Human Missions to Mars - Research Article from Macmillan Science Library: Space Sciences

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Mission Planning

Much of the mission planning for human exploration missions deals with finding appropriate trajectories for the trips out to Mars and back to Earth. Earth revolves around the Sun about twice as fast as Mars does. A spacecraft launched from Earth must "lead" Mars, aiming at the place where that planet will be in 5 to 9 months. Opportunities to do this only occur at 26-month intervals. By the time a spacecraft arrives at Mars, Earth has moved and it is necessary to wait for a similar leading trajectory opportunity from Mars to Earth. Trajectory options exist for long travel times (9 months) and short stay times (30 to 60 days) on Mars or somewhat shorter travel times (5 to 8 months) and long stay times (500 days). A total round trip requires 21 to 36 months. It is possible to shorten the transit time by increasing the velocity with which the spacecraft leaves...

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This section contains 1,172 words
(approx. 4 pages at 300 words per page)
Buy the Human Missions to Mars Encyclopedia Article
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Macmillan Science Library: Space Sciences
Human Missions to Mars from Macmillan Science Library: Space Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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