This paper shows the effect of the side clearance on the air-intake performance of a ramjet for the High Mach Integrated Control Experiment (HIMICO). As the result of the wind tunnel test, the mass capture ratio (MCR) of the original intake is 15-35% lower than the designed value. CFD analysis suggested that this is caused by the flow separation on the ramp surface due to flow leakage from a 1-mm side clearance located at the moving part. The mechanism of the side clearance effect is cleared by CFD, and the CFD results considering the side clearance almost agree with the experiment. Then, a new intake in which the side clearance is reduced to 0.25 mm was designed and tested. The maximum MCR of the new intake is increased approximately 14% compared to the original intake.

The solar paddle is a key component for generating electrical power to maintain satellite in space. In order to undertake and complete advanced space-based missions, it is necessary to develop a satellite capable of autonomous, high electrical power output via numerous photovoltaic cells on the solar paddle. Currently, the solar paddle design is large and heavy, with low rigidity against bending and torsion. The performance of the solar paddle can be estimated by using a power density function, where the generated power is divided by the weight of the solar paddle (W/kg). Furthermore, a satellite system demands more than 0.1 Hz eigenfrequency of the solar array structure's rigidity for maintaining attitude control. Thus, we propose a new concept for a lightweight solar array paddle with high rigidity. This new structure imparts a curvature to the panel attached to the thin solar cells. Moreover, the Storable Tubular Expandable Member (STEM) is placed on the panel. Rigidity can be increased after deployment because of the STEM. In this paper, we estimate the rigidity of the solar array paddle by comparing the finite element method with experimental data.

This study investigates the attitude rate damping control of a stratospheric balloon gondola using three-axis momentum-exchange devices, which are mounted on the gondola. To this end, we propose a steering law considering four single-gimbal control moment gyros. The stratospheric balloon system can be modeled as a three-rigid-body system comprising a balloon, gondola, and suspension string connecting the gondola with the balloon. Based on this model, the target torque for the rate damping control is derived from Lyapunov's stability theorem. We propose the analytical solution of time evolutions for the deflection of the suspension against the balloon and the mechanical energy of the stratospheric balloon system under control. Numerical simulations demonstrate that mechanical energy monotonically decreases. Moreover, the accuracy of the analytical solutions is also demonstrated.

The cost reduction of engine maintenance is an important issue for a future reusable launch vehicle. Toward reliable operation of a reusable rocket, a novel health monitoring method using the phase plane trajectory of feature extracted sensor data by principal component analysis (PCA) is verified. Because there are few failure data to estimate new method, a simple physical model is constructed to produce two kinds of failure data duct trouble and reservoir leakage, and examine the effectiveness of this new health monitoring method. Results indicate that presented phase plane trajectory method has good visibility to make the change clear and make it easy to detect and identify failures. This new approach will contribute to the improvement of health monitoring technologies based on sensor data not only for the reusable rocket engine systems but also for general systems.

A super-pressure balloon with a diamond shaped net is considered to be a vehicle which satisfies scientist requirements of a long duration balloon flight at high altitude. The development of the balloon was started in 2011, and ground inflation tests of scaled models and some flight tests have been performed. In 2016 and 2017, ground inflation tests of two 2,000 m³ balloons, NPB2-1 and NPB2-2, were performed. The meridian lengths and radii of the balloons were measured simultaneously as a function of the differential pressure between inside and outside the balloon to derive their ratio for the first time. Tension along the circumferential direction is resolved in the net balloon, the results show that within the error of a few percent, the ratio is same as that of the pumpkin shape, which withstands the differential pressure only by tension along the meridian direction. The time variation of the differential pressure between inside and outside the balloon was also measured. Based on a simple model, assuming that the balloon volume is a linear function of the differential pressure, the variation of the differential pressure due to the variation of the room temperature and the atmospheric pressure are corrected. Considering the residuals are all due to the gas leakage, the upper limit of a hole size of 0.3 cm² is derived for the NPB2-2 balloon.

A computational study is performed to investigate the impact of fuel sensitivity on a high-pressure combustion flow fields of a rocket-type injector through a comparison between two fuels, hydrogen and methane. A two-dimensional model with a splitter plate, which represents a rocket engine injector, is adapted. The investigation focuses on the near-field flow and combustion dynamics of both GOX/GH₂ and GOX/GCH₄ injectors. The compressible Navier–Stokes equations are solved with detailed chemical kinetic mechanisms in a manner of direct numerical simulation. The result demonstrates that the near-field flow and combustion structures of the injector are affected by changing the momentum flux ratio of injector condition. Non-uniform temperature distributions, established behind the injector post, are mainly determined with the amount of inflowing high-temperature combustion and unburned fuel gases. A comparison study using two fuels indicates that the trend of temperature distributions obtained by changing the momentum flux ratio is qualitatively similar between hydrogen and methane cases. A quantitative investigation using the relationship between the mixture fraction and temperature suggest that the combustion flow field behind the injector post can be regarded as a non-premixed flame for both hydrogen and methane cases, while there exists some slight deviation from the solutions obtained under a counter-flow flame assumption. The Damköhler number plots help to identify the relationship between flow transport and chemical reaction in the combustion flow fields. The trend of the Damköhler number in the combustion flow fields behind the injector post is quantitatively similar between hydrogen and methane cases. Thus, the present investigation demonstrates that the fuel sensitivity has less impact on the near-field flow and combustion structures of the injector under the conditions used in this study.

A nitrous oxide (N₂O) / ethanol propulsion system has been studying in ISAS/JAXA since 2003. The propellant combination can be characterized as a bi-propellant with extremely low toxicity, room temperature storability, low freezing point, and high energy density, which is applicable to spacecraft propulsion systems. So far, seven series of captive firing tests including high altitude tests were performed with a breadboard model (BBM) of 2 kN thrust class propulsion system which was built for evaluating its propulsive performance and system operability. In these tests, the capabilities of prototype of a like-doublet impingement injector and the durability of a combustion chamber made of a heat resistant fiber-reinforced ceramic composite (SiC/SiC) were evaluated. From the viewpoint of the engine system design, a relationship between the wall heat flux determined with the water cooling combustion chamber and the propellant mixture ratio was examined from the test results. Findings and issues to be associated with the injector design and the engine operation were also obtained in the present study. This paper presents an overview of the achievements of the technology demonstrations with the BBM.

The performance of pyroelectric X-ray generator (PXG) under high vacuum (down to 2.2 × 10^-5 Pa) is investigated with two different gases of dry air and N₂, in order to develop a high-intensity X-ray generator. For both gases, the X-ray intensity decreases for pressures less than 1 × 10^-4 Pa. It is required to control appropriate inner-gas pressure (1 - 10^-3 Pa) to obtain high X-ray intensity, when PXG is used as an active X-ray source for future planetary exploration missions. Furthermore, an analytical system with a carbon nanotube X-ray generator is also discussed for light-element measurement.

Water Electrolysis Propulsion offers a clean alternative to current toxic and detonable spacecraft propellants. Beyond the potential replacement of hydrazine as propellant, water based propulsion can be highly attractive for future exploration missions, since the availability of water on many potential landing sites offers the opportunity of refueling. The paper discusses components and state of the art of water propulsion and lists possible variants. A performance analysis is made by use of the chemical equilibrium code CEA. Trade-offs and comparisons are performed with conventional chemical and electric propulsion systems.

In recent years, as the demand for space use has increased, high-frequency and low-cost rocket launches have been desired. Solid fuel rockets are smaller, cheaper, and easier to handle than liquid fuel rockets. In solid propellants manufacturing, the kneading process has the risk of ignition because high shearing forces are generated by a metal planetary mixer. Further, the kneaded fuel is manually transported and cast. Thus, this is a high batch process in which mixing and transporting are separated processes. We focused on the intestine movements to implement safe and continuous fuel manufacturing and transportation. We developed a peristaltic mixer that simulates the intestinal movement and aimed for the safe and continuous mixing and transportation of solid propellant. Thus far, mixing and transporting solid propellants have been successful. A few of the practical problems for solid propellant production using this device include internal cleaning after mixing and transporting, avoiding bubbles from entering the material, and the quantitative management of the mixed materials. In this research, we propose the conveyance of quantitatively packed mixed materials to improve the problems associated with solid propellant production.

In recent years, expectations related to the discovery of novel resources and the understanding of planet origins in lunar underground exploration have emerged. In a lunar underground environmental survey, unmanned small excavators are required from the viewpoint of transportation cost and safety. Therefore, we have developed a small excavating robot, "LEAVO," which uses an earthworm's peristaltic motion as a propulsion method. Herein, we have proposed a distributed driving system (DDS) as a new driving system in an excavation unit for curving and horizontal excavation. First, we have developed and tested the DDS. Subsequently, we have confirmed the feasibility of the proposed system through performance evaluation and drilling experiments.

A precise prediction of the cryogenic fluid system is not an easy task especially at relatively smaller mass flow rates, because the heat input to the working fluid from the surroundings becomes significant. We conducted a series of flow tests with liquid oxygen to measure temperature, density, and the pressure loss characteristics at a flow rate of 100-200 g/s, and we compared them to the prediction. The heat input to the working fluid obtained from the experiment was about 14-18 kJ/kg. Also, the heat transfer coefficient through the insulated tube wall was calculated from the experiment. The temperature rise along the feedline was well explained with K = 0.28-0.79 W/m-K whereas the theoretical model gives K = 0.044 W/m-K.

The advancement of small satellites has greatly reduced the overall cost and development time of the satellite compared to conventional satellites fulfilling similar missions. Although there have been many developments on the satellite side, for missions like remote data collection the sensor nodes on the ground have been insubstantial because of its limitations in standalone operability and higher power consumption leading to higher cost and sparse area coverage. In this paper, we designed and developed a low power, low-cost remote sensor station with LoRa transmitters, which has the standalone operating capability. It is compact, mobile and it has a simple design. It is equipped with a self-sustaining power supply, LoRa transmitters, processors, antenna and sensors; mainly focusing on the weather monitoring parameters like humidity and temperature. The basic mechanism of data relay is to sense and transmit sensor data packets in real-time. The feasibility of the sensor station has been studied in terms of power budget, link budget, its operation outdoors and the overall development costs. The sensor station can be placed in areas where there are no ground infrastructures for communication.

In this paper, we propose methods to determine and propagate relative attitude using an earth sensor. Three-axis attitude determination using the Earth sensor is advantageous in terms of space consumption, but it is a fault that we cannot always use it. By detecting and propagating relative attitude information, we attempt to fill that time gaps. The difficulty is that the spacecraft cannot ignore its own translational movement when it looks at the earth, unlike when it looks at the stars. In this research, the attitude and position estimation method used in computer vision is applied instead of the traditional attitude determination method for spacecrafts used in STT and so on. The algorithms use the movement of a point common to two images taken with a time interval, and the translational movement information of the spacecraft obtained from orbit information. The obtained relative attitude is propagated using a Kalman filter to estimate the absolute attitude. The proposed algorithms are evaluated by numerical simulations. The results are as accurate as small MEMS gyro sensors, suggesting the possibility of being replaceable in the future.

The mechanical properties of low-melting-point thermoplastic (LT) fuels can be altered by adjusting their chemical composition. This study quantitatively investigated whether LT fuels undergo changes in performance due to adjustments in their chemical composition. Tensile, adhesion, viscosity-measurement, and static-firing tests were conducted using four LT fuels. The tensile test results suggest that the xylene resin contributes to increasing the elastic modulus. The adhesive stress of xylene resin-based LT fuel endures until approximately 0.5–0.7 MPa. Xylene resin is assumed to promote urethane bonding and improve adhesion properties. The dispersion of the LT fuel regression rate is within 0.24 mm/s under all oxidizer mass flux conditions. The results of the viscosity-measurement test suggest that the viscosities of the four LT fuels are similar above 100 °C. The fuel components do not significantly affect the characteristic velocity of the fuel. These results suggest that LT fuels have twice the fuel regression rate compared with hydroxyl-terminated polybutadiene (HTPB). Therefore, an appropriate LT fuel should be selected based on its chemical components, depending on the mechanical and adhesion property required by the associated motor size.

This paper clarifies the mechanism of significantly improved compact storage of membrane space structures where plain-woven textiles are used as the base membrane. Membrane space structures can be multifunctional by attaching various thin-film devices onto their surface; however, the non-negligible thickness of the devices should be accommodated to achieve compact storage. In this study, small scale models made of membranes with dummy thin-film devices are stored to show two significant aspects. Firstly, that textile membranes can be stored more compactly and uniformly than polymer films, because of the movement of layers caused by the flexibility of the textile. Secondly, that the locations of the movement between membrane layers to absorb thickness effect differ depending on the fiber orientation of the textile.

In this paper, the design of 3U-Cubesat bus, intended to improve versatility of the previous model, is described. The TRICOM-1R was developed to ensure practical satellites buses, within 3 kg and with international competitiveness, to be launched by the SS-520 rocket (ISAS/JAXA), a modification of former sounding rockets. The satellite succeeded all planned missions during the six-month orbital period in 2018, including camera, store and forward communications, and autonomous operation experiments. Considering the TRICOM-1R, a new satellite bus, named “TRICOM-2 (TC2)” standard bus, has been developed to improve versatility and productivity of the former model. We designed structure almost free of harnesses using a motherboard while maintaining the standard 3U size for deployment in the International Space Station. In addition, TC2 has a standard interface between mission payload, within 1.5U size, and the standard bus. Furthermore, a development team was created in cooperation with Fukui-prefecture industries, which develop many satellites at low cost. This modified satellite bus was used for Rwandan satellite (RWASAT-1), whose flight model is still being developed. All features, results of design and environment test of this satellite bus are further described in this paper.

This paper presents an overview of a guidance, navigation and control method used in descent operations of Hayabusa2. The method consists of on-board and on-ground guidance systems to control the spacecraft, and an image-based navigation technique using a shape model and ground control points of the asteroid. Hayabusa2 has performed descent operations 11 times as of mid-April 2019. Flight results of the operations demonstrate that the guidance, navigation and control system has satisfied accuracy requirements and shown an overall good performance.

Gap parameter γ between AP particles is proposed for viscoelasticity analysis in AP/HTPB composite propellant slurry. The particle-gap of γ = 0.5 was a threshold of shape-retaining in KCl/HTPB simulated propellant slurry consisting of monomodal particles, and the slurry viscoelasticity increased by over 5 times with a slight narrowing of the particle-gap at around γ = 0.5. The slurry showed the similar property also in the case of the different HTPB viscosity and KCl particle-diameter. These results suggest that the viscoelasticity of the dense slurry strongly depends on the particle-gap of the particulate structures.

Expansion of space utilization activities increases the number of large debris like an upper stage of the launch vehicle in congested orbit at altitude of 700-1000 km. These debris collide with others producing a lot of smaller debris that would cause further collisions to spacecraft and their destruction in orbit. For these reasons, some low-cost debris removal systems are proposed, and a part of fundamental technologies was already demonstrated by space agencies in space. The atmosphere at the altitude of 700-1000 km is composed of neutral particles of He, H, O and ions of O+, H+. One of the conventional deorbit system uses a deployable membrane capturing the neutral particles to produce a drag force. The drag force decreases orbital velocity of a spacecraft and then the spacecraft will move to the lower orbit to the earth. This type of deorbit system is very simple, but a large-scale structure is needed to produce enough drag force. In this research, we focus on the ion particles existing in the atmosphere at high altitude to enhance the drag force for the removal system. The concept of deorbit system utilize an ion sheath generated by a charged deployable thin film. In this paper, as a preliminary study, we describe the fundamentals of the debris removal system using the charged membrane, 1-D theoretical estimation of the drag force by the accelerated ions on the charged membrane in LEO, and the numerical analysis by a 3-D full particle electrostatic code to study the expansion of the sheath around the membrane and current collection on it.