O MAV foi modificado
Watney removeu o excesso de peso do MAV para conseguir ir rápido o suficiente. Na primeira parte do filme, presumivelmente não precisou escapar da gravidade de Marte:
It might be a wasted effort. The MAV isn't going to have much weight allowance when I launch. To intercept Hermes, it'll have to reach escape velocity, but it was only designed to get to orbit. The only way to get it going fast enough is to lose a lot of weight.
—The Martian
Além disso:
“Suffice it to say, ” Venkat interrupted, “It would be very difficult and dangerous. But we have a lot of clever scientists to help him trick out the rover. Also there would be MAV modifications.”
“What's wrong with the MAV?” Mitch asked.
“It's designed to get to low Mars orbit, ” Venkat explained. “But Hermes would be on a flyby, so the MAV would have to escape Mars gravity entirely to intercept.”
“How?” Mitch asked.
“It'd have to lose weight... a lot of weight. I can get rooms full of people working on these problems if we decide to do this.”
—The Martian
É especificamente mencionado que o MAV modificado sofrerá forças severas:
“He might be in bad shape when I get him, ” Beck said. “The stripped down MAV will get up to 12 g's during the launch. He could be unconscious and may even have internal bleeding.”
—The Martian
A razão pela qual o Hermes não pôde entrar em órbita (como presumivelmente havia feito antes) foi devido às demandas de combustível. Do script do filme :
MITCH: The problem is the intercept velocity. The Hermes cannot enter Mars orbit, or they’ll never have enough fuel to make it home. The MAV is only designed to get to Low Mars Orbit. So in order for Mark to escape Mars’ gravity entirely and intercept the Hermes...