Would it be possible to modify a human to be able to survive in space without protective gear?

Genetic engineering and cybernetic enhancement are both allowed, although when not in space the person in question should look completely normal.

I'd be interested both in modifications that allow emergency survival (for example functioning for 5 minutes in order to allow you to reach shelter after a hull breach) through to actually being able to live and work in space for extended periods of time wearing only minimal protective clothing.

  • $\begingroup$ What's your definition of 'limited'? A very basic inflatable bubble can do for injured or unconscious personnel for 5-10 minutes, for instance. $\endgroup$ Feb 11, 2015 at 14:23
  • $\begingroup$ An inflatable bubble would be a good idea to help keep people alive but isn't really what I had in mind as it is preventing you being exposed to space, rather than allowing you to survive exposure. $\endgroup$
    – Tim B
    Feb 11, 2015 at 14:27
  • $\begingroup$ In the longer term is space weather and exposure to various forms of radiation a concern here? $\endgroup$
    – Twelfth
    Feb 11, 2015 at 23:37

6 Answers 6


Surviving in space (a vacuum) is fortunately not that hard, the dangers are exaggerated in fiction.

How I would go about this is making whale-like modifications to humans, in many ways going from a high pressure environment to low pressure, is not too different to going from a low pressure to vacuum. So all the tricks which deep sea diving mammals such as whales use to retain functioning for minutes or hours under the sea, could be implemented to improve human functioning under extreme pressure and oxygenless environments. This includes: 1) Resistance to the bends. 2) The ability to store (or economize on) oxygen. 3) The ability to collapse the lungs. 4) Modifications to ensure the ongoing functioning of the cardiovascular system even under extreme conditions, much like the whales do it.

The next point of vulnerability is the eyes in particular, as the moisture rapidly boils away. A biological mechanism which could help is a tough transparent inner eyelid, such as many reptiles and fish have. By sitting flush against the eyeball, it would help protect against the vacuum, while the human could retain vision.

For more comfortable functioning in vacuum, it would likely be necessary to generally toughen up and improve the seal of the skin, we might want features such as ears and nostrils which can be closed tightly, thus protecting the delicate membranes within. In a vacuum we have no use for the ears or nose.

With relatively simple modifications like this, it wouldn't be healthy to be in a vacuum, but functioning may be retained.

If you want much longer functioning, one of the major issues is going to be oxygen. You simply need to store more of it. Whales can do up to 2 hours. It would probably be possible to push it even further with further modifications. Ultimately though there is no way to get oxygen in a vacuum, so a human is stuck with what they can store in their body. Also, as the human isn't breathing, it is also necessary to store CO2 in the body, until such time as the lungs can operate again. This CO2 makes for another constraint.

The other problem is temperature regulation, unless exposed to direct sunlight, the greater problem is going to be getting rid of excess heat, as vacuum is highly insulative. Sweating would continue to function, as water evaporates just fine in a vacuum. This then places another constraint on maximum duration - the amount of water we can store in our body, and stand to lose without passing out.

With a full suite of whale-like modifications, plus additional modifications for exposure to vacuum, a human probably could remaining functioning for about one hour in hard vacuum. Longer than that would likely require mechanical or nano augmentation, such as a unit capable of removing CO2 and replenishing oxygen in the bloodstream. Note that a human uses non-trivial quantities of oxygen, about 20L an hour, even with efficiency improvements storing oxygen is going to become a problem, and rather than storage you might be looking at some kind of externally powered unit which processes CO2 into carbon and Oxygen, thus giving extended operation without external oxygen. Biologically this process is called photosynthesis, and sunlight is available in space, but grafting vacuum-tolerant branches onto a person's back, and then putting them in the sun, would introduce a host of other problems. But in principle a well designed photosynthetic human might be able to operate in vacuum for extended periods, it's just the skin wouldn't have enough surface area - an entire mature tree only produces oxygen at about the same rate as one human burns it, so you would need a massively more efficient process, and it would need to operate in hard vacuum. So actually both oxygen storage, and oxygen recycling, would be problematic, making for something of a limit on how long a human could function in vacuum, without adding hundreds of kgs of mass onto him.

  • $\begingroup$ This answer is well thought out. Welcome to the site. $\endgroup$
    – James
    Feb 12, 2015 at 21:52
  • $\begingroup$ I don't understand why CO2 storage would be an issue, couldn't it just be dumped out into space (I'm sure modifications would be required but surely not excessive modifications) $\endgroup$ Feb 15, 2015 at 21:30
  • $\begingroup$ @RichardTingle normally humans dump CO2 out through their lungs, but the adapted human would collapse their lungs and not actually be breathing. As such, the usual gas exchange mechanism wouldn't be operational. In truth I don't know whether the lungs could release CO2 without an air mix low in CO2 to release it into (i.e. if the lungs can fill with pure CO2 from the blood - or if it depends on relative concentration in the blood vs air), it might be possible or it might not. In any case whales just store it in their blood until they surface. $\endgroup$ Feb 16, 2015 at 11:18

From what I have read, the boiling issue is actually not as large as it sounds. As you boil, the surface chills down rapidly. You'll suffer frostbite quickly as the outer layers of your skin/tongue/eye freeze, but you actually don't boil away all that fast because its limited by thermodynamics. The body is actually a pretty good bulk heat source.

The current limitation for human "spacewalking" is that we aren't equipped to hold onto air in space. It's really hard to hold 1 atmosphere of pressure. The air literally gets ripped right out of our lungs. These pressure differences are similar to those we see in diving mishaps where a diver surfaces without exhaling. Rising from 10m under the water (with SCUBA) without exhaling on the way is sufficient to cause high risk of pulmonary barotrauma. 10m of water happens to be roughly 1 atmosphere, which is what your spaceperson is experiencing. So one solution would be to beef up the lungs to take that kind of abuse. However, it's not easy to improve on such an amazing system as the lungs, so I'd suggest a different solution.

Give the brain a way to consciously route blood around the lungs instead of through them. Currently humans can survive 14 seconds in pure vacuum, if they exhale to avoid barotrauma. The limit is actually rather frustrating: at 0psia, hemoglobin releases oxygen rather than capturing it. All of the blood passing through the lungs releases its oxygen into space. It takes about 14 seconds for that completely deoxygenated blood to reach the brain and cause instant syncope. If you could route blood away from the lungs, you could cycle it and survive much longer. You would just have to build up your anaerobic tolerances in your muscles so that they don't use up oxygen that your brain needs.

We even have the starts of this hardware. The Fossa ovalis is a hole between the right atrium and left atrium of the heart. When we are still developing, and getting our oxygen needs from the placenta, this hole exists to allow most of the blood to bypass the lungs completely. The septum primum is a sort of valve that goes over it to prevent blood from going the wrong direction. During our first breath, the pressures in the pulmanary portion of our circulatory system to drop, pulling the septum primum shut, and we fuse it shut in very short order (having fulfilled its purpose). We do similar to the Ductus arteriosus and the Ductus venosus for the same purpose.

  • $\begingroup$ People can survive without difficulty in low-pressure environments if given pure oxygen to breathe (not generally done in practice because of the extreme fire danger). If a person with a lungful of 100% pure oxygen at 0.2atm of pressure were exposed to vacuum, would the reduced pressure allow the person to avoid having to exhale? $\endgroup$
    – supercat
    Feb 11, 2015 at 23:50
  • $\begingroup$ @supercat It would make sense that they could survive. It would still hurt quite a lot, but it'd hurt a lot less than the alternative. I had trouble finding good numbers for how much pressure our lungs can take. 0.2atm is roughly 3psi, which is apparently right around the most pressure the average person can exhale with. $\endgroup$
    – Cort Ammon
    Feb 12, 2015 at 2:35
  • $\begingroup$ If people can exhale with 3psi, I wonder if someone could survive for a decent length of time in vacuum with nothing but goggles,m a low-pressure breathing apparatus, and an elastic belt? $\endgroup$
    – supercat
    Feb 12, 2015 at 15:56
  • $\begingroup$ @supercat I'd be interested too. I've heard science fiction stories where pressure suits are nothing more than elastics. However, goggles would be tricky. You'd have to get a sufficiently airtight seal to hold enough pressure in to keep your eyeballs happy. Goggles usually are better at keeping pressure out. Something wraparound with a big wide seal might work nicely $\endgroup$
    – Cort Ammon
    Feb 12, 2015 at 15:59
  • $\begingroup$ I think the eyes would need about 0.5psi (vapor pressure of water at 25C). Goggles that are only designed for pressure might not seal against that, but it shouldn't be hard to make suitable goggles. If one was willing to accept a hose from the breathing apparatus it should be easy to keep the eyes happy; even without the hose it might still be doable. $\endgroup$
    – supercat
    Feb 12, 2015 at 16:06

If one only needs to survive a few minutes until rescue, only a few modifications need to be made.

The biggest issue is gas loss - the air in your lungs will immediately evacuate as humans cannot hold their breath that strongly. My solution would be primarily an artificial one - a cybernetic lung. Replace one lung with a backup oxygen supply and carbon dioxide scrubber. Upon pressure loss, the normal lung collapses and seals shut (prevents active loss of oxygen from the blood) while the artificial lung takes over using stored emergency supplies to keep the individual alive. People living in artificial atmospheres should be fully functional with only one lung, so this shouldn't be significantly damaging for daily life (depending on efficiency of the unit and expected service period, perhaps only one lobe of a lung need be removed). Without the artificial lung, the lungs need to collapse and seal off as the person immediately enters into a state of hibernation to slow metabolism as much as possible.

On the not strictly speaking necessary for short-term survival but would be nice list: All orifices will need some modification to protect the delicate tissues. The eyes could use some kind of robust nictitating membrane which could still provide visibility but seal shut the eye socket. This shouldn't really effect the appearance much, because it generally keeps out of the way, and we still have the vestigial remnants of one so it should be an easy adaptation. The nose clamping shut to protect the mucous membranes will require a little more musculature, but that should be minor and not necessarily change appearance (possibly a slightly more bulbous nose which some people have anyway), though some enhanced viscosity mucus could just plug the nostrils. The lips will need to be a little stronger to hold shut to protect the moist tissues - certainly not enough to hold in the breath, but just reduce moisture loss with partial pressure (uncertain as to how much good that can really do). The eardrums will need to be significantly strengthened to not be blown out in the initial decompression (very minor change).

Lower down, I'm thinking modified urethral/Bartholin glands secreting some kind of special protective mucus whose release is triggered by very low pressure. The mucus should protect the tissues by keeping the mucus membranes moist. Some analog could be used for the anus as well. This will somewhat protect the person in vacuum from the worst of it, but when decompression happens... wear a diaper.

The skin is probably sufficient but some finer stronger protein mesh reinforcing it might be desirable (an unexpected decompression may not be a safe event and a cut could become a more serious rupture in vacuum). Capillaries should likewise be toughened to reduce serious bruising, but this needs to be balanced with risks of arteriosclerosis. No visual changes here, just more resistant to bruising and lacerations.

This should keep a person alive for a few minutes in the event of getting thrown out an airlock, but not cause any obvious external changes.


I would say the first thing would be to modify the skin. It would need to handle at least short periods of extreme cold and also be able to prevent the body from freeze drying through moisture release as the body tries to equalize with the surrounding environment. Though of course having specialized body suits could help with this. If the body isn't loosing moisture or other matter it will dramatically slow the freezing process.

The next piece would be to protect the eyes. Both from freezing and from any light source that might blind you. There are different ways to do this as well. The easiest of course would be to replace eyes with cybernetic implants, allowing one to see the full EM (or much more of it any way) spectrum. One step back would be cybernetic goggles that have an interface to the brain and sit over the eyes but could be removed like glasses.

The last is the most difficult and most important. the lungs and enough oxygen. My biggest recommendation for the average space explorer would be something like this, this happens to be a bicyclers airbag, it blows out into a protective helmet. Having something like this that would expand to protect the head and supply some oxygen would be the most useful and likely to happen. It would have to at least encompass the torso with the head to allow the lungs to expand AND contract to allow breathing.

However, going cyborg, having a CO2 scrubber for your blood stream and a back up oxygen tank to work in place of the lungs might be what is needed. Of course having blood that can carry very large amounts of Oxygen would be extremely helpful, maybe even having nanobots that keep a 'backup' supply all throughout your body and in the blood. Then you just need to have a reflex not to exhale or try to inhale, when in a vacuum.

  • $\begingroup$ with air in the lungs and the head enclosed the chest would expand and the astronaut would be unable to exhale. Removing reliance on the lungs is needed to survive $\endgroup$ Feb 11, 2015 at 14:15
  • $\begingroup$ @ratchetfreak I'll need to make some adjustments to my answer! $\endgroup$
    – bowlturner
    Feb 11, 2015 at 14:17

The biggest problem is lack of oxygen. Over time radiation and evaporation due to low pressure become lethal as well. I don't think temperature as such would be a problem since vacuum is pretty good insulator. Heat loss would be thru radiation and evaporation only, no conduction or convection would happen.

For oxygen, the solutions would be storing it (whales do this), regeneration thru photosynthesis, switching to anaerobic metabolism, or, my favorite, making people carry oxygen masks. Second pick would be the anaerobic metabolism, our muscle cells already can do that under exertion, so it could be built incrementally on top of existing systems. You'd basically extend it to work on all cells and add something to deal with the lactic acid.

This would be enough to deal with emergencies, given some training. The issue is that the vacuum would probably mess up your senses with eyes drying up painfully due to evaporation and ears obviously being useless and probably hurting a lot. Without training this would probably cause lethal panic and disorientation. But if you knew where to go and what to do and kept your calm surviving the five minutes should not be an issue. Making blood store more oxygen would probably be enough as well. I think some divers can already do this, actually. So simple training might be enough without any genetic stuff.

The second most urgent issue would probably be protecting the eyes so you could see properly in the vacuum. A nictating membrane similar to what camels and polar bears use to protect their eyes should be enough since you just want to stop evaporation not to have a pressure differential. And we probably still have much of the genes...

Overtime evaporation from the lungs and elsewhere would become an issue. Some sort of protective mucus that dries and hardens in vacuum and stops loss of water might work. It doesn't really have to be that perfect since we'd still want to use evaporation for temperature control. I am guessing the easiest solution would be to simply have more fluid to begin with. A thicker, more rounded, body would help there.

The final killer would be radiation. Protective clothing would help, unless people want to go to space naked. It might be easiest to make the protective mucus mentioned before highly reflective so that it reflects most of the UV-radiation and much of the visible light. UV-radiation might also be a convenient trigger for releasing the mucus. And being highly reflective isn't a bad thing, if you are waiting to be rescued while floating in space.

Note that this answer only dealt with short term adaptations. For long term survival more extensive changes would be needed. It would probably be easier to use space suits or even robots. Remote controlled robots would probably be much more practical for vacuum work than adapting to live in vacuum.


A lot of living organisms produce shield like armor to defend against climatic extremes. This sort of behavior mainly happens on the microscopic level though. The process goes something like this: 1.) Environment gets tough 2.) bacteria start producing this shell (called an endospore) 3.) Bacteria go dormant until sustainable environment makes survival and reproduction possible.

While I am sure that, given a couple hundred years or so, we could modify our cells to do this, it is a highly unlikely solution to things like a hull breach because this protective shell is: A.) limited in what it can protect against B.) causes the organism to become dormant.

In short, rather than saving the person, I speculate that a massive case of endosporic cells would cause the person to go dormant and float into space if the breach is large enough. If you want to read more about bacterial spores check out this Wikipedia site.


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