Yoshiki Yamagiwa

Space Demonstration of Bare Electrodynamic Tape-Tether Technology on the Sounding Rocket S520-25

A spaceflight validation of bare electro dynamic tape tether technology was conducted. A S520-25 sounding rocket was launched successfully at 05:00am on 31 August 2010 and successfully deployed 132.6m of tape tether over 120 seconds in a ballistic flight. The electrodynamic performance of the bare tape tether employed as an atmospheric probe was measured. Flight results are introduced through the present progressive report of the demonstration and the results of flight experiment are examined as the premier report of the international cooperation between Japan, Europe, USA and Australia. Future plans for maturing space tether technology, which will play an important role for future space activities, are also discussed.

Generation and diagnostics of atmospheric pressure CO2 plasma by laser driven plasma wind tunnel

Atmospheric pressure CO2 plasma was generated by a laser driven plasma wind tunnel. At an ambient pressure of 0.38 MPa, a stable plasma was maintained by a laser power of 1000 W for more than 20 min. The translational temperature was measured using laser absorption spectroscopy with the atomic oxygen line at 777.19 nm. The measured absorption profiles were analyzed by a Voigt function considering Doppler, Stark, and pressure-broadening effects. Under the assumption of thermochemical equilibrium, all broadening effects were consistent with each other. The measured temperature ranged from 8500 K to 8900 K.

Development of vacuum ultraviolet absorption spectroscopy system for wide measurement range of number density using a dual-tube inductively coupled plasma light source

A vacuum ultraviolet absorption spectroscopy system for a wide measurement range of atomic number densities is developed. Dual-tube inductively coupled plasma was used as a light source. The probe beam profile was optimized for the target number density range by changing the mass flow rate of the inner and outer tubes. This system was verified using cold xenon gas. As a result, the measurement number density range was extended from the conventional two orders to five orders of magnitude.

Application of the Magnetic Flow Control System for Aerobraking Flight of the Reentry Vehicle

The applicability of the electromagnetic flow control system for aerobraking flight of the reentry vehicle is investigated by trajectory analyses. The numerical results suggest that the electromagnetic flow control system can drastically shorten the flight path of the aerobraking flight. This is due to that the vehicle is decerelated near the perigee point more effectively by the imposed magnetic field, compared to the typical aerobraking flight vehicle. By utilizing this system, the flight time of the aerobraking flight can be reduced to about 15% of the flight time without imposed magnetic field.

Atomic-Oxygen-Flow Generation by Laser-Driven Plasma Wind Tunnel as Low-Earth-Orbit-Environment Simulator

Cp = specific heat at constant pressure c = velocity of light hchem = chemical potential h0 = total specific enthalpy I = probe laser intensity K = integrated absorption coefficient k = absorption coefficient kB = Boltzmann constant Mav = average molecular weight m = molecular weight R = gas constant r = radial position T = translational temperature T = throat temperature Tref = reference temperature Troom = room temperature T0 = total temperature u = flow velocity x = position in the laser path y = distance between the flow axis and the laser path γ = specific-heat ratio ΔνD = Doppler width θ = incident-laser-beam angle to the axis ν = probe laser frequency νc = constant for Gaussian fit νshift = Doppler shift ν0 = center absorption frequency

Non-Ideal MHD Effect in the Flow Field of Magneto Plasma Sail

In this study, magnetohydrodynamic (MHD) analyses were conducted to simulate the flow field around a Magneto Plasma Sail (MPS). Firstly, based on the ideal MHD model, the thrust characteristics of MPS was evaluated; our results showed that a momentum change of the solar wind exerts on the spacecraft inside the magnetosphere through the Maxwell’s stress. Also, it was found that the MPS spacecraft could obtain a larger thrust level compared with pure Magnetic Sail when the plasma was injected from the spacecraft for a low β value <10 -3 at the spacecraft position. In addition to the ideal MHD simulation, some preliminary simulations were conducted to evaluate the non-ideal MHD effects on the magnetic field inflation process of MPS. According to the Hall MHD analyses, it was shown that the Hall effect had a negative impact on the magnetic field inflation process because the Hall current restricted the azimuthal current to inflate the magnetic field.

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.

Combined VUV Absorption and Laser Absorption Spectroscopy for Atomic Oxygen Detection

A combined vacuum ultraviolet absorption (VUV AS) and near infrared laser absorption spectroscopy (LAS) system was developed to measure atomic number density. As a VUV light source, inductively coupled plasma was used and its beam profile was determined by LAS. Firstly, this system was evaluated using cold xenon gas. As a result, the measured number density agrees with the that estimated from the partial pressure considering the absorption between the ICP and the window. Then, this system was applied to the ECR oxygen plasma. The measured number density of atomic oxygen was found to increase with the increase in the microwave power.

Emission Spectroscopy of High Pressure CO2 Plasma Flows

A high pressure CO2 plasma flows was generated by focusing a continuous wave laser beam. The generating conditions were the ambient pressure of 0.38 MPa, laser power of 600 W and mass flow rate of 0.69 g/s, respectively. To characterize the flow properties, emission spectroscopy was applied. Using the v=0 transitions of the C2 Swan band, the vibrational temperature was estimated assuming the Boltzmann distribution. As a result, the vibrational temperature was found 3600 K.

A Proposed Bare-Tether Experiment on Board a Sounding Rocket

A mission on board a sounding rocket to carry out two bare-tether experiments is proposed: a test of orbital-motio n-limited (OML) collection and the proof-of-flight of a technique to determine the (neutral) density vertical profile in the critical E-layer. Since full bias from the motional field will be small (~ 20V), corresponding to a tape 1 km long and vrocket << 8 km/s, a power source with a range of supply voltages of few kV would be used. First, the negative terminal of the supply would be connected to the tape, and the positive terminal to a round, conductive boom of length 10 - 20 m; electrons collected by the boom cross the supply into the tape, where they leak out at the rate of ion impact plus secondary emission. Determination of the density profile from measurements of auroral emissions observed from the rocket, as secondaries racing down the magnetic field reach an E-layer footprint, are discussed. Next the positive terminal of the voltage supply is connected to the tape, and the negative terminal to a Hollow Cathode (HC); electrons now collected by the tape cross the supply, and are ejected at the HC. The opposite connections, with current collection operated by tape and boom, and operating on electrons and ions, and through partial switching in the supply, allow testing OML collection in almost all respects it depends on.