Aerospike nozzles have been expected as a candidate for an engine of reusable space shuttles to respond to growing demand for rocket-launching and its cost reduction. In this study, the flow field structure in any cross sections around the linear-type aerospike nozzle are visualized and analyzed, using laser induced fluorescence (LIF) of NO seeded in the carrier gas N2. Since the flow field structure is affected mainly by the pressure ratio (P/P), the linear-type aerospike nozzle is set inside the vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 250. Flow fields are visualized in several cross-sections, demonstrating the complicated three-dimensional flow field structures. Pressure sensitive paint (PSP) of PtTFPP bound by poly(TMSP) is also applied successfully to measurement of the complicated pressure distribution on the spike surface.
This paper presents the concept of dynamic wind tunnel testing using captive flight method, in which the airplane is supported by three elastic lines mainly in the vertical direction, and given oscillatory motions by an external actuator. This experimental method is designed for the aerodynamic parameter estimation. Longitudinal and lateral dynamic tests are carried out sweeping driving frequency, and every mode except surging motion, of which damping is weak, was excited. Aerodynamic parameters estimated from flight data showed good accordance with reference data. This experimental method has the advantages of the experimental simplicity, quite small aerodynamic interference, stable flight and the capability of the excitation of motion necessary for the estimation.
This paper presents the new concept of a robot-oriented space system called “Space Environment Preservation System” that operates to maintain the satellite constellation and orbit by robots, and presents the technology development. The orbit maintenance vehicle requires the robots to assemble and capture the satellite, to diagnose, repair or replace malfunctioning units of the satellite in orbit, and to collect and carry the satellites out of the orbit at the end of life span. In order to realize the system, a new type of modularized satellite that can be easily assembled, maintained and disassembled by the robot is proposed. We developed the ground model of such a satellite, and the orbit maintenance vehicle that has the multifunctions of in-orbit satellite assembling factory and servicing station, as well as satellite capturing and disassembling. These functions were demonstrated in the simulated space condition.
Damage identification methods using finite element methods need a long computational time for large and complex structures. In this paper, we develop an effective damage identification method for large truss structures containing multiple damaged truss members using a successive iteration method of bounding domain and a domain decomposition finite element technique. The subdomains of truss structures which contain damaged truss members are first determined by a flexibility method. The subdomains are subdivided into smaller subdomains using a successive iteration method of bounding domain, and finally the damaged truss members are identified. By conducting the damage identification for a large three-dimensional truss structure, it is recognized that the damaged truss members and their residual stiffnesses can be identified precisely and the present damage identification method can reduce the computational time.
This paper describes a control of heading and flight-path angles of aircraft to time-varying command angles. The controller first calculates an acceleration command vector (acV), which is vertical to the velocity vector. acV consists of two components; the one is feedforward acceleration obtained from the rates of command angles, and the other is feedback acceleration obtained from angle deviations by using PID control law. A bank angle command around the velocity vector and commands of pitch and yaw rates are then obtained to generate the required acceleration. A roll rate command is calculated from bank angle deviation. Roll, pitch and yaw rate commands are put into the attitude controller, which can be composed of any suitable control laws such as PID control. The control requires neither aerodynamic coefficients nor online calculation of the inverse dynamics of the aircraft. A numerical simulation illustrates the effects of the control.
Dynamic properties of aerodynamic forces and moments acting on a delta wing were experimentally studied in a low-speed wind tunnel. The wing could make a smooth and periodic arbitrary motion, such as pitching, yawing, rolling, translation motions, and their combinations by a manipulator equipped with stepping motors controlled by a microcomputer, which had six degrees of freedom. The objective of the research is to analyze unsteady aerodynamics of the rolling delta wing with regard to the altitude from the ground. It was found that the hysteresis loops of lift, drag and rolling moment were drawn with the roll angles and amplified owing to the ground effect. The factors to determine the wing properties in the large angle of attack are the pressure on the windward side of the delta wing and the leading edge vortices which were broken down and reconstructed according to the wing motion. The pressure on the lower wing surface was also influenced by the clearance between the delta wing and the ground plate, which deduces the ventulli or stagnant effects.
This paper presents a new guidance law for a missile with varying velocity against a maneuvering target with a constant acceleration. Since an approximate missile velocity change during boost phase or after thrust cutoff can be calculated, the intercept point can be estimated if the target acceleration is measured. The guidance law presented guides the missile to the point directly. The guidance law is constructed by combining augmented proportional navigation and pure pursuit navigation with some mixture ratio. From some simulations, it is found that the guidance law presented is more effective and has the higher off-boresight ability and the smaller lateral divert requirements than conventional augmented proportional navigation or proportional navigation even if there exist the LOS angle noises.