I am designing a species specifically designed to be technician on spacecrafts, where their workspaces have low-gravity. Here is how they are currently designed:

  • They have two pairs of arms instead of the current human design, two arms and two legs.
  • They have a prehensile tail which can wrap around the various bars placed around the ship.
  • Their main body is quite small, with very long and thin arms.

What I want to ask is, what other attributes would help them survive and thrive in this environment? They should be able to survive in Earth-like gravity and conditions, and survivability in the case of a hull breach would be handy.

The basic idea is based on this article: BBC: Will we ever have genetically modified astronauts?

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Dec 5 '17 at 4:47

11 Answers 11


Definitely cephalopods, bring on the space octopi!

If 4 hands are better than 2, then 8 is twice as good! Plus tentacles allow one to reach in all those hard to reach spaces, did I mention they don't have any bones and can move their entire bodies into those tight spaces! Arms are very helpful, you don't just need an arm to turn the wrench, in zero-g this will just spin you, you need multiple arms to secure yourself and transmit torque to whatever you're working on.

The Earth varieties of cephalopods are actually quite intelligent, and trainable, so it's not much of a stretch to imagine an intelligent species following this body type.

You can adapt a species to survive in the air, provide them with water breather packs, or fill your engineering spaces with water.

They can swim in the air (or possibly expel fluid in a jet) to propel themselves in large open spaces in zero-g, or use their many arms to propel themselves using available hand holds in tighter spaces.

Some species survive in the deep ocean and can survive very large pressure changes, this ability may help in loss of pressure situations.

Plus bioluminescence, they provide their own light, for those low light engineering spaces.

Their eyes are used for hunting and they have very good vision, they can see polarization in light, and their color changing skins can actually detect light as well, they can see with their skin!

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    $\begingroup$ Talk about cephalapod eyes! They're really super freaking cool. Also, probably pretty useful. $\endgroup$ – Jakob Lovern Nov 28 '17 at 22:17
  • $\begingroup$ Great, reminds me of Niven's Jotoki. $\endgroup$ – ths Nov 29 '17 at 9:49
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    $\begingroup$ I wonder how creatures without bones handle acceleration. I could imagine both better (because nothing gets squeezed against their bones) and worse (because no bones provide any integrity). $\endgroup$ – Philipp Nov 29 '17 at 11:42
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    $\begingroup$ According to biology.stackexchange.com/questions/43456/… an octopus can survive out of water for a few minutes, and has some ability to absorb oxygen through its skin. Design for improved skin absorption and/or use a high-oxygen atmosphere on your spaceship. $\endgroup$ – Graham Nov 29 '17 at 12:13
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    $\begingroup$ Also, suction cups are better than hands to grasp into smooth surfaces! $\endgroup$ – T. Sar Nov 29 '17 at 18:42

You can use a prehensile-tailed gecko pretty much as is.

prehensile tailed gecko

  1. Prehensile tail, as specified.
  2. Feet can grasp. Or gecko feet can stick to flat surfaces via VanderWaals interactions.
  3. Small body, quick.

These guys would never be floating around. They would always be on a wall or hanging onto something.

They would crave peanut butter, just like real geckos.

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    $\begingroup$ +1, Perhaps give them wings like a flying squirrel and they could traverse across open spaces faster than moving along the inner surface. $\endgroup$ – KalleMP Nov 29 '17 at 22:25
  • $\begingroup$ @KalleMP. They wouldn't need wings in microgravity. No modification necessary. $\endgroup$ – Mad Physicist Dec 1 '17 at 17:37
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    $\begingroup$ @Mad Physicist - they would be faster in microgravity and atmosphere with wings for larger surface area to get a purchase on the air. But these master technicians would make wings - foldable fans in a sheath across the back. If you need to traverse open space unfold them and swim with them. The fan idea would work for humans too. $\endgroup$ – Willk Dec 2 '17 at 15:49
  • $\begingroup$ @MadPhysicist It would be nice to be able to swim to some inner surface if one is drifting in a large hold. Bio or tech wings could assist. $\endgroup$ – KalleMP Dec 3 '17 at 23:38

I really like what @BornToDoStuff and @Jakob Lovern said about eyes, and I think you could even build on that a bit more:

Binocular vision is the basis of depth perception (think fine manipulation and 3D rotation tasks necessary for repair/installation type work), and is greatly facilitated by having two forward-facing eyes.

Monocular vision, where an animal's side facing eyes function more independently to cover a much broader field of view, is excellent for keeping track of one's environment, like the location of tools, parts, the orientation of your body relative to the ship, movement of the ship relative to nearby objects (if working outside) etc.

So why not code in an extra set of side-facing wide-angle eyes for the space engineer's head, since you're already accounting for the additional (or maybe just differently allocated?) sensory-motor capacity to operate two more hands and a tail? Maybe they could close one pair of eyes at a time to avoid over-stimulation if they can't use both simultaneously.

Moreover, one's sense of balance (the Vestibular system) is not all that useful in free-fall and changes in pressure like you'd experience quite frequently in space travel while moving between enclosed environments have the potential to aggravate vertigo. Maybe a similar function could be tied into these additional side-facing eyes, but one that is unique to free-fall/low gravity. A sort of inherent motion/inertia tracking and spatial awareness(like a sort of 3-dimensional balance?) based on input to these side-eyes.

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    $\begingroup$ I would have thought the vestibular suystem is more valuable if you do not have a tactile reference to a gravity vestor. The vestibular system of humans is a 3 axis angular accelerometer. What every cheap quadcopter has is a set of 3 axis accelerometers to determin orientation which would be usefull but only under acceleration and a 3 axis compass that would also be usefull if there was a reference magnetic field in the ship by design or as a result of drive technology or space warping. $\endgroup$ – KalleMP Nov 29 '17 at 22:23

What about... Spider octopus monkeys? Yeah? The long arms are useful, but tentacle arms would be better. As for hands, you have some options. You said they were designed, so we can skip out on evolutionary hacks. One of the key features of hands is our ability to oppose our fingers. Can you expand this for greater grabbing ability? Finger suckers would be a good idea, too. I'll explain why, soon. Now...There's a problem with tentacles. They're highly motile, but... They're not very strong.. The lack of an internal bone structure is a great weakness.

But what if you copied the structure of snakes, instead? Recall that the boa constrictor literally crushes its prey to death. If your engineers had this, they would have strength while only sacrificing flexibility slightly.

Now, let's recap this. You've got a monster with long snakes for arms, covered in suckers. Its hands are highly opposable. But can it live? Probably. If you were to install handles and such all over your spaceships, especially on areas not designed for walking, your engineers could slothcrawl their way along the ship. In situations with gravity, they would be counterpulled downward.

Now, how to balance the ability to survive without air and living in a earthlike environment... What about isolation? If the outermost layer of the engineer is covered in a thick squamous tissue that seals it in, it wouldn't need to even consider atmospheres. Imagine a pressurized sack of air that the engineers keep within them, making them buoyant in liquid and able to respirate in the depths of space.

But isn't space cold?

No, it isn't. It's merely a vacuum. Things freeze because of the pressure differential. If your engineers were able to maintain a stable internal pressure (maybe via a form of exosuit?), then they could not only survive a depressurization incident, but they could EVA when needed.

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    $\begingroup$ Note: "Contrary to myth, the snake does not crush the prey, or break its bones. Also, contrary to previous belief, the snake does not cause suffocation by constricting the victim. Instead, a study of death caused by boa constrictors, showed that constriction "shuts off" blood flow (and therefore oxygen) needed by vital organs such as the heart and brain, which would lead to unconsciousness and death very quickly – in seconds – in other words, constriction can interrupt blood flow and overwhelm the prey's usual blood pressure and circulation." Wiki. $\endgroup$ – Ender Look Nov 29 '17 at 1:28
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    $\begingroup$ Ah, but you forgot that when telling stories, myth is more powerful than truth. A mere dash of hamdwavium, and now snakes crush their victims. $\endgroup$ – Jakob Lovern Nov 29 '17 at 1:29
  • $\begingroup$ Haha, you have right! Also people will believe that it's true! $\endgroup$ – Ender Look Nov 29 '17 at 1:32
  • $\begingroup$ @EnderLook yes, my pet snake, Elvis, would dispatch his prey in about a minute. I think whether bones are broken, dislocated, or whatever will vary with the relative size of the meal. $\endgroup$ – JDługosz Nov 29 '17 at 5:39
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    $\begingroup$ Suckers would be useful in pressurised environment - though they wouldn't work in vacuum, would the Van der Waals palms of geckos (as mentioned by another answer) work? Also such a creature may have an unbalanced energy budget, but this can be solved by atrophying the digestive tract, which would require much less energy. They can only eat an easy-to-digest baby food-like compote, but that shouldn't be a problem on spacecrafts. $\endgroup$ – Eth Nov 29 '17 at 17:41

I think that having a prehensile tail is very useful but would actually argue against the extra set of arms as they would be very complicated for them to use properly what with all the criss-crossing of limbs.

I think a better course of action would be to make them more like monkeys, able to grip with their feet so they have the same number of limbs as us yet are able to hold more. They could hold tools or apply force (to wrench or other somesuch) with their feet, and use their hands for fine motor applications while holding themselves up with their tail. If you look at the muscle structure of monkeys you may find more desirable traits as well, for instance monkeys have a few muscles/tendons that we either don't have or don't really use that improves their grip strength with their "less important" fingers. Improved grip strength seems like a useful feature.

Also: Gecko style fingers/toes. Heck yeah. It would make them amazing at sticking to walls and ceilings without having to use their tail and give them great grip on tools and small things, you know, like those tiny screws that dont want to come off the table unless you wet your finger or use a magnet?

If they regularly hold their whole bodyweight for extended periods with their tail it would probably be thicker than a monkey tail, I am imagining something more akin to a reptile tail in shape (thicker at the base, tapering at the end for more finesse) but that is covered in skin, like a rat tail, for good grip.

Diving Lungs
Alright, here me out on this one. Whales. Whales are mammals, they need air, but they can also hold their breath for a long time and their lungs don't strain under the pressure of the deep water. These creatures would still start losing all of the moisture in their cells in a total breach unless they were covered in a weird carapace due to the vacuum of space, but if they have very good lung capacity (or maybe more efficient oxygen usage, such as being able to purposefully slow their heart rate) they will be able to deal with very low pressure and low oxygen environments for periods of time. Ex: if there was a breach and the ship lost its atmosphere in the decompression but then an airlock closed off that section so its no longer a complete vacuum in the rest of the ship, even if it is missing the oxygen.
Its hard to give them survivability in a vacuum without making them really weird bug people.

When there is little or no gravity having boring human eyes can be very inconvenient. Anything could float into them, if there is liquid the surface tension of the liquid could make it stick all up in your face, and in space there isnt always a lot of light. Sure there are stars all over but you arent guaranteed one of them is close enough to give you good light.
I think that giving them a second transparent eyelid would help them deal with low gravity gunk not getting in their eyes, and making them have larger pupils/eyeballs would allow them to see in the theoretically lower light conditions of space.

  • $\begingroup$ To clarify, the second pair of arms are taking the place of where the feet would go. $\endgroup$ – OneSurvivor Nov 28 '17 at 20:54
  • $\begingroup$ I really like the section about eyes. You should take a look at cephalopod eyes. Their pupil has an hourglass shape which lets them see the polarization of light. Maybe add a bunch of special eye sensors, like IR and UV? Then they'd REALLY be spider monkeys! $\endgroup$ – Jakob Lovern Nov 28 '17 at 21:31
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    $\begingroup$ Throw in a long iguana tongue that can be fired to retrieve drifting tools and you got yourself an alien technician $\endgroup$ – Stephan Nov 29 '17 at 3:56
  • $\begingroup$ @JakobLovern how does the shape of the aperture affect polarization? For ref: en.wikipedia.org/wiki/Cephalopod_eye $\endgroup$ – JDługosz Nov 29 '17 at 5:40

I think that a major issue for any zero-g species is going to be control when not attached to anything. If something is floating away (beyond reach), then they need to go get it; but you don't want to have to travel all the way to the other side of whatever (possibly large) space you are in. The options (I think) are: jet or tail/wing.

  • Jet: this is propulsion like a squid, which requires ingest of some working fluid followed by expulsion. Possible, but seems like it would be weak.

  • Tail/wing: This is more interesting. Rather than prehensile, I would make them have large folding tails that could be used to propel themselves around. The primary working limbs are the arms (2, 4, 8, whatever) and do not need to be very strong (zero-g); the prehensile tail is superflous. The body can be light-weight. Then, you make the tail such that it can unfold and generate a significant thrust-to-weight ratio.


As I think about how a real hot-rod of a space ship might be built, I think of one thing: every cubic millimeter wasted on air and access space is likely to have a tremendously high cost. Therefore, I spurn the Jefferies Tubes of Star Trek lore and suggest that pipes, conduits, and even simply minimal access space between components, constructs, and emplacements is likely to rule the day.

To that end may I suggest evolving a human (who, IMHO, must be exceptionally well paid for this) that is amazingly flexible. Arms want to be thin, very thin, with very strong digits. The body just as much so. Bones originally designed for leverage now need positional control, so I'm thinking all major bones in the arms and legs are made to resemble vertebrae. The head narrow and long, the brain elliptical rather than spherical. I imagine the tech "snaking" through the ship to affect repairs. Several sets of eyes would be helpful, one on top to see where you're going, one or two on the sides to examine the work in front of you.

Very low atmosphere is also a plus, so I'm thinking elongated lungs and highly oxygenated blood.

Cybernetics is a must so that hands can be dedicated to doing the job. Also, embedding basic diagnostic equipment into the hands and arms would seriously save effort (and the need to carry really bukly repair kits).

"The Scream* by Edvard Munch embodies in art what I'm thinking in spirit — in every possible facet of comprehension. So might Slenderman... but I don't want to talk about him....


Having more limbs or eyes will effect the amount of their brain devoted to motor skills. Similarly with a small creature, even with a neuron density of 100% it would not be as smart as a human.

Motor control is a trivial task for a machine.

The perfect engineer would be a huge brain with just enough control to use robotic parts of a ship, possibly with use of a brain interface if the creature had a brain designed to be read by a device.

Using different robots would be adaptable so the same engineer could do precision work inside an engine, lift heavy machinery or dangerous work on the hull during a battle.


A designed space creature would benefit from something like a Gecko's disposable limb, a tail that can be regrown? Something massive that if an astronaut were floating away in space to their doom, they could hurl the severed limb in the opposite direction and give themselves a nudge back towards safety.

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    $\begingroup$ Right now this reads more like a comment than an answer. This is an interesting idea. I'd recommend that you edit your question to provide more detail and be less conversational. $\endgroup$ – sphennings Dec 1 '17 at 19:45
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Whatever that thing is, a few thousands thumb-sized repair insects will be more effective than a human. They can work together to move something big, or individually to make thousands of tiny welds at the same time.

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    $\begingroup$ I think various sizes will be required. It is very difficult to assemble really strong structures out of fine structures. Making a concrete foundation using piano wire is theoretically possible but reinforcing rods are more appropriate as the bulk material dimensions are scaled for the forces. Obviously in the limiting case a human is made of microscopic cells but the bone structure is macroscopic and is used to good advantage to handle tools. Ants and bees working together can only perform a few community tasks well like carrying and bucket brigades. $\endgroup$ – KalleMP Nov 29 '17 at 22:31


In practice a spaceship does not need continual maintenance work so there will be long periods when the techs do not have any work to do. Have them hibernate. Also a slow metabolism so they don't consume much oxygen, food, and water. In this way there is less consumption of scarce resources.


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