Takeshi Miyasaka

Numerical prediction of onset phenomenon in a 2-dimensional axisymmetric MPD thruster

Numerical codes of MPD thruster for 2dimensional axisymmetric flow are developed, taking into account the sonic conditions of ldimensional flow analysis. Using the codes, inlet values can be determined not by arbitrary experimental values but by physical principles. Thus flowfields can be calculated regardless of existence of experiments with the same conditions as the calculation. The calculations are performed for a fixed mass flow rate and different magnetic force numbers in a straight-configuration MPD thruster. Thus, the critical discharge current at which onset start is determined for the 2-dimensional axisymmetric flows by taking account the relationship between the electric field and back-EMF. From the analyses for different mass flow rates, the dependency of the critical discharge current on the mass flow rate is obtained.

Detonation Studies of High- Frequency- Operation Pulse Detonation Engine with Air/Hydrogen

An experimental study on pulse detonation engine (PDE) is conducted using hydrogen/air mixtures. Several key issues for PDE development, including valve operation, injection, mixing, filling, cycle repetition, ignition timing, DDT distance and propagation of detonation/quasi-detonation, are investigated. The fuel and oxidizer are injected into PDE from opposite sidewall directions to be well mixed by collision of two jets. The PDE performance is acquired to give the specific impulse about 2000 sec, which is measured from the pressure history on PDE head end. Operation at a maximum frequency 32 Hz is successfully performed. The deflagrationto-detonation transition (DDT) characteristics are measured in conjunction with operational frequency and ignition delay.

Laser‐Supported Detonation Concept as a Space Thruster

Similar to the concept of pulse detonation engine (PDE), a detonation generated in the “combustion chamber” due to incoming laser absorption can produce the thrust basically much higher than the one that a laser‐supported deflagration wave can provide. Such a laser‐supported detonation wave concept has been theoretically studied by the first author for about 20 years in view of its application to space propulsion. The entire work is reviewed in the present paper. The initial condition for laser absorption can be provided by increasing the electron density using electric discharge. Thereafter, once a standing/running detonation wave is formed, the laser absorption can continuously be performed by the classical absorption mechanism called Inverse Bremsstrahlung behind a strong shock wave.

Numerical Lifetime Evaluation of Ion Thruster's Ion Optics using the JIEDI Tool

The JIEDI (JAXA’s Ion Engine Development Initiative) tool has been developed as a numerical tool for the lifetime qualification of ion thruster’s ion optics with high precision and accuracy. The numerical wear test from beginning-of-life to end-of-life (EOL) by the JIEDI tool was conducted for the ion optics of HAYABUSA’s microwave ion thruster (10 engineering model (EM)). It becomes clear that the erosion profiles for high ion beam current hole are most important to estimate the EOL of 10EM ion optics. The ion optics of 10EM ion thruster encounters its EOL by structural failure of the decelerator grid, which is mainly caused by sputtering of ions and neutrals scattered by elastic collisions. The estimated lifetime of the ion optics is 545 khours at the longest. Through the numerical wear test for 10EM ion optics, the process for lifetime estimation of ion optics by the JIEDI tool was demonstrated.

On the Application of the Moment equations to the Thermally Induced Flows

Moment equations derived from the Boltzmann equation for the two‐dimensional flows were formulated and generalized slip boundary conditions for the moments were derived. Fifty one moments relevant to the eigenfunctions included in the Chapman‐Enskog solutions of the second order approximation were taking into account. These moment equations were applied to thermally induced flows in a two‐dimensional vessel. The moment equations were solved using the MacCormack’s difference scheme. Present results showed that the moment equations and the slip boundary conditions were applicable for the two‐dimensional flows in the transition regime. Thermally induced slip flow adjacent to the solid wall decreased linearly in accordance with the decrease of the Knudsen number relevant to the size of the vessel. The values of obtained slip coefficient, velocity/(gradient of temperature along the solid wall), increased as the number of moment equations increased. Present results suggested that moments should be selected so a...