Advanced Spacecraft Propulsion

Sail Propulsion using the Solar Wind: Magnetoplasma Sail

Fig.1 Concept of Magnetoplasma Sail

The Magnetoplasma Sail (MPS) is one of sail propulsion powered by the solar wind. The solar wind is captured by an artificial magnetic field, which is produced by a superconducting coil on the MPS spacecraft. You can easily image that a large sail produces large thrust. Plasma is injected from spacecraft in order to inflate the sail since the magnet alone can not produce large enough sail for space propulsion.

We have been conducting laboratory experiments and numerical simulations in order to obtain design criteria of the MPS spacecraft and attitude control laws. We plan a space demonstration of an 1 N-class MPS spacecraft near future, which uses one of the inflation technique of magnetic field with a plasma injection.

Fig.2. Flight Image of Magnetoplasma Sail
（Kajimura, AIAA 2010-6686）Fig.4 MHD Numerical Simulation of Magnetoplasma Sail
（Fujimoto, 2010）

Fig.3 Experiment of Magnetoplasma Sail
（Ueno, STEP 2011-009）

Electrode-less Plasma Thruster

The research objective is to realize a plasma thruster which can operate a long life time more than 5 years or even 10 years. Conventional plasma thrusters such as ion engines have a finite lifetime, which is caused by contact between acceleration electrodes and plasmas. Therefore, we focus on methods for plasma generation and acceleration without contact between electrodes and plasma (electrode-less).

A conceptual drawing of the plasma thruster under investigation is shown in Fig.1. The antennas which provide electrical power to generate and accelerate plasmas are isolated by the discharge chamber. We conduct ground test experiments for performance evaluation (Fig. 2).

Fig. 1. Concept of Electrode-less Thruster

Fig. 2. Operation of Helicon Plasma Thruster

Fig. 3 Helicon Electrodeless Advanced Thruster Group

This research is a collaborative research among Tokyo University of Agriculture and Technology (aka: TUAT), Tokai University, Kyushu University, Institute for Nuclear Research (Ukraine) and is also known as the HEAT (Helicon Electrodeless Advanced Thruster) project (Fig. 3).

Link to an explanation of the HEAT project:
http://www.jsps.go.jp/j-grantsinaid/12_kiban/ichiran_21/e-data/e67_shinohara.pdf

Magnetoplasmadynamic Arcjet

図：矩形型スラスタの検証実験の様子と推進性能予測ツールの計算結果

A magnetoplasmadynamic thruster (MPDT or MPD arcjet) is a form of the electric propulsion for spacecrafts, which its thrust (several tens N class) can be generated by the Lorentz force. The MPDT is expected to be used as the main engine of future large spacecrafts.

In order to put the MPDT to practical use, the comprehension of the plasma flow (e.g. hydrogen plasma), the improvement of the thrust efficiency, and the thermal design of a megawatt-class MPDT are conducted experimentally and numerically.

In these studies, researchers or students can conduct the quasi-steady experiment of the MPDT within the vacuum chamber, and the numerical simulation of the MPDT by the workstation or the JAXA supercomputer system (JSS).

Development of Numerical Tool for Ion Thruster: JIEDI

Fig. Lifetime Evaluation by Numerical Tool

Currently, ion thrusters are frequently used for North-South orbit control of geostationary satellite and also for orbital transfers. For these missions, ion thrusters greatly contribute to shorten mission trip time, or to increase a payload ratio.
The thrust created in ion thrusters is, however, very small compared to conventional chemical rockets. Accordingly, to take advantage of ion thruster's high specific impulse and high efficiency, long operation more than 10,000 hours is required.
The cost for a lifetime qualification test of an ion thruster is hence quite high, and this situation prevents quick development and introduction of an optimal ion thruster for a specific mission. If numerical simulation can replace some of ion thruster's life tests, cost and time for the development of an ion thruster can be drastically reduced. Following this concept, 　　the development of a numerical tool called JIEDI (JAXA's Ion Engine Development Initiative) started in JEDI/JAXA to assess the lifetime of the acceleration grid of an ion thruster within affordable computational resources and computational time.

Micro Ion Thruster Development for DECIGO/DPF

FEEP Thruster Laboratory Model

100 micro-Newton class thrusters for the Japanese formation flying spacecraft (DECIGO, Deci-hertz Interferometer Gravitational Wave Observatory) are studied. From a conceptual design of the DECIGO pathfinder, which is a small Japanese scientific satellite to demonstrate drag-free technology for the DECIGO mission, requirements for thrust precision (0.5 uN), thrust noise (0.1 uN/Hz1/2) are derived. By comparing four thruster options such as field emission electric propulsion (FEEP), colloid thruster, cold gas jet, and small ion thrusters, it is found that FEEP can provide the best capability to control its thrust-level with the lowest thrust noise level, and therefore FEEP system are under development.

Laser Micro-thruster

We conduct demonstration experiments of a repetitively-pulsed laser thruster. In this type of thruster, the repetitively-pulsed laser energy turn a target (metal etc) to propellant and produces thrust. The thrust of the laser thruster is generated while laser is ON and is proportional to the laser power. This enables precise thrust control with rapid-responses. This thruster is indispensable for drug free space missions and high precision formation flight missions which compensates for disturbance such as sun light.

Fig.1 Experimental Setup of Laser Thruster.

Fig.2 Operation of Laser Thruster.