Suspended animation vs. regular animation aboard a spaceship

Question

Scenario

I'm trying to design a colony spaceship.

My main character, a soldier, awakes prematurely from suspended animation (SA) to find that the colony ship she is on, headed for Tau Ceti e, is in a mutiny. The journey was supposed to last about 14 years, but she's awoken halfway through the journey. There are 26,000 people total on the ship, of which there are about 400 trained soldiers, and 5,000 children.

Originally, I had almost everyone in suspended animation before the mutiny. The mutineers had pre-planned coming out of SA early and "taking over" the ship. However, as I thought about it, this wouldn't make sense with some plot points that I'd like to remain in place:

• The mutiny must take place between years 4 and 10 of the journey. This period constitutes a communication "dead zone". Any sooner or any later, and the ship can send a distress signal to either Earth or the existing colonies on Tau Ceti e, which can then remotely control the ship and suppress the mutiny.
• The destination remains Tau Ceti e.
• The main character must be in SA, because of reasons, and come out of it when the mutiny starts (okay, I suppose it's not necessary that she be in SA, but it's important to note that SA exists in this world).
• SA works by replacing the person's blood with a saline solution, and essentially freezing the body until it's time to come out of it, at which point the blood is returned, the body warmed up, and the heart shocked into beating again. Basically, cryonics. See this answer to a related question.
  • Normal brain function is retained by way of science
  • Some physical/mental recovery after SA is necessary, usually a week.
  • The space requirements per person in SA is 275 cu. ft.
  • Once out of SA, you can only go back in by the help of 2 highly trained technicians.
• Presumably, the mutineers would still want most people to survive the rest of journey. Perhaps not the soldiers, though.

If everyone were in suspended animation, then the mutineers couldn't survive the rest of the journey after their planned mutiny. There wouldn't be enough food, water, life support, etc., to sustain them. Even if it was just one person coming out for the mutiny, there is probably no way that this person could live for the rest of the trip. Perhaps one or two mutineers could survive, assuming there would already be a small group of technicians awake. But there are problems with this too, not the least of which is that this doesn't make for an interesting story.

So I'm designing a ship where everyone is awake and alive for the 14 year trip. All necessary considerations would be in place: artificial gravity, food sources, water recycling, life support, recreation, education, social structures, etc.

Question

I'm having trouble reconciling the fact that suspended animation exists in this context, but they aren't putting everyone in it for the duration of the journey. It seems like it would be way too expensive, and just a lot of trouble, to design and operate a ship where everyone is conscious; after all, they could just basically kill everyone and revive them later.

What are the costs, maybe in terms of energy, of having everyone awake and alive, vs the costs of putting everyone in suspended animation? In the case that it's much cheaper and easier to use SA (which is what I'm expecting), why would they not use suspended animation for the journey?

Edit

One advantage that I thought of for everyone being awake...the ship could be designed to gradually acclimate the colonists to the environmental conditions of their new home. This couldn't happen if everyone were in SA. I don't know the details of that environment yet, except that acceleration due to gravity would be about $1.4\ g$. Atmospheric pressure would be higher, but I'm not sure yet by how much. I'm also not sure how much benefit this would provide; I may ask another question about acclimating to a different gravity/pressure.

Answer 1

If suspended animation is a plausible tech, it would absolutely be used for practically everyone. The biological needs of 26 thousand people for 14 years would be massive - oxygen, food, water, CO2 scrubbing, heat dissipation, etc. A recycling system/biome would certainly help, but the more people it has to support, the bigger and more complex it needs to be. Providing for 26k people for 14 years is a massive incentive to keep as many people frozen as possible.

One way around your problem is to limit the safety of long-term suspended animation. If it is not safe to remain in a suspended state for the entire journey, people may need to be awoken on a rotating basis. If cellular degradation becomes a concern if frozen long-term (no processes working to heal radiation damage in a dormant body), necessitating a couple of weeks for medical evaluation and period of healing every 8 to 10 years of suspension, everyone will need to have a recuperation period mid-trip. This should not likely be something fatal, but increasing the possibility of harm the longer they are under (risk of mild brain damage, personality shifts, memory loss, etc - the physical damage can heal but those memories are gone).

Aside from a small crew who remain awake to service the vessel and maintain the systems, perhaps only a few hundred people are awake at any given moment? During the middle third of the trip, passengers are being woken up, have a 2 week checkout and recovery period, then refrozen. Those planning the mutiny arrange to all be part of the same group, thus they can overwhelm everyone else and take control.

Safety margins for life support should allow a few hundred extra people up and around (though maybe slightly degrade systems long-term as it is pushed a bit). They are not killing the other passengers by shrinking the number being cycled through health checks, just increasing the risk of damage by exceeding safety protocols (hopefully no non-recoverable injury will occur, and if some unfortunately does happen, just acceptable collateral damage for the cause). This puts the mutineers able to take over, and your protagonist is part of the next cycle of passengers (albeit of reduced numbers).

Suspended animation limits like this may not fit your plot (not sure what the mutineers expect to accomplish), but gives you mid-trip timing and a protagonist waking up in the middle of it, as well as addressing why the ship would have supplies to keep extra people up and awake.

Answer 2

I think you can stick with your original plan with a slight modification. The key is to consider what needs to happen at the end of the journey.

Official Plan: All colonists asleep. Most soldiers/security asleep (probably 1-2 awake). 10-12 technicians awake at any time, working in 1-year shifts with overlap.

At the end of the journey, the colonists must be woken up in large groups on the ship, allowed to recover, and then shipped down to the planet. This requires a temporary boost in the ship's life support - probably something that couldn't normally be sustained for the full trip, but could be used for a couple of months to get the colonists down.

Mutineer's Plan: The mutineers will make use of that temporary boost in life support. Instead of using it to support thousands of people for a 1-2 months, they'll ration it out so that it can support the 100-200 mutineers for the remaining duration of the trip.

Once they arrive at their destination, they will replenish the life support from Tau Ceti, letting them eventually get the colonists out of SA and down to the planet. This will delay the colonists getting to the planet, but gets them their alive so the mutineers consider it acceptable.

Answer 3

The human body uses less energy when it's asleep than when awake: slower breathing, slower heart rate, reduced brain function, etc. If there's no one around, you don't need to leave the lights on or provide power to food/water storage. So using SA is, in terms of energy consumption, far more efficient than having everyone banging their head against the walls for a dozen years.

Why wouldn't they use SA? Simple: precautionary measures to prevent mutinies (and avoid other scenarios) dictate at least X% of crew must be awake at any given time. They'd keep a specialist or two on hand, enough soldiers to hold off a small boarding party/group of mutineers, and crew sufficient to ensure the ship continues to run smoothly. While machines could do this, there's been a persistent desire for a human to be in control and perform routine visual inspections.

This protection only concerns the crew and guards on board. Civilian colonists wouldn't need to be awake for the entire duration unless they were utterly opposed to the idea being held in SA. (You can be certain there will be some like this.)

Answer 4

Arguably the most plausible scenario is that the colonists destined for the planet are kept in SA, while a small crew stays awake for the journey to run the ship. This way you keep your life support requirements low (only enough for the e.g. 15 technicians, don't need anything more than the SA gear for the 26,000 colonists), don't need near as much food, etc. Depending on how your SA bays work, they may not even need to remain pressurized during the journey, which further reduces the costs of keeping your small crew functional during the journey.

To execute a mutiny, then, they'd just need an insider or two on the awake crew, and some way to reach and wake the others. On a quiet 14-year journey, it would be no problem for even just one mutineer to sneak off on occasion and wake up another 2 or 3 people (of course sabotaging the monitoring gear so as to prevent anyone else noticing what's going on) or bring them some food and supplies. Then they'd start by isolating the "loyalists" one or a few at a time, neutralizing them (maybe they kill them, maybe they just stuff them into the recently-vacated SA pods, or maybe they just tie 'em up in a corner -- up to you, really), until only the mutineers are awake and thus de facto in control of the ship.

Even if in communications range of either end of the journey, no one outside the ship would have any idea what's going on.

Unfortunately (for the mutineers), in tampering with the SA monitors, they accidentally woke up one of the soldiers, who now has to figure out what's going on (while trying to shake off the after-effects of SA) and then deal with the problem somehow...

Answer 5

Energy requirements in suspended animation

This depends on how SA works in your world.

If you just cool people down and swap out their blood with saline, energy requirements will be very low. One of the main resources that's common in space is cold, so you won;t have to run expensive cooling equipment to maintain a state of cryostatis for your colonists.

It's likely, though, that you'll want to replace their blood with something more complex than saline for a long trip like this, probably something with the ability to sustain the cells (their metabolic rate is very low, but not zero) and prevent decomposition (bacterial metabolic rates are similarly low, but also not zero). This substance may be expensive, but it only needs to be injected into a person at the start of the journey.

Of course, that's assuming that the suspension fluid lasts for the whole journey. If suspended animation is possible, but the fluid used to do so needs to be replaced every day, you're looking at 5 liters of fluid per day per person. If this is also something that can't be produced mid-flight (perhaps it requires a huge lab and lots of energy), the volume and mass of the suspended animation fluid required to keep the whole ship hibernating for 14 years may be more than the cost of just feeding them.

Energy requirements for a regular person

Roughly: 2000 kCal/day. Water and air can be recycled indefinitely, but energy from food will be burned for live humans in the form of irrecoverable heat. Even if carbon etc. can be recovered and re-formed into food via an internal ecosystem with plants and whatnot, fusion energy is going to be required to grow all of the plants. Furthermore, all of the water, air, and food recycling infrastructure takes up space and has mass. The more mass you space craft needs to transport, the more energy it will require to move. Even if it's something like a solar sail, a bigger sail will be needed to move a heavier ship, which will cost more.

So which costs more?

Up to you! You can definitely come up with plausible reasons for suspending someone to take more energy or for leaving them up and running to take more energy. For your story, it probably makes more sense to assume that lots of resources are needed to keep someone in suspended animation.

So why use SA for some people?

One of the key uses for SA proposed in the modern world is for medicine. People in suspended animation won't die due to blood loss or massive organ failure. Maybe, as part of the mutineer's plot, most of the security guards got baked with radiation while leaving the solar system. The hero of our story survived, but the damage was so extensive that he had to be put under SA for months while nanobots repaired damage at a cellular level.

The mutineers, after all, don't need everyone in suspended animation, just the people who would stop the mutiny. They could trigger some sort of medical emergency, wait for the guards to get put in SA, and then strike. Unbeknownst to the mutineers, one soldier evaded the worst of the damage and wakes up early. Is he early enough to stop them? Find out by reading The Early Riser.

Answer 6

I don't think you need to wake all your mutineers up for this

Think about it - you don't need the ship to go somewhere else. You don't need the people to do anything they weren't already doing. All you're trying to change is the circumstances when you arrive.

(Borrowing some aspects from Dan's plan above)

So your constraints are:

• you need to maintain radio silence after the mutiny (or at least prevent any distress calls)
• you can't increase the number of awake crew for any substantial amount of time (due to life support)
• someone on the boat has to be awake as a setup. (Preferably a guard, but let's assume it's a sympathetic tech.)
• Your slave crew has the skills needed to run the ship (since your life-support budget can't afford the extra security)

The (admittedly harsh) plan:

1. Tech wakes up the "prize crew".
2. If this can be done without alarms, flush the tubes of the sleeping guards. (Removes possibility of them being awoken later). If this can't be done without alarms, do this after you've secured the ship.
3. Kill out the alive guards as quietly as possible. (And you're in space, so you have options up-to-and-including just venting atmosphere in their compartments)
4. Freeze (or space; their choice) the current techs on duty (if the ship can be controlled remotely, you can't afford someone being a hero and hitting the panic button down the road).
5. Optional: find whatever mechanism allows remote-command of your ship and disable it (may not be an option in your world)

At this point, the only people awake are your people, your casualties are the guards plus any tech who didn't want to go into SA, and so long as the authorities planet-side aren't tipped off, you're good to go.