Effects of anchor head shapes on loading anchors on debris structures were investigated through numerical simulations and experiments. Four types of anchor head shapes, cone, flat, sphere and double bladed, were employed and their penetration behaviors were numerically analyzed and compared. It was observed from the results that the minimum penetration velocity of double-bladed head was lower than those of the other head shapes and it indicates that the required kinematic energy for capturing can decrease. Then, the experiments on capturing using metal anchors with the double-bladed head have been carried out. It was also observed from the experimental results that the pulling strength using the metal anchor with double-bladed head was very small and it is difficult to achieve an appropriate capturing state. Some mechanisms will be required to the anchor with double-bladed head shape for capturing space debris.

In recent years, the number of space debris in orbit around the earth has increased. The cause of the increase is mutual collision between space debris. In order to reduce future space debris growth, large space debris must be actively removed. Since space debris is not controlled in attitude and is a non-cooperative body without signs or markers, image measurement is indispensable. However, due to the optical environment peculiar to the universe and the use of wrinkled glossy materials, the problem of erroneous recognition by image measurement remained. Therefore, attitude estimation by the eigenspace method is performed using a monocular camera

This paper proposes an effective observation planning method targeting fragmentation debris originated from several different breakup events. Given orbital elements of fragmentation debris in a database, or two-line element set (TLE) of cataloged debris, their orbital configurations can be predicted for a specific date, as well as their orbital directions from a specific observation site. The method proposed in this work utilizes the observation angles (azimuth and elevations) obtained from such predicted data to efficiently detect known and unknown fragmentation debris occurred from several fragmentation events. Finally, this paper tries to validate the effectiveness of the proposed observation planning method through actual experimental data obtained from an observation campaign using EISCAT radar system in 2019.

In the touchdown operation of Hayabusa2, scattering of surface particles by thruster plume impingement flow has observed. There are risks that flying particles effect equipment such as sensors and cameras, so it is necessary to assess the behavior of particles that scattered by thruster injection. In order to clarify the parameters that affect the phenomenon and elucidate the mechanisms, we conducted experiments that inject gas onto soil simulated celestial surface. We used a method of visualizing crater formation using an acrylic transparent plate and capturing the flying particles by irradiating a line laser. In addition, conducted experiments in a microgravity environment using 50 meters drop tower “Cosmo-Torre”. From results, in microgravity environment, the bearing capacity of the soil released, shearing occurred inside the soil, and it scattered as a layered mass. When using different soils, the scattering direction differed depending on the particle size, and the Phobos simulant maintained the bearing capacity of the soil and did not cause large erosion. The outline and results of the experiments conducted are described.

Recently, countries around the world pay more attention to the construction of lunar bases. Many of the lunar polar points where lunar bases are expected to be constructed in the future are steep terrain such as crater central hills, rims, vertical holes, volcanoes and valleys. Although it exists, we try to land on stable terrain by the guidance control of the spacecraft. However, it has also been confirmed that guidance control causes the spacecraft to have a residual horizontal velocity with respect to the terrain, which is the cause of the spacecraft overturning. In this paper, it aims to prevent overturning even with a horizontal velocity. we verified a relationship between foot pad shape and foot pad angle by using RFT model between spacecraft and surface of the celestial body. As a result, it was found that the fall can be suppressed most when pad shape is 174 deg and when pad angle is 19 deg.

This paper is related to the design method of CubeSat using MBSE (Model-Based Systems Engineering) and the purpose is to solve the difficulty of designing a complicated system with strong inter-element coupling such as CubeSat for scientific observation. There are barriers to using MBSE due to the lack of well-defined procedures for introducing it. In this research, we use "SysML", which is one of the standard languages of MBSE system model. This language is characterized by expressing the system from four viewpoints, structure, behavior, requirements and parametric constraints. The procedure for introducing MBSE to CubeSat is explained step by step. For CubeSat, it is difficult to grasp the structure of the problem at the time of design change due to the influence of the strength of inter-element coupling and the complexity of the system. The contents represented by each model written in SysML are sorted. The contents represented by each model written in SysML are summarized.

Prototype solid fuels for a hybrid rocket were fabricated by using a multi-material 3D printer and conductive thermoplastic composite to construct a ladder-shaped resistance inside the electrically-insulated thermoplastic solid fuel and to measure the time-resolved fuel regression. In this type of fuels, the remaining fuel thickness is monitored by the voltage applied to the resistance that changes according to the number of rungs of the ladder-shaped resistor. For comparison with the proposed measurement, the time-resolved fuel regression was optically measured by using a high-speed video visualization. The solid fuel regression history with the proposed technique agreed well with that with the optical measurement considering the uncertainties in the measurement methods. Errors that cannot be explained by these uncertainties were found to be ±0.15 [mm], corresponding to ±1 layer of the stacking pitch of the 3D printer applied in this study. This paper also shows a preliminary firing test result using a post-processed 3D-printed cylindrical solid fuel grain as a preparation for the application of the proposed technique to the cylindrical solid fuel.

In this study, a dynamic response model of a propellant valve has been developed, to build a system-level integrated model that enables accurately prediction of transient thrust fluctuations of a spacecraft liquid propulsion system. The purpose of this study is to achieve a more accurate prediction of flow rate than before by taking into the account the effect of upstream pressure changes on the open-close response of the valve. The upstream pressure of the valve varies greatly due to the drop in tank pressure or crosstalk. By introducing the proposed model to a one-dimensional system analysis of the spacecraft propulsion system, the propellant flow rate of various operational conditions can be predicted with high accuracy. In order to validate the proposed model, a verification test in a simplified single pipe system of the spacecraft propulsion system was conducted. The prediction error of the flow rate to the thruster has been reduced from about 72.6 % in the conventional model to about 5.73 % in the proposed model.

Combustion oscillation is a combustion instability in solid propellant rocket motor and that occurs when the pressure oscillation is amplified by the resonance frequency of rocket motor internal shape. In this study, the acoustic analyses were conducted in the internal shape of rocket motors. The results of analysis show that the modal damping ratio of star-forward shaped grain is larger than the star-aft shaped grain and qualitatively correspond with the combustion test results. Prior to the acoustic analysis, the conditions for acoustic analysis were studied by a simple test models for simulating the internal shape of rocket motor.

In recent years, space structures have become larger and more complex in order to achieve increasingly sophisticated space missions. Deployable structures are used to contain large and complex structures in a rocket fairing. The feasibility of deploying these structures in space has been thoroughly investigated from the design stage by means of simulations, and it is necessary to conduct ground tests to confirm the validity of the simulation results during the manufacturing of the actual structures. However, the effect of gravity cannot be ignored when conducting ground tests. Therefore, a gravity compensator is used to counteract the effects of gravity. We have developed a gravity compensator to solve the problems of previously used gravity compensators. However, since we were not able to test its performance, we constructed a truss structure that simulates the support structure of a space-deployed antenna. The deployment characteristics of the truss structure are confirmed through simulations and experiments, and the effect of the gravity compensator on the deployment mechanism is clarified.

Deployable truss is used in space structures for various purposes such as an optical bench of space telescope. In the case of the optical bench, the high shape accuracy is required for the deployable truss. Deployment repeatability of the truss is one of the important factors which affects the shape accuracy. The objective of this study is to evaluate the effect of design parameters of a deployable truss on its deployment repeatability. A two-dimensional truss model was investigated. The results show that the friction coefficient and the hole diameter have a large effect on deployment repeatability of the truss, compared with the size of the gap between pin and hall and so on. As a result, a guideline to improve the deployment repeatability was suggested.

The variable geometry truss (VGT) is a component technology that can realize various frame shapes by expanding or contracting one member or all members of the truss frame. We are trying to observe attitude analysis of 3D-VGT by using non-linear finite element method. At that time, we think the structure in which any axial forces do not work. Supposing that a parabolic antenna is attached to the upper surface of the 3D-VGT, we consider a problem that the normal vector and center of gravity on the upper surface of the truss are brought to close to the prescribed direction and position. To solve these problems, we introduce a genetic algorithm. The objective function of simple GA is the inner product of the target normal vector and the unit normal vector of upper triangle and distance to target center of gravity, and the former solution closer to 1 and the latter solution closer to 0 are determined as the optimal solution. When an optimal solution cannot be obtained for the target normal vector with a single-bay VGT, it is shown that slight adjustment is possible to make the structure a multi-stage.

In this report, the nonlinear finite element analysis of three-dimentional scissors structure composed of beam-like members with hinge points is described. We have already formulated the FEM of the 3D scissors structure by introducing 3D Green-Lagrange Strain, which does not cause strain with respect to the rotation of the rigid body, and using the virtual work principle. Also it is possible to correspond to shaft rotation by using the torsion angle of the member axis.The numerical calculations are carried out, and 3D scissors structure is analyzed. We will verify the results and show the usefulness of the analysis.

In this study, I will propose a deployable cubic structure called Jackson Cube, which is based on origami. The size is 10cm x 10cm x 1cm when stored and it deployed 1U. This structure has two advantages. First, it can mount on CubeSat, because it has square cross section. Second, it can combine several structures to form the large structure. I conducted the vibration tests to investigate the stiffness and deformation modes of a deployable structure. I compared the results with the PSDs obtained from the structural analysis. Finally, I discussed the difference of structural analysis and vibration test.

To construct large space structures, a modularized structure as an assembling structure has been proposed. Non-ideal modular structure has geometrical errors such as errors in manufacturing and assembling. These geometrical errors cause initial stress in statically indeterminate structure. In this paper, we analyze initial stress on a two-dimensional large modular structure constructed by equilateral triangle or square modules. The geometrical errors are assumed to follow a Gaussian distribution. Numerical simulation using random numbers is carried out to investigate the maximum initial stress and its special distribution. The result shows that maximum initial stress of the structure follows an extreme value distribution because the stress of most members are independent and identically distributed. Space distribution of maximum stress does not have peak since structure is symmetry. Although the initial stress increases as the degrees of indeterminacy increase, the maximum value is not divergent but converge to a value. This result suggests that the geometrical error accumulation does not cause extremely large initial stress.

In recent years, there has been a need to improve satellite communications services and develop the satellite communications business. In addition, the sophistication of satellite missions is increasing. As a result, there is a need to develop satellites with high accuracy and large aperture antennas. For this reason, cable-mesh antennas have been developed. The cable-mesh antenna consists of a metal mesh, a cable network and a support structure. However, the surface accuracy of the metal mesh is reduced due to deformation called pillow deformation. In addition, the tension of the mesh shifts the nodes and reduces the accuracy of the mirror surface. The design of cable mesh antennas includes sag insertion geometry to improve shape stability and an offset parabolic model to maintain a large diameter. In this study, we focus on sag and offset parabolas to investigate the effect of cable mesh tension on the cable network mesh tension. The results show that the sag ratio degrades the surface accuracy the most due to the relationship between cable tension and facet size. It was also found that the mirror surface accuracy tended to deteriorate as the offset angle increased. Therefore, it is necessary to set the appropriate sag ratio for the center and offset parabola.

We propose a retractable deployable boom based on self-deployable connected convex boom. A conceptual models were demonstrated to investigate the possibility of deployment and retraction using tethers. As a result, deployability and retractability are confirmed by the demonstration. On the other hand, some unstable properties were observed in the course of deployment and retraction.

Thin membrane such as polyimide film and metal mesh have been widely used in light-weight space structures. Engineering Test Satellite “KIKU 8-go” and Radio Astronomy Satellite “HALCA” are two of the great examples of membrane deployable structures in space. By using cables, AstroMesh and others light-weight deployment structure allow to create a precise curved membrane in space. On the other hand, a deployment structure that enable to deploy a flat membrane with high planar precision is rare. In this research, by using rigid-foldable panel structures, a new-type of flat deployable membrane structure with high plane precision is proposed.

Membrane structures are highly sensitive to shape deformation, and even minute disturbances in outer space can affect motion, so it is desirable to grasp and control the exact shape in orbit. However, the membrane shape data that can be acquired in orbit is lost due to various factors such as the influence of sunlight, camera placement, angle of view, and sampling rate. So far, the motion has been estimated by estimating the main modes of membrane motion from the missing data and optimizing the mode coefficients in the sense of sparse estimation. However, the weighting coefficient that adjusts the sparseness of the mode coefficient was arbitrarily determined, and it was unclear whether it was the optimum solution. In this research, we propose a motion estimation method using a learning algorithm that determines the optimum weighting coefficient from the obtained data, and consider the results and the validity of the estimation accuracy.

A real-time simulation method for cantilevered beam is presented. In this method, a point load acting on deforming cantilevered beam is estimated in real-time by using the Kalman filter, and the deformation of cantilevered beam is simulated by using estimated point load at the same time. The Kalman filter is widely known as the method which estimates uncertain parameters utilizing both numerical model and experimental data in sequential processing. And the parameters estimated by above-mentioned method can be strong likelihood for actual phenomenon included in analysis object. But operating Kalman filter needs to make the suitable state space model for analysis target. In this study, a simple experiment is conducted to verify the effectiveness of real-time estimation and real-time simulation for deforming cantilevered beam by using the Kalman filter and strain measurement. Experimental results show that the real-time estimation and real-time simulation are operated satisfactorily with deformation of cantilevered beam under the particular configuration of the Kalman filter.

This paper proposes a simplified estimation method for Shock Response Spectrum (SRS) using a substructure synthesis method with a reduced impedance method. Since this method can compute SRS from each vibration characteristic of the space component and shock test apparatus, it has an advantage of estimating the SRS actually measured in shock test at the previous design stages. A novel method to improve the computation efficiency of the traditional impedance method is also proposed. This paper introduces a computation algorithm implemented in the traditional impedance method, and discusses the effectiveness of the proposed SRS estimation method.

Physics model-based quantitative safety analysis method should be established both for meeting the strict flight safety requirement and maximize the mission flexibility of the flagship liquid rockets. Tank destruction model of the crack propagation triggered by the pre-generated longitudinal slit hole has been developed, based on the dynamic explicit FEM analysis, and the crack propagation test methods for the model validation. The crack propagation test method for the flat panel with and without rib structures was proposed and demonstrated to obtain the valid data for the investigation of the destruction mechanisms and the model validation. Computed crack propagation speed was agreed well with the experimental data, thus the test method was demonstrated for the material model parameter identifications.

This paper describes the design, analysis and flight results of the low-shock separation mechanism for payload adapter. The low-shock separation mechanism is based on a simple four-bar linkage, which makes the release speed of the clamp band tension lower than the current pyrotechnics system. In this paper, we describe the result of development, flight demonstration with using dummy payload ring and flight with actual satellite.

Spacecrafts are exposed to a variety of mechanical environments during launch. The shock environment generated during the separation of the satellite and rocket parts and the deployment of solar paddles and antennas is one of the typical mechanical environments. Since the shock environment is a short time transient phenomenon, it is often difficult to simulate the real environment in ground tests. Also, there is a lack of improvement and horizontal deployment as shock testing is rarely focused on the development process. JAXA's research and development and current issues are introduced about shock testing.