Hermes makes a 124 day trajectory from Low Earth Orbit to Low Mars Orbit. This orbit is implausible. There seems to be some confusion about the departure orbit. Some have argued there were hyperbolic fly bys of Earth and Mars. But these fly bys take place in the latter part of the story. The 124 day trajectory takes place prior to Watney getting stranded. [1:15 of Neil Degrasse Tyson's trailer][1] has Hermes departing from low earth orbit. Departure from LEO is also in the [movie's backstory][2]. > Crew readies for transport via traditional shuttle launch to > rendezvous with the main vessel harbored in low orbit. In addition here's a graphic from [Inside Science][3] (thank you Pearson Art Photo). I underlined the relevant phrase. [![enter image description here][4]][4] About 6 days after Mars arrival a windstorm hits and most the crew leaves. They ascend in a MAV to rendezvous with the Hermes. Later in the story Weir says MAVs are ordinarily designed to deliver a 4.1 km/s delta V budget. To stick around Mars for 6 days and rendezvous the MAV, Hermes had to enter Low Mars Orbit. This establishes that Hermes did indeed leave Low Earth Orbit and arrived at Low Mars Orbit. Now here is what is wrong with the trajectory... Weir has said in several places Hermes can accelerate at 2 mm/s^2. With this sort of acceleration it would take Hermes more than a month to spiral out of earth's gravity well (most of that slow spiral would be through the Van Allen belts). See [General guidelines for modeling a low thrust ion spiral][5] For similar reasons it would take Hermes a week or two to spiral down to low Mars orbit. That leaves 80 days to go from an one A.U. heliocentric orbit to a 1.52 A.U. heliocentric orbit. Which couldn't be done with 2 mm/s^2. Another unrealistic part is the wind storm. Since Mars atmosphere is near vacuum, the high winds would not threaten to topple the MAV. Weir has fessed up to this error. [1]: http://www.youtube.com/watch?v=-fdKyszL1Zo&t=1m15s [2]: http://s3.foxfilm.com/foxmovies/dev/films/108/assets/ares-mission-guide.pdf.zip-1442438953.zip [3]: https://www.insidescience.org/content/inside-spaceflight-martian/3251 [4]: https://i.stack.imgur.com/l69dr.png [5]: http://space.stackexchange.com/questions/8420/general-guidelines-for-modeling-a-low-thrust-ion-spiral