Cold Equation

Everything About Fiction You Never Wanted to Know.

A spaceship has been damaged and is Almost Out of Oxygen (or food or fuel). But then someone calculates that if they had one less crewmember, they just might make it back safely...

Can also apply to circumstances outside of Science Fiction. Such incidents have even happened in real life, involving sailors in lifeboats running out of food or freeboard. These seldom involved any fine calculations, just desperate people willing to do anything to live a bit longer. Those who travel on spaceships are presumed to be a different breed, or perhaps they're just more educated; therefore expect a Lottery of Doom or Heroic Sacrifice.

See also No Party Like a Donner Party.

Note: Please do not include discussions on the short story The Cold Equations on this page. Post them on the page for that story.

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Cold Equation include:

Anime & Manga

  • In the second season of Vandread, The Stoic Meia has to take care of Ezra's baby daughter when a space battle breaks out and in the confusion, they accidentally launch in an escape pod. When oxygen begins to run out, Meia has no choice but to throw herself out of the airlock (with a smile, no less) to make sure Karu lasts until the pod is picked up by Nirvana. It turns out, the pod has just been picked up, and Meia didn't notice until she walked out.
  • Lampshaded in the Martian Successor Nadesico episode "The Lukewarm 'Cold Equation'", where Anti-Hero Akito gets stranded without fuel after piloting his Humongous Mecha out of range of the Cool Starship, and the two leading contenders in the Love Dodecahedron get stranded with him when their rescue attempts fail due to enemy attacks. Akito ejects the mecha's limbs to get it moving, but the oxygen issue comes up again. Akito finally decides to Take a Third Option before they discover that they'd drifted back in range of their starship.
  • Subverted in Planetes, where the exact situation comes up. The testees are placed in a situation where they do not have enough oxygen to outlast the test, either they give up or kill someone to preserve the oxygen they have. Instead, they lower the temperature of the room to reduce their metabolism and oxygen consumption.
    • Also Ai debating whether to steal a terrorists' air tank to save herself.
      • Ultimately, is unable to bring herself to steal the air tank and begins suffocating. She suffers enough neurological damage from the oxygen-deprivation before they're rescued that she is left in a wheelchair, though it's suggested that she may recover with time and physical therapy.

Comic Books

  • It is alleged that Godwin (author of "The Cold Equations") essentially took the story from a story published in EC Comics' Weird Science #13, May–June 1952, called "A Weighty Decision," scripted by Al Feldstein. In that story there are three astronauts who are intended to be on the flight, not one, and the additional passenger, a girl that one of the astronauts has fallen in love with, is trapped aboard by a mistake rather than stowing away. As in "The Cold Equations", various measures are proposed but the only one which will not lead to worse disaster is for the unwitting passenger to be jettisoned. Other sources note that the theme of Feldstein's story is itself strikingly similarly to the story "Precedent", published by E.C. Tubb in 1949; in that story, as in the others, a stowaway must be ejected from a spaceship because the fuel aboard is only enough for the planned passengers. These sources argue that neither Feldstein nor Godwin intentionally "swiped" from the stories that came before, but merely produced similar variations on an ancient theme, that of an individual being sacrificed so that the rest may survive.
  • In the Tintin comic album Explorers on the Moon, when Thompson and Thomson turn up as stowaways on the Moon-Rocket, Calculus worries that, since oxygen supplies were assessed for only four people, there might not be enough for six. It gets worse when Colonel Jorgen is revealed to have smuggled himself on board, with the help of The Mole. He intends to maroon Tintin and his companions on the surface of the Moon, pointing out that they don't have enough oxygen to bring prisoners back to Earth. Later when the villains are overpowered, Tintin refuses to leave them behind despite having exactly the same problem. After Jorgen is killed in a Gun Struggle, Wolff decides to atone for his actions by stepping out the airlock. Even so Tintin and his companions almost don't make it back to Earth.
  • Rick Random: Space Detective, a comic of the 1950's. In "Kidnappers from Mars!" Space Pirates get their vessel caught in a 'space tide' and realise the only means of escape is the two-man shuttle. The Big Bad and his Femme Fatale girlfriend hide until all the other pirates have killed each other fighting over the shuttle, then take off in it.
  • Twisted for a XXXenophile story. The bomb shelter will only hold two, and the female character tells her two male companions that if she has to repopulate the Earth she wants to enjoy herself doing it, so "auditions" are now in order. World War III did not just break out, she said it had as an excuse for threesome sex.
  • Echoed and possibly referenced by Mark Verheiden and Mark A. Nelson's follow-on graphic novel set ten years after Aliens. Hicks smuggles Newt aboard a weight-critical ("gravity-balanced") ship on its way to the alien homeworld. The situation is averted on this occasion, as he took pains to dump stores equivalent to her weight before takeoff.


  • Woman in the Moon (1929). After a struggle punctures the oxygen tank, the two male crewmembers draw straws to see who gets to return to Earth on the rocket. The Dirty Coward gets the short straw and breaks down sobbing, so the hero makes the Heroic Sacrifice and stays behind on the Moon instead.
  • Destination Moon (1950). The rocketship loses reaction mass landing on the moon, so someone has to stay behind even after they've thrown out every piece of equipment they can unbolt. While the Campbellian Heroes are arguing over who gets to make the Heroic Sacrifice, the Plucky Comic Relief sneaks outside and laconially tells the others to take off without him. Fortunately someone realises how to dispose of an extra piece of equipment so they can all return safely.
  • Alien (1979). After the xenomorph does some snacking, there are four crew members left.

Lambert: "I say that we abandon this ship. We get the shuttle and just get the hell out of here; we take our chances and hope that somebody picks us up!"
Ripley: "Lambert, the shuttle won't take four."
Lambert: "Well why don't we draw straws then--"
Parker: "I'm not drawing any straws. I'm for killing that goddamned thing right now."

  • Starflight One (1983). Disaster movie involving a hypersonic passenger plane that gets stuck in orbit. Most of the passengers are successfully evacuated and the crew intends to try and achieve reentry, but they're running out of oxygen (the plane is only meant to pass through space for a short time before returning to Earth). A Corrupt Corporate Executive on the ground half-heartedly suggests that if there were a couple less passengers... whereupon the pilot retorts that if he survives this experience there's going to be one less executive.
  • Lifepod (1993), set in an escape pod ejected from a sabotaged spaceship with limited air, food and water. Stating that their odds of survival would increase if one of them dies, a blind passenger tries to cut his wrists. He's actually the saboteur, and did it knowing the others would stop him.
  • Sunshine (2007). Icarus II is damaged on its mission to reignite the sun, but the crew realise they can still get there if one of them dies. A scientist who's lapsed into depression after indirectly causing the death of The Captain is an obvious candidate. All but one of the crew vote to kill him (their mission is, after all, to save the entire human race) only to find he's already killed himself. Or he was killed by a stowaway whose presence makes the whole question moot.
    • Also when there's only one spacesuit to cross back to the Icarus—the other crewmen immediately start putting Capa (the only man who can fire the bomb) into the suit, ignoring the protests of their commander.
  • Marooned (1969 -- made before the Apollo 13 disaster). The crew of an Apollo mission is left stranded in orbit with no means to re-enter earth and a dwindling oxygen supply. Both an emergency rescue mission and a passing cosmonaut eventually help the crew, but not before the mission's commander decides to sacrifice himself.
  • This is evoked at one point in Red Planet, and one of the three still-alive crewmen decides to try and reach the old Russian module alone. The second crewman later dies protecting the third one.
  • Played for Laughs in Chitty Chitty Bang Bang, when the crew of Baron Bomburst's airship have to jettison excess weight in order to carry Grandpa's hut back to Vulgaria. (This occurs during Grandpa's song "Posh!".) After exhausting everything not critical to the airship's function, they toss the two spies overboard. (Non-fatally -- the spies manage to swim back to Vulgaria just in time to see the Baron overthrown.)


  • The Trope Namer is of course The Cold Equations, the classic 1954 sci-fi short by Tom Godwin famous for averting the Always Save the Girl trope. A young girl stows away on a shuttle carrying vital medicine to a planetary colony, not knowing that its fuel has been precisely calculated and her extra weight is enough to cause disaster.
  • Arthur C. Clarke's excellent short story "Breaking Strain" is about a spaceship with only two astronauts that is running out of oxygen. It follows one of the character's thoughts as he becomes more and more tempted to murder his companion. It has two different Adaptation Expansions: the novel Venus Prime 1: Breaking Strain, and the film Trapped in Space (which expands the crew to six people and has a more And Then There Were None kind of plot with successive murders).
  • The Engines of God by Jack McDevitt. Hutch is piloting a spaceship which crashes into an alien artifact, shutting down their fusion engine. The spaceship starts to lose heat (so much that it starts snowing inside) and the oxygen pumps fail, leaving them with only a week's worth of air in the shuttle and the nearest rescue ship ten days away. A Lottery of Doom is half-heartedly suggested, but Hutch tells everyone to sleep on it, then sneaks out with the intention of committing suicide (as pilot it's her responsibility to ensure the safety of the others). At the last moment Hutch realises all they have to do is melt the 'snow' (actually frozen atmosphere) to get the needed oxygen. Later on another pilot is looking at his shuttle—named after a pilot who famously performed a similar sacrifice—and bemoans the fact that such exciting heroics don't happen now that spaceflight has become routine and safe.
  • Stanislaw Lem played with this scenario in Moon night. And an entirely sensible punchline turned it into great Black Comedy.
  • The Dragonriders of Pern story Rescue Run had this problem turn up when the rescued colonists try to smuggle in several hundred kilos of precious metals (Which turned out to be less valuable than the homemade medicines they packed legitimately), throwing the mass calculations off. Instead of spacing people, the crew spaces the metal, along with some furniture.
  • In Down To A Sunless Sea by David Graham, at one point the narrator's Boeing and his new girlfriend's Antonov are fleeing to Antarctica to escape the nuclear devastation of the entire civilised world. Unfortunately, they run into heavy cloud which is lethally contaminated with fallout, and the Antonov doesn't have the fuel to make the trip at the higher altitude required to clear the fallout. So the Russian co-pilot calls for volunteers and opens the Anti's cargo doors, and leads a procession of about one-third of the passengers on the long drop into oblivion. In some editions of the book, it turns out that they were the lucky ones when all was said and done.
  • Invoked in Frederik Pohl's Gateway. It's one of the many occupational hazards of space travel when all your ships are alien craft with preset trips of unknown length.
  • A non-space example shows up in The Book of Questions, a book with scenarios with no clear-cut answer intended to provoke thought. It involves getting trapped in a cave-in with another miner. You have a gun with two bullets and sleeping pills. You know that there is only enough air for one sleeping person to survive for six hours and it's likely to take at least six for the rescuers to reach you. After agreeing to that conclusion, the other miner takes the sleeping pills, hands you the gun, and says it's your decision.
  • Subverted in Starquake, the sequel to Dragons Egg. When the crew of a starship discover they'll be stuck in orbit for six months, with an insufficient food supply, The Spock of the group calculates that they'll need to kill and eat two crewmembers to survive. Then she points out that they'd never feel at place again among humans if they did, and suggests they accept death with dignity instead. They are later rescued by the Cheela, who are by then a Higher-Tech Species with few of our limitations.

Live Action TV

  • Star Trek: Enterprise ("Shuttlepod One"). Trip Tucker and Malcolm Reed are stranded on a shuttle, and Tucker decides to throw himself out the airlock to give his companion more time, only to be ordered back at phaser-point by Reed.
    • Sci Fi Debris really tore that "Shuttlecraft One" episode a new one, because Trip doing that was when there was the most hope for a rescue, not the least hope.
  • Star Trek: The Original Series episode "The Galileo Seven". When the shuttlecraft Galileo crash lands on a planet, it loses so much fuel that it can't even reach stable orbit unless they lighten their load by 500 lbs. It's immediately pointed out that 500 lbs. is the weight of three men. Two of the crew die while on the planet, and they eventually take off and achieve orbit. Unfortunately they had to use the boosters to do so, so they're guaranteed to burn up on re-entry.
    • Another Star Trek: TOS episode "The Conscience of the King" had this, not in a space ship but on a planet. Kodos "the Executioner", former governor of the Earth colony of Tarsus IV, was responsible for the massacre of over 4000 people, including members of Kirk's family. Governor Kodos had ordered the executions of more than half Tarsus IV's population after the food supply was all but destroyed by a fungus. This would have allowed the rest of the population to survive until relief came. It so happened that the vital resupply ships that could have saved the whole colony arrived much sooner than Kodos had anticipated, rendering all the executions unnecessary. However, part of his infamy came from the fact that he didn't choose randomly or pragmatically, but rather based on some eugenics formula he had developed.
  • Blakes Seven episode "Orbit". Anti-Hero Avon and Dirty Coward Vila are on a shuttle desperately trying to achieve escape velocity. They throw out everything they can but are short seventy kilos. It turns out that the shuttle is being weighed down by a piece of super-dense matter. Once Avon finds it all he has to do is push it out the airlock - if he can, because it's so damn heavy. Trouble is, he can't get Vila to help him because he's scared Vila into hiding.

Avon: "Not enough, not nearly enough! DAMMIT! What weighs 70 kilos?!"
Orac: "Vila weighs 73 kilos, Avon."
Avon: (pulling out a handgun) "Vila..."

  • In one episode of Bones twins had been abducted by "The Gravedigger," who buries his victims and demands ransom or they will die in exactly 24 hours (due to suffocation). Except in this case since the Gravedigger didn't expect to abduct two people they only have 12 hours of air. One was seriously injured and killed himself so the other might be able to hang on a bit longer.
  • An episode of Space: Above and Beyond involved a vast ship with a bunch of survival modules, one of which had to be sacrificed for power. The guy has trouble pushing the button, because his younger sister is in the one module that isn't full.
  • The lifeboat version is mocked in an episode of Monty Python's Flying Circus.
  • Played for Laughs in Red Dwarf. Due to the ship exploding, the crew are stuck in a Starbug shuttle, with limited supplies, and neither enough fuel nor oxygen to get to the nearest planet.

Rimmer: (to Kryten) Well, you and I don't use oxygen, do we? So, if we kill [Lister and The Cat] and dump their bodies out the airlock, will that save us enough fuel to get to safety?
Kryten: The point is moot, sir, as we only have enough battery power [to run your holographic emitter] for two minutes.

  • Dads Army. Captain Mainwaring is presented with this scenario to test his decision-making skills: You are in a balloon over enemy territory that is slowly running out of air; who do you throw out? Mainwaring decides on Godfrey, who doesn't look very happy.
  • In Lost's fourth-season finale, as the group of main characters attempts to finally leave the island, Frank notices that the helicopter is running low on fuel, and says they'll have to jettison someone to stay in the air. It initially looks like Hurley will have to jump (judging by his reaction when Frank says this), but Sawyer performs a selfless act by jumping out of the aircraft himself and allowing everyone to escape.


I was in a lifeboat designed for ten
Ten and only
And anything that systematic would get you hated
It's not a deal nor a test nor a love of something fated
The selection was quick, the crew was picked
In an order
And those left in the water were kicked off our pantlegs
And we headed for home

Tabletop Games

  • One Paranoia mission includes a Running Gag with malfunctioning elevators to the 99th floor, one of which is airtight and slo-o-o-ow. Sure, the PCs could just use their lasers to ventilate the wall - and face a fine for damaging Computer property - but, this being Paranoia, they're just as likely to instead ventilate the traitors who were using up all the air.

"Gentlemen, how many citizens does this sector really need?"

Video Games

  • In one ending of Ever 17, Tsugumi and Takeshi find an escape module with which to leave LeMU, but it turns out not to be able to carry both of them to the surface, so one of them ends up having to sacrifice themself for the other.


  • Narbonic parodies "The Cold Equations" here; when the pilot is Dave and the cute stowaway is Mell, it's not the stowaway who's going out the airlock.

Western Animation

  • In an episode of Futurama, this occurs when the Space Titanic is sinking into a black hole. The main characters board an escape pod, but the extra weight of Bender's Girl of the Week is causing the escape pod to drift towards the black hole, so she willingly lets go, saving the other characters. She is, of course, killed by falling into the black hole, and is never heard from (or even mentioned) again.
  • The nuclear shelter scenario is spoofed in The Simpsons episode "Bart's Comet". A comet is about to strike Springfield and so the entire towns' population tries to cram into Ned Flander's bomb shelter. They somehow manage this, but can't get the door closed. After arguing about who should be sacrificed Homer points out that the one skill future society doesn't need is the ability to sell left-handed products, so Ned gets thrown out of his own shelter. Eventually they all feel guilty about this decision, so leave the shelter to die with him. The comet ends up striking the bomb shelter and destroying it.
  • This crops up in Transformers: The Movie, with the Decepticons (who are retreating from a battle on Earth back to Cybertron) finding out that there's not enough fuel to make the voyage with the current amount of weight on the shuttle. Starscream (of course!) suggests airlocking the wounded Decepticons so the healthy ones will survive. Surprisingly, the Decepticons put it to a vote; the wounded Decepticons vote against the idea, the uninjured ones vote for it. Since the uninjured outnumber the wounded, out the airlock they go.
    • Given that Transformers can breathe in space and that there were plenty of other planets closer than Cybertron around, it's pretty clear they could have easily Taken A Third Option if they were really inclined. Starscream just wanted to finally get rid of Megatron, who was one of the wounded.
  • In the first episode of The Mighty Ducks, the Ducks' ship is traveling through dimensional limbo. Unfortunately, the ship will fall apart unless some weight is jettisoned, and everything onboard is bolted down. Team leader Canard decides to jettison himself. Wildwing tries to stop him, but only manages to save the mask of Drake Dukane.


  • That scenario that was supposed to test "decision making" but was actually a Space Whale Aesop regarding the evils of nuclear proliferation. You know the one: there's six people but only room in the nuke shelter for five—whom do you throw out? There would usually be an obvious Red Shirt character like a priest, supposedly proving the irrelevance of organised religion. These scenarios never included the details that would matter in real life, such as who was your best buddy, who was an attractive member of the opposite sex or who was holding a firearm at the moment the crucial decision was made.
  • There's an urban myth where people found the dead body of a man in the desert holding a piece of straw. In a line from his body are clothes and equipment. It's impossible for him to have walked and there are no tracks leading away from a vehicle. The solution to the mystery is that he was on a balloon that was descending over the desert; the passengers threw out everything they could to gain height, before realizing one person would have to go. The corpse drew the short straw.

Real Life

  • Apollo 13 actually ran into this dilemma. After the oxygen tank in the command module explodes, the crew is forced to use the life-support systems of the LEM module. Normally, this wouldn't have been a problem, but the LEM was only designed to support two people, not the full crew.[1] Luckily, they succeeded in MacGyvering a few ways to work around this that didn't involve murder, and NASA wanted their LEMs to have a big fat margin of error if something went awry. NASA didn't expect the LEM to have to last for 3 men for the entire mission, but it did.
  • Two famous court cases involving survivors of shipwrecks who took to the lifeboats and were charged with murder for their subsequent actions are United States vs. Holmes in which sailors forced passengers (including women) off an overcrowded lifeboat, and R vs. Dudley and Stephens in which sailors murdered the weakest member of their lifeboat crew, on the grounds that they were starving and he was likely to die anyway. Both cases ended with the accused being charged of murder (albeit with vastly reduced sentences), setting the precedents that self-preservation does not excuse the murder of an innocent.
  • Lawrence Oates went out into a blizzard after supplies for the ill-fated Scott Antarctic Expedition ran low, in an ultimately futile attempt to save his companions.
  1. In an ordinary mission, two crew members would land on the moon in the LEM and explore the surface while the third stayed on the command module in lunar orbit.