The space transportation system using capsule/rocket configurations such as Apollo and Soyuz are simple compared with Space Shuttle, and have several merits from the viewpoint of reliability. The capsule/rocket system will take over the Space Shuttle, after it retires in 2010. As the Space Shuttle accidents had been caused by several factors, e.g., aerodynamic interaction of shock waves ahead of its wing, advanced abort systems such as LAS (Launch Abort System) are required for the capsule/rocket system. In the present study, as a baseline configuration, a combination of a cone and a cylinder is employed as a CEV (Crew Exploration Vehicle), which consists of a capsule (LAV: Launch Abort Vehicle) and a rocket (SM: Service Module). By changing the relative position of the two components as well as the profile area of the rocket, their effects on the capsule/rocket aerodynamic interaction and characteristics (drag and pitching moment) are experimentally and numerically investigated at a supersonic speed (M∞ = 3.0). It is found from the results that the clearance have little effects on the flow field for the case of the baseline configuration. The capsule always showed a positive drag (CD = 0.34), which means that thrust is required to overcome the drag. Otherwise the capsule will recontact the rocket. However in the case where the rocket contact area is 2.2 times as large as the capsule profile, more favorable effects were obtained. Especially in the case of a certain clearance (h/D = 0.40), the drag coefficient of the capsule is CD = −0.35, which means that the capsule suffers a thrust force from the aerodynamic interaction. Under this condition, if capsule has a pitch angle with 5 degrees instantaneously, then pitching moment coefficient becomes CMp = −0.41 therefore capsule stabilize. However, in the case of a very small clearance (h/D ∝ 0.00), the flow becomes unsteady involving pulsating shock wave, leading to a potentially risky separation of the capsule.
A wing rock is known to be a self-excited rolling oscillation of a delta wing that is induced by unsteady aerodynamic forces. In previous studies, we carried out coupled simulations of a flow simulation (CFD) and an equation of motion of a delta wing to reproduce and understand a wing-rock motion observed by low-subsonic wind-tunnel experiments. The objective of the present study is to simulate high-subsonic wing rock phenomena and compare simulations with the visualized flow data by the latest experiments. A numerical model of a friction torque around the rolling axis in the experiment is introduced to search the reason for the discrepancies between the experiments and the simulations. Unsteady pressure changes on the wing obtained by the pressure sensitive paint (PSP) technique show reasonable agreements.
We proposed new thrusters using Dimethyl ether (DME) as propellant: DME arcjet thruster and liquid propellant thruster using plasma assisted combustion. DME has a freezing point of −143ºC, a boiling point of −54ºC, and liquefies at 6atm under room temperature. Thus, DME can be stored as a liquid without cryogenic device. DME has little toxicity and is chemically stable. A DME arcjet thruster prototype operated in a discharge power range from 1000W to 1600W and a plenum chamber pressure reached 160kPa. We also designed a liquid propellant thruster prototype using DME plasma assisted combustion. The plasma successfully sustained the combustion of DME and Hydroxyl Ammonium Nitrate oxidizer. At a discharge power of approximately 3kW, the measurement of the thrust chamber pressure yielded a C* efficiency of 0.39 and an estimated specific impulse of 114s.
In the previous study, the authors proposed the generalized characteristic interface conditions (GCIC) for high-order finite difference multi-block computation in the structured grid system. The GCIC can realize single point connection between adjacent blocks, and allows metric discontinuities on the block interface, however, the grid points of the adjacent blocks have to be collocated correspondingly on the block interface. In this study, in order to enhance the flexibility of the GCIC, by incorporating the high-order interpolation method such as the Lagrange or B-spline interpolation, the GCIC+I (GCIC with Interpolation) are newly developed and introduced. The GCIC+I can solve multi-block problem with non-uniform staggered grid connection on the block interface, and the grid resolution can be arbitrarily changed in each block. In this article, their theoretical concept is briefly presented, and suitable numerical test analysis of inviscid or viscous flow is conducted in order to validate the proposed theory. As a result, the successful functions of the GCIC+I are confirmed.
Liquid Natural Gas (LNG) will be used as propellant of near future space vehicles and rocket engines. Cooling characteristics of engines, especially methane thermal cracking characteristics depend on material candidate for nozzle and chamber cooling passage material temperature. This paper describes these effects on coking and sample analysis method is suggested.
In order to develop a quiet supersonic transport, it is necessary to reduce shock waves around the transport. Shock waves, in general, are the cause of the airplane's sonic boom. Authors have been studying an aerodynamic feasibility of supersonic biplanes based on the concept of the Busemann biplane. In this paper, the three dimensional effect of wing geometries on their wave drags, including wing tip effects and the interference effects between the wing and a body (Wing-Body configurations) are investigated, using CFD code in Euler (inviscid) mode. As a result, we can conclude that the supersonic biplane wings at their design Mach number (M∞=1.7) are still capable of reducing wave drag significantly similar to that of the 2-D supersonic biplane.