I thought about what kind of animals could make it to space, and I thought about how vertebrates can apparently withstand the G forces need to travel to the ISS, but I hadn't really thought about invertebrates, which I thought may not make it due to the G forces involved, depending on how fragile the organism was.

Then I looked up the list of types of animals who've made it to space, and it appeared to be quite varied, lots of different organisms appear to be able to make it to orbit.

Are there, however, some animals which physically couldn't/can't realistically make the journey?

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    $\begingroup$ More narrow version of this question that immediately popped up in my head: are there animals that do not survive being weightless (even if their surrounding has the appropriate medium and pressure)? $\endgroup$ – DarkDust Sep 25 '19 at 7:01
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    $\begingroup$ I cringe to imagine a giraffe undergoing the g-forces of a launch. $\endgroup$ – Caleb Hines Sep 25 '19 at 17:41
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    $\begingroup$ Fish. How would they stay in the water? Unless it was a sealed globe. $\endgroup$ – Chloe Sep 25 '19 at 22:12
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    $\begingroup$ @Chloe See the "list of types of animals" link. There have been fish that have been sent to and then sent back from space alive. $\endgroup$ – whn Sep 25 '19 at 22:59
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    $\begingroup$ @CalebHines Presumably it would be sedated and launched while prostrate (lying on it's side relative to the direction of thrust) on a padded, shaped surface. So the ugly situation you're imagining with those thin legs and neck would not be an issue, all of that would be securely supported by its acceleration couch...just like humans. $\endgroup$ – user3067860 Sep 26 '19 at 16:04

To keep an animal alive, a spacecraft needs to create conditions (e.g. temperature, pressure, concentrations of gases or electrolytes) within the animal's normal physiological range. We can recreate nearly any environment; however, the resources necessary to do this may be prohibitive. Thus, the answer to the question is that it may be possible, yet unfeasible, for many animals.

Some examples:

  • There are many animals that exist only in deep seas. Attempts to harvest such animals have often failed, as they live at very high pressures, and burst when brought to the surface. You'd need to design a container that operates from collection in the deep sea, to preparations at sea level, through the flight into space.
  • Some animals are simply way too massive and voluminous. You would need a giant space capsule to keep an elephant or a whale. (Sorry, Star Trek IV.)
  • Many wild animals get stressed in the small environment of a space capsule.
  • If you are going to keep the animal for a while, you need to feed it. Many animals will only eat live food, so then you have to keep that alive as well.
  • Every animal has limits to the acceleration they can tolerate, and some species (e.g. giraffes) need low acceleration. Getting to orbit requires reaching orbital velocity. You can reach orbital velocity with a lower acceleration, but you will then need to burn the rocket for a longer time. However, doing so requires more energy (and thus fuel, mass, and cost). That's why most rockets use as high of an acceleration that can be tolerated by the passengers and and spacecraft.
  • An alternative solution to the acceleration issue would be to construct a space elevator.

If you have unlimited money, mass, and volume, then these aren't problems.

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    $\begingroup$ @Uwe: You could constantly accelerate them (using propulsion) to create artificial gravity. Again, possible but not feasible. $\endgroup$ – DrSheldon Sep 25 '19 at 17:55
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    $\begingroup$ I think this answer could be improved by adding a comment about how a low-G launch (think 1.1 or even 1.01 G) is completely possible from a physics standpoint; it's just materials- and cost-prohibitive at the moment. $\endgroup$ – Phlarx Sep 25 '19 at 19:40
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    $\begingroup$ "... some species (e.g. giraffes) need low acceleration" Citation? $\endgroup$ – bishop Sep 26 '19 at 1:01
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    $\begingroup$ @JohnDvorak, no, I don't know how to calculate something like that, but it would be a huge amount. Like orders of magnitude more. We can see the technology in action now with the SpaceX hover test; just hover and accelerate slightly upward, slightly orbitward until you are in orbit. However, SpaceX's tests only span a few hundred meters at most, and never travel very fast, so I'm not sure that their numbers would be particularly useful. The total time to reach orbit will be vastly increased, and you'll need fuel to fight gravity for that whole duration, in addition to the normal launch costs. $\endgroup$ – Phlarx Sep 26 '19 at 15:24
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    $\begingroup$ @Phlarx: if you're going to use a low accel profile, you might as well get some aerodynamic lift. i.e. a spaceplane. Or at least the first stage should have wings and air-breathing engines. It's still less efficient than a high-G rocket that just gets up and out of the atmosphere quickly, but if you aren't going to do that you can do far better than hovering a brick on rocket thrust. $\endgroup$ – Peter Cordes Sep 27 '19 at 16:33

The two extremes are the most-likely sources of death for creatures in space - weightlessness and the g-force of takeoff.

Weightlessness could be a critical issue for any creature which relies totally on gravity for swallowing - it's likely that some bird species would not be able to properly eat or drink in space. In the long-term, it's likely that a few weeks of weightlessness won't kill many terrestrial creatures, even if it causes some difficulty.

Crushing damage or heart failure from G-force are much more likely causes of death. Small creatures are probably going to be fine - many small creatures regularly submit themselves to far higher G-force than takeoff... just by hopping around. Froghopper bugs hit ~400G regularly. Fleas hit 100G's. I'm sure house cats break 3G easily, and that's space flight. The square-cubes law helps explain this - proportionate strength makes is more likely for small things to hit higher G-force in their daily existence.

As a back-of-the-envelope calculation, since we know that humans can survive, we can assume (pretty safely) that any creature smaller than a human will probably survive the G-force of takeoff.

So what about the big boys? Elephants are unlikely to survive. An elephant at 3G is going to be experiencing ~36,000 pounds of force, although most elephants seem capable of handling roughly ~1.5G for a limited period of time - ask National Geographic about how that works. 36,000 pounds still sounds lethal to me. Giraffes would die - their hearts are already taxed by 1G. Whales are absolutely toast - they can't survive 1G out of water for long, you can forget about 3G in any circumstance. I have no idea where the line will be drawn, and I imagine that other factors matter as well... but I think that anything larger than a grizzly bear is likely to suffer fatal complications from extended 3G forces. It's just more than their circulatory system can handle.

Some creatures may be able to survive an otherwise fatal journey if placed into a gel or other liquid substance, although the container would have to be immensely strong or perhaps also serve to immobilize them (good luck building a tank that can survive an angry whale.) I don't think this would prevent all circulatory issues, although it would serve to spread out pressure and reduce damage from crushing.

Ultimately, we're unlikely to know unless we test, and I'm not enthusiastic about the ethics of the tests that would be required.

  • $\begingroup$ +1 for the square-cube law. $\endgroup$ – Pere Sep 26 '19 at 9:27
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    $\begingroup$ What if you partly submerge the large animals in water or some kind of gel? Swimming works identically in all kinds of gravity. $\endgroup$ – Michael Sep 26 '19 at 10:09
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    $\begingroup$ What does a giraffe's blood pressure look like if it is sedated and prostrate (on a supportive acceleration couch)? Can we use some kind of compression garment on the neck to help there? $\endgroup$ – user3067860 Sep 26 '19 at 16:32
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    $\begingroup$ Why do you need to prevent the whale/elephant touching the container? I suspect a blue whale in a tank would fine take-off about as difficult as a human. $\endgroup$ – Martin Bonner supports Monica Sep 27 '19 at 8:21
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    $\begingroup$ @MartinBonner: The side of the tank is a red herring. Does anything weird happen when you touch the side of a pool? No. The container is perfectly capable of exerting a force on the part touching it, just like water. But I would worry about the extra Gs on internal organs, e.g. the heart hanging from whatever supports it in the body cavity. Much of what's in there is liquid-like and uncompressible so being immersed does help, but any density differences let gravity / acceleration have an effect. $\endgroup$ – Peter Cordes Sep 27 '19 at 16:41

Lugworms living in the sand below tidal sea waters. They need gravity to burrow in and feed from the tiny animals living between sand particles. They would survive some weeks without food.

Starfish, sea urchin, sea cucumbers could not live in microgravity for longer time. They need the ocean floor to move and search for food. Starfish and sea urchins do not swim in the water as they do not have fins. Some sea cucumbers swim only for a short time.

Green Bonellia (bonellia Viridis) is another marine worm living on and partially in the ocean floor. See 1 and 2.

Those animals are part of the submarine eco system which they need to survive. They may survive the trip to space but would not live very long in microgravity.

Small air breathing marine mammals like beavers and sea otters could not swim and dive in water and then return to surface as they are used to for breathing.

Water birds used to fly in the air, walk on land, swim at the water surface and dive in the water will be restricted to fly only.

Giraffes will experience problems caused by very high blood pressure in the head during zero gravity. Narcosis on Earth is risky due to very high brain blood pressure when head and heart are on the same level in a lying position. A narcosis may be limited to an hour or less but zero gravity may be days orweeks.

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    $\begingroup$ I suspect space beavers would do just fine, but the Canadian Space Agency has not yet approved my proposal. $\endgroup$ – Roger Sep 25 '19 at 15:09
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    $\begingroup$ Microgravity can be solved with e.g. spinning space stations if we really want that, there are no insurmountable technical problems there other than the cost and size - it's impractical to make a small space station with 0.5-1g artificial gravity, but quite plausible for a larger habitat. $\endgroup$ – Peteris Sep 25 '19 at 23:37
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    $\begingroup$ @Peteris: It makes you wonder how much gravity you need to swim. $\endgroup$ – MSalters Sep 27 '19 at 9:50
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    $\begingroup$ @MSalters I suspect very little, if any. It's just displacement of material, just like a rocket engine when it comes down to it, only with an external propellent. I'd be far more concerned with the difficulty of breaching the surface and exiting the water, as it has the tendency to flow over any surface it comes into contact with quite effectively. I'd love to test and see how easy it would be, but I'd definitely insist on a scuba set for at least the first trial, and some way to ensure I can get out of the water properly. $\endgroup$ – Baldrickk Sep 27 '19 at 10:00
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    $\begingroup$ @MSalters I figured it was worth a follow up question $\endgroup$ – Baldrickk Sep 27 '19 at 10:15

No, because the "space" is mostly just "no gravity" but the gravity can be simulated just by rotation.

Also, any animals are unlikely to die immediately without the gravity because otherwise just turning upside down would kill them on the Earth. This is differently from human-made devices like pendulum clocks or even car engines - these are not normally designed to work inverted.

Only if we consider longer times (maybe cannot feed, maybe cannot reproduce, maybe cannot properly behave, maybe something degrades), then the presence of gravity may matter.

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    $\begingroup$ This does bring up the question, have we ever attempted the "flip them and see if they die" experiment on (say) elephants, giraffes, or whales? $\endgroup$ – John Dvorak Sep 25 '19 at 18:00
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    $\begingroup$ The question seems pretty focused on the hazards of the actual journey to space, which this answer doesn't address at all. This seems to be hand waving the entire trip aside and discussing what would happen if they were already there. $\endgroup$ – Chris Hayes Sep 25 '19 at 18:05
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    $\begingroup$ @JohnDvorak: Judging by this random video I found on YouTube, elephants at least do seem to be able to survive being (at least somewhat more than halfway) upside down. (Not to mention being underwater and having a couple of other elephants climb on top of them.) $\endgroup$ – Ilmari Karonen Sep 25 '19 at 23:08

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