A computer code for charring ablation and thermal response analysis has been developed for simulation of one-dimensional transient thermal behavior of multi-layer stack of isotropic charring ablation materials used for re-entry capsules. Mathematical model of charring ablation including governing equations is summarized. Analytical solutions of several thermal response problems with or without ablation agreed very well with numerical results that are obtained with the charring ablation analysis code. Arc-heated tests of CFRP ablator models were carried out and measured results including temperature response data were compared with the simulation results of the ablation analysis code. Test results and the simulation results agreed very well. These results show that the analysis code based on the present mathematical model are available for the thermal response prediction of CFRP ablator used in the re-entry capsules such as USERS/REM.
To grasp effects of such ground effect parameters as rotor height, ground inclination angle, and location of the rotor hub center from the edge of ground plane, on blade flapping motion of a rotor hovering above finite inclined ground plane, a hovering test of the rotor was conducted using a finite ground effect plate and a model rotor. The thrust, torque, and blade flapping motion of the hovering rotor were measured for a wide variety of ground effect parameters. A very unique behavior of the blade flapping motion due to flow separation around a finite ground effect plate edge is clarified.
The Air Turbo Ramjet (ATR) is a combined cycle engine which performs like a turbojet engine at subsonic speeds and a ramjet at supersonic speeds and therefore the ATR is an attractive propulsion system for the wide operation range (e.g. Mach 0 to Mach 4). The ATR can provide a higher specific impulse than a solid fuel rocket engine and a higher thrust per frontal area than a turbojet engine. The major ATR components are the inlet, fan (compressor), turbine, gas generator, combustor and exhaust nozzle. In the ATR, the turbine drive gas is generated by a decomposed liquid or solid fuel gas generator. In order to carry heavier payloads and to attain shorter flight time, the compact and high thrust engine is required. In this study, the ram combustor with the double-staged flameholders and the fan with tandem blade were introduced to shorten the engine length and to increase the fan pressure ratio, respectively. Furthermore, the engine testing was carried out on sea level static condition to confirm the engine component integration technologies for the ATR propulsion system.
This paper presents flight control designs of an unmanned space vehicle, HOPE-X, vehicle using interpolation gain scheduling techniques. There are three flight phases from deorbit to landing in HOPE-X; reentry, terminal area energy management (TAEM), and approach and landing. This paper is addressed to the TAEM phase in which an amount of lateral maneuvers are required. Two interpolation gain scheduled state feedback laws were designed with respect to the Lyapunov functions used for guaranteeing the global stability of the closed-loop system, and were applied to the numerical simulations of the HOPE-X. As a result, the gain scheduled control law showed better control performance in the entire of TAEM phase than fixed state feedback laws. The gain scheduling using a parameter-dependent Lyapunov function was superior to the one using a conventional Lyapunov function.
The quasi-steady MPD thruster MY-III was operated to study the exhaust plasma plume characteristics. Both emission spectroscopic and rotatable double probe measurements were made to evaluate electron temperatures, plasma number densities and plasma flow directions. The plasma was slightly expanded radially outward downstream within the extrapolation line of the divergent nozzle regardless of gas species and discharge current although it was intensively expanded outside the line. Both the electron temperature and the plasma number density decreased radially outward at a constant axial position. The angle of radial expansion decreased with discharge current. The angle for H2 was relatively small compared with cases for Ar. Nozzle angle was expected to influence the downstream flow characteristics although a core flow, i.e., the cathode jet, with a high temperature and a large plasma density existed on the central axis.
Experimental Studies have been conducted to investigate velocity disturbances observed inside the short bubble formed on NACA0012 airfoil. Measurements were done at the angle of attack 10° and at the Reynolds number of 1.3×105 based on the chord length. In the transition area in the short bubble, a dominant low frequency velocity fluctuation was observed. This frequency is much lower than that reported in the previous short bubble measurements. The phase averaging technique has been applied to analyze this low frequency velocity fluctuation. It is shown that the direction and the amount of the flow velocity vector inside the separated layer just after the separation point changes periodically. The frequency of these behaviors agrees with the observed low frequency velocity fluctuation.