Discussed in this paper is a lunar approach strategy tolerant of a lunar orbit injection (LOI) failure. LOI is one of the most critical events for a lunar orbiting mission. If LOI is not performed, the spacecraft flies by the moon, and in the worst case, it escapes not only from the moon but also from the earth, which leads to mission failure. The proposed strategy is to design a trajectory so as to re-encounter the moon even when LOI is not performed. It provides an opportunity for mission recovery even in the case of an unexpected fly-by. A trajectory design procedure is introduced and an example of the designed trajectory is shown.

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In this paper, the translunar trajectory of the simple sequence is investigated. The trajectory discussed in this paper is a two-burn ballistic trajectory from the low earth parking orbit to the low lunar orbit. The problem is practical in that the geometric relation from the launch site to the moon is fully considered. The paper includes three subjects. First is the structure of the problem and the solution space. The problems are defined and the solutions are grouped by the properties of the lunar transfer sequence. Second are the characteristics of optimal solutions. The topics discussed are the transition of the required velocity increment based on the launch date, and the difference according to the property of the lunar transfer sequence. Third is the sensitivity analysis of a number of items to the deviation of the parameters from the optimal solution.

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浮遊炉（ＥＬＦ）は，国際宇宙ステーション（ISS）への搭載が期待される材料科学分野の実験装置のひとつである．その主な特徴は，クーロン力により実験試料を電気炉内に浮遊させた状態で，溶融／固化実験を行えることである．われわれは宇宙ステーションの擾乱環境下においてこれを実現するために，３種類のそれぞれ特徴的な制御ロジックを考案した。しかしながら，1998年にこれらの制御ロジックを検証するために実施した小型ロケットでの試験飛行において，実験試料の位置が予想外に動揺する現象が観察された．その後の解析によりこの現象は，実験試料が高温になり，しかも加熱レーザが点灯しているときに制御力が低下して起こったことが分かった．実際のところ，ある一定以上の高温になったときにレーザの照射を受けると，実験試料の帯電量が顕著に減少することが知られている．これに対処するため，オンラインモデル推定法を応用した逐次最小二乗アルゴリズムを採用することで，実験試料の帯電量をリアルタイムに同定できる制御ソフトウェアを再設計した．計算機シミュレーションの結果では，帯電量が著しく変化する条件下においても，実験試料の運動をうまく制御することができた．結論として，本適応制御技術は静電浮遊炉のみならず，使用中にパラメータが大きく変動するような他のシステムにも適用可能な技術であると言える．

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The main objective of the current study is to clarify the influence of ion beam waveform and to investigate the momentum producing capability of flyer acceleration for propulsion applications, which is produced by irradiating target materials with pulsed ion beam. Al thin foil with a thickness of 50 μm was used to form the high-pressure, high-temperature, and high-energy density ablation plasma when it interacts with pulsed ion beam. The analytical procedures are based on one-dimensional hydrodynamic equations together with a real gas equation of state. This paper presents not only the physical parameters of pulsed ion beam interaction with a target, but also shows the effects of ion beam waveform on momentum production. In addition, we describe the mechanism of ablation pressure formation and compare the results obtained for the rectangular and the parabolic waveform of ion beam irradiation. An ion beam with parabolic waveform produces ablation pressure more efficiently than a rectangular waveform. Propulsion performance is also estimated. An impulse bit of 50.7 mNs and a specific impulse of 5200 s are obtained at an electric power consumption of 1677 W.

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