KP
K. Pernapati
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Coupled DSMC Simulation of an Air-Breathing Electric Propulsion Intake and Thruster Interface
Effects of thruster interface, and Chamber Shape on Neutral Gas Delivery
Master thesis
(2026)
-
K. Pernapati, Ferry Schrijer, P.P. Sundaramoorthy, M.I. Gerritsma, Imre Bakker
Air-breathing electric propulsion (ABEP) captures residual atmosphere at very low Earth orbit as thruster propellant, removing the need for stored propellant to maintain sustained operation below 250 km. Passive intake studies report collection efficiencies against a fully absorbing downstream boundary that represents the thruster as an idealized neutral sink. For a gridded ion thruster, this boundary excludes the neutral population reflected by the extraction grid, which is a substantial fraction of the flux incident on it. The present study investigates the effect of the ion-optics interface on the intake performance through direct simulation Monte Carlo, resolving the ion optics as a partial-transmission boundary within the intake domain.
The framework is first validated against the non-gridded conical intake and applied to four passive baseline configurations combining two intake profiles with two discharge-chamber geometries. The intake profile produces sub-percent differences at the throat and discharge-exit planes, as expected because diffuse re-emission removes the directional memory the profile would otherwise carry. The chamber geometry produces a measurable effect on the throat measurement, indicating that the throat responds to the downstream boundary at the level of a passive chamber wall alone.
The framework is then applied to the SITAEL split-ring architecture, scaled to a 16U CubeSat platform and coupled to the RIT-µ3 ion optics at 215 km. The interface is modelled as an absorbing-diffuse boundary at the neutral transparency τn = 0.25, with the central blank resolved as a physical surface. Resolving the interface changes the reported performance. The chamber density is 1.67× the fully absorbing-boundary prediction, the delivered flux is 0.43× it, and the residence time is 4.05× it. These corrections exceed the differences between the intake geometries reported in the literature.
The study then examines three geometric parameters at the exit face against the resolved interface: the blank surface profile, the intake capture area, and the discharge-chamber cross-section. The blank surface profile redirects the returned population within the chamber without altering the flux delivered to the thruster. The intake capture area enters the reported collection efficiency through its normalization alone and leaves the delivered flux unchanged at fixed exit geometry. Only the discharge-chamber cross-section alters the delivered flux through the exit area it presents to the thruster. The beam extraction requirement of the ion optics fixes both parameters that govern that flux. ...
The framework is first validated against the non-gridded conical intake and applied to four passive baseline configurations combining two intake profiles with two discharge-chamber geometries. The intake profile produces sub-percent differences at the throat and discharge-exit planes, as expected because diffuse re-emission removes the directional memory the profile would otherwise carry. The chamber geometry produces a measurable effect on the throat measurement, indicating that the throat responds to the downstream boundary at the level of a passive chamber wall alone.
The framework is then applied to the SITAEL split-ring architecture, scaled to a 16U CubeSat platform and coupled to the RIT-µ3 ion optics at 215 km. The interface is modelled as an absorbing-diffuse boundary at the neutral transparency τn = 0.25, with the central blank resolved as a physical surface. Resolving the interface changes the reported performance. The chamber density is 1.67× the fully absorbing-boundary prediction, the delivered flux is 0.43× it, and the residence time is 4.05× it. These corrections exceed the differences between the intake geometries reported in the literature.
The study then examines three geometric parameters at the exit face against the resolved interface: the blank surface profile, the intake capture area, and the discharge-chamber cross-section. The blank surface profile redirects the returned population within the chamber without altering the flux delivered to the thruster. The intake capture area enters the reported collection efficiency through its normalization alone and leaves the delivered flux unchanged at fixed exit geometry. Only the discharge-chamber cross-section alters the delivered flux through the exit area it presents to the thruster. The beam extraction requirement of the ion optics fixes both parameters that govern that flux. ...
Air-breathing electric propulsion (ABEP) captures residual atmosphere at very low Earth orbit as thruster propellant, removing the need for stored propellant to maintain sustained operation below 250 km. Passive intake studies report collection efficiencies against a fully absorbing downstream boundary that represents the thruster as an idealized neutral sink. For a gridded ion thruster, this boundary excludes the neutral population reflected by the extraction grid, which is a substantial fraction of the flux incident on it. The present study investigates the effect of the ion-optics interface on the intake performance through direct simulation Monte Carlo, resolving the ion optics as a partial-transmission boundary within the intake domain.
The framework is first validated against the non-gridded conical intake and applied to four passive baseline configurations combining two intake profiles with two discharge-chamber geometries. The intake profile produces sub-percent differences at the throat and discharge-exit planes, as expected because diffuse re-emission removes the directional memory the profile would otherwise carry. The chamber geometry produces a measurable effect on the throat measurement, indicating that the throat responds to the downstream boundary at the level of a passive chamber wall alone.
The framework is then applied to the SITAEL split-ring architecture, scaled to a 16U CubeSat platform and coupled to the RIT-µ3 ion optics at 215 km. The interface is modelled as an absorbing-diffuse boundary at the neutral transparency τn = 0.25, with the central blank resolved as a physical surface. Resolving the interface changes the reported performance. The chamber density is 1.67× the fully absorbing-boundary prediction, the delivered flux is 0.43× it, and the residence time is 4.05× it. These corrections exceed the differences between the intake geometries reported in the literature.
The study then examines three geometric parameters at the exit face against the resolved interface: the blank surface profile, the intake capture area, and the discharge-chamber cross-section. The blank surface profile redirects the returned population within the chamber without altering the flux delivered to the thruster. The intake capture area enters the reported collection efficiency through its normalization alone and leaves the delivered flux unchanged at fixed exit geometry. Only the discharge-chamber cross-section alters the delivered flux through the exit area it presents to the thruster. The beam extraction requirement of the ion optics fixes both parameters that govern that flux.
The framework is first validated against the non-gridded conical intake and applied to four passive baseline configurations combining two intake profiles with two discharge-chamber geometries. The intake profile produces sub-percent differences at the throat and discharge-exit planes, as expected because diffuse re-emission removes the directional memory the profile would otherwise carry. The chamber geometry produces a measurable effect on the throat measurement, indicating that the throat responds to the downstream boundary at the level of a passive chamber wall alone.
The framework is then applied to the SITAEL split-ring architecture, scaled to a 16U CubeSat platform and coupled to the RIT-µ3 ion optics at 215 km. The interface is modelled as an absorbing-diffuse boundary at the neutral transparency τn = 0.25, with the central blank resolved as a physical surface. Resolving the interface changes the reported performance. The chamber density is 1.67× the fully absorbing-boundary prediction, the delivered flux is 0.43× it, and the residence time is 4.05× it. These corrections exceed the differences between the intake geometries reported in the literature.
The study then examines three geometric parameters at the exit face against the resolved interface: the blank surface profile, the intake capture area, and the discharge-chamber cross-section. The blank surface profile redirects the returned population within the chamber without altering the flux delivered to the thruster. The intake capture area enters the reported collection efficiency through its normalization alone and leaves the delivered flux unchanged at fixed exit geometry. Only the discharge-chamber cross-section alters the delivered flux through the exit area it presents to the thruster. The beam extraction requirement of the ion optics fixes both parameters that govern that flux.