Doc

Factual error: Prior to and during the orbital rendezvous rescue scene, the dialog states that a) the capsule with Watney is on a parabolic trajectory and will drop back to Mars b) the Hermes is on a swing-by trajectory that will carry it past mars c) the Hermes doesn't have the fuel to spare to do more than swing-by, i.e. They can't brake enough to even enter an orbit (yes, when one is on a fly-by, one has to brake to get into an orbit. Watney would be way slower still) d) the relative speed of the spaceships at the time of rendezvous is less than 20 m/s e) the spaceships are at a distance of less than 200m. All those statements can't be true at the same time. What orbit you are on is pretty much defined by your altitude and speed. If the speed and altitude of two spacecraft are the same, they are on the same (general shape of) orbit. Conversely, if they are on the same altitude but one is on a suborbital trajectory and one doing a swing-by, the latter is faster than the former by hundreds, if not thousands of m/s. By comparison, the rendezvous depicted in that scene would be like granny with her walker trying to "rendezvous" with an Amtrak train at full speed.The dialog states explicitly that the Hermes can't brake into orbit of Mars to pick up Watney because it doesn't have the necessary reaction mass to do that and get home too. If they can't even brake into orbit, they can brake to match Watney's speed even less. Even without that dialog, it wouldn't make sense either way. The acceleration required to do that would be measured in thousands of m/s. Translated into fuel, that would be dozens, if not hundreds of tons. No spacecraft this side of complete science fiction carries that much spare fuel, for the simple reason that lofting the extra weight to orbit would be prohibitively expensive.

Doc ★