Yuya Oshio

The Use of Dipole Plasma Equilibrium for Magnetic Sail Spacecraft

Plasma equilibrium in an artificial magnetosphere in interplanetary space is proposed to apply the idea of plasma equilibrium for magnetic sail spacecraft, which obtains a thrust force based on the interaction between solar wind particles and an artificial magnetosphere made by electromagnets onboard spacecraft. It is numerically shown that when releasing a low-velocity plasma from a magnetic sail spacecraft, an equatorial ring-current is excited around the spacecraft, which makes a larger magnetosphere and correspondingly a larger thrust level becomes possible. In our preliminary MHD and particle simulations, it is shown that thrust by magnetic sail using plasma equilibrium is more than three times larger than that of pure magnetic sail without releasing plasma, and this result shows promising feature of on magnetic sail using plasma equilibrium.

Magnetoplasma Sail with Equatorial Ring-current

A magnetoplasma sail (MPS) spacecraft produces an artificial magnetosphere to reflect the solar wind particles approaching the coil, and the corresponding repulsive force exerts on the coil to accelerate the spacecraft in the solar wind direction. In this paper, numerical study of plasma equilibrium in an artificial magnetosphere in interplanetary space is updated to check if the idea of plasma equilibrium is applicable to for MPS or not. It is numerically shown that releasing a low-velocity plasma from an MPS spacecraft excites an equatorial ring-current, which makes a larger magnetosphere and correspondingly a larger thrust level becomes possible. Thrust gain, which is defined as a thrust ratio between MPS and pure magnetic sail without releasing plasma, was found to be as much as 40; this thrust gain is predicted from a limited model describing the interaction between a dipole magnetic field and ions. In addition to the limited simulation, some full numerical simulations of MPS, including a solar wind to magnetosphere interaction as well as plasma equilibrium in a magnetosphere, were conducted to indicate a thrust gain as much as 3.77 is possible in an MHD regime.

Plume Characteristics of a Quasi-Steady Magnetoplasmadynamic Arcjet

The plasma plume of a 1-MW-class quasi-steady magnetoplasmadynamic (MPD) arcjet is studied to determine the plume structure and plasma plume fluctuations in a downstream plume region (250-1250 mm away from the MPD arcjet). By using a double probe and a high-electron-temperature ( ~ 5 eV) and high-number-density (~8 ×1019 m-3) region, so-called “cathode jets” are found along the central axis of plasma plume close to the MPD arcjet. Moreover, the plasma plume radial profile is constant in a downstream plume region (≥ 750 mm from the MPD arcjet). The power spectrum density (PSD) of the ion saturation current is proportional to 1/f1.6 (f: frequency) for f >; 80 kHz, and in this frequency range, PSD decreased with distance from the MPD arcjet. In contrast, in the frequency region <; 80 kHz, the PSD-f curve is at a constant value. Although a peak in the discharge voltage is attributed to the generalized lower hybrid drift instability (GLHDI), this instability is not found in the plasma plume near the MPD arcjet. The influence of the GLHDI is limited only to the discharge chamber, and fluctuations caused by the instability are random in the downstream region.

Experimental Investigation of Magnetoplasma Sail with High Beta Plasma Jet

Magnetoplasma Sail (MPS) is one of the next generation in-space propulsion systems that utilize the interaction between the solar wind and the magnetosphere inflated by the plasma injection around a spacecraft. An important issue of MPS is thrust increase by the plasma injection. Experimental validation of the thrust characteristics is very important before applying the idea of the thrust increase by the plasma injection to realistic spacecraft design. In order to conduct a scale model MPS experiment, a laboratory simulator was designed and constructed inside the space chamber (2 m in diameter). As a solar wind simulator, a triple magnetoplasmadynamic arcjet generates a high-speed (>20 km/s), high-density (>10m) hydrogen plasma jet of 0.8 ms duration. A small coil (76 mm in a diameter) and Mini-MPD arcjet as a MPS simulator was immersed inside the simulated solar wind. The thrust characteristics of MPS with plasma injection have been experimentally investigated as a function of the magnetic moment M and the dynamic pressure of the injected plasma Pinf. The thrust gain is growing both with βk value which is ratio of the dynamic pressure of the injection plasma to the magnetic pressure, but the thrust saturation was observed at the high βk condition at the injection point (βk~1). The maximum thrust gain in this paper which is the ratio between the thrust with plasma injection and the thrust without plasma injection was about 4.1.

Experimental Simulation of Magnetoplasma Sail for Thrust Measurement

Magnetoplasma Sail (MPS) is one of the sail propulsion system using the solar wind and suitable for deep space exploration. MPS uses an artificial magnetic field for capturing the solar wind, which is generated by a combination of a coil and a plasma injection. In order to measure thrust of a miniature MPS directory, a parallelogram-pendulum-type thrust stand was developed and installed on MPS ground simulator. In comparison with 0.6 N of Magnetic Sail thrust for 90 mm-magnetosphere, when the magnetospheric size for 115 mm was produced, 4.0 N thrust of the miniature MPS was obtained. The thrust value may include thrust originated with MPD arcjets used for magnetospheric inflation. Our next step of thrust measurement is evaluation of thrust increment for magnetospheric inflation.

Experimental and Numerical Investigations on the Thrust Production Process of Magnetoplasma Sail

Research status of spacecraft propulsion using the energy of the solar wind in Japan is overviewed. Experimental and numerical studies showed that moderately sized magnetic sails in the ion inertial scale magnetosphere (~100 km) could produce Newton-class thrust. In the same scale length, magnetic cavity size was successfully controlled in the laboratory experiment of magnetic sail with a plasma jet (Magnetoplasma sail, MPS), but so far, no significant thrust increment was observed in the experiment. On the contrary, MPS concept was tested in MHD scale by numerical simulation, and thrust increment from pure MagSail to MPS as much as 90% was obtained. Currently, we are continuing our experimental and numerical efforts to make a feasibly sized Magnetoplasma sail (10~100 km magnetosphere) in a transitional regime between ion scale and MHD scale by optimizing the magnetic field inflation process of MPS.

Laboratory Facility for Simulating Solar Wind Sails

Magnetic sail (MagSail) is a deep space propulsion system, in which an artificial magnetic cavity captures the energy of the solar wind to propel a spacecraft in the direction leaving the sun. For a scale‐model experiment of the plasma flow of MagSail, we employed a magnetoplasmadynamic arcjet as a solar wind simulator. It is observed that a plasma flow from the solar wind simulator reaches a quasi‐steady state of about 0.8 ms duration after a transient phase when initiating the discharge. During this initial phase of the discharge, a blast‐wave was observed to develop radially in a vacuum chamber. When a solenoidal coil (MagSail scale model) is immersed into the quasi‐steady flow where the velocity is 45 km/s, and the number density is 1019 m‐3, a bow shock as well as a magnetic cavity were formed in front of the coil. As a result of the interaction between the plasma flow and the magnetic cavity, the momentum of the simulated solar wind is decreased, and it is found from the thrust measurement that the ...

Laboratory Facility for Simulating Magnetoplasma Sail

Magnetoplasma sail (MPS) is a deep space propulsion system, in which an artificial magnetic cavity captures the energy of the solar wind to propel a spacecraft in the direction leaving the sun. This paper describes an improved facility for the scale-model experiment of MPS. We employed a magnetoplasmadynamic arcjet as a solar wind simulator. It is observed that a plasma flow from the solar wind simulator reaches a quasi-steady state of about 0.8 ms duration after a transient phase while initiating a discharge. During this initial phase of the discharge, a blast-wave was observed to develop in a vacuum chamber. Then, a quasi-steady interaction continues when a solenoidal coil (MPS scale model) is immersed into a 45-km/s-velocity and 10-m-number-density plasma flow. As a result of the interaction between the plasma flow and the MPS scale model, a bow shock and a magnetic cavity were formed in front of the coil. Thrust measurement was conducted for only a few limited cases, but the momentum of the simulated solar wind is found to decrease, and as a result, it is found that the solar wind momentum is transferred to the solenoidal coil simulating MPS consisting of only a solenoidal coil.