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Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...
The diagram shows a Hohmann transfer orbit to bring a spacecraft from a lower circular orbit into a higher one. It is an elliptic orbit that is tangential both to the lower circular orbit the spacecraft is to leave (cyan, labeled 1 on diagram) and the higher circular orbit that it is to reach (red, labeled 3 on diagram).
The launch vehicle's delta-v needed to achieve low Earth orbit starts around 9.4 km/s (5.8 mi/s). The pull of gravity in LEO is only slightly less than on the Earth's surface. This is because the distance to LEO from the Earth's surface is much less than the Earth's radius.
It takes 250 days (0.68 years) in the transit to Mars, and in the case of a free-return style abort without the use of propulsion at Mars, 1.5 years to get back to Earth, at a total delta-v requirement of 3.34 km/s. Zubrin advocates a slightly faster transfer, that takes only 180 days to Mars, but 2 years back to Earth in case of an abort.
For Earth this means a period of just under 12 hours at an altitude of approximately 20,200 km (12,544.2 miles) if the orbit is circular. [16] Molniya orbit: A semi-synchronous variation of a Tundra orbit. For Earth this means an orbital period of just under 12 hours. Such a satellite spends most of its time over two designated areas of the ...
The lowest energy transfer to Mars is a Hohmann transfer orbit, a conjunction class mission which would involve a roughly 9-month travel time from Earth to Mars, about 500 days (16 mo) [citation needed] at Mars to wait for the transfer window to Earth, and a travel time of about 9 months to return to Earth. [9] [10] This would be a 34-month trip.
When the central body's mass is much larger than the spacecraft, and other bodies are sufficiently far away, the solution of orbital trajectories can be treated as a two-body problem. [9] This can be shown to result in the trajectory being ideally a conic section (circle, ellipse, parabola or hyperbola) [10] with the central body located at one ...
A spacecraft traveling from Earth to Mars via this method will arrive near Mars orbit in approximately 8.5 months, but because the orbital velocity is greater when closer to the center of mass (i.e. the Sun) and slower when farther from the center, the spacecraft will be traveling quite slowly and a small application of thrust is all that is ...