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I have a crew that need to spend a couple years traveling via spaceship.

Because it's inefficient to have to provide every passenger with living-space and rations, I'd much prefer if it were possible to put them in some sort of stasis for the duration of the trip. Though not by means of cryonics. I'm not fond of replacing people's blood with antifreeze.

I was thinking more along the line of artificially inducing a state of extreme hibernation. The crew's metabolisms would be suppressed as much as possible and that way they'd only need a pods-worth of room and we might not even have to carry any food onboard at all. Stranger still, perhaps the aging process would almost entirely cease. This would be a good thing, because many people might object to wasting 2 years of their lifespans onboard a spaceship.


So I'm wondering, are these ideas plausible?

  • Can you slow an individual's metabolism to the point where they wouldn't need to eat for 2 years?

  • Would doing so circumvent the normal aging process?

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    $\begingroup$ For humans? We don't know whether it's possible or not; research is ongoing -- humans do not hibernate naturally. For lemurs, or ground squirrels, or hedgehogs? Yes, it is probably possible -- they do hibernate. Aging most likely does not progress much while hibernating, because by definition hibernation implies a strong diminution of metabolic activity (hypometabolism). $\endgroup$ – AlexP Mar 26 '18 at 21:42
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    $\begingroup$ To the close voters, would you mind mentioning why you think this question is too broad? $\endgroup$ – AngelPray Mar 27 '18 at 9:46
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    $\begingroup$ @AlexP Yes, I am asking about humans. My passengers are going to consist of humans, not hedgehogs (unfortunately, because that'd be pretty cute), hence why I included the "humans" tag. $\endgroup$ – AngelPray Mar 27 '18 at 9:49
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    $\begingroup$ I think you're describing what exactly what cryonics is intended to do. $\endgroup$ – Unassuming Guy Mar 28 '18 at 19:46
  • $\begingroup$ Human's don't hibernate naturally (of course), I can only think of one quick fix for that using any science or tech that appears to be on the horizon that (putting all ethical & legal concerns aside) might be plausible, so is genetic engineering off the menu as well as pumping out the blood & filling the veins with antifreeze? $\endgroup$ – Pelinore Apr 3 '18 at 19:07
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Can you slow an individual's metabolism to the point where they wouldn't need to eat for 2 years?

Humans do not hibernate. The closest you can get to that is medically induced coma. This is not without adverse effects:

Induced coma usually results in significant systemic adverse effects. The patient is likely to completely lose respiratory drive and require mechanical ventilation. Gut motility is reduced. Hypotension can complicate efforts to maintain cerebral perfusion pressure and often requires the use of vasopressor drugs. Hypokalemia often results. And the completely immobile patient is at increased risk of bed sores as well as infection from indwelling lines.

Also notice that a person in a coma requires medical monitoring. Each subject would in the very least require a fully automated intensive care unit. Alternatively, some of the people in the trip could forgo such suspended animation, so as to care for the ones in induced coma.

Would doing so circumvent the normal aging process?

Probably not. There are some studies claiming that caloric restrictive diets (such as one would get while in a coma) slow aging in humans, but those studies are disputed.

However, any civilization advanced enough to send humans in such a long trip to space should have more advanced science than we do in the real world. That could include better knowledge of how we age, so you can just handwave the part about people not aging significantly while in suspended animation.

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There are quite a number of examples on earth of animals using hibernation to survive adverse environments.

  • The polar bear is one for example: it buries itself under snow for a considerably long period.

  • There are many insects which can do the same. The grasshopper is one example. It can survive subzero temperature for more than a year and fly right after the snow melts. It can even reproduce successfully after that.

What I mean by quoting these examples is that there are specific proteins that can help preserve cell architecture & form even after freezing below subzero temperatures. Human bodies could hibernate if injected with one of these proteins before sending them off to another planet.

Repeated injections may be needed as a foreign protein will degrade. Obviously, that protein must be stabilized against degradation and be safe from elimination from the body, which could be handwaved using nanotechnology.

I remember hearing about a laboratory in Italy that was experimenting on using proteins like I've described on rats — but I don't know the details or any outcome.

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Can you slow an individual's metabolism

It's not only plausible, it's in use today. It's called Therapeutic Hypothermia, and it's often used after cardiac arrest. The patient's core body temperature is reduced to around 89°F. It reduces heart rate, blood pressure, and brain function, while maintaining enough metabolism to keep cells alive. This has the effect of slowing or preventing cell death from oxygen starvation while still allowing healing to go on.

There are theoretical plans and designs out there for hibernation systems that could keep astronauts in a state of extended hypothermia for the duration of an interplanetary flight.

to the point where they wouldn't need to eat for 2 years?

It would still be necessary to wake astronauts occasionally for exercise periods and ship operations. At present, therapeutic hypothermia is only used for periods of about 24 hours or so, but in theory, with proper medical maintenance and monitoring, it could be continued almost indefinitely.

Would doing so circumvent the normal aging process?

It's unclear at present. As mentioned, it's only normally used for 24 hours or so; theoretically, however, an extended period of hypothermic hibernation might reduce aging to a degree.

Aging is a combination of wear and tear on the body's systems with a reduced ability to repair them as our DNA's protective telomeres are worn down. Reduced metabolism would affect both of these, with the body's systems not having to work as hard and cells not dividing as much.

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I note from the question you're not asking "how" it would be achieved but I think you probably need some gene editing / therapy for someone to be able to hibernate, the biological processes involved need to be identified first (because I don't think they have been yet?), the genes responsible for those identified & where to insert them in the human genome without causing undesired effects.

That aside lets look at what you did ask.

  • Can you slow an individual's metabolism to the point where they wouldn't need to eat for 2 years?

Based on the limits you place on the question (that it's some sort of hibernation & cryogenics is off the table) the answer has to be no.

The longest period of hibernation I can find any mention of is 344 days for a bat in captivity so it would seem two years may be pushing it.

While you hibernate biological processes are slowed rather than stopped & the animal survives off it's body fat, your crew are going to starve to death while they sleep if you keep them in hibernation for two years.

I think it's unlikely you can beat the bat & slow a persons metabolism sufficiently for them to need no food for two years while they hibernate.

Clarification / Rationale: if you want to reduce body temperature during hibernation so far that cellular activity is negligible enough they'll need (practically) no food (metabolized body fat) or oxygen then you'll be on the very cusp of freezing them.

The smallest temperature fluctuation might freeze them, then ice crystals form & they're dead.

It's far too delicate a balance & the best way to mitigate against an accident is to just saturate their tissues with a bio-antifreeze. Once you've done that (if you can) there's no point not going the whole hog & just freezing them for the whole trip.

But then you've got cryogenic freezing, which is not hibernation.

Best case scenario, you have to wake them after a year & feed them a high calorie diet for a few weeks to fatten them up again then you can put them back in hibernation. They need less food & oxygen on the journey with a slower metabolism but these needs won't be completely negated.

Or you can (as Ynneadwraith suggests) drip feed them intravenously while they sleep so you don't need to wake them, which means they're being fed so the answers still no of course.

  • Would doing so circumvent the normal aging process?

No it wouldn't, hibernation only slows the metabolic processes.

Small rodents that hibernate are known to have longer lifespans in general than similar species that don't so it's reasonable to extrapolate that aging is slowed a little, which is expected anyway due to the lower body temperature during hibernation & the slower cellular activity that produces.

If you want to stop aging you are going to have to freeze them.

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    $\begingroup$ You may not be able to slow their metabolism enough for them to survive for two years without sustenance, but I'm certain there would be significant savings in slowing their metabolism and feeding them via something like an intravenous drip-feed. No need to wake them up and get them to stuff their faces ;) $\endgroup$ – Ynneadwraith Apr 4 '18 at 13:27
  • $\begingroup$ @Ynneadwraith That's a good workaround, it still leaves us with a no answer to both the OPs two questions though :) $\endgroup$ – Pelinore Apr 4 '18 at 13:49

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