New spacecraft system uses air as fuel to offer endless electric propulsion

Interesting Engineering carries an article about air-breathing electric propulsion (ABEP) which uses upper atmospheric air as a fuel to power an electric thruster on a satellite, Caliber.Az reprints the article. 

Afuel-free satellite system that sucks in the air may be able to provide unlimited propulsion for longer-duration orbital operations one day.

University of Surrey’s Surrey Space Centre researchers are developing a new breed of spacecraft that will be propelled by capturing the air rather than standard propellants. 

This innovative concept, called air-breathing electric propulsion spacecraft, will fly near our planet in the very low Earth orbit (VLEO). This orbit is between 95 and 250 miles in altitude. This orbital location has the potential to dramatically improve Earth observation, climate monitoring, and satellite communications. 

The center recently received £250,000 from the UK Space Agency to advance the development of the air-breathing electric propulsion concept. This grant will enable them to create a conceptual design, perform propulsion tests, analyze orbital mechanics, and perform aerodynamic simulations. 

Air-breathing electric propulsion

Air-breathing electric propulsion (ABEP) uses upper atmospheric air as a fuel to power an electric thruster on a satellite. 

In a nutshell, a satellite’s device collects air from the upper atmosphere and channels these air particles into a specialized ionization chamber. Inside this chamber, the air particles are bombarded with energy, turning them into a super-hot, electrically charged state called plasma. This process can be used to propel the spacecraft.

“We’ve been developing a cathode, or neutraliser, to work in electrostatic thrusters operating in the thin air found in ultra-low Earth orbit,” explained Mansur Tisaev, a postgraduate research student at the university. 

“By collecting and compressing the gases at that altitude, we can create a propellant flow that is ionized (i.e., transformed into a mix of charged particles) and accelerated using combinations of electric and magnetic fields, harnessing electrical power from solar panels.”

Overcoming VLEO’s atmospheric drag

VLEO offers various advantages over low Earth orbit (LEO), where most of the current satellites are launched and placed. VLEO is less congested, with almost no issue of space debris, and much closer to our planet. 

From this orbital position, the new air-breathing spacecraft can provide more detailed observations and imagery of our planet.

“There are benefits to flying in very low altitude orbits, like being able to operate Earth observation at much higher resolutions than offered at present,” Andrea Lucca Fabris said in the press release.

“It could also mean faster telecommunications, and it opens the door to new scientific discoveries about conditions in the ionosphere, which could help develop more accurate atmospheric models.”

Despite these benefits, satellites are not yet launched into VLEO due to one big challenge: atmospheric drag at highly low altitudes. Low Earth Orbit enables satellites to sustain their orbits with minimal propulsion as they continuously circle the Earth.

At VLEO, constant thrust is required to prevent satellites from falling or deorbiting. This newly proposed air-breathing satellite concept may solve this issue and provide unlimited propellant capacity.  

Moreover, satellites in orbit encounter a significant challenge due to their limited onboard propulsion. Even when the satellite’s instruments and hardware are fully functional, it can become inactive once it exhausts its fuel. This system will enable satellites to function for longer durations. 

This air-breathing system will also lower satellite development as it would not require onboard propellant tanks.