Investigation of a Novel Atmosphere-Breathing Electric Propulsion Platform and Intake

Abstract: Very Low Earth Orbit (VLEO) provides many benefits for space missions, including better image resolution for Earth observation, better telecommunication link with ground stations, lower launch cost, lower risk of collisions, and fast end-of-life disposal. The last point in benefit is also the main challenge for placing satellites in VLEO. Being so close to the Earth’s surface, with mean orbital altitude below 450 km, there’s still a significant amount of atmospheric particles left in VLEO, which causes drag force. A spacecraft operating in VLEO will de-orbit within months or even less if the drag force is not compensated. Atmosphere-Breathing Electric Propulsion (ABEP) is a potential solution for this challenge. An ABEP system comprises an atmospheric particle intake and an Electric Propulsion (EP) system. The intake collects particles and delivers them to the electric thruster’s Discharge Channel (DC), the EP system then ionizes the particles and accelerates them out to generate thrust. The ABEP design by Institute of Space Systems (IRS) at the University of Stuttgart has been ongoing, where various design concepts for the intake were studied, and the specular intake design has been selected for further investigation. Subsequent simulations at IRS showed stagnation and backflow inside the new specular intake, with increased intake length and frontal diameter. So, for this thesis, Direct Simulation Monte Carlo (DSMC) simulations were performed for the specular intake to investigate its geometry sensitivity. It was found that due to high particle thermal velocities in the VLEO, the collection coefficient (intake collection ability) decreases with the increase in intake length. And in combination with the drag analysis of the specular intake, it was concluded that, for a specular intake with a DC diameter of 37 mm, the optimum intake length is below one meter.