Earth to Mars

Earth to Mars Human Travel. The complexity of Space Travel

The most complex part for the human to reach Mars is the energy needed for transfer between planetary orbits or delta-v, The energy is lowest at intervals fixed by the synodic period. For Earth-Mars travel, the period happens every 26 months, That's why missions are typically planned to coincide with one of these launch periods. Due to the eccentricity of Mars's orbit, the energy needed in the low-energy periods varies on roughly a 15-year cycle with the easiest periods needing only half the energy of the peaks. In the 20th century, a minimum existed in the 1969 and 1971 launch periods and another low in 1986 and 1988, then the cycle repeated. The next low-energy launch period occurs in 2033.

Different types of mission plans have been proposed and planned, including opposition class and conjunction class, or the Crocco flyby. The less energy transfer to Mars is a Hohmann transfer orbit, which would involve a nearly 9-month travel time from Earth to Mars, about 500 days at Mars to wait for the transfer window to Earth, and a travel time of about 9 months to return to Earth. This would be a 34-month trip.

Quicker Mars mission plans have round-trip flight times of 400 to 450 days, or under 15 months, but would require significantly higher energy. A fast Mars mission of 245 days (8.0 months) round trip could be possible with on-orbit staging. 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 crewed spacecraft would get a flyby of Mars and Venus in under a year in space. Some flyby mission architectures can also be extended to include a style of Mars landing with a flyby excursion lander spacecraft. Proposed by R. Titus in 1966, it involved a short-stay lander-ascent vehicle that would separate from a "parent" Earth-Mars transfer craft before its flyby of Mars. The Ascent-Descent lander would arrive sooner and either go into orbit around Mars or land and, depending on the design, offer perhaps 10–30 days before it needed to launch itself back to the main transfer vehicle.

During 1980s, it was suggested that aerobraking at Mars could reduce the mass required for a human Mars mission lifting off from Earth by as much as half. As a result, Mars missions have designed interplanetary spacecraft and landers capable of aerobraking.

In near future SpaceX starship will be capable of traveling faster and reducing the journey time.