A moon motor that uses atmospheric gases as energy shows commitment in lab tests and modeling, but its achievement on a goal remains unproven.
Choosing an orbit for a moon involves balancing benefits and drawbacks. Very Low Earth Orbit (VLEO), which spans approximately 100 to 450 km (62 to 280 miles) complete Earth, offers multiple advantages. Remote sensing cameras can grasp sharper images, communications and radar systems need small power, and atmospheric drag helps eliminate idle satellites from orbit naturally.
That identical ambiance additionally creates a important challenge. Even at these altitudes, air opposition slows spacecraft down, so satellites must create drive nearly continuously to remain in orbit. Conventional drive systems necessitate onboard fuel, frequently costly gases specified as xenon.
As part of his PhD investigation at the University of Stuttgart, published on arXiv, Francesco Romano explored a distinct approach. His idea uses the atmospheric molecules liable for drag as energy for a plasma engine, possibly allowing satellites to remain in VLEO indefinitely without carrying a accepted provision of propellant.
The innovation belongs to a category known as atmosphere-breathing electric drive (ABEP). These systems collect the extremely lean air in forefront of a spacecraft (or, in several cases, a missile) and straightforward it into an electric engine. The motor converts the incoming molecules into plasma and expels it from the rear to create thrust.
The essential idea is straightforward, but turning it into a applicable drive scheme requires solving multiple difficult engineering problems.
Atomic oxygen eats distant at engines
First is nuclear oxygen (AO). In the high atmosphere, UV radiation splits O2 into this aggressive, sole nuclear form of the gas that we all need to breathe. AO is notoriously oxidative, corroding metal element electrodes, acceleration grids, and equal the cathodes used in norm Hall thrusters or another types of ion engines.
Perhaps most importantly, AO burns through the cathodes used in the “electron gun” that neutralizes the spacecraft so that the entire item doesn’t rotate into charged and merely suck the charged particles correct rear to itself, nullifying the drive they provide. Without that feature, the entire ion drive scheme fails.
Another difficult characteristic whenever designing engines for use in VLEO is the variability of the ambiance itself. It changes according to the day/night cycle, the latitude, and equal sun-related activity. Making certain an motor can continually run in all these distinct conditions has proven difficult so far.
A mirror that gathers lean air
To resolve these problems, Romano developed a contactless, neutralizer-less radio-frequency (RF) helicon plasma thruster and paired it alongside an optimized atmospheric intake system. Let’s tackle the intake scheme first.
He really trialed three distinct versions of an intake – one called an “enhanced chimney design,” which acted as a molecular trap to grasp air particles that are dispersed so far distinct they never run into all other. Next, he used a “diffuse intake” that used a compact hexagonal scheme made out of a coated titanium alloy. And finally, he designed what he called a “specular intake,” which is a parabolic mirror coated alongside graphite or silicon dioxide that bounced particles immediately into the engine.
The apparent winner, the two in conditions of gathering effectiveness and alignment sensitivity, was the specular intake. It collected ~94.3% of the particles of air (which was AO, argon, or nitrogen in a breeze tunnel test), and the effectiveness lone dropped by 8% whenever subjected to a 15° tilt.
A plasma jet without a neutralizer
To scheme the thruster, Romano turned to a medicinal equipment for inspiration. Using a birdcage antenna, akin to those used in MRIs, he managed to scheme a thruster that ensured 99% of the delivered electric power really entered the thruster, an extremely high-efficiency threshold that improved upon norm cable coils that would scorch through several of the power since of their own reactance. A solenoid wrapped about the motor creates a magnetic site that pushes the plasma out the rear in a quasi-neutral jet – the two affirmative and negative ions are pushed out of the thruster, ensuring no neutralizer is needed.
Testing the scheme proved its reliability. Romano used a vacuum area to intentionally simulate a VLEO atmospheric concentration of the three chief gases the thruster would encounter at that altitude. The motor generated dependable streams of plasma alongside lone 50-60W of RF power, fine inside the capabilities of traditional spacecraft sun-related panels.
Could atmospheric energy keep satellites aloft?
After that experimental validation, he took an additional stage and applied models of the drive scheme to genuine real-world use cases. This included the GOCE satellite, which famously launched into VLEO alongside a Xenon ion thruster, and eventually ran out of fuel.
According to the thesis’ calculations, the new motor could run indefinitely between 190 and 250 km using small than 1.6 kW of power, which is motionless fine inside the generation limits of norm spacecraft sun-related panels. But the use cases aren’t constricted to Earth. Mars has an ambiance dominated by CO2, and, according to the thesis, the motor could assistance a spacecraft indefinitely complete the Red Planet at a height of 120-160 km, which is much nearer than existing orbital satellites.
Ultimately, there is no justify this thruster volition always see use exterior of a lab. But the idea is intriguing, and there are plentifulness of possible business applications for it if it can be de-risked and proven to activity on an genuine mission. It’s unclear whether Dr. Romano has any plans to prosecute that track, but his activity on it so far at smallest shows the scheme has possible – perchance person out there is consenting to prosecute it.
Reference: “RF Helicon Plasma Thruster for an Atmosphere-Breathing Electric Propulsion System (ABEP)” by Francesco Romano, July 1, 2026, arXiv.
DOI: 2607.02635
Adapted from an part initially published in UniverseToday.
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