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A porkchop plot (also pork-chop plot) is a chart that shows contours of equal characteristic energy (C3) against combinations of launch date and arrival date for a particular interplanetary flight. By examining the results of the porkchop plot, engineers can determine when launch opportunities exist (a ''launch window'') that is compatible with the capabilities of a particular spacecraft.〔("Porkchop" is the First Menu Item on a Trip to Mars ), NASA. Accessed December 30, 2007.〕 A given contour, called a porkchop curve, represents constant C3, and the center of the porkchop the optimal minimum C3. The orbital elements of the solution, where the fixed values are the departure date, the arrival date, and the length of the flight, were first solved mathematically in 1761 by Johann Heinrich Lambert, and the equation is generally known as ''Lambert's problem'' (or ''theorem'').〔 == Math == The general form of ''Characteristic Energy'' can be computed as: : where : is the orbital velocity when the orbital distance tends to infinity. Note that, since the kinetic energy is , C3 is in fact equal to twice the magnitude of the specific orbital energy () of the escaping object. 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「porkchop plot」の詳細全文を読む スポンサード リンク
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