The analysis and evaluation of spacecraft charging are important tasks related to spacecraft design. Plasma parameters and charging potential data are needed for charging and discharging predictions. A new type of electrostatic analyzer using two-stage parallel electrodes has been developed to measure the charging potential of a spacecraft over a wide range, from one volt to tens of kilovolts. The spacecraft charging potential is determined by analyzing the energy spectrum shift. A proof-of-concept model of the new electrostatic analyzer was tested in a vacuum chamber filled with Xe plasma. The experimental results agreed very well with the theoretical predictions. The device, made of two parallel plate electrodes, can measure the charging potential by scanning the electrode voltage over only one-tenth of the actual charging potential. The simple structure and low-voltage operation make the device suitable for operation on a small satellite.

View full abstract

To introduce an alternative fuel to a combustion system or develop a more sophisticated system used in aeronautical and other engineering fields, the combustion characteristics of the fuel must be fully understood. Therefore, some effects of radical species, which are involved and play a significant role in the combustion process, must be understood to arrive at a new technology, such as for super-lean combustion or low-quality fuel utilization, which in turn would lead to solutions for recent energy issues. We have developed an original experimental apparatus which can selectively supply radicals appearing in the combustion process by making use of a plasma torch and can be used to understand their effectiveness. A series of trial experiments conducted with di-methyl ether as the test fuel demonstrate that the experimental method proposed is valid and practical, and can be used to evaluate the role of radical species for the ignition/combustion of various gaseous fuels.

View full abstract

The intrinsic instability of premixed flames at sufficiently low activation energy was studied by two-dimensional unsteady calculations of reactive flows, based on the compressible Navier-Stokes equation including a one-step irreversible chemical reaction. A sinusoidal disturbance with small amplitude was superimposed on a planar flame to obtain the relation between the growth rate and wave number, i.e. the dispersion relation, and the average local burning velocity of a cellular flame. When the Lewis number was smaller (larger) than unity, the growth rate and the average local burning velocity decreased (increased) as activation energy became lower, because of the decrease of the Zeldovich number. When the Lewis number was unity, the growth rate decreased slightly at sufficiently low activation energy, and the average local burning velocity was almost constant. In addition, the dependence of the average local burning velocity on the Lewis number became weaker at sufficiently low activation energy.

View full abstract