24E09
Research on Advanced Electrodeless Plasma Rocket: HEAT (HeliconElectrodeless Advanced Thruster) Project
先進的無電極プラズマロケットエンジンの研究：HEAT (Helicon ElectrodelessAdvanced Thruster) Project
Hiroyuki Nishida,1 Shunjiro Shinohara,1 Takao Tanikawa,2 Tohru Hada,3 Ikkoh Funaki,4 Takeshi
Matsuoka,4 Fumiko Otsuka,3 Konstantin P. Shamrai,5 Taisei Motomura,3 Takahiro Nakamura1 andTimofei S. Rudenko5
112
西田浩之 , 篠原俊二郎 ，谷川隆夫 ，羽田 亨3，船木一幸4，松岡健之4，大塚史子3，Konstantin
P. Shamrai,5 本村大成3，中村隆宏1，Timofei S. Rudenko5
1Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
2
Tokai University, Hiratsuka, Kanagawa, 259-1292, Japan
3
Kyushu University, Kasuga, Fukuoka 816-8580, Japan
4
Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, 252-5210, Japan
5
Institute for Nuclear Research, Nauki, Kiev 03680, Ukraine
1
東京農工大学 〒184-8588 小金井市2東海大学 〒259-1292 平塚市
3九州大学 〒816-8580 春日市
4
宇宙航空研究開発機構 〒252-5210 相模原市5Institute for Nuclear Research, Nauki, Kiev 03680, Ukraine

Electric thrusters can provide high specific impulse; therefore, they are suited for long time missions.
However, many of conventional plasma thrusters suffer from the life-time limitation due to the electrodeerosion, and the electrodeless configuration is one solution for the problem. We have initiated the HEAT
(Helicon Electrodeless Advanced Thruster) project to develop an advanced plasma thruster using a helicon
plasma source and RF-based electrodeless plasma acceleration schemes. We have been conducting
experimental, numerical and theoretical studies, and our research activities are reviewed in this paper.

1. Introduction
Electric propulsion can provide significantly
higher specific impulse (Isp = ve/g; ve and g are theexhaust
velocityandthegravitational
acceleration, respectively), that is, higher velocity
increment of a spacecraft can be obtained. The
successful mission of HAYABUSA, which
utilized ion engines, shows the effectivity ofelectric propulsion in a long time space mission.
However, many of conventional electric
propulsions have a problem in life time due to theelectrode erosion in plasma production andacceleration
processes.
Theelectrodelessconfiguration is a promising solution, anddevelopment of electrodeless plasma thruster is
one of the important issues. Several electrodelessthruster concepts have been investigated worldwide(for example, see [1]), and we have initiated HEAT
(Helicon Electrodeless Advanced Thruster) project
to investigate our original idea of electrodelessplasma thruster. Our concept is based on theutilization of a helicon plasma source (high density
up to 1019 m-3) and RF (Radio-Frequency) based
plasma acceleration schemes. In this paper, as areview of our project, the development of a helicon
plasma source and current research status of theplasma acceleration schemes are presented.
2. Thruster Concept
Figure 1 shows the schematic of our thruster
concept. In the plasma production part, dense
plasma is produced using helicon waves. In thedownstream of the plasma source, additional inputof RF power accelerates the plasma to high velocity
in the static divergent magnetic field. We consider
three acceleration schemes: 1) a Rotating Magnetic
Field (RMF) acceleration, 2) a Rotating Electric
Field (REF) acceleration, and 3) the ion cyclotron
resonance (ICR) acceleration with a ponderomotive
force acceleration (PA).
3. Helicon Plasma Source
Helicon plasma source can efficiently produce
dense plasma with a wide-range of the control
parameters; therefore, it is suited for the application
to plasma thrusters. We have developed helicon
plasma sources of various sizes (from 2.5 cm to 74
cm in diameter), and successfully produced dense
plasma (ne up to 1019 m-3) which is applicable tovarious-scaled plasma thruster (from laboratory
small models to high power large thrusters) [2].

the peak of the RF wave energy density. In thisscheme, the ICR and the PA are inseparable, but
the PA is preferred because this scheme has lesseffect of the wall interaction. We have conducted
test particle simulations, and the ICR/PAacceleration mechanism through the resonancepoint was clarified (Fig. 3 shows a typical result ofthe particle simulation). Now, we have initiated aproof of principle experiment at Tokai University.
Fig.1. Thruster and plasma acceleration schemes.
4. Rotating Magnetic Field Acceleration
This idea is originated from the Field-Reversed
Configuration concept [3]. The azimuthal electron
current (jθ) driven by the RMF is a source of theelectromagnetic force accelerating the plasma; i.e.
jθ×Br in the static divergent magnetic field, where Br
is the radial component of the field. The theoreticalestimation shows several tens mN of thrust, whichis enough for a thruster, can be obtained in ourtypical experimental condition. The initial RMF
experiments have been conducted using the Large
Mirror Device at Kyushu Univ. Almost full
penetration of RMF into plasma was confirmed
using a magnetic probe, and a small increment ofthe Mach flow velocity was measured by an axialprobe. Further experiments have been conducted atTokyo Univ. of Agriculture and Tech. (TUAT).
5. Rotating Electric Field Acceleration
In this scheme, the jθ is driven by the REF; theE×B drift gyration motion of electrons at the REF
frequency is a source of jθ [4]. Feasibility study isunder way using several approaches. Theoreticalthrust model has been developed and the analysis
shows that several mN thrust can be obtained in ourtypical experimental condition. The REF
experiments have been conducted at TUAT, and asmall velocity increment has been observed by aMach probe (Fig. 2). We are trying to optimize theexperimental condition with the aid of thetheoretical and numerical analysis. Direct thrustmeasurement has been started at ISAS/JAXA, andseveral mN thrust force without REF wassuccessfully measured by a thrust stand, where Isp isabout 100-200 s.
6. ICR/PA Acceleration
In this acceleration scheme, ions are heated by theICR, and their perpendicular energy is converted
into the parallel energy while ions travel throughthe divergent magnetic field. Additional
acceleration by the pondermotive force [5] can beexpected, when the resonance point corresponds toFig.2. REF experiment; radial distribution of theplasma velocity in the plasma plume.

Fig.3. Particle simulations; (left) ion trajectory,(right) perpendicular energy vs. parallel energy.
7. Summary
In order to develop the electrodeless plasma
thruster, we have initiated the HEAT project.
helicon plasma sources of various sizes have beensuccessfully developed. We have proposed threetypes of plasma acceleration schemes (RMF, REF
and ICR/PA), and feasibility studies are under way
using theoretical, numerical and experimental
approaches.
References[1] Chang-D íaz:Sci. Am. 283 (2000) 90.
[2] S. Shinohara, T. Hada, T. Motomura, K. Tanaka, etal.: Phys. Plasmas 16 (2009) 057104 1-10.
[3] I.R.Jones: Phys. Plasmas 6 (1999) 1950.
[4] T. Nakamura, K. Yokoi, H. Nishida,et al.: 29th Int.
Electric Propul. Conf., Wiesbaden, 2011.
[5] I. Y. Dodinand, N. J. Fisch and J.M. Rax: Phys.
Plasmas 11 (2004)5046.
Acknowledgments

This work has been partly supported by theGrants-in Aid for Scientific Research underContract No. (S) 21226019 from the Japan Societyof the Promotion of Science.