To protect a satellite from accidents due to spacecraft charging, Kyushu Institute of Technology (Kyutech) is developing a device called ELFs-Charm, which stands for ELectron-emitting Film for Spacecraft CHARging Mitigation. Electron emission from ELFs-Charm was already confirmed in Polar Earth Orbit in 2012 via flight experiment onboard HORYU-II. As a next step, we are considering the practical operation for spacecraft charging mitigation. The present emission level is not enough to increase the satellite potential. We focus our efforts on improving two properties, charging property and the emission threshold. The charging property is measured by how well the differential voltage between the ELFs-charm insulator surface and the satellite chassis increases. The emission threshold is measured by the differential voltage when the electron emission starts. This paper reports the laboratory experimental results to measure the two properties of various samples. The sample made of fluorin resin coating had a good combination of the charging property and the emission threshold that makes it possible to emit electron under realistic ambient electron current density in orbit.
Flow visualization within rocket combustion chambers remains to be a challenge, especially under high pressure and high heat flux. In the present study, glass tubes chamber was proposed to observe the flame in conditions equivalent to those in past test with occurrence of combustion instability. No cooling gas injection was adopted to reproduce the test conditions. Inner / outer glass tube configuration was adopted to separate thermal load and mechanical (pressure) load. This non-cooling configuration survived for more than 5 seconds under chamber pressure of 7.5 MPa. Design and test procedure are herein described.
AP/HTPB composite propellant is the most typical solid propellant that currently used. In order to obtain excellent combustion characteristics and reliability as a solid rocket motor, it is necessary to measure the dispersion state of AP particles and voids in solid propellant. In this study, we propose the measurement method of the mixed degree that represents the dispersion state of AP particles and voids in by using X-ray CT imaging. The mixed state of the AP/HTPB composite propellant is quantified by analyzing the brightness histogram obtained from the CT image. In the brightness histogram, mixed degree shows the difference between the ideal and measured propellant compositions in the image. Solid propellants with different mixing time were scanned by X-ray CT apparatus. The characteristics of the solid propellant at each mixing time were visualized. The mixing degree decreased as the mixing time longer.
A feasibility study was conducted to investigate the potential performance advantages of Supersonic Retro-Propulsion in support of future high-mass Mars robotic landing missions. A notional reference architecture for a potential future Mars Sample Return formed the basis for assuming a 4.7 m diameter SRP entry vehicle containing the Mars Ascent Vehicle element. Configuration analysis was conducted to ensure that the payload and required SRP components (including engines and propellant) fit within in the capsule volume. Optimized trajectory analysis highlighted several key performance sensitivities of SRP for ballistic coefficients of 150, 300, and 450 kg/m2. These results indicated a broad SRP ignition envelope (1-4 km altitude, 300-750 m/s velocity), as well as relatively small propellant mass fraction sensitivities to SRP thrust/weight, landing site elevation, and the application of a 4-g entry deceleration constraint (relevant for future crewed mission trajectories). Finally, mass-sizing was performed to assess sensitivities to ballistic coefficient and entry velocity, and showcased the ability of the SRP system to land payload masses on the order of twice that of MSL.
In 2015, Tokyo University of Science (TUS) started the TUS Space Educational Program (T-SEP). This program includes not only lectures on space science and technology but also hands-on trainings with onboard equipment and project-based learning utilizing parabolic microgravity flight and CANSAT. During such project-based learning process, students learn the complete process involved in space missions, such as mission design, implementation, project management, and operations regarding various constraints. Such learning is very effective for acquiring individual knowledge of space science and technology and also acquiring skills required for space missions. The first author of this paper was one of the first T-SEP students in 2015 and one of the best examples of the impact of this program. In addition, he continues to participate as a mentor to support T-SEP. This paper outlines T-SEP results since 2015 from the viewpoint of a mentor having experience as one of the first students.
To achieve high throughput to effectively accommodate users, multi-beam systems reusing several frequency bands with small beams are effective. Using a reflector antenna with a very large aperture on the satellite is a promising option for next-generation mobile communication satellites for small user terminals with small beams. A deployable reflector is a flexible structure instead of the hard dish reflector. To improve the electrical performance of the antenna and avoid performance deterioration caused by aberration, the parabolic reflector must be accurately shaped. We propose continuous beam stabilization by optimizing the parameters for the phased array. If the reflector shape can be measured precisely while in orbit, the beam pattern and antenna performance can be corrected continuously by updating the excitation parameters based on the measured reflector shape with a brief time delay. For the proposed algorithm to perform antenna-pattern stabilization effectively, the shape of the reflector surface should properly determine the optimized phased array parameters to compensate for the deterioration of the antenna pattern. The objective of this study is to confirm the feasibility of the approach to beam pattern correction. The simulations of deformed reflector surfaces deteriorating the antenna pattern reveal that the application of optimized phased array parameters for the reflector shape can compensate for the deformation and recover the antenna pattern.
In this paper, we briefly introduce the result of the Human Resource Development program conducted in 2014-2016 under the collaboration of eight colleges. As a result of this program, Tokuyama College has considered a new program for application in an actual college class. A combination of experimental and laboratory classes can be expected to cultivate a student's engineering ability in terms of Engineering Design Education.
This research proposes estimation algorithms of relative position and attitude during interplanetary proximity rendezvous and docking by using ultra-wide-band (UWB) devices—which are small, low-power devices to be used for communication between several spacecraft, and are suitable to be mounted on micro- or nano-spacecraft. The device provides high-precision ranging and high-speed communication between two spacecraft during rendezvous and docking, whose information is used for estimating their relative position and attitude. This paper proposes two estimation algorithms using UWB properties. The first one estimates the relative position by using the ranging data of the UWB devices and the relative attitude information, which is shared by the UWB communication and provided by the attitude sensors. In the second algorithm, assuming that the attitude sensor of the chaser cannot be used, the relative attitude is estimated using the multiple ranging data of the UWB devices. This research evaluates the estimation accuracy of the two proposed algorithms using a rendezvous simulator, which reveals the conditions to obtain accurate and stable relative position and attitude estimations. This paper will contribute to autonomous navigation method for the proximity rendezvous and docking phases of micro- and nano-spacecraft, which have strict limitations of size and power for navigation sensors.
Our research team is developing a balloon-borne telescope system for optical remote sensing of planets. To obtain high-quality imaging data from planets, pointing-control technology is indispensable. Our team has continued developing pointing-control systems for balloon-borne telescopes. This paper reports the characteristics of our pointing-control system and describes a performance-improvement method for future development.
The power system is one of the most important subsystems for a successful space mission. Any failure in this subsystem leads to a direct loss of a satellite. This creates a need for a power schedule to be effectively and efficiently produced, especially if requirements are constantly changing. This paper presents the application of linear programming techniques to solving the power schedule problem, with the more specific usage of mixed-integer linear programming (MILP). The illustration of the approach is applied to a Swedish student satellite, which consists of the necessary subsystems and eight separate experiments. Two programs are developed, one studying the satellite lifetime in terms of orbital cycles and the other studying the individual orbit cycle. Simulating the lifetime of the satellite over 5000 orbit cycles, the battery level did not decline below 76.35%. Using a computer with an Intel i4 processor, this simulation took 3.2 hrs, with individual orbits taking 2.3 s each. Further work includes developing the program to be completed on-aboard the satellite, adapting to new scenarios, and incorporating a model for the decline of battery performance over time.
The pumpkin shape design is one of the most effective methods for super-pressure balloon design. In this paper, the method of designing a pumpkin super-pressure balloon is studied and equivalent strength concept is introduced in the design process. Fabrication method is also discussed. In order to verify the method, a 6 meters test balloon was fabricated and tested. The maximum differential pressure matched with the design value and the design method proved to be usable. Through the test, intuitive understanding of pumpkin super-pressure balloon was obtained and method of designing was verified.
JAXA has operated the heavy ion telescope located on the ISS/JEM-EF since 2009, and prepared for the publication of data. Due to the long-term operation, there are concerns over the degradation of its silicon sensors and circuits. The calibration operations were conducted in May 2012 and August 2016. We checked for such deterioration but have not yet to confirm the degree of degradation. For the correct determination of atomic number and incident energy, a more accurate calculation method was examined and then applied. As a result, a good correlation with CREME96 was confirmed.
This paper is dedicated to the numerical simulation and analysis of the "Dzhanibekov's Effect" - non-stable "flipping" motion of the rigid body with periodic change by 180° of the direction of the main axis of its rotation, always occurring when the body is provided with the main rotation about its axis with intermediate principal moment of inertia. In this work we are proposing and developing a new concept of "inertial morphing" of the spacecraft for the versatile control of the "Dzhanibekov's Effect", enabling manipulations with the attitude of the spacecraft without employing classical gyroscopes. We are demonstrating that applying controlled changes to the inertial properties of the system, the "Dzhanibekov's Effect" flipping motion can be completely stopped, if this motion is undesirable. Similarly, the "Dzhanibekov's Effect" flipping motion can be activated on the stable, non-tumbling spacecraft, if this is desired for the purposes of the mission. We are also showing that the frequency of the flipping motion can be controlled within a wide range. For the implementation of the transformations between stable and unstable modes of motion, we are proposing two main conceptual solutions, involving changes to the system, resulting in the intermediate moment of inertia becoming the smallest or largest principal moment of inertia of the body. Development of the conceptual 6-mass model of the spacecraft enabling controllable switching OFF of the "Dzhanibekov's Effect" flipping is presented. Furthermore, we also exploring the possibilities of utilization of the "Dzhanibekov's Effect" for possible future new space missions, employing periodic change in the attitude orientation of the spacecraft. It is believed, that new results of this research may have multiple applications for possible future space missions. In particular, we are suggesting assistance in establishing formation flight; thruster direction control and control of the period of the "flipping" motion of the spacecraft.
We investigated the influence of injectant species and air total temperature to mixing characteristics to find out dominant parameters to simulate mixing process in a dual-mode combustor with non-reacting mixing experiment, the combustor being capable to operate can in a ramjet-mode (subsonic combustion) and in a scramjet-mode (supersonic combustion). To evaluate mixing efficiency, Pitot pressure measurement and gas sampling at the several cross-sections were carried out with plural gases (helium, nitrogen, or argon) injected at sonic speed from wall-flushed mounted injectors to M2.5 cold (room temperature) or hot (1000K, 2000K) airflow without or with pseudo-shock wave system. By matching dynamic pressure ratio, the influence of injectant species to mixing characteristics was negligible in ramjet- and scramjet-mode cases, but the influence of air total temperature was not negligible in the ramjet-mode case.
In recent years, high power electric propulsion systems in the range of several tens to 100 kW are under development for the cargo of the manned missions or the satellite market. The thrusters for these propulsion systems require around 100 A of the discharge current. For these applications, we have been developing a 100 A class hollow cathode. To appropriate the electron emission processes of the LaB6 insert in a 100 A class Hollow Cathode, the characteristics and the diagnostics by single Langmuir probing were investigated. In this paper we report the results and the guidelines for the next step in a 100 A class heaterless hollow cathode.
This paper presents a new method of optimal trajectory design for formation flying. Under linearized assumptions and a quadratic performance index, we introduce an attractive set of optimal control based on the linear quadratic regulator theory. The attractive set is defined as a set of all initial states to reach a desired state for a given cost. In particular, we consider attractive sets for two problems: a fixed final-state, fixed final-time problem and an infinite-time problem, and the optimal initial state is found based on the geometry of the attractive set. The optimal trajectories for two problems are evaluated in terms of L1-norm of control input and termination time.