Showing papers in "Transactions of The Japan Society for Aeronautical and Space Sciences in 2003"
TL;DR: In this paper, the prototype of a solid propellant rocket array thruster for simple attitude control of a 10 kg class micro-spacecraft was completed and tested, and the prototype has 10×10 φ0.8 mm solid-rockets arrayed at a pitch of 1.2 mm on a 20×22 mm substrate.
Abstract: The prototype of a solid propellant rocket array thruster for simple attitude control of a 10 kg class micro-spacecraft was completed and tested. The prototype has 10×10 φ0.8 mm solid propellant micro-rockets arrayed at a pitch of 1.2 mm on a 20×22 mm substrate. To realize such a dense array of micro-rockets, each ignition heater is powered from the backside of the thruster through an electrical feedthrough which passes along a propellant cylinder wall. Boron/potassium nitrate propellant (NAB) is used with/without lead rhodanide/potassium chlorate/nitrocellulose ignition aid (RK). Impulse thrust was measured by a pendulum method in air. Ignition required electric power of at least 3–4 W with RK and 4–6 W without RK. Measured impulse thrusts were from 2×10−5 Ns to 3×10−4 Ns after the calculation of compensation for air dumping.
60 citations
TL;DR: The design concept of a visual servoing system for a space robot and the results of an on-orbit experiment using Japanese Engineering Test Satellite VII (ETS-VII) that was designed based on this concept are presented.
Abstract: On-orbit servicing, such as refueling, repairing, and orbit recovery, will be essential for space activities in the next generation for both manned and unmanned space systems. One of the most important and most difficult tasks in on-orbit servicing is capturing a “customer satellite” using a manipulator that can move dynamically in a wide range of space. A visual servoing technique that controls and guides the manipulator based on a camera image is required to perform this dynamic task. It is necessary to establish boundary conditions; in other words, to specify the task by assessing the environment and setting proper conditions for in order to execute it under the constraints of on-board computing power and the severe lighting conditions of space. This paper describes the design concept of a visual servoing system for a space robot and presents the results of an on-orbit experiment using Japanese Engineering Test Satellite VII (ETS-VII) that was designed based on this concept.
37 citations
TL;DR: In this article, the numerical studies of a plume exhausted from the ion engines of the MUSES-C mission are described. But the results for the operation of a single ion engine are compared with experiments conducted at the Institute of Space and Astronautical Science (ISAS).
Abstract: The MUSES-C mission is being prepared at the Institute of Space and Astronautical Science (ISAS). The MUSES-C spacecraft is equipped with four ion engines, and usually three ion engines are operated simultaneously. This paper describes the numerical studies of a plume exhausted from the ion engines of the MUSES-C. The direct simulation Monte Carlo (DSMC) method is employed for determining the flowfield of the neutral atoms, and the particle-in-cell (PIC) method is combined with the DSMC method to deal with the motion of the ions. The simulation results for the operation of a single ion engine are compared with experiments conducted at ISAS. It is revealed that the profiles of the ion beam are sensitive to the ion beam divergence angle at the engine exit and the electron temperature of the flowfield. Based on the simulation results of a single ion engine, a three-dimensional DSMC-PIC simulation for the simultaneous operation of three ion engines is carried out, and the interaction between plumes from the ion engines and the behavior of the CEX ions are investigated.
21 citations
19 citations
TL;DR: In this paper, two series of experiments were conducted to identify flight dynamics: constrained flight tests, and indoor free-flight tests, using a full-scale blimp, and the results suggest that analytical formulas for estimating the parameters, including added mass effects and stability derivatives may yield values consistent with experimentally identified ones.
Abstract: A blimp is introduced as a stable platform for remote-sensing instruments required for unmanned aerial observation and surveillance. In order to develop flight control systems for a blimp, two series of experiments were conducted to identify flight dynamics: constrained flight tests, and indoor free-flight tests. This paper addresses the blimp configuration, experimental set-up, method for identifying dynamics, and the results of identification in comparison with the analytical estimation for each experimental method. Both tests employed a full-scale blimp. The identification method for the constrained flight tests used the extended least-squares method involving the gradient algorithm, and the indoor free-flight tests, the eigen-system realization algorithm involving the autoregressive model fitting algorithm. The results suggest that analytical formulas for estimating the parameters, including added mass effects and stability derivatives, may yield values consistent with experimentally identified ones.
18 citations
TL;DR: With several three-dimensional applications, it is demonstrated that the present method significantly improves robustness for problems concerning large body motion without much penalty in CPU time.
Abstract: In this paper, a simple and robust method of unstructured dynamic mesh with surface mesh movement method for unstructured triangle/tetrahedral meshes is proposed. The method is developed to avoid the generation of squashed invalid elements by considering each elemental shape. With several three-dimensional applications, it is demonstrated that the present method significantly improves robustness for problems concerning large body motion without much penalty in CPU time. The use of the present method for mesh movements on curved surfaces is also discussed. Its capability is demonstrated for the surface mesh movement in the tail-fuselage juncture region of an airplane.
16 citations
14 citations
TL;DR: In this article, a Navier-Stokes simulation was performed on the aerospike nozzle flow field and it was shown that the shear layer is squeezed more towards the nozzle axis when base bleeding is induced and forces the stagnation point to move closer to the base surface.
Abstract: Aerospike nozzle flow fields are computationally analyzed by Navier-Stokes simulations. The secondary flow from the base surface is induced for the purpose of increasing total thrust. The computed result shows that base pressure efficiently increases when base bleeding is induced from the tip region of the base surface and injected radially inward towards the nozzle axis. The base bleeding induced at the tip of the base and injected horizontally with the axis produces maximum base thrust because the momentum thrust does not produce any divergence loss and the base pressure is kept high. Base bleeding induced against the existing recirculation flow results in lower base pressure distributions. Base bleeding that produces maximum thrust interacts with the exhaust flow and creates shock waves that emanate from the tip of the base. The shear layer is squeezed more towards the nozzle axis when base bleeding is induced and forces the stagnation point to move closer to the base surface.
12 citations
TL;DR: In this paper, the characteristics of a laser ablation igniter were investigated systematically and the minimum ignition energy was found to be lower than 2 mJ, and the required ignition energy decreased with increasing pressure in the combustion chamber.
Abstract: The characteristics of a laser ablation igniter were investigated systematically This kind of igniter is expected to realize a lightweight rocket engine system that consists of many combustion chambers, such as the Reaction Control System (RCS), without having heavy spark igniters In this igniter, ignition is accomplished utilizing a high-temperature metal vapor produced by focusing a high-intensity laser pulse transmitted through an optical fiber The laser ablation igniter was tested in a GH2/GOx thruster (dia 1 cm) As a result, the minimum ignition energy was found to be lower than 2 mJ, and the required ignition energy decreased with increasing pressure in the combustion chamber
10 citations
TL;DR: In this article, the performance characteristics of a 20 kW-class arc-heated wind tunnel and the investigation of material catalysis as an application of this facility were described, and the applicable conditions for reentry simulation or thermal protection tests were discussed based on the experimental results.
Abstract: This paper describes the performance characteristics of a 20 kW-class arc-heated wind tunnel and the investigation of material catalysis as an application of this facility. First of all, stagnation heat fluxes and pressures are measured in high-enthalpy air and nitrogen arc jets that are generated by a constrictor-type arc heater. Total enthalpies of the arc jets are estimated based on Pope’s theory. The total enthalpies are 7.5–22 MJ/kg for nitrogen and 13–19 MJ/kg for air. The operation envelope of this arc-heated wind tunnel and the applicable conditions for reentry simulation or the thermal protection tests are discussed based on the experimental results. Finally, as an application of this arc-heated wind tunnel, evaluation tests of wall catalysis have been attempted by the use of two flat-faced cylindrical models equipped with two kinds of specimens of catalytic material. The evaluation tests are composed of heat flux measurements and spectroscopic measurements. It is found that there is a certain difference in obtained heat fluxes between the two catalytic materials. Emission spectra from a shock layer formed in front of the model are measured, and wall catalysis is discussed based on the spectra measurements. The results show the existence of catalytic wall effects.
9 citations
TL;DR: In this article, the residual lifetimes of 11 spacecraft and five rocket bodies, covering a broad range of inclinations and decaying from orbit in a period of high solar activity, were determined using three different atmospheric density models.
Abstract: In order to estimate the intrinsic accuracy of satellite reentry predictions, the residual lifetimes of 11 spacecraft and five rocket bodies, covering a broad range of inclinations and decaying from orbit in a period of high solar activity, were determined using three different atmospheric density models: JR-71, TD-88, and MSIS-86. For each object, the ballistic coefficient applicable to a specific phase of the flight was obtained by fitting an appropriate set of two-line orbital elements, while the reentry predictions were computed approximately one month, one week and one day before the final orbital decay. No clear correlation between the residual lifetime errors and satellite inclination or type (spacecraft or rocket body) emerged. JR-71 and MSIS-86 resulted in good agreement, with comparable reentry prediction errors (∼10%), semimajor axis residuals, and ballistic coefficient estimations. TD-88 exhibited a behaviour consistent with the other two models, but was typically characterised by larger reentry prediction errors (∼15–25%) and semimajor axis residuals. At low altitudes (<250 km), TD-88 systematically overestimated the average atmosphere density (by ∼25%) with respect to the other two models.
TL;DR: In this paper, the design, fabrication, and experimental and calculation results for three cavity solar thermal propulsion (STP) thrusters made of single-crystal molybdenum (SC-Mo), developed in the National Aerospace Laboratory of Japan (NAL), were detailed.
Abstract: We detail the design, fabrication, and experimental and calculation results for three cavity solar thermal propulsion (STP) thrusters — medium, small, and very small — made of single-crystal molybdenum (SC-Mo), developed in the National Aerospace Laboratory of Japan (NAL). We obtained very high temperatures — 2,300 K for the propellant gas and 2,200 K on the outer surface of the thruster — at an appropriate propellant flow with the small thruster by solar-heating with a suitable concentrator of 1.05 m in diameter, which corresponds to an 800-second-class specific impulse thruster. Temperatures obtained in experiments were much lower than expected, however. To find points for improvement and evaluate thruster performance in space, we conducted a model calculation that confirmed the thruster could achieve an 800 to 900-second-class specific impulse with a 0.1–2 N class thrust magnitude in space. STP is thus a candidate for near-future propulsion in applications such as upper stages of orbit transfer vehicles.
TL;DR: In this paper, a new laminated plate theory for cylindrical bending of laminated plates is presented, which assumes that inplane displacements vary exponentially through plate thickness and provides displacements and stresses very accurately as compared to 3D elasticity solutions.
Abstract: This paper presents a new laminated plate theory for cylindrical bending of laminated plates. The new theory assumes that inplane displacements vary exponentially through plate thickness. The accuracy of the new theory is examined for symmetric/antisymmetric cross-ply, angle-ply and unsymmetric laminates under cylindrical bending. The numerical results show that the new theory provides displacements and stresses very accurately as compared to three-dimensional elasticity solutions. In particular, transverse shear stresses obtained from constitutive equations are predicted very accurately. The results are compared with those obtained from the first-order shear deformation plate theory and the classical laminated plate theory.
TL;DR: In this article, a comparative performance analysis based on design conditions has been made to give normalized algebraic expressions convenient to steady-state temperature and pressure predictions of a loop heat pipe (LHP).
Abstract: A comparative performance analysis based on design conditions has been made to give normalized algebraic expressions convenient to steady-state temperature and pressure predictions of a loop heat pipe (LHP). In analytical modeling of the LHP, a novel concept of pump efficiency is introduced to define the rate of heat loss or leakage through evaporator capillary wicks. Also introduced are general concepts of evaporator temperature effectiveness, condenser activeness, and subcooler temperature effectiveness. A simplified practical method is used to make a probable pressure loss estimate. The model was then mathematically evolved into a solution algorithm applicable to LHP off-design operation problems. In finding the solution, the radiation temperature is first calculated from specified heat load and sink conditions to give a possible condensation temperature, upon which other state variables are determined. Predicted thermohydraulic states are graphically shown in the figures to provide a better understanding of the operability of a commonly configured LHP. A few ground test results are also provided.
TL;DR: In this article, a semi-active control system was proposed for vibration isolation and shock attenuation in a satellite pointing system, and the performance of the system was compared with those of a passive system and a semiactive system with a previously proposed semiactive control law.
Abstract: The concept of applying semi-active control systems to vibration isolation and shock attenuation is proposed. In this paper, a semi-active isolator for enhancing the pointing performance of optical equipment on-board satellites and its characteristics are first introduced and then a generally applicable semi-active control law is proposed for vibration isolation. The isolation performance of the semi-active control law proposed in this study is evaluated through numerical simulations. The performance of the system with the semi-active control law proposed in this study is compared with those of a passive system and a semi-active system with a previously proposed semiactive control law. Next, to investigate whether or not the isolator is also effective for attenuating shock that is induced by rocket lift-off and pyrodevice ignition for inter-stage separation, we also performed numerical simulations and evaluated its effectiveness.
TL;DR: In this article, a wavelet-based vector compression technique was proposed as a new technique of PIV post-processing for efficiently eliminating erroneous vectors and reducing physical storage, and the correction of erroneous vectors can be realized by increasing the compression ratio to 16.
Abstract: A wavelet-based vector compression technique was proposed as a new technique of PIV post-processing for efficiently eliminating erroneous vectors and reducing physical storage. To determine the effect of the choice of wavelet bases, the velocity vector field obtained from standard PIV images was compressed using some known wavelet functions, such as Daubechies, Coifman and Baylkin families. It was found that the lower-order wavelet bases provide good compression performance because they have good physical localization, which in turn, increases energy compaction. When being applied to the PIV result of a jet, the correction of erroneous vectors can be realized by increasing the compression ratio to 16.
TL;DR: In this paper, an experimental study on the pulse detonation engine (PDE) was conducted using hydrogen-air mixtures, where fuel and oxidizer are injected into the PDE from opposite sidewall directions so as to be well mixed by collision of the two jets.
Abstract: An experimental study on the pulse detonation engine (PDE) is conducted using hydrogen-air mixtures. Several key issues for PDE development, including valve operation, injection, mixing, filling, cycle repetition, ignition timing, DDT distance and propagation of detonation/quasi-detonation, are investigated. The fuel and oxidizer are injected into the PDE from opposite sidewall directions so as to be well mixed by collision of the two jets. A good agreement is obtained between the calculated and measured mixing ratios, indicating the occurrence of nearly instant mixing. Before the detonation velocity has reached the CJ value, it was found that the wave propagation velocity at the PDE exit increases with the increase in diameter, length and blockage ratio of the Shchelkin wire, and initial pressure. The PDE performance acquired was a specific impulse of about 2000 s, which was measured from the pressure history at the head end of the PDE.
TL;DR: In this paper, a control design method was proposed to suppress flexible appendage vibration while controlling the attitude motion of space structures simultaneously using two different actuators; one a slow actuator, and the other a fast actuator.
Abstract: In this paper, we propose a control design method to suppress flexible appendage vibration while controlling the attitude motion of space structures simultaneously using two different actuators; one a “slow” actuator, and the other a “fast” actuator. Because the frequency of flexible appendage vibration is much higher than that of attitude motion, this system naturally exhibits a two-time-scale dynamic behavior. After describing this system as a singularly perturbed system, the control laws of each subsystem were determined to have the following properties: the slow actuator only controls the attitude motion of space structures, and the fast actuator only suppresses flexible appendage vibration. A composite state feedback control is obtained by combining the slow subsystem and fast subsystem control laws. Simulation results are presented to show the effectiveness of this control design method.
TL;DR: In this paper, the development of localized disturbances generated by an oscillating point source in compressible boundary layers with a zero pressure gradient at Mach numbers from 0.2 to 2.0 is studied theoretically on the basis of the linear stability theory.
Abstract: Development of localized disturbances generated by an oscillating point source in compressible boundary layers with a zero pressure gradient at Mach numbers from 0.2 to 2.0 is studied theoretically on the basis of the linear stability theory. The method of complex characteristics recently proposed by Itoh as an extension of Whitham’s kinematic wave theory, is applied to describe wave propagation from the oscillating source. The analysis demonstrates distinct differences in the development of localized disturbances between the subsonic and supersonic boundary layers. Importantly, maximum growth occurs away from the midspan in supersonic boundary layers, while it occurs at the midspan in subsonic boundary layers.
TL;DR: In this article, a step-nose with various step lengths and heights, attached to a square cylinder, can significantly reduce the drag coefficient compared to that of the square cylinder.
Abstract: A stepped-nose with various step lengths and heights, attached to a square cylinder, can significantly reduce the drag coefficient compared to that of the square cylinder. The underlying physics are that (1) the vortices trapped in the step regions produce the thrust forces acting on the step surfaces facing against the uniform stream which cancel the drag force acting on the front surface of the stepped-nose obstacle, and (2) the tangent reattachment of the flow separating from the front surface edges to the side surfaces of the main body decreases the suction pressure acting on the back surface of the main body. In the present study, these favorable effects of the stepped-nose are experimentally documented by presenting the measurement results of surface pressure coefficient, streamwise velocity, and turbulence intensity of side flow and flow visualization pictures. It is demonstrated that when step height takes a value of about one-tenth of the main body length, there is a rather wide range of step length, for which the net drag force acting on the stepped-nose almost vanishes and the side flow is stabilized by the stepped-nose.
TL;DR: In this paper, a sliding-mode control method incorporating a strategy to avoid singularities during target capture for a space robot equipped with a manipulator is proposed, where the position and attitude of the end-effector of the manipulator are controlled by a conventional slidingmode control employing the transpose of the generalized Jacobian.
Abstract: The present paper proposes a sliding-mode control method incorporating a strategy to avoid singularities during target capture for a space robot equipped with a manipulator. The position and attitude of the end-effector of the manipulator are controlled by a conventional sliding-mode control employing the transpose of the generalized Jacobian. In the proposed algorithm, the attitude/position of the main body of the space robot is controlled to increase the manipulability when the manipulator approaches a singularity. The direction of the main body translational motion is selected in order to effectively avoid the singularity, and the direction for acceleration of the end-effector is modified taking into account the acceleration of the main body. The gain scheduling technique is also incorporated in order to reduce the control input effort at the beginning of operation as well as to suppress the steady-state error. The effectiveness of the proposed method is verified through numerical simulations for a simple model of a space robot.
TL;DR: In this article, the authors proposed a tether configuration called "balance tether" for an orbit transfer system that transports a payload from LEO to GEO using multi-stage spinning tethers.
Abstract: An orbit transfer system that transports a payload from LEO to GEO using multi-stage spinning tethers is studied in this paper. We propose a tether configuration called “Balance Tether.” The variations in the total mass and mission duration of the system are analyzed for different numbers of stages and different lengths of tethers. In addition, the possibility of debris impact damaging each of several tether system configurations is also analyzed. As a result, we obtain the guidelines for a system design that minimizes total system mass while also taking into account the system lifetime as limited by debris impact. In addition, it is shown that the Balance Tether can reduce the total system mass compared to a single-tether system. The results also show the effectiveness of the spinning-tether system as compared to a conventional chemical propulsion system for the same orbit transfer mission.
TL;DR: An extension of classical theories for a two-dimensional thin airfoil oscillating in an incompressible flow is achieved by assuming arbitrary and constant convection velocity of the wake vortices as discussed by the authors.
Abstract: An extension of classical theories for a two-dimensional thin airfoil oscillating in an incompressible flow is achieved by assuming arbitrary and constant convection velocity of the wake vortices. The well-known Theodorsen function is replaced by different functions composed of the Theodorsen function and a new function. Their vector properties, which depend on the magnitude of the convection velocity of the wake vortices, are presented. The extended results include classical theories as special cases.
TL;DR: This method is directly useful for attitude rate determination right after orbit injection even when the attitude rate is relatively large, because it requires no priori attitude states or identification of STT acquired images.
Abstract: This paper proposes a method to detect spacecraft attitude rate without rate gyros. In this method, a spatial velocimeter is applied to images acquired by a star tracker (STT), where a spatial velocimeter is normally used to detect object velocities from optical image data. The proposed method requires no priori attitude states or identification of STT acquired images. Therefore, it is directly useful for attitude rate determination right after orbit injection even when the attitude rate is relatively large.