This paper describes experimental analysis of contact (impact) dynamics for lunar landing on regolith. In the current space development, space explorations are focused on by many space agencies in the world. Next lunar missions will be required to land on steep surface among rocks and craters. Then, contact dynamics model is much important for evaluation of landing mission. In this paper, a lander with four landing-gears was employed for the experiment. Numerical simulation results by the existing model and the experimental results have been evaluated from the view point of turning and overturning of a lander. Then, it has been noted that tip end (pad) shape of a landing gear much influences on lander motion. It is considered that contact force from regolith, especially in friction force, becomes small when the tip end of a landing gear penetrates in regolith. Such contact dynamics keeps a lander with four landing-gears from overturning.
A precise and accurate trajectory prediction is indispensable for efficient air traffic management with a large traffic throughput achieved by four-dimensional trajectory prediction. Recent aircraft are able to fly along their optimum trajectories. The configurations of these optimum trajectories also depend on aircraft mass. However, information on aircraft mass are generally unavailable for air traffic controllers; they are seldom applied for actual operations. To overcome such inconvenience, recent studies demonstrated aircraft mass estimation from their flight trajectories. This study further aims at applying the mass estimation for the prediction of cruise flight time. Aircraft mass are estimated from actual climb trajectory data, and the correlation between the estimated mass and flight time error are confirmed. The regression and correction has revealed that the presented methodology is able to reduce the mean square error of the flight time prediction by half.
This paper addresses the design problem of Gain-Scheduled (GS) flight controllers, in which only inexact scheduling parameters are available, for aicraft motion control. Most of existing design methods for GS controllers implicitly suppose that exact scheduling parameters are available. However, this does not always hold true in practice, which has invoked the research on the design of GS controllers depending on inexact scheduling parameters. We design a GS flight controller for the lateral-directional motion of JAXA's fixed-wing experimental aircraft MuPAL-α using a recently proposed design method which guarantees the pre-defined control performance under the bounded uncertainties in the provided scheduling parameters. We examine the applicability and performance of our controller by flight tests.
A wing of a human-powered airplane is generally constructed with foam, balsa wood, plastic film and CFRP to achieve light-weight structure. Thus, the structure can be bent and deformed easily. The change of the wing shape may cause the performance degradation. In this study, we physically built the deformed wing model to measure the deformation by using 3D scanner. CFD was used to investigate the influence of the deformation of airfoil on aerodynamic performance in cruise condition through the comparison with original shape. As a result, the deformation causes the fluctuation of pressure distribution, and it also deteriorates the aerodynamic coefficient.
Congested airspace causes flight delays, which result in extra fuel burn, extra CO2 emissions, and additional workload for air traffic controllers in charge. Unlike road vehicles, once airborne, aircraft cannot stop in the air and turn off their engines. When the airspace of the arrival airport is going to be congested, however, airport can be delayed before their takeoff at the departure airport. Such traffic flow control, often referred to as ground holding, has been implemented in many countries already, with Japan being no exception. Currently, when flights are expected to be delayed in the air for more than a certain time (called buffer here), the ground holding program assigns delayed departure times. If there are no uncertainties in departure time and flight time, the optimal buffer can be easily determined. In reality, however, late passengers, for instance, can delay the departure. This research considers the uncertainties in departure time and enroute flight time to determine the optimal buffer applied by the ground holding program. Adopting values used by other researchers, the authors evaluate the cost of ground delay, airborne delay, and the cost of lost capacity, to determine the total cost of delay which is used as the metric for determining the optimal buffer. Results from Monte Carlo simulations show that there exist an optimal buffer for each traffic flow queue, but robustness can be achieved by implementing a sub-optimal buffer depending on the overall congestion only. Directions for further study and discussions are also presented.
In this study, a model of uncertainty of estimated time of arrival on a cruise route is derived, and its effectiveness for ground-based 4D trajectory management is demonstrated. Uncertainty of estimated time of arrival inevitably increases because of fluctuations in meteorological conditions, even though the Mach number, flight altitude and direction are controlled constant. Actual flight data and numerical weather forecasts are processed to obtain a large collection of flight and meteorological conditions and flight time error. Through the law of uncertainty propagation, an uncertainty model of estimated time of arrival is derived as a function of the Mach number, flight distance, wind, and temperature. The coefficients of the model are determined through cluster analysis and linear regression analysis. It is clearly demonstrated that the proposed model can estimate the uncertainty of estimated time of arrival without underestimation or overestimation at an arbitrary flight distance, even under moderate or severe weather conditions. Through numerical analysis of a 4D trajectory management using actual track data, it has been clearly demonstrated that the proposed model is able to improve both safety and efficiency of 4D trajectory management simultaneously.
One of the technologies to make the future planetary exploration more flexible and valuable is a vehicle which can fly freely in the Martian atmosphere. Our group proposes a parafoil-type vehicle which has an inflatable wing. The parafoil can be packed compactly when a launch and cruising phase and can be deployed to a large aerodynamic device only when necessary, that is, flight in atmosphere. However, a conventional parafoil which is ram air type might be not inflated by lower ram pressure at low density atmosphere environment. To realize the planetary probe, we developed new-type parafoil which can be deployed by small gas injection. In this paper, the structure of partial closed type parafoil is summarized as compared with previous type parafoils. Moreover, aerodynamic characteristics and deployment-ability of partial closed type parafoil was obtained by wind tunnel test and deployment test. As results, this type parafoil can realized the stable flight in the wind tunnel. And the parafoil has high aerodynamic characteristics which maximum L/D is 6.6 and quick deployment-ability which taken less than 1 second.