An efficient design method is proposed for robust low-boom design considering sonic boom loudness at both on-track and off-track positions. There exists an efficient design method for on-track low-boom design based on a reversed equivalent area distribution without using optimum design methods. The proposed method extends the existing method to consider off-track loudness. The characteristic of the proposed method is a conversion and a unification by weighted average. In the conversion, reversed equivalent area distributions at off-track positions are converted to that at the on-track position. In the unification by weighted average, converted distributions are unified into a single distribution based on loudness estimation using the F-function of the converted reversed equivalent area distribution so that sonic boom loudness at on-track and off-track positions can be balanced. Once the unified distribution is defined for the on-track position, the existing method can be applied. The proposed method is applied to a 50-seat class supersonic airliner, and the maximum loudness of front part of sonic-boom signature at both on-track and off-track positions is successfully reduced by 6.5dB in terms of Stevens Perceived Level Mark VII from 91.6dB to 85.1dB.

In an earth observation satellite or a space observatory, micro vibration caused by a mechanical cryocooler is one of the problems that make the performance worse. In this article, we propose an active control method with feedforward signal for a cryocooler. The vibration of a cryocooler appears as a distinct spectrum. This algorithm identifies the transfer function of the control target and calculates the optimal control signal by giving feed-forward signals to this spectrum several times in advance. The effectiveness of the proposed method is confirmed by experiments using a cryocooler, and the effects of fluctuations in the spectrum of vibration and noise are discussed.

This paper proposes a new concept of a deployable nozzle made of superelastic titanium-alloy sheet. A concrete design of deployable nozzle is determined by FEM analyses based on the condition of a kick motor on a certain launch vehicle. A 1/4-scale model of the nozzle was produced in trial and its storing and deploying test was completed.

In this study, an improvement in the low-temperature strength of composite double-lap bonded joints was developed based on the residual plastic strain through preloading at room temperature. The finite element method was employed to calculate the adhesive layer stress and energy release rate between the adhesive layer and the inner adherent of the bonded joint at low temperatures. In the calculation, the residual plastic strain of the adhesive layer was considered. The numerical results indicated that the residual strain of the adhesive layer could increase the low-temperature strength of the composite bonded joints. The strength improvement of the bonded joints was experimentally evaluated at -150^ºC. From the experimental results, the low-temperature strength of the bonded joint preloaded at room temperature increased by approximately 7%.

This research proposes an efficient pointing accuracy analysis method applying a support vector machine (SVM), one of machine learning methods, to reduce computational cost sufficiently for a highly precise space truss consisting of multiple-stage structures with uncertainties of member lengths and the node clearances. The SVM is applied to classify the nodal position definiteness of the truss structure in terms of the uncertain variables to avoid useless pointing accuracy analysis for the instable structures. For an efficient classification, the nodal position definiteness for a larger-stage truss is estimated from learning results for a fewer-stage truss. Through numerical examples, the nodal position definiteness for 20- or 30-stage truss is demonstrated to be efficiently classified by the learning results for only 3-stage truss structure. Then, the pointing accuracy evaluated as the direction angle distribution is confirmed to be identical to the result by Monte Carlo simulation.

We have studied an antenna system using a smart sub-reflector for a high-resolution radio astronomy mission. This antenna system realizes extremely high antenna gain by adjusting the surface shape of the smart sub-reflector corresponding to a surface distortion of the primary reflector measured by a grating projection method. However, the antenna performance will be deteriorated under operational uncertainties such as the measurement uncertainty on the surface shape measurement, the approximation uncertainty in calculating the actuator output and the actuator output uncertainty. This study investigates effects of the uncertainty propagation derived from the operational uncertainties and proposes a multiobjective optimal actuator layout method considering the uncertainty propagation. Then, validity of the proposed method considering the operational uncertainty is discussed through numerical examples.