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

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.