Atmosphere-Breathing Electric Propulsion systems (ABEP) are currently investigated to
utilize the residual atmosphere as propellant for drag-compensating thrusters on spacecraft
in (very) low orbits. The key concept for an efficient intake of such a system is to feed a large
fraction of the incoming flow to the thruster by a high transmission probability Θ for the inflow
while Θ for the backflow should be as low as possible. This is the case for rarefied flows
through tube-like structures of arbitrary cross section when assuming diffuse wall reflections …