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深宇宙探査を対象とした新しいサンプルリターンミッションに向けて薄殻エアロシェル型カプセルが提案されている．本カプセルのコンセプトにおける一番の特徴は，軽量・大面積エアロシェルを用いることで空力加熱を避けることである．本カプセルはパラシュートレスでの帰還が想定されていることから全速度域で空力的に安定に飛行することが求められている．実機は，直径0.8m，総質量10kg, 機軸周りの慣性モーメント0.58kg m2, 機軸垂直周りの慣性モーメント0.32kg m2のカプセルを想定している．薄殻エアロシェル型カプセルの低速域における動的不安定性を評価するために，2022年7月1日にゴム気球を用いた自由飛行実験RERA(Rubber balloon Experiment for Reentry capsule with thin Aeroshell) を実施した．気球実験機として，直径0.8m，総質量1.56kg，機軸周りの慣性モーメント0.033kg m2, 機軸垂直周りの慣性モーメント0.020kg m2のカプセルを使用した．カプセルは高度25kmにおいてゴム気球から切り離され，自由飛行を開始し，海上着水した．実験中のオンボードセンサーによる計測データとカメラによる撮影画像は地上局へ送信された．自由飛行においてカプセルは姿勢振動していたもののピッチ方向に縦回転することはなかった．自由飛行時のカプセル周りの流れ場はマッハ数0.15以下，レイノルズ数10(exp 5) オーダーであった．このことから再突入時と同オーダーのレイノルズ数環境下で試験を実施できた．実験機は低速域においてピッチ・ヨー方向の振動運動が発散しないことが示唆された．, A sample return mission to deep space has been proposed. The orbital velocity in the atmospheric entry in the deep space sample return reaches 15 km/s, which results in extremely severe aerodynamic heating to the sample return capsule (SRC). To reduce the severe heating environment by efficient aero-deceleration at high altitudes, a new concept of SRC with a lightweight and large-area aeroshell is proposed. The SRC is needed to be aerodynamically stable at all speeds because it is expected to be operated without a parachute in the atmospheric entry. To evaluate dynamic stability in attitude for capsule with thin aeroshell, the Rubber balloon Experiment for Reentry capsule with thin Aeroshell (RERA) was conducted on July 1st, 2022. The capsule with a mass of 1.56 kg and a diameter of 0.8 m was dropped from the balloon at an altitude of 25 km, and then, started the free flight. In operation, data measured by onboard sensors and photographs by a camera were successfully transmitted to the ground station. The capsule was in low oscillation in attitude without a vertical rotation. The flow field around the capsule during the operation was 0.15 in Mach number in maximum and an order of magnitude 10(exp 5) in Reynolds number. This indicated that the present experiment reproduced a flow field around the actual deep space SRC at low speed. Although the moment of inertia of the capsule for the present experiment was different from the actual SRC, it was suggested that the capsule was dynamically stable in the low-speed region., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2230025003, レポート番号: JAXA-RR-22-008

Ordinary, method by the polarity of constant term in a characteristics equation is used to detectof vehicle stability. This paper describes that the definition of static stability and dynamic stabilityand generating mechanism of these stability. This analysis using state plane shows that the statevector made by planer half model expressing the stable or unstable conditions. This analysis resultis able to define that the static stable or unstable, dynamic stable or unstable corresponding topole placement of vehicle characteristics equation. Also it shows that dynamic instability for OSvehicle is not defined. This result will bring out that design the stability margin to distinguishstatic stability and dynamic stability at important process to design the control law for the activecontrolled SBW (Steer-by-Wire) vehicle.

本研究では, 復元力低下領域における構造物の動的応答特性の基本的な理解に向けて, 振動中心軸の移動(ドリフト)を伴う非線形一自由度系の動的安定性に関する理論的および解析的検討を行った. 具体的には, 外力振動数に対するドリフト量の応答倍率を導出し, 数値解析によりその妥当性を検証した. この結果, 応答倍率から算出される理論値を, 解析により再現することができた. また, 応答倍率から導かれるドリフト量-外力振動数関係上の特異点において, 応答が急激に片側に発散する傾向が確認された. それにより, 応答倍率における特異点のドリフト量が, 構造物の動的安定性を考える上で重要な指標となり得る可能性が示された., In this study, the dynamic stability of nonlinear single-degree-of-freedom systems with the movement of oscillation center axis (drift) is theoretically and analytically investigated to understand basic dynamic response characteristics of structures in the region of reduced restoring force. Specifically, The response magnification factor of the drift to forced frequency is derived and validated by numerical analysis. As a result, the theoretical value calculated from the response magnification factor was reproduced by the analysis. In addition, it was confirmed that the response diverges to one side rapidly at the singularity on the drift-frequency relation derived from the response magnification factor. Thereby it was suggested that the amount of drift on the singularity may be an important indicator for the dynamic stability of structure systems.

本研究では, 骨格曲線にある程度の靭性と負勾配を有する構造物に対して, 終局後の荷重低下領域での動的安定性に関する理論的な検討を行った. その際, 理論的検討としてCaugheyにより導出された方法を用いた. これは運動方程式に関して定常応答を仮定することで, 入力と応答の関係式である周波数応答関数を導出し, 更に非線形振動特有の運動方程式の解が不安定となる条件を2つ導出する方法である. 本研究での検討の結果, 構造物が荷重低下領域で安定した定常応答をする範囲は, 骨格曲線の靭性と荷重低下時の剛性により決定されることが分かった, また, 靭性と荷重低下時の剛性に関してパラメトリックスタディを行ったところ, 靭性が過大の場合, 荷重低下領域での動的安定性が確保できない可能性が示唆された., In this study, the dynamic stability of a structure with negative stiffness in the skeleton curve was theoretically investigated. For theoretical research, the frequency response function derived by Caughey and the discriminant of the instability of the response solution are used. As a result, it was found that the range in which the structure shows a stable steady response in the range where load decreases is determined by the ductility of the skeleton curve and the negative stiffness in the range. Moreover, as a result of conducting a parametric study about ductility and negative stiffness in the range where load decreases, it was suggested that dynamic stability is not secured in the range where load decreases if ductility is too large.

The Unmanned Space Experiment Recovery System (USERS) was launched on September 10th, 2002 from Tanegashima Space Center with the H-2A launch vehicle. On May 30th 2003, the re-entry and recovery operations were successfully conducted, bringing experiment samples and beneficial information back to Earth. USERS became the first national project to succeed in recovery from orbit. In this paper, aerodynamics characteristics of USERS capsule and attitude dynamics that are predicted in design phase are summarized and in-flight attitude dynamics are evaluated., 資料番号: AA0048710003, レポート番号: JAXA-RR-04-045

A SPS (Solar Power Satellite) which is a part of the Space Solar System (SSPS) project has been studied at the USEF. Quasi-static analysis had been carried out for the practical SPS. The present purpose is to evaluate the attitude stability of the SPS under construction. During construction, it is assumed that the modules of 100 x 95 sq m are arranged in the shape of line. As the result of quasi-static analysis, it is shown that the roll and yaw angular frequencies of attitude motion are twice and once as large as orbital angular velocity in first step of the construction, respectively. Furthermore, as the result of dynamical analysis, amplitudes of the roll and yaw angles tend to divergence in first step. To avoid such a divergence, another model was proposed which is constructed keeping similar configuration. The construction way is called construction with similarity. From the result of simulations, it is shown that divergences in the roll and yaw angles can be avoided in the construction with similarity. However, the stability around the pitch and yaw axes are weak in first step for construction with similarity. In particular, maximum amplitude around the pitch axis is 5 deg. Therefore, both constructions need active attitude control because there are problems in first step of the constructions., 資料番号: AA0047275019

資料番号: AA0045440033

建築構造に用いられるシェル・空間構造の防災研究は個々の形態、構法により、耐震、耐風、耐雪、耐火の諸方面からなされねばならず、筆者は耐火問題を除いて種々研究を遂行してきた。ここでは、特に球形シェル及び屋根型円筒シェルの地震応答に関する一連の研究を概説する。, Safety of shells and spatial structures is especially necessary, because the scale of these structures is usually large and large number of people are contained. The author has been engaged in the research of shells and spatial structures for several ten years from the viewpoint of safety security for the natural disaster.At the factor of the natural disaster, there are earthquakes, wind, snows, etc.. One of thses disaster factor should be taken into consideration according to the shape and structural characteristics of these structures in disaster prevention research. Here, a part of the authours research concerning earthquake response of spherical domes and roof type cylindrical shells is summarized. And how these researches are promoted is shown.

The vibration, buckling and dynamic stability of a cantilever rectangular plate subjected to in-plane concentrated load at the free edge is studies in this paper. The small deflection theory of the thin plate is used. The Rayeigh-Ritz method is employed to solve vibration and buckling of the plate. The dynamic stability problem is solved by using the Hamilton principle to drive time variables. The resulting time variables are solved by the harmonic balanace method. Buckling properties and natural frequencies of the plate are shown at first. The regions of instability which contain combination resonances and simple parametric resonances are discussed for various aspect rations, dampinf constants and staticv loads.

This paper presents a study on the dynamic stability of a 2" floppy disk-head-stabilizer assembly. The effect on the disk stability of the air film stiffness between the disk and the head-stabilizer system is studied. Next, the disk shock response to the half-sine axial and pitching acceleration is investigated in detail. A solution is obtained by introducing the multimodal expansion approximation and applying the Galerkin method to the governing equations of the system and is calculated numerically by introducing the Newmark β method. The obtained results show that the stability of the disk is strongly affected by the air film stiffness between the disk and the head-stabilizer system. Furthermore, the maximum disk displacement takes the peak value when the duration of acceleration input is about 1 to 10 times the half-period of the fundamental (0, 0) mode. A significant decrease of peak displacement with an increase of the air film stiffness is also revealed.

本研究では、弾性支承の一種である Pasternak 基礎上に置かれた温度勾配をもつ変断面長方板の振動, 座屈および動的安定性解析を行う. 長方形板の境界条件としては, 単純支持, 固定および自由の組合せを採用し, Pasternak 基礎剛性, 変断面パラメータ, 温度パラメータのもとに, Pasternak 基礎上の温度勾配をもつ変断面長方形板の固有振動特性, 座屈特性および動的不安定領域を明らかにする., The vibration, buckling and dynamic stability of a non-uniform rectangular plate on a Pasternak foundation under the action of a pulsating in-plane load is studied. The small deflection theory of the thin plate is used. This problem is solved by using the Hamilton principle to drive time variables. The dynamic stability is solved by the harmonic balance method.Natural frequencies and buckling properties are shown at first. Then, regions of instability which contain simple parametric resonances and combination resonances are discussed for various boundary conditions and parameters of Pasternak foundation, non-uniform cross-section and thermal gradient.