山本 高行

Japan Aerospace Exploration Agency (JAXA) successfully achieved the world's first solar power sail technology by IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) mission in 2010. It demonstrated a photon propulsion and thin film solar power generation during its interplanetary cruise. The 200m2-span sail was deployed and kept extended by centrifugal force of the spacecraft rotation. IKAROS also succeeded in accelerating and controlling the orbit by actively exploiting solar radiation pressure, and thus became the world's first actual solar sailer flying an interplanetary voyage. This paper presents the design of IKAROS solar sail system, operation results and introduces a perspective of this new technology to apply to the next generation mission toward Jupiter and Trojan asteroids.

The Japan Aerospace Exploration Agency (JAXA) makes the world's first solar power sail craft IKAROS demonstration of photon propulsion and thin film solar power generation during its interplanetary cruise. The spacecraft deploys and spans a membrane of 20 meters in diameter using the spin centrifugal force. It also deploys thin film solar cells on the membrane, in order to evaluate its thermal control property and anti-radiation performance in the real operational field. The spacecraft weighs approximately 310kg, launched together with the agency's Venus Climate Orbiter, AKATSUKI on May 21, 2010. This paper presents the summary of development and operation of IKAROS.

On the ascent path of the vehicles like spaceplanes, the optimal steering shows the different behavior from that of conventional rockets. This is because both thrust and lift force varies depending on the change of the atmospheric dynamic pressure. This indicates that it is required the new guidance strategy for these kind of vehicles. In this paper, we propose a new guidance strategy which has only four parameters to be determined. This method is derived from some analytical assumptions and approximates the steering in simple linear and logarithmic function. Only by carrying out the numerical integration of this, the parameters are easily determined to satisfy the terminal boundary conditions.

本論文では，いわゆる空力上昇径路を飛行する機体の最適誘導則を新たに提案する．まずDCNLP法により最適解を示す．次に直接最適法であるSQP法により別の解を示す．後者の手法ではある直交関数で表現された操舵角を利用することにより，効率的にまた容易に実行することができる．本論文の主な結果は操舵則の解析的表現を示したことである．これは最適性の議論に関連するものである．これによ り従来の線形タンジェント則は揚力を発生しない機体のみに適用可能であることがはっきりと結論される．同時に最適誘導則は三角関数形式を従来の線形タンジェント則に加えることで得られることが結論づけられる．本論文で得られた結果はさらに数値的デモンストレーションによる誘導方策へと最適化プロセスを拡張している．線形化遷移運動が解析モデルによく一致しているため，本論文の結果 は実際的な正当性を示すことに成功している．機体パラメタがノミナル値から変化したり，パラメタ値に対する感度といった誘導計算例もまた示される．