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Mars landing
(詳細はspacecraft on the surface of Mars. Of multiple attempted Mars landings by robotic, unmanned spacecraft, seven were successful. There have also been studies for a possible human mission to Mars, including a landing, but none have been attempted.
==Methods of landing==
All methods of landing on Mars require an aeroshell and parachute sequence, but after that there are three choices. A stationary lander can drop from the parachute back shell and ride retrorockets all the way down, but a rover cannot be burdened with rockets that serve no purpose after touchdown. One method is to enclose the rover in a tetrahedronal structure which in turn is enclosed in airbags. After the aeroshell drops off, the tetrahedron is lowered clear of the parachute back shell on a lanyard so that the airbags can inflate. When it nears the ground, the tetrahedron is released to drop to the ground, using the airbags as shock absorbers. When it has come to rest, the tetrahedron opens to expose the rover. If a rover is too heavy to use airbags, the retrorockets can be mounted on a ''sky crane''. The sky crane drops from the parachute back shell and, as it nears the ground, the rover is lowered on a lanyard. When the rover touches ground, it cuts the lanyard so that the sky crane (with its rockets still firing) will crash well away from the rover. All three methods have advantages and disadvantages, requiring careful consideration by the engineers.
For landers that are even heavier than the Curiosity rover (which required a 4.5 meter (15 feet) diameter aeroshell), engineers are developing a combination rigid-inflatable Low-Density Supersonic Decelerator that could be 8 meters (28 feet) in diameter. It would have to be accompanied by a proportionately larger parachute.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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