A Million Ways To Die in the
Let's face it, there are way too many ways this can end. I mean, yeah, it all starts with stupid, but the endings themselves are just too varied to cover in any detail. (And yes, shutting down your drive without a guarantee that you can start it back up again is a stupid, convoluted way to commit suicide.)
Humans die for a few tens of thousands of reasons, but the following broad categories seem to be fairly likely in this case:
- Asphyxiation - not enough O2 or too much of other things.
- Nutrition - from running out of food to specific deficiency.
Yeah, those are pretty broad and immediate. Let's step back to earlier causes that can lead to one or more of the above.
Either you're running on stored power (batteries, capacitors, flywheels, whatever) or you have a way to generate power from some long-term source. If it's stored power then you probably don't have much time. Same with limited generated power. Long-term generation from things like RTGs (radioisotope thermoelectric generator) last for a long time, but they don't tend to produce a particularly high output - great for powering pacemakers, not so good for spaceships.
You need power to produce the lights that keep your air plants alive and producing oxygen for you to breathe. You need it to run the fans that move air around the spaces on the ship to stop toxic buildup of CO2 and so on. You need it for heat or cooling, depending on the thermal balance in the area of space you're traversing. And there are probably a ton of other things sucking up your power - better to disconnect everything that isn't on the critical list.
When the power finally dries up though? The air stops moving and CO2 builds up in concentrated pockets wherever you are. Stop moving for 10 minutes or so and you'll use up all of the oxygen in your local space and end up sitting in a growing concentration of CO2. If you're lucky you'll pass out from lack of oxygen before the fire in your lungs gets too unbearable.
Asphyxiation is, I'm told, a particularly dreadful way to go.
Unless you're hauling a cargo of food and dietary supplements, odds are that you're only carrying a couple of months worth of food in the galley. Mostly the extra food is for the sake of variety and emergencies, but eventually you're going to run out. You can ration it, reduce your energy expenditure to extend it somewhat, but at some point you're going to open your last freeze-dried ration pack.
What then? You can eat some of your air plants - spinach is apparently quite good at producing oxygen - but it's far from a completely balanced nutritional intake. And each plant you eat is a little less oxygen generation until it grows back. You can live indefinitely on the right blend of vegetables, but do you really have enough room in your truck to grow a nutrionally complete crop? I very highly doubt it. For one thing the amount of plant growth you can support is limited by your personal CO2 output.
At some point you're going to start developing problems due to a lack of some critical vitamin or mineral in your diet. If you're lucky it'll be vitamin C and your teeth will fall out. If you're not and you run short on niacin (vitamin B3) due to a lack of peanuts or grains in your meagre crops then you can look forward to some quite nasty symptoms before the dementia makes you incapable of looking after yourself. At least you won't be around to experience most of it I guess.
And don't forget that you need plenty of power for those plants to grow. They need light to photosynthesize and heating or cooling to maintain an optimal temperature range.
Depending on where you are and how your hull is insulated against the external environment, you're either going to be losing heat or gaining it. You want to be losing heat because there are a few ways to easily generate it. Too much heat buildup on the other hand is a major problem because there aren't too many simple ways to get rid of it. You can shuffle it around a bit, but in the end you'll run out of thermal capacity and start to boil. Or bake.
Too cold isn't an issue so long as you have a good long-term energy supply. Running heating elements on batteries is a very short-term solution, and you need that power to keep your life support systems pushing oxygen around the ship. It's enough that you have to keep the air (and food) plants at a consistent temperature, wasting power on heating the ship as well isn't going to prolong your life much.
Assuming that you have a good supply of canned O2 and scrubbers, you might be able to survive for a while after the power goes off. If you extend it long enough you get to sit in the frozen ship while the heat is leeched from your body, dropping your core temperature closer and closer to the hypothermia zone. Circulation cuts off to your extremities and unimportant things like fingers and toes die and start to rot. Gangrene takes a while to set in, by which point your body is already in a near hibernation state. Your brain shuts down and never starts up again. Eventually everything stops and, as the temperature drops further, the water in your cells turns to ice, expands and tears your cells into pieces. Even if they find your corpsicle in a few thousand years, you're never coming back from that.
In the other direction your body heats up and you sweat out every ounce of moisture you can spare. Dehydration starts to break down your ability to process information, and eventually the various processes in your body that rely on all that extra water hanging around stop working. Organs shut down and so on. A little after you die the proteins in your body are denatured by the heat and you cook all the way through.
Either option sounds fairly excruciating to me. I'm going to go ahead and guess about a 13 on the standard 1-10 scale of nastiness.
Ooh, there are just so many of these it's hard to know where to start. You're driving a glorified truck after all, you're almost certainly not carrying the sort of spare parts needed to fix everything that can go wrong. You have backup systems for most of the really important stuff, maybe even double or triple redundancy for the critical bits, but 90% of the time when something breaks you can't do a damned thing about it. And if what breaks is something critical to life support, temperature regulation or power distribution then... yeah, it's not going to be fun.
This is also where your main options for physical trauma come in. Attempting to disassemble things, diagnose them and make whatever repairs you're able to while in transit is a potentially dangerous task. You just have to slip up once in the right way to lose a limb or end up trapped in a piece of equipment. Heck, just failing to secure a heavy chunk of tech and having it drift into you at an inopportune moment might be sufficient.
Or perhaps you screw something up and let the air out. We've all seen Total Recall, right? You know, the one with Arnie? He survived the low pressure on Mars for long enough to truly, deeply regret being exposed to it before he was saved by Deus Ex Machina. I'm afraid you're not going to be so lucky if you pierce the wrong seal.
And that's by no means an exhaustive treatment. I never touched on disease, for one thing. Or poison. Or... and so on.
Ultimately, whatever the case, it's probably going to be nasty. You're going to have to figure out how far your character will take it before they take a walk out an airlock or stick a needle of poison in their veins. It's probably the better option once you've confirmed there's no way out.