So, continuing along the basic storyline of this last question: Is it possible for a human to be cryonically preserved in vacuum?

What I took away from the answer (note singular) and comments there (very helpful, thanks guys) was that Jeff needs a cryoprotectant to basically stop his tissues being damaged by the freezing. So, let’s say that Jeff has ingested some form of cryoprotectant before his little space accident. What form should it be? That is, what cryoprotectants could he naturally ingest with food and which will be most effective?

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    $\begingroup$ your title is asking one thing which is different from the question in the body $\endgroup$
    – L.Dutch
    Jan 31 at 14:26
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    $\begingroup$ Just to help tease out the actual question, cryoprotectant needs to exist within every cell to prevent them from expanding when they freeze and rupturing the cell walls. To my knowledge, this isn't something you can just take a pill for. At minimum, you'd need to introduce it directly into the blood stream. $\endgroup$ Jan 31 at 17:11
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    $\begingroup$ VTC: Please stop asking story-based questions. What form should it take? How should we know? There's no such thing as a "cyroprotectant." Does your story make it easier to ingest as food? as fluid? as a gas? as a topical? Intravenously? What if it's just a mindset and we pre-program the mind through a blast of light and color? And you want to know how that can happen accidentally? Like, tripping and breaking a bottle that spills on him? Per the help center, "When asking questions keep in mind that the goal of the site is to help you build your world, not to tell your story." $\endgroup$
    – JBH
    Jan 31 at 17:34
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    $\begingroup$ Related? Or maybe just an answer? worldbuilding.stackexchange.com/questions/146567/… $\endgroup$
    – Willk
    Jan 31 at 17:37
  • $\begingroup$ If you're tempted to edit someone else's question and "fix" it without their permission published in comments, please be aware that the Help Center states one may edit "to clarify the meaning of the post (without changing that meaning)." By definition changing a story-based question to a non-story-based question is changing the meaning of the question. Get permission from the OP or help the OP learn to write well-asked questions. @user98816, if you approve of the previous edit, then you can roll back to it. $\endgroup$
    – JBH
    Feb 1 at 2:45

3 Answers 3


Presumably the cryoprotectant needs to be dispersed throughout most/all of his cells. To me, that implies the amount needed isn't small. Thus it would be unlikely to accidentally ingest it in the same way a person doesn't accidentally ingest a gallon of water.

Furthermore, it seems reasonable that a cryoprotectant needs the be dispersed throughout the body quickly, otherwise it might start breaking down or being cleared out of some cells. Generally speaking, other options than the digestive tract would probably be better for very rapid dispersion, such as injections directly into the bloodstream.

So these points make it sound unlikely that ingesting it would work for what you want. At least based on where my intuition and understanding of science leads me.

But on the other hand, we're talking about a fictional substance. Plenty of sci-fi stories just hand-wave around this. (In fact, consider the many cases that don't even mention a cryoprotectant at all. A person just gets in a tube and is cryogenically frozen. That's all the detail they give.)

So there's nothing really stopping you from proposing a super-effective cryoprotectant has been invented that's only needed in a small enough quantity to be a small pill and dispersed through the body rapidly.

If I saw this kind of plot show up in an episode of Star Trek, for instance, I wouldn't be put off by trying to figure out how "realistic" the cryoprotectant was.

Personally though, I would still wonder why someone brought such pills outside of the cyro room and was being careless enough to drop one in some food. But I'm sure there's a way to make that work.


This one is easy. One of the other characters spiked Jeff's tasty lunchtime lasagne with a pill of

Cryogestium B

enter image description here

Looking to go into cryosleep for that last-minute voyage to Alpha Centauri? Try our new Cryogestium B. The patented formula will distribute the cryprotectant around your body like a warm blanket. Say goodbye to spiky ice crystals. No more punctured cell membranes for you!

The new formula means there is no nasty enema or ghastly liquid immersion required. Simply purchase the pill from your local pharmacy before breakfast, swallow it with water at lunch, and then settle into your cryo-pod after dinner.

Interstellar travel has never been easier.


Such cryoprotectants don't exist... yet

Currently, it is not possible for a human to survive being frozen (or a vacuum for that matter). The expanding substances in our bodies ruptures cell walls killing us on a cellular basis. The cryoprotectants you would need will need to be a fictional substance that would fortify human cell walls in a way that allows a human to survive being both frozen and subjected to a vacuum. Because this technology does not exist yet, it means that this drug can take on any form you so choose. When/if anyone ever discovers a workable cryoprotectant, maybe it will be something you can eat, maybe not, but until then, it is writer's choice. Since the drug could come in any form, then any way you could consume anything would be a possible delivery method; so, just make up what ever scenario you find most interesting.

Easiest way to accidently take it

Cryoprotectants will most likely be handled as a medical resource, just like we let doctors handle vaccines, radiation pills, antidotes, and other drugs that can help us prepare for hostile conditions. So whatever the cryoprotectant is, it will most likely be stored under lock and key in the ship's medical facilities. This means that accidently getting this medicine in your food is highly unlikely.

However, what does sometimes happen is that a doctor will administer the WRONG medicine. So, it's not that your protagonist was not trying to ingest some medicine, it's just that some overworked or under experienced pharmacist grabbed the wrong thing from the cabinet. So when you're poor protagonist isn't feeling well and goes to the infirmary for some Bismuth Subsalicylate, instead he gets a nice dose of cryoprotectants. On the down side, he does not feel any better after taking his medicine, but I guess getting to survive the vacuum of space in the next chapter is a fair trade-off.

  • $\begingroup$ Yeah, Human can survive hypothermia to some point, mainly because there is no freezing involved. I'd suggest adding to the answer that freezing destroys body down to a cellular level (water in them freezing ruptures their walls), so method and temperature is not important - it's the passing the water freezing point that's the issue. $\endgroup$
    – AcePL
    Jan 31 at 15:29
  • $\begingroup$ Apparently, mice can survive being frozen solid (and warmed back to consciousness in a microwave). There's a Tom Scott video about this on YouTube. Humans, however, are too big to freeze or thaw evenly enough. $\endgroup$
    – Zeiss Ikon
    Jan 31 at 16:56

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