Atmosphere-Breathing Electric Propulsion Systems

Updated 22 August 2025

Atmosphere-breathing electric propulsion systems are technologies that extract in situ atmospheric gases to generate thrust, eliminating the need for stored propellant.
Key designs include diffuse, specular, hybrid, and cryogenic intakes that optimize particle collection efficiency—with specular intakes achieving up to 0.94 efficiency under ideal conditions.
Integrated plasma generation methods, such as magneto-plasma compressors, EHD, and RF thrusters, deliver high thrust-to-area ratios to enable extended missions in VLEO and planetary environments.

Atmosphere-breathing electric propulsion systems are advanced technologies designed to utilize ambient atmospheric constituents or residual gases as in situ propellant to produce thrust for aircraft, spacecraft, satellites, or high-altitude platforms. These systems eliminate or minimize the need for stored propellant, offering a potential for extended operational lifetimes, cost reduction, and new mission capabilities in environments ranging from low altitudes in Earth's atmosphere to very low Earth orbit (VLEO) and even near-space environments on other planetary bodies.

1. Fundamental Principles and Classification

Atmosphere-breathing electric propulsion encompasses several mechanisms that share the common principle of collecting local gases, ionizing or accelerating those particles, and ejecting the resultant flow or plasma to generate thrust. Unlike conventional engines relying on combustion or stored propellant, these systems actively scavenge the local environment.

Key categories include:

Magneto-plasma compressors and pulsed plasma systems: Utilize fast, high-current electrical discharges to compress and accelerate atmospheric gases via self-generated magnetic fields (Goksel et al., 2016).
Electrohydrodynamic (EHD) propulsion devices: Rely on high-voltage corona discharge at electrodes to create ionic wind and thrust by momentum transfer from ions to neutrals (Ieta et al., 2019).
RF and inductive plasma thrusters: Employ radio-frequency electromagnetic fields (with or without static magnetic fields) to ionize, heat, and accelerate atmospheric molecules, often via helicon or inductive coupling mechanisms (Yuan et al., 2020, Romano et al., 2020, Romano et al., 2021).
Cryogenic active intakes and phase-change compression concepts: Use cryocondensation-regeneration cycles to dramatically increase the density of collected propellant before ionization and acceleration (Moon et al., 3 Mar 2025).

Atmosphere-breathing electric propulsion systems are often designed with modular intakes, contactless plasma generation stages, and advanced control or diagnostic subsystems.

2. Intake Design and Particle Collection

The intake subsystem directly determines the efficiency with which atmospheric particles are captured and supplied to the propulsive discharge system. Designs are deeply informed by the physics of rarefied free-molecular flow, relevant at VLEO, and by gas-surface interaction models simulated via tools such as DSMC-PIC (Romano et al., 2021, Romano et al., 2022, Parodi et al., 17 Apr 2025).

Key intake concepts:

Diffuse intakes: Employ multiple ducts and rely on fully diffuse (thermalizing) gas-surface interactions for particle accommodation. Typical collection efficiencies ( $\eta_c$ ) are limited to $0.43$–$0.46$ due to backflow and scattering (Romano et al., 2021, Romano et al., 2022).
Specular/parabolic intakes: Engineered with optical focusing (parabolic surfaces) exploiting specular reflection, often achieving efficiencies up to $\eta_c \approx 0.94$ under ideal alignment (Romano et al., 2021, Romano et al., 2022). Misalignment robustness is higher compared to diffuse cases, but performance can degrade abruptly at misalignments $\gtrsim 15^\circ$ .
Hybrid intakes: Combine diffuse and specular surfaces, adjusting for trade-offs between backflow reduction and alignment sensitivity.
Active/cryogenic intakes (CRAID): Implement a cryopanel cooled to $\sim 20\,\mathrm{K}$ , condensing atmospheric particles for later regeneration and discharge. Achieved compression ratios ( $CR^{\mathrm{eff}}$ ) can exceed $3\times10^7$ , at least $1000\times$ higher than passive intakes, with effective $\eta_c \approx 0.26$ in a full cycle (Moon et al., 3 Mar 2025).

Experimental methodologies for validating intake designs include pressure-difference measurement and gas sensor techniques (e.g., QCM sensors to quantify atomic oxygen flux) cross-validated by DSMC simulations (Cushen et al., 10 Jun 2024).

Intake Concept	$\eta_c$ (Efficiency)	Robustness to Misalignment
Diffuse ducts	0.43--0.46	Low
Specular parabolic	Up to 0.94	Moderate
Active (CRAID)	$\sim$ 0.26	High (during cycle)

3. Propulsive Discharge and Plasma Generation

Atmosphere-breathing electric propulsion systems employ advanced plasma generation mechanisms that avoid electrode erosion and maximize energy coupling. The main thrust stages are:

Magneto-plasma compressor (MPC): Uses coaxial electrodes in configurations such as “(3-2-7) mm” to produce high-current ($15$– $30\,\mathrm{kA}$ ), nanosecond-scale discharges. Nanosecond excitation pulses ( $4\,\mathrm{ns}$ rise time) induce self-organized plasma channels for reliable ignition of dense plasma focus discharges at atmospheric pressure (Goksel et al., 2016). Pinch-driven compression reaches $100$– $150\,\mathrm{bar}$ and $10^{17}$ – $10^{18}\,\mathrm{cm}^{-3}$ densities.
Electrohydrodynamic (EHD) flow: Begins with high-voltage fields at sharp electrodes, producing ionic wind and rotational torque; thrust-to-power ratios reach $0.64$– $6.23\,\mathrm{N}/\mathrm{kW}$ , exceeding those of many conventional jet engines (Ieta et al., 2019).
RF inductive thrusters (IPT, SURE): Use RF antennas (birdcage or solenoidal geometries) for contactless plasma generation—often with a static magnetic field for helicon wave excitation (Romano et al., 2020, Yuan et al., 2020). RF frequencies (e.g., $40.68\,\mathrm{MHz}$ , $13.56\,\mathrm{MHz}$ ) and auto-matching networks are tuned for resonance; quasi-neutral plume ejection is realized via $E\times B$ drift with measured plasma densities up to $2.23\times10^{18}\,\mathrm{m}^{-3}$ and electron temperatures of $2.79\,\mathrm{eV}$ (Yuan et al., 2020).
Inductive plasma generators (IPG6-S): Demonstrate electric-to-thermal coupling efficiencies of $25$– $30\%$ on $O_2$ and $CO_2$ , translating to exhaust velocities $c_e \approx 3900\,\mathrm{m}/\mathrm{s}$ (Romano et al., 2021).
Cryogenic active intake regeneration: Regenerated gases from the cryopanel are supplied at controlled flow rates (e.g., $20\,\mathrm{sccm}$ per thruster) to twin RITs, ensuring stable discharge conditions even as atmospheric densities vary (Moon et al., 3 Mar 2025).

Critical design and operational equations include:

Energy efficiency: $n = \frac{W_a}{W_b} = \frac{\int I_a(t)\, U_d(t)\, dt}{\tfrac{1}{2}\,C_b\,U_b^2}$
Collection efficiency: $\eta_c = \frac{\dot{N}_{\mathrm{out}}}{\dot{N}_{\mathrm{in}}}$
Compression ratio: $CR = n_{\mathrm{out}} / n_{\infty}$
Drag compensation requirement: $F_D = \tfrac{1}{2} \rho v^2 C_D A_f$
Power consumption: $P_{\mathrm{req}} = \frac{\dot{m} v_e^2}{2 \eta_t}$

4. System Integration, Scalability, and Performance

Efficient integration of atmosphere-breathing electric propulsion requires tight coupling between intake and thruster design, as the flow, pressure, and species composition directly affect plasma discharge characteristics (Romano et al., 2022, Parodi et al., 17 Apr 2025).

Performance metrics:

Thrust-to-area ratios for pulsed plasma MPC systems are $50$– $150\,\mathrm{kN}/\mathrm{m}^2$ , competitive with jet engines, if operated at $10^3$ pulses per second (Goksel et al., 2016).
Intake mass flow and system scaling: For a VLEO satellite ( $A_f \sim 1\,\mathrm{m}^2$ ) and $\eta_c$ approaching $0.94$, much lower exhaust velocities are needed for drag compensation, with the integrated system able to support reduced spacecraft mass and extended lifetime (Crisp et al., 2021, Vaidya et al., 2022).
Compression ratio and continuous supply: Active intake devices such as CRAID can supply propellant at $1000\times$ higher compression than passive intakes, enabling operation down to $190\,\mathrm{km}$ altitude (Moon et al., 3 Mar 2025).

Diagnostic and simulation tools:

Particle-based simulation methods (DSMC for neutrals and PIC/MCC for plasma) verify global mass and energy balances, electron velocity distributions, and drift physics (Parodi et al., 17 Apr 2025).
Experimental facilities deploy pressure difference and QCM sensor methods for sub-scale intake validation, supported by DSMC modeling (Cushen et al., 10 Jun 2024).

5. Challenges and Solutions

Atmosphere-breathing electric propulsion systems must address several technical challenges:

Electrode erosion: Pulsed plasma or MPC systems face electrode wear after $10^3$ ignitions, especially in the cathode diverter region; solutions include optimizing geometry, materials, and using fusion-derived surface treatments (Goksel et al., 2016).
Efficiency and energy loss: Increasing capacitor voltage boosts energy input but reduces discharge efficiency above $400\,\mathrm{V}$ ; ongoing work seeks an optimal balance for plasma generation (Goksel et al., 2016).
High-frequency operation: Systems designed for kilohertz repetition rates require robust electrical, thermal, and plasma controls; especially relevant for pulsed MPC and EHD devices.
Material durability: Exposure to atomic oxygen, especially at VLEO, necessitates new materials or coatings for intakes and thrusters (Crisp et al., 2021).
Operational envelope: Passive intakes are constrained by atmospheric density at low altitudes; CRAID devices expand operational boundaries to lower altitudes via improved compression and supply regulation (Moon et al., 3 Mar 2025).
Oscillation control: In plasma thrusters, spatial ion back-flow regions can induce breathing mode oscillations, which, depending on context, may destabilize operation or be tuned for diagnostic purposes (Chapurin et al., 2021).

Future research aims to improve efficiency, robustness, and system integration by leveraging advanced simulation, high-speed diagnostics, and innovative intake/thruster concepts.

6. Applications and Mission Architectures

Atmosphere-breathing electric propulsion systems have been proposed and demonstrated for a diverse set of mission profiles:

VLEO satellite stationkeeping: ABEP enables continuous drag compensation, prolonging mission lifetime without onboard propellants (Crisp et al., 2021, Vaidya et al., 2022).
High-altitude flight: Arrays of MPC-based thrusters could launch ground-based aircraft and airships to $>50\,\mathrm{km}$ altitudes (Goksel et al., 2016).
Planetary orbit maintenance: ABEP architectures are applicable to Mars, Venus, or Titan, using local atmospheric composition for propellant (Vaidya et al., 2022).
Space tug and refueling scenarios: Collected atmospheric gases can be transferred for re-boost of other satellites or used for orbital transfer maneuvers (Vaidya et al., 2022).
Earth observation and communications: The increased mass flow and reduced drag attainable with ABEP allow lower-altitude, higher-resolution EO, and improved communication payload performance (Crisp et al., 2021).

Case studies have demonstrated system-level savings of up to $75\%$ in total mass and over $50\%$ in cost for VLEO platforms compared to conventional designs (Crisp et al., 2021).

7. Future Directions and Research Frontiers

Advancements in atmosphere-breathing electric propulsion are driven by ongoing work in several areas:

Materials science: New surface coatings and alloys for erosion resistance, particularly against atomic oxygen and aggressive atmospheric species.
Cryogenic/active intakes: Further optimization of condensation-regeneration cycles, cryocooler integration, and flight hardware maturation (Moon et al., 3 Mar 2025).
High-fidelity simulation: DSMC-PIC frameworks will continue to play a central role in system optimization and validation, reducing the need for costly and time-consuming ground or orbital tests (Parodi et al., 17 Apr 2025).
Integrated system modeling: Coupled aerodynamic, plasma, and materials models inform design trade-offs for best-in-class efficiency, mass reduction, and lifetime extension (Vaidya et al., 2022).
Advanced diagnostics: High-speed imaging, B-dot probes, and QCM sensors expand understanding of plasma dynamics and intake performance (Cushen et al., 10 Jun 2024).

Sustained research and development in atmosphere-breathing electric propulsion systems are expected to enable new classes of cost-effective, long-duration, and versatile Earth and planetary missions, with implications for future aerospace and satellite design.