We investigated the power loss due to the sustained arc between primary satellite power cables. If the multi layer insulation (MLI) film on a satellite is electrically floating, energetic electrons in space will charge this film. We carried out an internal pressure measurement of MLI and ESD test on cable with cracks and wrapped with this film. When the negative voltage on the MLI exceeded -1kV, a trigger arc discharge occurred between the MLI and the cables. Subsequently, a secondary arc discharge occurred between the cables themselves. In the specific condition, this secondary arc caused sustained arc which burned out the cables. The heat caused by arc tracking between the hot and return cables made them burn out. If this phenomenon had occurred in space, the satellite would have suffered great damage.
In this paper, the patching efficiency in cracked aircraft structural panels repaired with single-sided and double-sided piezoelectric patches is investigated. A two-dimensional finite element method is used to obtain the patching efficiency which has relation to stress intensity factors at a crack tip. The aircraft structural panel and piezoelectric patch are modeled as layers composed of Mindlin plate elements, and the stress intensity factors are calculated using the modified crack closure method. By performing numerical analysis, the effect of location of an active piezoelectric actuator on the patching efficiency is examined in the case of a single-sided piezoelectric patch. Moreover, the optimization of electric fields applied to piezoelectric actuators for maximizing the patching efficiency is conducted. In the case of double-sided piezoelectric patches, we also perform the numerical analysis of the patching efficiency, and finally demonstrate experimentally the enhancement of patching efficiency due to the activation of piezoelectric actuators as a step toward the practical use of piezoelectric patches.
Three-dimensional reactive full Navier-Stokes simulations of hydrogen/oxygen flow in a nozzle having area ratio of 140 is evaluated using a detailed chemical kinetics reaction model. The flow over each overlapped grids is computed using a unified zonal method technique. The flow field computed by the present CFD code shows good agreement with the flow field computed by the TDK code except the position of the weak compression wave focusing on the nozzle axis. Isp profiles of the subscale nozzle computed by the CFD code assuming a laminar condition agree well with the experiment and those calculated by the TDK code. The measured heat flux distributes at higher nozzle expansion ratios also agree well with the laminar CFD results. The inconsistency of the prediction of turbulent boundary layer loss between TDK and CFD leads to some difference on Isp. The effect of grid resolution turned out to be small on Isp in the present conditions.
This paper describes a structure design method of deployable structures using similarity index value. Similarity index value is defined as the difference of the nominal deployment force between a module structure and the whole structure (which consists of some module structures). The differences are generated by the size of a module structure, the connection errors and the synchronization errors of the whole structure. By comparing the experimental and analysis results, we quantitatively evaluate the changes of the nominal deployment force in each factor. We introduce an index that indicates the number of modules in the structure design of large deployable structures. We design the antenna reflectors which are 10 or 20m in diameter using similarity index value.
The acetylene/air counter flow flame formed by a porous cylinder in electrical fields was studied experimentally and numerically. The temperature and OH radical distributions in the flame were measured in experiments. The numerical simulation with a detailed reaction model was conducted to explore the effect of ionic wind on the flame behavior. The experimental results show that the temperature and OH radical distribution shifts to the negative electrode side in electrical fields, which is good agreement with the prediction. It is indicated that the shift of flame zone in electrical fields may be due to the change in the bulk flow velocity induced by the ionic wind.
How can a prolate spacecraft spinning about its axis of minimum moment of inertia be attitude-stabilized by using dual spin? To this question, we find a simple, clear answer. We replace the spacecraft with an equivalent point-mass model and describe its attitude motion as small deviations from its nominal attitude. We show that a friction-like torque applied to the spin axis would reduce wobble motions, and that a similar torque is generated by a wobble damper on a de-spun platform. Thus, we derive a simple attitude-stability theory using minimal mathematical analysis, and this theory is applicable to the spin stabilization of geosynchronous communication spacecraft.
Most airplanes use their ailerons to compensate the lateral displacement deviation from a reference flight-path. This study proposes a method of lateral flight-path control due to the rudder steering under constraint of automatic roll angle hold. This control method is estimated analytically to produce quicker lateral displacement response than the control due to aileron. Then, experiments using a flight simulator are carried out to evaluate the control characteristics on the task of holding the flight path. The pilot’s evaluation results show that, the rudder steering method gives better flying qualities than aileron steering method. Furthermore, as the more practical control measures, the mixture type of method is worked out, which is transferred from aileron steering to rudder steering depending on the lateral displacement deviation from a reference flight-path.