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Atmosphere-breathing electric propulsion
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Atmosphere-breathing electric propulsion
Atmosphere-breathing electric propulsion, or air-breathing electric propulsion, shortly ABEP, is a propulsion technology for spacecraft, which could allow thrust generation in low orbits without the need of on-board propellant, by using residual gases in the atmosphere as propellant. Atmosphere-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible.
The concept is currently being investigated by the European Space Agency (ESA), the EU-funded BREATHE project at Sant'Anna School of Advanced Studies in Pisa and the EU-funded DISCOVERER project. Current state-of-the-art conventional electric thrusters cannot maintain flight at low altitudes for any times longer than about 2 years, because of the limitation in propellant storage and in the amount of thrust generated, which force the spacecraft's orbit to decay. The ESA officially announced the first successful RAM-EP prototype on-ground demonstration in March 2018.
An ABEP is composed by an intake and an electric thruster: rarefied gases which are responsible for drag in low Earth orbit (LEO) and very low Earth orbit (VLEO), are used as the propellant. This technology would ideally allow spacecraft to orbit at very low altitudes (< 400 km around the Earth) without the need of on-board propellant, allowing long time missions in a new section of atmosphere's altitudes. This advantage makes the technology of interest for scientific missions, military and civil surveillance services as well as low orbit communication services with even lower latency than Starlink.
A special intake will be used to collect the gas molecules and direct them to the thruster. The molecules will then be ionized by the thruster and expelled from the acceleration stage at a very high velocity, generating thrust. The electric power needed can be provided by the same power subsystems developed for the actual electric propulsion systems, likely a combination of solar arrays and batteries, though other kind of electric power subsystems can be considered. An ABEP could extend the lifetime of satellites in LEO and VLEO by compensating the atmospheric drag during their time of operation. The altitude for an Earth-orbiting ABEP can be optimised between 120–250 km. This technology could also be utilized on any planet with atmosphere, if the thruster can process other propellants, and if the power source can provide the required power, e.g. sufficient solar irradiation for the solar panels, such as Mars and Venus, otherwise other electric power subsystems such as a space nuclear reactor or radioisotope thermoelectric generator (RTG) have to be implemented, for example for a mission around Titan.
The first studies considering the collection and use of the upper atmosphere as propellant for an electric thruster can be found already in 1959 with the studies on the propulsive fluid accumulator from S. T. Demetriades.
In the development of atmosphere-breathing ion engines, a notable extension of Child's Law led to its implementation in the ABEP concept in 1995. Originally, Child's Law modeled the flow of charge between an anode and a cathode with the assumption that the initial velocity of ions was zero. This assumption, however, is not applicable to ion thrusters operating in low Earth orbit, where ambient gas enters the ionization chamber at high velocities.
Buford Ray Conley provided a generalization of Child's Law that accounts for a non-zero initial velocity of ions. This adaptation has been significant for the theoretical modeling of ion propulsion systems, particularly those that operate in the rarefied conditions of low Earth orbit.
The generalization of Child's Law has implications for the design and efficiency of atmosphere-breathing ion thrusters. By accounting for the high-velocity ambient gas that enters the ionization chamber in low Earth orbit, the modified law allows for more accurate theoretical modeling. Once the ambient gas is ionized in the chamber, it is electromagnetically accelerated out of the exhaust, contributing to the propulsion of the spacecraft.
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Atmosphere-breathing electric propulsion
Atmosphere-breathing electric propulsion, or air-breathing electric propulsion, shortly ABEP, is a propulsion technology for spacecraft, which could allow thrust generation in low orbits without the need of on-board propellant, by using residual gases in the atmosphere as propellant. Atmosphere-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible.
The concept is currently being investigated by the European Space Agency (ESA), the EU-funded BREATHE project at Sant'Anna School of Advanced Studies in Pisa and the EU-funded DISCOVERER project. Current state-of-the-art conventional electric thrusters cannot maintain flight at low altitudes for any times longer than about 2 years, because of the limitation in propellant storage and in the amount of thrust generated, which force the spacecraft's orbit to decay. The ESA officially announced the first successful RAM-EP prototype on-ground demonstration in March 2018.
An ABEP is composed by an intake and an electric thruster: rarefied gases which are responsible for drag in low Earth orbit (LEO) and very low Earth orbit (VLEO), are used as the propellant. This technology would ideally allow spacecraft to orbit at very low altitudes (< 400 km around the Earth) without the need of on-board propellant, allowing long time missions in a new section of atmosphere's altitudes. This advantage makes the technology of interest for scientific missions, military and civil surveillance services as well as low orbit communication services with even lower latency than Starlink.
A special intake will be used to collect the gas molecules and direct them to the thruster. The molecules will then be ionized by the thruster and expelled from the acceleration stage at a very high velocity, generating thrust. The electric power needed can be provided by the same power subsystems developed for the actual electric propulsion systems, likely a combination of solar arrays and batteries, though other kind of electric power subsystems can be considered. An ABEP could extend the lifetime of satellites in LEO and VLEO by compensating the atmospheric drag during their time of operation. The altitude for an Earth-orbiting ABEP can be optimised between 120–250 km. This technology could also be utilized on any planet with atmosphere, if the thruster can process other propellants, and if the power source can provide the required power, e.g. sufficient solar irradiation for the solar panels, such as Mars and Venus, otherwise other electric power subsystems such as a space nuclear reactor or radioisotope thermoelectric generator (RTG) have to be implemented, for example for a mission around Titan.
The first studies considering the collection and use of the upper atmosphere as propellant for an electric thruster can be found already in 1959 with the studies on the propulsive fluid accumulator from S. T. Demetriades.
In the development of atmosphere-breathing ion engines, a notable extension of Child's Law led to its implementation in the ABEP concept in 1995. Originally, Child's Law modeled the flow of charge between an anode and a cathode with the assumption that the initial velocity of ions was zero. This assumption, however, is not applicable to ion thrusters operating in low Earth orbit, where ambient gas enters the ionization chamber at high velocities.
Buford Ray Conley provided a generalization of Child's Law that accounts for a non-zero initial velocity of ions. This adaptation has been significant for the theoretical modeling of ion propulsion systems, particularly those that operate in the rarefied conditions of low Earth orbit.
The generalization of Child's Law has implications for the design and efficiency of atmosphere-breathing ion thrusters. By accounting for the high-velocity ambient gas that enters the ionization chamber in low Earth orbit, the modified law allows for more accurate theoretical modeling. Once the ambient gas is ionized in the chamber, it is electromagnetically accelerated out of the exhaust, contributing to the propulsion of the spacecraft.