* I'm glad others brought up the wind-storm problem. That was a Large Helping Of Suspended Belief there, for me.
I had the opportunity to hear Andy Weir give a lunchtime talk at Google LA last month, and he addressed this pretty clearly. He had some alternative realistic scenarios for getting Watney stranded on Mars, but they felt too contrived and arbitrary to him, so it was a conscious decision to go for the more visceral and less realistic scenario of the windstorm. Perhaps he could have had the MAV positioned on unstable tilted terrain, where 175kph wind could actually blow it over, or undermine the sand under its landing legs.
Andy actually said that the LEAST realistic part of the entire book, in his opinion, was the supposition that NASA would actually fund something as staggeringly expensive as HERMES
The drama around the MAV intercept at the end was also, as others have pointed out, completely unnecessary; HERMES' ion engines would have allowed it to create its own additional intercepts a few hours later. This plot hole could have been easily worked around by giving Watney a more limited air supply, for instance. Or there could even have been an impending solar storm, to make time of the essence.
I haven't even seen the movie yet... very much looking forward to it. Even if there are some bones to pick, I think Andy did a truly amazing job.
Thanks for those details!
However, I don't understand how the Hermes could have "created its on additional intercepts a few hours later" (in fact I don't quite understand the sentence). From the book and my other readings about ion thrust engines in reality my understanding is that acceleration/deceleration using these kinds of engines is a very slow process, hence they had to plot a new course a very long time before returning to mars, missing the earth, swinging around (gravity assist), going back to Mars, swing around Mars (gravity assist) then back to earth. Now I don't believe there is any plausible way they could have used the ion thrusters to quickly change that and swing around Mars twice for example? Also Watney in the MAV would keep going at a constant pace away from Mars after he got away from it's gravitational field, right? Or maybe he just got himself in to some kind of high orbit? Anyway, I think that if they didn't intercept with him on the first attempt it would have taken them weeks or months to get another attempt, right?
The important thing to note is that both the MAV and HERMES are already on nearly-identical escape-velocity trajectories back to Earth. The MAV is not in Mars orbit. The difference between orbiting mars and escaping mars is about 1500 m/s; the velocity difference between the MAV and HERMES (before any course-correction) is only 11 m/s. That's nothing.
At 2mm/s^2, the HERMES' ion engines could correct those 11 m/s in about 90 minutes, and close their 67km gap in about 6 hours. (accelerating for the first half, decelerating for the second half). In the novel, HERMES uses 75% of its attitude-thruster fuel to give it a quick boost toward Watney's trajectory, where they will intercept him much sooner but at 42 m/s. It would have been better to use half that fuel to boost towards an intercept a couple hours later, and the other half to slow down when they get there. (with ion engines assisting all along.) The moment of closest approach of their original trajectories is irrelevant; the book treats it as if that moment is make-or-break. Better to make a different trajectory (for HERMES) to intercept at a later moment, at a tamer relative speed.
Of course, if Watney only has 1 hour of air in his EVA suit, then the drama is necessary to create the intercept ASAP. But I don't think the book mentions this. NASA's current spacesuits allow for 6-8 hour EVA's, plenty of time to allow for a less-dramatic and safer intercept in the Martian scenario.
I would agree. I wasn't as impressed by it as everyone else seemed to be. They didn't explain things very well (he was shown planting an entire potato to get back one potato plant. What's the point in that?). They made passing reference to using math, but never actually showed anyone even mentally calculating anything, or even writing down some numbers (other than counting things - is that the highest level of math they were comfortable showing, counting?). They spent too long in the beginning showing his despair, and not enough showing how he problem solved. Jeff Daniels was boring as the NASA administrator.
The ending was silly. The chemical bomb was thrown together in 10 minutes yet somehow managed to have a timer, beeping lights and a beeper? The ironman thing was ridiculous, and will someone please tell directors about the conservation of angular momentum? The movie Gravity had the same problem. When things are spinning around each other, they don't magically stop spinning unless you give a countervailing force.
The zero G sequences mostly weren't believable. Every time they had to turn, they just ... turned, without somehow canceling out their forward momentum.