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A human mission to Mars has been the subject of science fiction, engineering, and scientific proposals throughout the 20th century and into the 21st century. The plans comprise proposals to land on Mars, eventually settling on and terraforming the planet, while utilizing its moons, Phobos and Deimos. Exploration of Mars has been a goal of national space programs for decades. Preliminary work for missions that would involve human explorers has been undertaken since the 1950s, with planned missions typically being cited as taking place 10 to 30 years in the future when they are drafted. The list of manned Mars mission plans in the 20th century shows the various mission proposals that have been put forth by multiple organizations and space agencies in this field of space exploration. Nonetheless, a human mission to Mars has been criticized for minimizing the "harsh realities and bitter truths that underlie the dream". In terms of the current U.S. space program, NASA's long-term program Orion has a projected pace of development such that, as of late 2014, human spaceflight to Mars is anticipated in about 2035. That mission will be preceded by shorter flights for the up to four-person capsule involved, with experiments taking place to better the technologies protecting Mars-bound astronauts from the radiation of deep space. In October 2015, NASA presented the next steps in the effort in more detail, as well as a related health hazards report. In fiction, the concept of humans traveling to and terraforming Mars has been explored in books, graphic novels, and films. Examples include: Kim Stanley Robinson's ''Mars'' trilogy, ''Mission to Mars'' (2000 film), ''Red Planet'' (2000 film), ''Robinson Crusoe on Mars'' (1964 film), ''The Martian'' (2015 film and 2011 book) and ''Total Recall'' (1990 film). The appeal of space-travel to the planet is a major aspect to Mars in fiction. ==Travel to Mars== The energy needed for transfer between planetary orbits is lowest at intervals fixed by the synodic period. For Earth / Mars trips, this is every 26 months (2 years and 2 months),〔 so missions are typically planned to coincide with one of these launch windows. The energy needed in the low-energy windows varies on roughly a 15-year cycle〔 with the easiest windows needing only half the energy of the peaks.〔Page 18-19 in Chapter 3 of David S. F. Portree's ''Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000,'' NASA Monographs in Aerospace History Series, Number 21, February 2001. Available as (NASA SP-2001-4521 ).〕 In the 20th century, there was a minimum in the 1969 and 1971 launch windows and another low in 1986 and 1988, then the cycle repeated.〔 Several types of mission plans have been proposed, such as the opposition class and conjunction class,〔 or the Crocco flyby.〔Page 15-16 in Chapter 3 of David S. F. Portree's ''Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000,'' NASA Monographs in Aerospace History Series, Number 21, February 2001. Available as (NASA SP-2001-4521 ).〕 However, typical Mars mission plans have round-trip flight times of 400 to 450 days.〔(【引用サイトリンク】title=Popular Science )〕 A fast Mars mission of 245 days round trip could be possible with on-orbit staging.〔(Folta, et al. - FAST MARS TRANSFERS THROUGH ON-ORBIT STAGING. (2012) )〕 Using Hohmann transfer orbits is a common plan. In 2014 Ballistic capture was proposed, which may reduce fuel cost and provide more flexible launch windows compared to the Hohmann. In the Crocco grand tour, a "humanned" spacecraft would get a flyby of Mars and Venus for under a year in space.〔(The Gaetano A. Crocco's grand tour goes on by Luisa Spairani )〕 Some flyby mission architectures can also be extended to include a style of Mars landing with a flyby excursion lander spacecraft.〔(WIRED - To Mars by Flyby Excursion Mode )〕 Proposed by R. Titus in 1966, it involved extending a flyby mission with a short stay lander.〔 Basically, a short stay lander-ascent vehicle would separate from a "parent" Earth-Mars transfer prior to its flyby of Mars.〔 The Ascent-Decent lander would arrive sooner and either go into orbit around Mars are land, and depending on the design offer perhaps 10–30 days before it needed to launch itself back to the main transfer vehicle.〔 (see also Mars flyby) 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「Human mission to Mars」の詳細全文を読む スポンサード リンク
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