s orbit is getting so populated that the space industry is now developing technologies to remove space debris left by satellite launches from an over-crowded low Earth orbit (LEO).
There is an untapped orbit above Earth, though. The very low Earth orbit (VLEO) would allow satellites to fly in a less crowded space closer to home and take more detailed pictures of our planet.
The reason many satellite operators have ignored VLEO to date is that working at an altitude with air would require more force to propel the satellite and keep it from falling back down to Earth.
Recently, many scientists have suggested the air in the VLEO could be used as a propellant. A team of scientists from the George Washington University (GWU) and the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have collaborated to develop a proof of concept for an air-breathing satellite.
A satellite that uses air as a propellant could utilize charged particles of air-breathing plasma to propel its thrusters.
Yevgeny Raitses is a managing principal research physicist at PPPL who is leading the Lab’s work on the project. He explained in a press statement, “There is air available at VLEOs. So, instead of launching rockets with these propellants, such as xenon, krypton, or argon, we can use what is naturally available: air. This should allow us to reduce the mass of satellites or allow them to dedicate the difference in mass to other aspects of the device. It might also extend the lifetime of the device.”
Traditional satellites in LEO and higher orbits have limited lifespans because they can only use a limited amount of propellant to generate plasma. The thruster proposed by the GWU and PPPL team would avoid this problem by making use of the surrounding air to generate plasma. Any satellite using this system would essentially have free, unlimited propellant.
Given the great potential of this project for low-cost satellite operations that will enable more detailed imaging, it has captured the attention of the U.S. government. The Defense Advanced Research Projects Agency (DARPA) has already supplied four hundred thousand dollars of an anticipated one million dollar grant for the project.
The GWU and PPPL teams aren’t the only organizations researching air-breathing satellite technology. Jan Mataró is the CTO of the Spanish company Kreios Space. In an interview in 2022, He explained that “right now, very low Earth orbit is an unused orbit simply because of the lack of propulsion systems capable of staying in this orbit. But it could allow for a huge increase in the resolution for both telecommunications and Earth observation.”
That company is developing an air-breathing generator for satellites. It claims that the generator will provide a 16x increase resolution for Earth observation and telecommunications satellites.
Of course, some challenges must be overcome before the technology is feasible. The GWU and PPPL teams are working to ensure that positive and negative particles released from their thruster leave at the same rate so that there is no net electric current in the plasma plume expelled by the satellite.
Raitses explained that “It is important in order to avoid charging the satellites.” A charged satellite could cause charged particles to be released from the thruster. These would be attracted back to the satellite which could cause a damaging recoil effect.
According to the team’s press statement, it is developing a thruster capable of neutralizing the particles. This will allow for smooth operation in VLEO.