Almost all re-entry capsules such as HAYABUSA re-entry capsule are dynamically unstable in transonic region. We researched dynamic stability characteristics of Mars entry capsule (70º sphere-cone capsule model) at low speed. In order to avoid significant sting interference, the tests were conducted using magnetic suspension balance system (MSBS). Angle of attack and Reynolds number effects on drag coefficients were measured. Dynamic stability derivatives were measured by forced oscillation method. Drag coefficients were barely affected by Reynolds number and angle of attack. The dynamic stability derivatives of Mars entry capsule were small negative value. These results showed that Mars entry capsule was slightly dynamically unstable.
Nonlinear stability of three-dimensional supersonic boundary layers on JAXA's experimental airplane called NEXST-1 is investigated for the case in which first-mode instability is dominant. Several nonlinear mode interactions are numerically examined by solving nonlinear parabolized stability equations. The existence of the standard initial amplitude is assumed, and its value is estimated from the flight data of the NEXST-1. It is shown that disturbances with a critical parameter (ω0, β0) predicted by linear parallel stability theory are linearly amplified until transition sets in. Then the initial amplitude correlates with the measured transition location is found to be approximately 10-6 regardless of nonlinear interactions presented.
In recent years, investigating moon is once again drawing attentions of several countries. In Japan, an image-based autonomous navigation method is studied for a moon investigating project by the small lunar lander. The purpose of this paper is to propose a safe landing areas detection method for lunar environmental suitability that uses brightness values and to propose a landing point determination algorithm in a limited calculating area for the actual lunar lander. In addition, we study acceleration of the processing speed for hardware implementation and robustness of the proposed method.
A low-boom design method using a reversed equivalent area (Ae,r) and an aging process is proposed for aft-boom shaping that is affected by three-dimensionality of a flow field. Because near-field pressure distributions are used to calculate Ae,r, three-dimensionality of a flow field is captured by Ae,r. However, nonlinear effects appeared in the pressure propagation from a body to a near-field location is not considered in the calculation of Ae,r, which reduces the accuracy of Ae,r. Thus, an aging process is inversely applied in order to calculate accurate Ae,r. The present method is applied to aft-boom shaping of a small-sized supersonic transport. The inversely applied aging process enables accurate estimation of required Ae,r distribution for aft-boom shaping, which realizes the low-boom signature in accordance with the design intent.
Flat-turn maneuver, which means turning without banking, is a useful method for ground observations. Former studies suggest fixed-wing small unmanned aerial vehicles equipped with side-force plate (SFP) to improve turning performance. However, the turning performance of flat turn is usually much inferior compared to conventional banked turn. This paper presents an aircraft design suited for flat turn by showing indoor flight test results. In order to turn in a high rate, the aircraft should turn by skidding. In addition, the SFP should be located fore of the center of gravity as a vertical canard. Furthermore, the main wing should be designed not to generate rolling moments when turning. The results of the flight tests reveal that applying both rudder and SFP is very effective in turning the aircraft in a high rate without banking.