Numerical Simulation of Microwave Plasmain Air Breathing Ion Engine
Takahito Motoyama1, Hideyuki Usui2, Yohei Miyake2, Akihiko Hashimoto2,
Masahito Tagawa1 and Kumiko Yokota1
1Graduate School of Engineering, Kobe University
2Graduate School of System Informatics, Kobe University
1.

Introduction
Lowering of the orbiting altitude provides many
advantages for Earth observation satellites such as
high-resolution and small consumption power etc. Super-Low
Earth Orbit (SLEO) satellite was pioneered by Gravity Fieldand Steady-State Ocean Circulation Explorer (GOCE) whichorbits at the altitude of 200 km. It equips ion engine tocompensate drag of the upper atmosphere. Ion engine carries
xenon gas as propellant. Large volume of high-pressure
xenon tank weighs on the available volume inside the satellites
for mission equipments. Moreover, SLEO satellites have toreduce the cross-section of the satellites because of the drag in
the upper atmosphere. Air Breathing Ion Engine (ABIE)
concept was proposed by Nishiyama for such applications in2003 [1]. ABIE does not carry propellant. The Upperatmosphere is compressed inside ABIE and microwave plasma
was formed by the compressed atmosphere which is composedof atomic oxygen and molecular nitrogen. Since the pressureof atmosphere at the altitude of 200 km is not high enough tomaintain plasma, compression and plasma formation processesof the upper atmosphere is the key technology of ABIE.
However, formation of continuous gas flow at 8 km/s in aground-based facility is not an easy task [2]. Laser detonation
method, originally developed as a laser thruster, has been used
to simulate 8 km/s atomic oxygen flow in the ground-based
facility for material degradation studies. However, it forms
pulsed beam and not suitable for ABIE studies. Thus, ABIE
has been studied only in theoretical basis [3].
In this study, plasma formation property inside ABIE wasstudied by a numerical simulation based on Particle-In-Cell(PIC) method.
Electromagnetic Spacecraft Environment
Simulator (EMSES) was applied in this calculation. The
purpose of this simulation is to establish the design guideline ofABIE.

2.

Simulation model

EMSES is a computational code based on Maxwell’sequations and Newton’s law developed for studying spacecraft
plasma interactions [4]. In our simulation, plasma particles
can collide with neutral particles, of witch spatial distribution is
stationary, in the collision process only movement of electron
is considered. For electrons moving in one direction (beam),
electron density is affected by the impact ionization or
scattering with neutral atoms. Decrease in the electron beam

density is given by the equation below:(1)
whereis electron density (or intensity),is neutral
particle density, x is the beam direction, and σ is thecross-section of election/neutral collision.
The reaction
between neutral and electron is characterized by σ which
depends on the collision energy [5]. Null-collision method
was applied for the classification of reactions [5]. Collision
probability of electrons per unit time Δt is given by(2)

whereis speed of the incident electron,
neutral particle density at .

( ) isThe simulation space consists of 108 x 108 x 108 grids.
To emit microwave, the dipole antenna consisted in two
5-grid-long electrically conducting rods with a 2-grids spacing
was located in the center of the simulation space as shown inFigure1. The diameter of dipole antenna was ignored because
the actual diameter of antenna was much smaller than thewavelength of microwave. For electron cyclotron resonance(ECR) with microwave, dipole magnetic field given by
Equation (3) was used in this calculation.
(3)

where r is position vector from the center of magnetic field,
andis dipole moment vector [6]. In order to reflectmagnetic field to plasma dynamics, the magnetic field
distribution over the computational area was calculated. Then,all plasma particle in simulation reflect the magnetic field
distribution in the equations of motion shown in Equation (4)In the figure the electron flow from inside to outside near theECR points.

(4)
3.2
3.
3.1

Computational results and discussion
ECR simulation
The accuracy of ECR simulation was confirmed by thephase diagram (Figure 2). The simulation parameters areshown in Table1. The red lines in the each panel’s abscissa
are the resonat points of ECR theroretically obtained. From
the figure we can confirm that electrons are accelerated in bothx- and y- directions at the ECR points. It was, therefore,
confirmed that the EMSES calculation in this study provides
spacially accurate results. Figure 3 shows the electron density
distribution in the yz plane at x = 54 (middle of antenna gap).

Collision simulation
Collision between neutral particles and electrons wasincluded in the same computational model as shown in theprevious section. The collision frequency of 1E-4 Hz and 3
type of magnetic field (= 34, 340 and 3400 T) wereintroduced. The number of ions generated by the impact
ionization was plotted in Figure 4. A strong correlation
between the number of ions and magnetic field are shown inFigure 4. Although not shown in figure difference in spatial
distribution in the ions is also observed. These results would
give important information to optimize the antenna and magnet
design inside ABIE.
4.

Conclusions
Numerical simulations on microwave plasma inside theABIE were carried out with The EMSES code. Because theprecise ground-based experimental simulation is difficult for
ABIE, the design guideline of ABIE would be establishedthrough the combination of limited ground-based experimentand computational results obtained in this study.
References[1]. Nishiyama K：A Study of Air Breathing Ion Engine, JSASS,Vol.4, (2005), pp.21-27[2]. Tagawa M, Kishida K, Yokota K：Calibration of Atomic
Oxygen Sensors adoard Satellites, ISAS/JAXA, Space
Utilize 26, (2010)[3]. Fujita K：Air Intake Performance of Air Breathing Ion
Engine, JSASS, Vol.52. (2004), pp.514-521[4]. Miyake Y, Usui H：New electromagnetic particle
simulation code for the analysis of spacecraft-plasmainteractions, PHYSICS OF PLASMAS 16, (2009)[5]. V.Vahedi,M.Surendra：A Monte Carlo collision model forthe particle-in-cell method, applications to argon andoxygen discharges, Computer Physics Communications,Vol.87, (1995), pp.179-198[6]. Optical Sosity of Japan：Introduction to electromagnetic
field analysis, OPTRONICS, (2010)