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I am planning to write about long term cryosleep (more than 100 years). As far as I know, several science fiction works addressed the problem of irreparable cell damage (due to ice crystals) by using low doses of microwave radiation and cryo-protectant solution to create a controlled freezing in order to prevent ice from forming and destroying cells.

But, as far as I know, this technology is usually used for shorter period of time (less than 100 year) and how longer period will affected an individual or the tech behind it is mostly underdeveloped (other than brushing it off, as usually done for longer period cryo-related-technology).

So, based on this specific technology so far (aka the prevention of ice-related harm already taken into consideration), how would said character fare, both physically and psychologically?

All I know for now, beside the information I have written above, are...

  1. Usually there are still possibility of failure and death (more or less 1%) but which part affected this failure is still unknown
  2. Babies can not be put in cryo-sleep, for unnamed reasons (maybe growth related, maybe moral related)
  3. The technology of cryosleep is developed gradually so the technology (the sleep technology itself as well as medical technology and knowledge) when the characters was first put to sleep and when they awaken would be vastly different

(Edited)

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    $\begingroup$ Welcome Hanzie. Unfortunately this seems to me at least to fall afoul of our "no third-party worlds" rule. Unless you can demonstrate that you are in fact James Cameron (or one of the writers on the films or official cannon books), then this would be off-topic. Even if it were your work, it becomes somewhat a matter for the writer to decide what their story needs - after all, there's no real-life science (in mammals) to compare the writer's assertions to. Bacteria and some protozoans can manage millennia, frogs can live for months, I'm happy if I can get 8 hours. $\endgroup$ Commented Jan 15 at 8:30
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    $\begingroup$ Hello Hanzie, and welcome to WorldBuilding SE. As @Escapeddentalpatient. has explained, explicit fanfiction is not allowed here. There is a very easy fix for you though: make it not be fanfiction. All you need to do is add "In the style of" or "modelled on"... or simply do not mention copyrighted elements, which usually comes down to avoiding names. Also, quite frankly, you will not be writing in that universe anyway, because that is a blatant copyright violation, and you do not want to be doing that, now do you. ;-) $\endgroup$ Commented Jan 15 at 9:22
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    $\begingroup$ Monica's answer on our meta is about the closest to a rule that we have. Perhaps we might have a word with a friendly mod to see if the help centre has "room for a little one". @MichaelK As someone regularly points out, no-one can obey rules that exist only in someone's head. $\endgroup$ Commented Jan 15 at 10:48
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    $\begingroup$ @Escapeddentalpatient. I took a bit of liberty to clean up the question from copyright violations, so we can at least pretend that we are not dealing with outright fan fiction. $\endgroup$ Commented Jan 15 at 11:02
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    $\begingroup$ Does this answer your question? worldbuilding.stackexchange.com/questions/113944 $\endgroup$ Commented Jan 15 at 17:18

4 Answers 4

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Do you need to care?

As per Chekhov's Gun: only make it a problem, if you need it to be a problem. Only mention side-effects, if you intend to do something with them.

If not, if it is mentioned only for "realism", then do not. Ignore, or hand-wave it away, because all you are doing is spending the reader's time on dealing with a dead end.

"But I do want to care, I want there to be issues"

Then invent whatever issues you need for the story, either as plot devices, or as flavouring ‒ do not ignore flavour for your world, but think "spices" ‒ use to enhance the main taste, not to overpower it.

When it comes to suspended animation, there is an endless palette of possible side effects to choose from to inject into the story.

Physiological effects

  • Memory loss
  • Muscle atrophy
  • Immunity issues
  • Gastrointestinal dysfunction
  • Sterility, temporary or permanent
  • Allergies to new immuno-irritants
  • DNA degeneration, from radiation and/or thermal motion
  • Impaired motor functions, fine-motor skills in particular
  • Lack of space travel experience (hellooo space motion sickness!)

Psychological effects

  • Identity lag
  • Culture shock
  • Survivor's guilt
  • Lack of peers / dead loved ones
  • Ethical and moral vertigo/disconnect
  • Obsolescence, skills and knowledge hopelessly outdated

...and more

Pick and choose whatever you want, because no matter what that is, you can always find a way to crowbar their presence ‒ or absence ‒ into the story.

Author decides

Willing Suspension of Disbelief is not(!) about realism, but making things credible.

Unless you are going for extremely "hard" sci-fi, remember: you are the autocrat of your story, the supreme dictator... whatever you say will happen, happens.

You do not need worry about respecting reality.

All you need consider is: can I sell this to the reader?

Realism makes it easier to achieve credibility, but things like Star Wars shows that realism is not at all necessary.

A word on works inspired by others

Note, I am not a lawyer, this is not legal advice.

Straight up use of third-party worlds is frowned upon on Worldbuilding SE, because that ‒ usually ‒ results in copyright violations, and the questions become more about canon rather than helping to develop the author's own world.

However...

Copyright protects expression, not ideas.

Concepts and themes are (usually) not copyrightable.

What this means is that whatever made it onto paper is what is protectable, not the thoughts that made things end up on paper.

Copyrightable elements are...

  • Identifiable characters, meaning a totality of looks, mannerisms, name(s), backstory and similar
  • Identifiable, unique plot elements
  • Unique world mechanics
  • Unique names/terms/jargon

This is why, for instance, Eragon does not fall afoul copyright against Star Wars: A New Hope, despite the plot being a blow-by-blow copy.

So in your case, this would mean you avoid names and descriptions that makes the reader say "Okay, that's obviously Pandora and Na'vis." or "Totally Colonial Marines... you stole that straight off of Cameron".

Avoid running into that, and you can write to your heart's content.

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    $\begingroup$ An additional (and likely actual) problem with cryo-sleep is that our bodies are actually radioactive. Even if you protect the body from outside radiation, its own sources of radioactivity are enough to cause serious damage over long periods of time and that with the metabolism significantly slowed or stopped, the body will not be able to heal itself and counter this damage. $\endgroup$ Commented Jan 15 at 16:24
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    $\begingroup$ @MichaelRichardson Hm, that one was interesting. Yes, of you also suspend the DNA repair mechanisms, then the dose from internal decay will add up. I asked Chat GPT for a quick estimation and it landed on about 1.5 mSv per 10 years. Now that is not a lot. And for 100 years, 15 mSv is also not a lot, it is below the yearly dose limit for nuclear workers. But when we reach 1000 years, we have accumulated a dose of 150 mSv, and now it is getting hairy... that will start to nudge at the odds of getting cancer. $\endgroup$ Commented Jan 15 at 20:29
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    $\begingroup$ +1 This is as good an answer as this question can have without actually developing the technology, waiting a hundred or so years, and then performing autopsies. $\endgroup$ Commented Jan 15 at 20:55
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    $\begingroup$ @MichaelRichardson Also, I just realised... chemical decay of DNA is also an issue. So either you got cryo... and put up with the radiation damage, or(!) "warm" enough to keep DNA repair going, but them you also pretty much have to keep the metabolism going to provide antioxidants and similar. $\endgroup$ Commented Jan 15 at 20:59
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    $\begingroup$ @JBH Thank you kindly for the nice feedback. :-) $\endgroup$ Commented Jan 15 at 20:59
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Radiation

Alpha (charged ions) and neutron radiation can be visualized as your cryosleeper being shot through by a light calibre railgun trillions of times during the trip.

When un-iced, the human body repairs the damage. And, as long as it's not too much all at once, it's endurable.

On-ice is different. The damage of all of these tiny gunshot wounds goes unhealed until you awake. So it builds up.

Instead of counting bullet holes, radiation damage is measured in energy. Lethal injury begins as a possibility at 200 Joules of accumulated damage. It is a near certainty (LD100) at 600 Joules of accumulated injury.

The typical amount of radiation in deep space is 1.6 microwatts (millionths of a watt).

A year contains 60 x 60 x 24 x 365 = 31.5 million seconds.

A lightly shielded cryopod, then, takes on about 50 Joules per year of radiation. Therefore anything longer than a 4 year journey has the possibility of killing the sleeper. And any journey at or greater than 12 years is guaranteed to be fatal.

Shielding

There's not really any technology out there to protect from cosmic rays (1 GeV Fe). You need a few kilometers worth to provide real protection.

About 8 meters of ultra dense stuff like d*(2380) (32 tons per cubic meter) should be complete protection against average levels. This would enable long cruises.

Edit: Thinking about this overnight, a vessel traveling close to the speed of light (%c) has reduced the relative speed of cosmic ions arriving from aft enough that they are not a great concern. Also, if the ship does not have to turn around to brake (side-pods instead of a centrally mounted engine), you can concentrate the shielding for the entire ship in an up-front plate.

Also because F = qvB sin(theta) magnetic shielding is exceptionally effective at directing away high-speed charged ions. 100 Teslas of permanent magnet at the bow can protect a 10 meter wide starship

Weather

Some sources of radiation produces exceptionally high energy (10 GeV, 100 GeV) radiation that would pierce even this shielding. These are usually momentary, but can last for days before subsiding.

It would then be up to how miserable the weather was, and how well the shielding material held up, to determine an individual spacers health when he or she woke from cryo.

Death

Which brings to how death by radiation sickness looks. Based on the folks at Chernobyl you feel really good for about 24 hours, then get sick... fatally so within a few weeks.

Engineering Around This

You could keep sleepers on a schedule where every year they are woken up for a month to heal accumulated radiation damage. Then back to ice they go.

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    $\begingroup$ Alpha particles will be a small issue. They themselves will scatter on contacting the hull, but the remains might be troublesome. Neutrons will decay long before they reach the stellar wind boundary, so you are probably thinking of protons, as they make up the majority of the interstellar medium (not counting neutrinos, of course). $\endgroup$ Commented Jan 16 at 13:19
  • $\begingroup$ Ok but the several-weeks doses at Chernobyl didn't get planned-in-advance treatment. Yes your body has to repair all over the place, which takes time (and you risk cancer, but let's ignore that). The Liquidators died because they didn't get that time. After Cryosleep you could easily have the waking people hooked to dialysis+ machines that basically do everything to your blood that functional organs would (oxygen, cleanup, food etc.). $\endgroup$ Commented Jan 16 at 15:31
  • $\begingroup$ not true. alpha iron 1GeV plus will go right through $\endgroup$ Commented Jan 16 at 16:25
  • $\begingroup$ @QuestionablePresence, I agree treatment will help. I'm not sure dialysis is a magic bullet, though. $\endgroup$ Commented Jan 17 at 13:46
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I suggest you a reference from a hard sci-fi, which makes it an important plot point instead of glossing over it: Fiasco from Stanisław Lem.

In that novel, cryogenic freezing is a very unreliable and dangerous process, and is only used for emergencies. They build it into the cockpits of giant mechas used for engineering and construction projects in dangerous areas, so that in case of an accident the pilot could use it as a last resort. In that time in-universe, the technology to revive them did not yet exist. The author describes that the real-life (so, in-universe, the past) attempts where rich old people were frozen would not work, as all the brain cells will be damaged so that revival would not be possible.

That emergency cryogenic device is described in a very detailed way, and it's quite gory. To preserve the brain mostly intact, it has to be frozen from all sides as quickly as possible, so tubes crash violently through the face and the jaws, to inject liquid nitrogen, shattering most of the skull in the process (while the victim is still alive and awake). Even many decades later, when the technology for revival exists, it is not an easy task. Most of the victims do not survive at all, and the one they can save (in a very controlled, low-gravity environment), still requires extensive surgery, long recovery time, and suffers from severe memory loss.

If I remember correctly, they call it vitrification, as it does not just freeze the body (crystallization would destroy the cells), but they purge all the blood, and most fluids out of the body. Revival is less like waking up from sleep, and more like rebuilding the patient out of a completely mangled mess where the only body part preserved (more or less) intact is the brain.

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The answer by Jame McLellan offers a good overview of part of the danger (radiation), assuming safe freezing, but there's a few things to note:

Medical Technology

Since you've specified this is a science fiction setting, better medical technology and especially better treatment for acute radiation poisoning may exist. If this is the case, the time spent in cryosleep safely could be longer. And the medical technology upon waking is most relevant, as that is when the patient will be treated.

It's plausible that with adequate medical treatment, radiation poisoning would cease to be a concern at all; outside of DNA damage, biology is actually extremely radiation tolerant. Even extremely fatal doses are primarily deadly because of knock-on effects from DNA damage. Any sort of medical technology that allows for treating the DNA damage would largely solve the problem.

A good point of comparison is other living organisms. Almost no living thing on Earth has needed to adapt to high radiation fluxes and so they are essentially defenseless. The scarce few that have adapted to it are hundreds, thousands, or even millions of times more resilient to exposure. So our relative vulnerability to radiation is more of a oversight, and the right technology could eliminate it.

Space exposure

Secondly, the background radiation varies significantly depending on where you are. In space it will be vastly higher in the Van Allen Radiation Belts, near Jupiter, or otherwise outside a planetary/solar magnetic field. While a person may accumulate 3-6 milli-Sieverts from a year on the ground, they could be facing 300mSv per year on the ISS, and as much as 600mSv per year interplanetary flight!

James does vastly overestimate the amount of shielding required, though. Shielding spacecraft tends to be impractical because of a strict need to minimize mass. But literal meters of lead are not necessary to stop a majority of cosmic radiation.

Ground exposure

That aside, you never really specified that this has to be in space. Of course, background levels on Earth are low enough to cryosleep for hundreds of years in relative safety. Immediately dangerous doses tend to be in the low Sievert, although long-term effects can emerge at lower doses. So of course at a couple thousanths of a Sievert per year, it would take quite a while to reach a dangerous accumulated dose.

A specially-prepared shielded room could provide even better protection. It is, after all, far easier to shield a room on the ground than in space. This could range from a concrete bunker, to a special hermetically-sealed room built out of materials which have been carefully selected for their low concentration of radiation-emitting isotopes (aka 'low-background' materials). Regardless, it's easy enough to reach a point where it's far more likely that equipment failure or unforeseen issues will be the demise of anyone in cryosleep long before radiation is a concern.

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