The Martian - November 2015 - Starring Matt Damon

[TimothyC]

See the rational part of my brain understands that, but it's also thinking "surely someone thought about this in the planning stages." They're already committed to building Hermes, which must have taken a lot of effort, and since said vehicle only has to to round trips from Earth to Mars, I see no reason why the requisite fuel could be carried, a heavier MAV taken. So Hermes herself needs more fuel, she already has a continual-thrust engine of some kind with a lot of delta-V. Surely it can't be that hard.

The MAV isn't delivered via Hermes. The MAV is launched on a conventional Hohmann trajectory that takes about 50-75% longer than the Hermes can do the run in.

[Eternal_Freedom]

Yes I know that. Do you have something to add beyond nitpicking that point? An explanation for how they landed on the surface for instance?

[jwl]

I haven't seen the movie yet, but I've read the book, and because its gimmick is the accurate science, I have to ask, did they fix the glaring error with the stoichiometry and turning liquid oxygen into liquid water? In the book, one of the most glaring errors that took me completely out of the story was Watney saying that 125 L of liquid oxygen would make 250 L of liquid water, which isn't true because their densities are different.

[cutting that horribly artifacted image]

Even assuming that the oxygen will react completely to make water, Watney only gets about 1.28 L of water for every 1 L of liquid oxygen. I don't know, for a book that claims to be scientifically accurate, that one part just completely ripped me from the story, and I want to know if the error was ever fixed for the movie.

They don't go into *that* much science in the movie, probably as a concession to largely non-nerdy movie watchers. His trick for getting water is mostly 'burn hydrazine, get blown up, burn less hydrazine, see the dew form'.

He doesn't burn the hydrazine directly, he turns it to hydrogen and burns that. I don't know much about hydrazine combustion, but I imagine burning it directly might create a load of nitrous oxides his oxygenater would struggle to deal with.

[TimothyC]

Yes I know that. Do you have something to add beyond nitpicking that point? An explanation for how they landed on the surface for instance?

It's Mars Direct. You fly it into a parking orbit, and you use parachutes and methane (Methane has the advantage that it is only semicryogenic and thus can be stored for long periods in space - just like LOX) in the tanks to land it on the surface. Control for the descent is done by the prior crew (The Ares 3 crew landed the Ares 4 MAV) when they get to Mars orbit. That's how Whatney knew the Ares 4 MAV was on the surface and where it was.

[Q99]

Hm, I'm trying to picture doing a survival story somewhere else in the solar system like, say, Europa, but I'm having trouble picturing how it'd be done... it'll be tricky to do Martian-esque stories in real locations.

Now, fictional star systems could be doable.

[Adam Reynolds]

With regard to the issue of Mark being left behind, I wonder if this is a problem for those who just saw the movie because we see him being left behind. In the book, the opening chapter is him being left on Mars. We don't see the events that caused this scenario until chapter 12. So we start off with Mark left behind and thus don't question the idea when it occurs later.

Hm, I'm trying to picture doing a survival story somewhere else in the solar system like, say, Europa, but I'm having trouble picturing how it'd be done... it'll be tricky to do Martian-esque stories in real locations.

Now, fictional star systems could be doable.

Mars is unique in that it is inhabitable but that it offers the ingredients for life. What I would suggest for most other locations is a much shorter duration. Something I thought would be interesting would be a much shorter trip in which the entirety of the survival situation takes place with the character wearing a spacesuit.

Something akin to this scenario from Kerbal:

[Zaune]

Yes I know that. Do you have something to add beyond nitpicking that point? An explanation for how they landed on the surface for instance?

This is probably one of those bits of exposition that got left out of the film for pacing purposes. The Ares crew took a one-use Mars Descent Vehicle to the surface that consisted of a cabin with enough life-support to last a few hours, some braking thrusters and a parachute.