This paper addresses a 3-impulse Lunar transfer orbit design method using a real-coded genetic algorithm (real-coded GA). The real-coded GA is applied to the transfer orbit design taking into account the constraint of argument of perigee induced by a launch vehicle. SLIM is a Lunar lander which is developed in JAXA. SLIM is planned to be launched by the solid motor launch vehicle, Epsilon. Since the third motor of Epsilon employs spin stability, the argument of perigee of the injected orbit is constrained to maximize the launch capability, which makes it difficult to reach Moon directly from the injected orbit. Considering such unique characteristics by the launch vehicle, a mid-course maneuver is applied after the trans-Lunar injection to connect to the lunarcentric orbit. The proposed orbit design method using the real-coded GA generates a suboptimal orbit with sufficiently small computational burden, and can be widely applied to an orbit design including mid-course orbit control maneuvers.
Current control of arrival flights at Tokyo International Airport is studied using real traffic data in order to predict performances which could be realized by a future arrival management system. The current control procedure employs radar vectoring which uses relatively wide airspace including en-route cruise phase before the descent. A stochastic model presenting the queueing mechanism of the procedure is constructed. Parameters in the model are derived from real traffic data. Various cases of different parameters are analyzed by Monte Carlo simulation in order to examine influences of various conditions upon flight time delay. It explains that the randomness of the entry time as well as the controlled time of separation inevitably derives some flight time delay even if the traffic volume is light, and the real system selects the traffic volume in order to make the delay at an acceptable level. It indicates that the traffic volume could be increased by 20 % if the error of controlled time for separation is reduced to the half.
Laminar flow control is next-generation technology which is expected to improve aerodynamic performance greatly. As for an application of laminar flow control in the aircraft design, it is important to consider comprehensive effects of laminar flow control system on design results. In this paper, we include the effects caused by additional laminar flow control system into the aircraft conceptual design tool and consider interactive effects on aerodynamic, propulsion and secondary power systems. Two types of laminar flow control technology have been considered and were applied to 200 passenger class transport aircraft. They are natural laminar flow (NLF) and hybrid laminar flow control (HLFC). Results indicated that NLF can improve lift / drag ratio and fuel consumption, and hence decreases the aircraft empty weight. Applying the HLFC improves lift / drag ratio and fuel consumption further. However, because of the additional weight of HLFC system, the maximum take-off weight of HLFC aircraft is equivalent to that of the NLF.
IKAROS is a solar power sail demonstrator launched by JAXA in 2010. IKAROS successfully deployed its large sail by a centrifugal force due to the spin motion of the spacecraft body and obtained a solar power sail navigation. In the evaluation of IKAROS membrane shape, some unexpected phenomena were observed; (1) tether connecting IKAROS membrane and main body got loose in spite of normal spin rate, and (2) the membrane was not warped by photon pressure in spite of low spin rate. The purpose of this paper is to understand generation mechanisms about these unexpected phenomena. Because thin-film devices of thin-film solar cell and reflectivity control device are multilayer film structures, curves occur. The bending stiffness of IKAROS membrane is increased due to the curve. This paper presents the multi-particle model of the membrane considering curve and bending moment of thin-film device. The membrane shape is estimated by numerical simulations and the influence of the thin-film device is made clear.
SLIM (Smart Lander for Investigating Moon) is the Lunar Landing Demonstrator which is under development at ISAS/JAXA. SLIM demonstrates not only so-called Pin-Point Landing Technique to the lunar surface, but also demonstrates the design to make the explorer small and lightweight. Realizing the compact explorer is one of the key points to achieve the frequent lunar and planetary explorations. This paper summarizes the preliminary system design of SLIM, especially the way to reduce the size.
Thanks to recent lunar exploration missions, high-resolution lunar surface observation data was obtained. In future lunar exploration, landing is being requested at a specific point having higher scientific interest than other areas. The SLIM project is demonstrating pinpoint landing technology, which entails a combination of “autonomous image-based high-precision navigation technology” and “autonomous guidance technology intended to generate a fuel-optimum landing trajectory.” This paper presents powered descending trajectory design in terms of trajectory optimization. As usually considered in general space mission development, an optimal solution in terms of minimum fuel consumption is the basis of investigation. This study addresses trajectory optimization considering specific objective functions derived from practical constraints regarding mission design, such as altitude, downrange length, and visibility from ground stations. In this paper, nominal trajectory design considering minimum fuel consumption is first presented, followed by parametric studies to identify the sensitivity to changes in initial conditions under which powered descending starts. Finally, trajectory optimization results with various types of objective functions are presented.
This paper is on optimal trajectory of future lunar lander with coasting in powered descending phase. For the light weight/low cost lunar lander, optical navigation using onboard cameras to identify their current state is one of very few techniques available to achieve the pin-point landing. The optical navigation is to be operated between the powered descending phases, when the orbital maneuvering engine (OME) is turned off. This paper shows the series of different coasting conditions and discusses the effect of the coasting to the trajectory and fuel consumption. The results give some ideas for future gravitational planetary missions, which uses coasting during their powered descending phase. In addition, optimal trajectory with double coasting for the SLIM project is shown in this paper.
SLIM project which aim for pinpoint landing on the moon surface. For achieving this plan, it is necessary to estimate the flight position of the space probe. The estimation is performed by matching the detected craters with database. This paper introduces a crater detection method using Principal Component Analysis (PCA) and its evaluation. This method is capable of real-time processing under low computational resources such as Field-Programmable Gate Array (FPGA). In this research, we report improvement of robustness at detection and high accuracy of crater size measurement.
Next generation moon landing mission will require autonomous pinpoint landing capability because of requirements for landing on specific terrains in a limited area. This capability requires precise absolute self-localization of the lander during braking descent phase. The purpose of this paper is to propose an algorithm to estimate the lander position and to evaluate its mountability to a space-grade FPGA. In this method, the position estimation is performed by matching crater point patterns with database point patterns by finding topological correspondences using crater-based linear features. In addition, we confirmed the resource amount and the calculation time when this algorithm is implemented on the FPGA using high-level synthesis.
In this paper, the authors propose a novel landing method named “Two-step Landing Method” for small lunar lander which is needed to be designed considering constrains from envelope area of rocket and the weight of the lander. The proposed method enforces intentional body tumbling at the contact of main leg. We analyzed its dynamics by three-dimensional simulations which consider lander’s attitude and lateral velocity and landing site’s slope angle. Numerical simulation models have been designed on Mechanical Dynamics Software “ADAMS”, and lander models refer to “SLIM” which is a small lander proposed by ISAS/JAXA. It is found that the proposed landing method can land on steep slope by tilting body attitude toward inclination direction of landing site. Especially in the case of landing with lateral residual velocity, the proposed method has higher landing stability than conventional landing method.