This paper proposes a method to improve turning performance of small UAVs with side-force fins. In a steady flat turn, inside aileron suffers from decreased stall angle, and thus cannot sufficiently reduce the rolling moment caused by wing lift notably when the radius of turn is small. The proposed method compensates deficiency in airspeed of inside wing using propellers. The efficiency of this method is studied in an analytical way and demonstrated through flight test of an experimental aircraft.
In recent space missions, high performance antenna such as high surface precision, multi-use frequency and large aperture is required to realize complexed and advanced service mission. Meanwhile, the weight of space structure must be reduced due to limitation of launch vehicle performance. Thus, mesh surface antenna had been developed and employed in a number of missions. In general, the tensile forces of the edge cables become several times greater than those of the center cables. Therefore, the total strain energy of the cables depends on the tensile force distribution including the edge cables. The total strain energy of the cables increases with the number of cables. Consequently, a support structure, e.g., a truss rib structure or a hoop structure, must be sufficiently rigid to prevent deformation of the surface. Thus, reduction of the reflector's weight can be achieved if the tensile force of the cables decreases, while maintaining the required surface accuracy. Therefore, we propose a surface design method in which several compression members are equipped instead of tensile cables. The total strain energy of the cables and the tensile force applied to the support structure can be reduced. However, the actual antenna structure includes cable manufacturing and assembling errors. In this study, we evaluate light weighting effect of the support structure by using an experiment model with adjustment of the surface accuracy. We measure the surface accuracy and cable tension of cable network and axial force and the support structure of a member of bending strain energy. As a result, the total cable strain energy of the cable network with compression members can be decreased and reduce to weight of support structure.
The re-entry capsule tracking radar is considered based on the long-range detection experiment results of the small flight object. In the experiment, the object with the radar cross section of 0.159m2 could be detected up to 17.5 km. In the consideration based on the results, the possibility of the over 20 km detection is shown by achieving assumed output power, and the automatic tracking is examined to save the operation cost. By these considerations, the feasibility of the re-entry capsule tracking system as a shared/dual-use technology with commercial products is increased.
Microsatellites are now in vogue and a lot of and a variety of missions using them are progressed in the world, some of them require propulsion system to realize a highly precise attitude control or orbit transfer. In order to satisfy the requirements, we are developing Microsatellite-Friendly Multi-Purpose Propulsion System, MFMP-PROP, with capabilities of both mono-propellant and bi-propellant modes to provide both of small impulse bit and large delta-V, under the policies of Safety First, Border Free, Effective COTS, and Easy Scalability, based on the techniques of 60wt% Hydrogen Peroxide. We conducted captive tests of a thruster for mono-propellant mode under bi-propellant mode to confirm its stable ignition and continuous operation, and obtained performances under its pre-heating temperature and mixing ratio of hydrogen peroxide and ethanol, of 160 seconds of specific impulse at the highest.
Air turbulence is the most significant cause of aviation accidents. As a way to reduce the number of such accidents, JAXA has developed the onboard air turbulence detection system based on Coherent Doppler LIDAR (CDL). The flight experiment with a small jet plane measured and compared how the aerosol particle number concentrations responded to backscatter coefficient and the maximum observation range according to altitude. The flight experiment with a large jet plane measured the maximum observation range and the airspeed measurement accuracy at various altitudes. Although we were able to verify that the observation distance was sufficient to provide information for go-around judgement to the pilot during landing approach, the effectiveness of the turbulence induced accident prevention is likely to be limited because of mostly short observation distances at high altitudes. However, the results indicated the errors between the airspeeds measured by CDL, by the Pitot tube and by the speed-course method were quite small. This suggests the airspeed measurement by the CDL can be used as the true airspeed sensor and remote sensor for the gust alleviation control.
This paper addresses shock absorption behavior of 3-D additive manufactured truncated octahedron for the landing gear of lunar and planetary explores. The deformation modes of truncated octahedron were predicted by the form finding analyses. The collapse load of each deformation load was calculated by the plastic hinge theory. The predicted load--displacement curve agreed with the experimental results, and thus, the proposed prediction method was verified.
This paper reports the experimental study on train kites for Airborne Wind Power Generation (AWPG). We studied the dynamics and operation characteristic of the train kites, which is a platform for transporting a wind turbine used for AWPG to the sky. Three steps of experiment were conducted to investigate the dynamics and operating characteristics of the train kites. Two types of train kites: longline type and stack type, are treated for the verification of their aerodynamic characteristics. The tension of these kite tether was calculated from the wind speed, lift and drag coefficients and tether angle to the ground, and compared with the experimental values. As a result, the operational characteristics such as payload weight and the number of kites necessary for train connection. Thus a prototype system is obtained where the wind turbine can be actually transported into the sky to carry out power generation.
Today, the need for Fluid-Structure Interaction (FSI) analysis technique for flexible wings is increasing. Various methods with structured/unstructured grid based CFD solvers have been proposed. However, few studies have applied cartesian grid CFD solvers to FSI problems. In this study, a cartesian grid CFD solver, UTCart is applied to static aeroelastic analysis of a high-aspect ratio rectangular wing. The iterative calculation is conducted automatically without any mesh deformation algorithms. In order to validate the reliability of the developed FSI code, the results are compared with previous research.