Predicting aircraft flight performance using ground tests is important for development but difficult, and flight-to-wind-tunnel correlation methods have been developed and improved over many years. This paper examines the flight-to-wind-tunnel correlation of the aerodynamic characteristics of the Japan Aerospace Exploration Agency’s (JAXA) “Hisho” Flying Test Bed by applying typical methods to flight test data. It was found that the minimum drag coefficient of a business jet geometry test model follows the gradient of the Schoenherr equation well for forced turbulent flows. After that, the reference condition for the correlation was set, but discrepancies in the lift and drag coefficients remained between the flight and wind tunnel tests. A preliminary study identified force differences parallel to the axis of the engine nacelle as being caused by spillage drag due to the difference in the capture area ratio (CAR) between the flight and wind tunnel tests. However, the test data were insufficient to reasonably attribute the difference in the normal force component to lift yielded by the engine nacelle. This was due to the fact that the flight test parameters showed an interdependency and the effects of relevant parameters were not fully investigated in wind tunnel tests.
This paper explores the feasibility of using elastic nets for active capture of space debris. We present a systematic analysis of the strains and stresses in the ejected flying nets during various cases of impact with spacecraft models. The main objective of the paper is development of the method of interaction between the edged spacecraft structures and elastic nets. A finite element method featuring numerical simulation capabilities is utilized to simulate the elastic nets. This enables the modeling of various stages of interaction between the satellite models and the capturing nets. These include a rigid body being wrapped by the net, sliding of the net along the edges, crawling of the net over the corners, and debris escaping from the “missing” corners of the net. This paper focuses on simulating successful captures; however, our simulations also include analysis of representative scenarios of unsuccessful attempted captures, where capturing targets were “bounced” by the nets and where targeted objects managed to “escape” or “fly through” the elastic nets (with cases, not involving rupture of the net segments) during high-speed impacts. Dynamic forces, strains, and stresses are analyzed for various geometrical nets and recommendations are formulated for the most efficient configurations.
In this research, a method for direction control of a primary jet with a Coanda surface is investigated as part of a fundamental study of fluidic thrust vectoring. The effect of the velocity amplitude ratio (i.e., ratio of time-averaged velocity to velocity fluctuation amplitude) of the secondary flow on the flow characteristics of the jet was experimentally investigated. It was determined that the jet deflection angle was maximized under the suction condition wherein the secondary flow exhibited velocity fluctuation. The relationship between the jet deflection angle and the momentum ratio between the primary jet and the secondary flow is presented, in which the dimensionless frequency of the secondary flow was used as a parameter. Although the jet deflection angle depended on the dimensionless frequency and the momentum ratio, it was difficult to adjust this parameter using only the momentum ratio in the hypothetical saturated region where this ratio is large. In addition, unsteady characteristics were also discussed for several conditions.
Rotating detonation combustors (RDCs) are among the combustors that use supersonic combustion waves known as detonation waves, and are expected to simplify engine systems and improve thermal efficiency due to their supersonic combustion and compression performance using shock waves. Research is also being actively conducted worldwide on a cylindrical RDC; a RDC without an inner cylinder, which is expected to simplify and downsize the combustor. However, most of the research was performed using gas propellants, and liquid propellants were rarely used. Since liquid propellants are used in many combustors, it is important to evaluate the performance of RDCs with liquid propellants. In this study, a cylindrical RDC with a liquid ethanol–gas oxygen mixture was constructed and tested at a flow rate of 31.5 ± 5.0 g/s, an equivalence ratio of 0.46–1.39, and a back pressure of 14.5 ± 2.5 kPa. The thrust was shown to depend strongly on the combustor bottom pressure history. In addition, the start-up process of the cylindrical RDC with liquid fuel was clarified by self-luminous and CH* radical visualizations. It was found that the detonation wavefront propagated at a distance of 2–3 mm from the combustor bottom, and the main combustion region was 10–15 mm in height.