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Ballistic capture is a method of achieving orbit around a planet - a spacecraft moving at a lower orbital velocity than the target celestial body is inserted into a similar orbit, allowing the planet or moon to move toward it and gravitationally snag it into orbit around the celestial body.〔 〕〔http://arxiv.org/abs/1410.8856, http://www.universetoday.com/117615/making-the-trip-to-mars-cheaper-and-easier-the-case-for-ballistic-capture/〕 It was first used by Japanese scientists in 1991.〔http://www.scientificamerican.com/article/a-new-way-to-reach-mars-safely-anytime-and-on-the-cheap/〕 It reduces fuel costs and is useful for remote planets like Mars, Jupiter, and Pluto. Hohmann transfer orbit (詳細はLow-energy transferを参照) Low energy transfer was proposed in 2014, although it built off concepts invented over the past 30 years. The spacecraft is launched into a broad orbit that places it ahead of the target planet's orbital path. As the planet approaches the spacecraft, the planet's gravity draws the craft into the desired orbit. This saves energy by reducing the need for a high-fuel orbital burn in order to enter the planet's atmosphere. Instead, the planet's gravity pulls the craft into the atmosphere, and the friction of the atmosphere slows the spacecraft down to the appropriate speed. Smaller burns then lower the craft to the desired altitude. Some advantages include higher stability, lower fuel costs, and flexibility of launch period from the earth. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ballistic capture」の詳細全文を読む スポンサード リンク
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