Mars mission duration

Conjunction and opposition mission trajectory.

Manned missions to Mars split in two different types. They are named after astronomical names of the moments of departure of the ships from Mars: conjunction and opposition. Opposition type mission have less total time but more time spent travel in weightless conditions, conjunction mission have much more time spent in Mars surface. Сonjunction and opposite mission type examples:

Mission type	Total mission duration, days	Earth-Mars trip, days	Time spent at destination	Mars-Earth trip, days	Total ∆V, km/s	Trans-Mars Injection, km/s	Mars Orbital Insertion, km/s	Trans-Earth Injection, km/s
Conjuction	1005	198	558	197	2.81	0.50	1.25	1.06
Opposition	560	177	40	342	5.69	0.61	1.75	3.33

Conjunction and opposition Mars mission duration comparison.

Mars have very elliptical orbit relatively to Earth. The eccentricity of the orbit of Mars is 0.0935 – second among the planets after Mercury. Launch windows to Mars opened approximately every 2.14 years (26 months) but because of Mars orbit eccentricity and differences in his orbital speed this time changes a little bit from time. The same way changes a distance between Earth and Mars in moment of oppositions, time travel to Mars and necessary for this delva-V.

Mars Oppositions from 1995 to 2007 year

The required parameters change at intervals of 15-17 years.

Mars oppositions from 2012 to 2061 year.

Examples of the near-future missions opportunities:

Mars short-stay (opposition) mission

Departure Date	Mission Duration (years)	Time spent at destination	Injection (C3/∆v), km/s	Post-escape ∆v, km/s	Destination Aerocapture (∆V/Inertial), km/s	Earth Aerocapture (∆V/Inertial), km/s
19-Jul-2020	1.50	1 month	14.5/3.87	2.80	1.41/6.2	0.86/11.8
22-Oct-2021	1.39	1 month	14.4/3.86	2.80	3.48/8.2	0.47/11.4
14-Sep-2023	1.64	1 month	25.7/4.34	0.99	3.29/8.0	0.48/11.4

Mars long-stay (conjunction) mission

Departure Date	Mission Duration (years)	Time spent at destination	Injection (C3/∆v), km/s	Post-escape ∆v, km/s	Destination Aerocapture (∆V/Inertial), km/s	Earth Aerocapture (∆V/Inertial), km/s
4-Aug-2020	2.53	1.40 years	15.7/3.92	1.45	0.70/5.5	0.80/11.7
15-Sep-2022	2.63	0.85 years	14.4/3.86	0.94	0.88/5.6	0.50/11.4
14-Oct-2024	2.62	0.87 years	12.1/3.76	0.82	0.73/5.5	0.58/11.5

For reducing crew time exposure to weightless, interplanetary radiation and the risk of being hit by solar flare it is possible to use increasing delta-V. For some of these variants it is possible to use the option of free-return trajectory - trajectory with ability return back to Earth with small amount of delta-V spending safe if the main spacecraft engine will fail to start. Options for free-return trajectories:

Departure Velocity, km/s	Orbit Period, years	Time to Earth Return, years	Transit to Mars, days	Mars Aeroentry possibility
3.34	1.5	3.0	250	Easy
5.08	2.0	2.0	180	Acceptable
6.93	3.0	3.0	140	Dangerous
7.93	4.0	4.0	130	Impossible