The relationship between the ice accretion shape and ambient conditions is quantitatively investigated via analysis of variance (ANOVA) and is qualitatively studied using self-organization maps (SOMs). The independent variables of this study are liquid water contents (LWC), mean volumetric droplet diameter (MVD), flight speed (free stream velocity) and ambient temperature. The ranges of these variables follow appendix C of FAR part 25. The ice accretion shape is quantified through parameterization of ice accretion area, maximum thickness, ice heading and icing limits. SOMs and ANOVA can be used for parameter analysis. We determine the associated parameters, although the parameters are examined under non-linear conditions. The range of temperature, -40–0°C, is divided into 10°C intervals. Three distinctive temperature groups are found, depending on the response of the ice shape to the ambient conditions. They are rime (-40–-20°C), mixture (-20–-10°C) and glaze (-10–0°C). The ice accretion area and maximum thickness are determined by free stream velocity and LWC over the entire temperature range, while ice heading is affected by the temperature, free stream velocity and LWC. Different variables affect the icing limits on the upper and lower surfaces. On the upper surface, runback dominates the formation of icing, while on the lower surface the dominant factor is where limits are impinged.
Prognostics and health management (PHM) has an important part in aerospace systems. Information sensing and testing are the bases of PHM, and design for testability (DFT) developed concurrently with system design is considered a fundamental way to improve PHM performance. The traditional DFT, which is only based on the requirements of fault detection and isolation, is not suitable for sensor design and optimization for PHM. Aiming to solve this problem, the intrinsic requirements of PHM for testability are firstly analyzed qualitatively and the corresponding testability indexes are defined quantitatively. Then, a sensor selection/optimization process for PHM is presented. Fault detection uncertainty is also analyzed systematically from the view of fault attributes, sensor attributes and fault-sensor matching attributes, respectively. Based on the requirements and process, the object and constraint models of sensor optimization selection problem are studied in great detail. For aerospace system health management, a sensor optimization selection model is constructed that treats sensor total cost as the objective function and the proposed testability indexes under uncertainty test as constraint conditions. Due to the NP-hard property of the model, a generic algorithm (GA) is introduced to obtain the optimal solution. The application examples show that the proposed model and algorithm are effective and feasible.
This study aims to verify an established study on the theoretical analysis of the thermal structural response of a flexible space structure through comparison with the experimental analysis results using an experimental configuration of a reduced asymmetric solar array model. The solar array model is composed of a blanket, two flexible booms and a rigid spreader bar. To reproduce the thermal structural response of a solar array model subjected to solar heat flux in space, the experiment is executed inside a vacuum chamber. The experimental results are analyzed by measuring the boom tip deflection, and are compared with theoretical analysis results under various experimental conditions. The theoretical results are obtained using quasi-static and dynamic response analyses. Through the comparison with experimental results, we are able to quantitatively and qualitatively verify the quasi-static response, and quantitatively verify the dynamic response.
This paper proposes a biased proportional navigation guidance (PNG) law to control the impact time, that can be used for salvo attacks or cooperative missions of missiles. To derive the guidance command of the proposed law, we introduce a polynomial function of the command with two coefficients, one of which is to achieve zero miss-distance and the other is to satisfy the terminal impact time constraint. Since the proposed guidance law has an arbitrary guidance gain, it is possible to shape the homing trajectory and acceleration command profile by choosing a proper guidance gain in consideration of the missile's capability and operational conditions. Numerical simulations for the various forms of the guidance command are performed to investigate the characteristics and performance of the proposed law.
The realization of a sustainable manned Mars stay mission cannot be achieved using conventional methods because the mission conditions, such as available resources, hazards and journey time, differ significantly from previous manned space missions. Therefore, construction of a sustainable interplanetary transportation network, a Mars-based resource management system and a hazard management system should be considered. In addition, new technologies such as a fully regenerative environmental control and life support system (ECLSS), Mars in-situ resource utilization (ISRU) and advanced propulsion systems (APS) are very important. Hence, the logistics system constructed in this research considers not only mission requirements, such as human transfer time and stay time, but also available technology levels and required safety levels. As a result of the simulation of the logistics system, the required initial mass in low earth orbits (IMLEO) to operate the Mars base is approximately 370 t/year with current technologies. However, the IMLEO decreases to approximately 90–140 t/year using a nuclear light bulb engine or water extraction on Mars. In addition, to further minimize IMLEO, it is also suggested that the development of advanced technologies can lead to a change in the optimal interplanetary transportation method from the cycler transportation to stop-over transportation.
Combined with the large eddy simulation (LES), a 3rd-order WENO scheme and the adaptive mesh refinement (AMR) technique, the hypersonic compressible flow (Ma=5) past wall-mounted square cylinders with different heights is simulated numerically. Our results reveal that with the variation of cylinder heights, the pressure distributions of the flat plane in front of the cylinder are similar and have multiple peaks. The different flow patterns of the flow field around the cylinders are shown and discussed in detail. Our calculated results are in good agreement with corresponding experimental data which can provide important data for related research.
In this paper, a twin-body fuselage configuration is discussed for advanced supersonic transport. This twin-body fuselage concept is inspired by the wave reduction effect of the supersonic biplane airfoils proposed by Kusunose et al. The wave drag characteristics as well as the wave drag reduction are discussed by inviscid CFD computations at our design Mach number of 1.7 utilizing an aerodynamic design optimization method. Aerodynamic shape optimizations of single/twin-body fuselages are executed to explore the lowest wave drag configurations. The optimally designed non-axisymmetrical twin-body shows the best aerodynamic performance. Wave drag of our proposed twin-body shows 2/3 that of the Sears-Haack body. It is well known that the Sears-Haack (single) body has the lowest wave drag for given volume and length of the body. The increment of skin friction drag is also discussed for the twin-body fuselage configuration. Based on the total drag analysis, the superiority of the optimal twin-body fuselage configuration over the conventional single-body fuselage configuration is clearly demonstrated.