The premise of Stowaway, a new movie from Netflix, as shown in the teasers: a crew of three leaves for a two-year mission to Mars, and after departure discover an injured worker from the launch pad onboard -- not really a stowaway in that he didn't plan for this, but there he is. But the safety margins don't account for an extra person.
I immediately thought of "The Cold Equations", a classic SF short story. It seemed clear that there could not be a happy ending, but I was curious which of the several possible outcomes we'd get. IMO they chose the wrong one.
The trio consists of the captain (Marina) and two younger researchers who've gotten their Mars-dependent research projects approved. Zoe is a medical researcher and David is a biologist trying to cultivate algae on Mars. The accidental fourth is Michael, who's designed to tug all the right heartstrings: pursuing an engineering degree while working to support his younger sister (no other family), hard worker, personable.
Marina is a seasoned captain and is on what's planned to be her last mission. In case you're wondering how a seasoned captain could miss the extra weight, especially when they've been given very small weight allowances for personal effects, it's addressed plausibly.
Zoe is caring and compassionate. We also see her medical knowledge play important roles twice early on -- treating Michael's critical injuries from the accident that caused him to be unconscious on the ship during takeoff, and also treating the captain's broken arm.
David, on the other hand, is so focused on his research that when the captain asks him to activate some of his algae samples to filter carbon dioxide from their air so they don't all die, he objects because it will waste years of his work. Yes, that sucks and I'd expect him to be upset, and he's not career space crew with the corresponding training, but it still left me disliking him.
David lost more points with me by trying to take matters into his own hands to get rid of Michael. Presumably even those who aren't career space crew, as condition of being on the ship, have been thoroughly drilled in things like chain of command. It's a short chain in this case.
There are setbacks and the crew tries everything they can to mitigate them, but it's clear to all that four people will not arrive alive on Mars. There's some sort of Plot Reason that I didn't understand about why they can't turn back, but they can't. So they have to deal with this and obviously there is not going to be a happy ending for all four of them.
There could have been a redemption arc where David steps up. This is the outcome I was hoping for. Instead, we arguably got the worst possible outcome, from a dispassionate perspective of trying to maximize survival chances. If it wasn't going to be David, there was another obvious candidate other than what happened, and it's not even as cold as those equations.
(I'm not trying to completely spoil it here even behind a spoiler warning, but I make no promises about what happens in comments if you click through to the original post.)