I know a submarine would NOT make the greatest spaceship in the universe, but could it allow people inside to live in space?

A submarine can resist pressure, can hold oxygen inside, and there is a heating system... I think radiation would cause some issues, but is it the worst problem my poor hypothetical submarine people will encounter?

If a submarine with people inside was suddenly send into space, would they survive for a while?

Other questions:

  • If they don't, what will kill them so soon?
  • If they do survive for a while, how long?
  • If they do survive only for a while, what is going to kill them first?
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    $\begingroup$ there are possibly parts in the sub that are held shut by the outside pressure, and that would open in case of inside pressure. $\endgroup$ – njzk2 Aug 27 '15 at 17:58
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    $\begingroup$ I think you're overlooking a serious problem with the issue of pressure. Submarines are designed to resist external pressure trying to crush the hull. In space, you have to worry about the opposite problem: All the pressure is inside, trying to get out. The dynamic is one of explosion versus implosion. The engineering is exactly opposite. $\endgroup$ – Wad Cheber Aug 28 '15 at 5:25
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    $\begingroup$ This question is answered in "What if?" book from Randall Munroe (the creator of XKCD). $\endgroup$ – Florent Bayle Aug 28 '15 at 7:16
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    $\begingroup$ Relevant Futurama: youtube.com/watch?v=O4RLOo6bchU $\endgroup$ – Travis Christian Aug 28 '15 at 16:36
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    $\begingroup$ Professor Farnsworth: "Dear Lord! That's over 150 atmospheres of pressure!" • Fry: "How many atmospheres can the ship withstand?" • Farnsworth: "Well, it's a space ship, so I'd say anywhere between zero and one." $\endgroup$ – deltab Aug 28 '15 at 16:37

12 Answers 12


Okay, hold on. Let the actual submariners weigh in.

I spent 8 years of my life in the United States Navy aboard Los Angeles Class submarines as a Nuclear Electricians Mate. I have a background in engineering and radiological controls as a result. Please treat this as an extended comment - the answer as given is, in fact, no. But there are number of misconceptions that you guys are flailing around.

I can unequivocally and without a doubt say that it would not explode. The air would leak out from around the shaft that makes the screw go around, but you'd likely weld that shut before spending several billion dollars flying something that heavy that high. You'd also have to seal a few cable ways but sonar doesn't work in space, so no big loss.

As far as oxygen - (classified). But that kind of machine uses very very clean water, and uses it pretty slowly. It's not like it needs access to the ocean to work. Look up commercial grade systems and you'll understand.

As far as radiation - bring it. The whole charged particle thing is simply incorrect. A beta particle or an alpha particle simply won't cause an avalanche cascade in steel. There's not a significant neutron source up there. That leaves the gamma rays that everyone has to deal with.

As far as power - (classified). But no nuclear reactor anywhere can operate without a heat sink. That's just thermodynamics. And submarines sink heat to the Main Seawater Expansion Tank, aka the ocean. Period. No water, no power. Forget it - no workarounds.

As far as burning up - the ISS is a thing that is real. Polish it shiny and paint it white and there is no real risk of burning up. The reactor is down so, meh.

The biggest thing that everybody missed is that all submarines are built assuming that gravity is a thing that exists. The entire design of a nuclear reactor must take into account this very basic thing. Shoving something like this into microgravity means water starts coming out of the tops of tanks and pooping gets real risky. Steam that should be on top gets on bottom and water destroys your turbines while us enlisted men take turns opening various valves to naked vacuum because we like to watch things disappear into space - which is the real reason why we'd all end up dead from hypoxia.

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    $\begingroup$ @SDiv which is several orders of magnitude worse of a heat sink. $\endgroup$ – ratchet freak Aug 29 '15 at 11:34
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    $\begingroup$ @user2813274, even going sideways (90 degrees) would be catastrophic to personnel and equipment. We're not strapped in down there. For reference go back and watch The Hunt for Red October. The American sub they were calling Dallas was a composite of a few subs, mostly the USS Houston. You actually get to see the real control room in several shots. $\endgroup$ – Sean Boddy Aug 30 '15 at 16:37
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    $\begingroup$ @JorgeAldo, I would go to a federal prison for quite a long time telling you exactly how to poke a hole in a submarine. I will tell you that no weapon appropriately classified as an automatic weapon, that fires nothing larger than a rifle round, will even make us check the hull. We respond with deadly force on board the ship without regard to the pressure hull, with belt fed weapons if necessary. If you want to know more, go enlist and volunteer to be a submariner. $\endgroup$ – Sean Boddy Aug 31 '15 at 1:08
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    $\begingroup$ From now on, on Wikipedia, instead of [citation required] I want to see [classified]! $\endgroup$ – CJ Dennis Aug 31 '15 at 5:30
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    $\begingroup$ A submariner with a decent grasp of physics and enough domain knowledge to legally be a danger to himself - I can't think of a better authority to answer this question! $\endgroup$ – Mark K Cowan Aug 31 '15 at 14:21

I'll start with the spoiler: They are going to die. I'm not sure exactly how long it will take (because I can't find details on reserve oxygen capacity or submarine nuclear reactors...might be classified)...but they'll either suffocate or cook--and whichever happens will be their choice. A submarine's main limitation to how long it can stay under, in the ocean, is food...but this changes dramatically when they go to space.

The reason that a submarine can stay underwater so long is that it produces its own air from the water around it. It pulls the water in, splits it into Hydrogen and Oxygen with Electrolysis, and vents the Hydrogen back into the ocean. It deals with the Carbon Dioxide by use of scrubbers that use amine as a scrubbing agent...the CO2 is then vented into the ocean as well.

The sub has oxygen tanks where it stores extra oxygen, but there isn't nearly enough in there to last as long as their food stores would. This is why power failure on a sub is a big deal. It stops producing oxygen for the crew to breathe.

When their oxygen starts to run low, they could start taking their reserve of drinking water and feeding it into the oxygen generator to produce more, but...again, this is a finite supply. While it is possible that they would dump all of their drinking water into the oxygen generator, and thus die of dehydration, it is more likely that they would attempt to ration things so that they would run out at about the same time, thus allowing for the maximum possible time in order to be rescued.

But, there's a bigger problem. A nuclear submarine dumps the heat from its reactor into the ocean. A diesel sub does the same thing with the heat from its engines. In the ocean, this is great...because water is awesome at absorbing energy. The vacuum of space? Not so much.

Contrary to popular belief, the biggest temperature danger in space isn't freezing to death...it's burning up. On Earth, we can shed heat via conduction, convection, and radiation. The first two are dependent on something being present for the heat to be absorbed by...and radiation is massively less efficient than the other two. In space, you only have radiation.

Think of a submarine in the vacuum of space as the inside of a thermos. Big insulated tube. And you have a nuclear reactor as a roommate. Things are going to get very, very hot.

So, this is where you have the choice. Do you shut down the reactor so you don't all burn to death, and hope that whatever low-power reserve generator you have doesn't either run out of fuel or cook you all before you run out of water to convert into air? Or do you leave the reactor running to maintain effectively unlimited power, but burn yourselves to a crisp within short order?

Either way...not a good ending.

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    $\begingroup$ Yup. Subs are designed to be cooled by the ocean. No ocean means you roast. $\endgroup$ – Loren Pechtel Aug 27 '15 at 20:05
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    $\begingroup$ @fotijr That thing's what keeps the lights on and the air-thingies producing air. $\endgroup$ – hiergiltdiestfu Aug 28 '15 at 14:42
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    $\begingroup$ And you are flat wrong about power failure and oxygen. Submarines move like airplanes in the water - if we lose propulsion we say hello to crush depth. If we lose power we won't be able to sustain propulsion for long. The O2 generator would be shut down first thing when we have any kind of problems. Hydrogen and oxygen = bomb. $\endgroup$ – Sean Boddy Aug 29 '15 at 16:59
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    $\begingroup$ @Sean Boddy It's insulated by the vacuum of space, not whatever insulating a submarine has in of itself. $\endgroup$ – Piomicron Sep 10 '17 at 13:08
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    $\begingroup$ @piomicron, which is true in the space case, but the answer actually implies that it's built like a thermos and is insulated. The insulation is so poor that I was wearing a jacket in an operational nuclear engineroom, depending on where we were in the world. $\endgroup$ – Sean Boddy Sep 10 '17 at 16:49


  • A submarine is not designed to hold air in.
  • A submarine is not even designed to keep water out.
  • A submarine is designed to keep the rate of water ingress below the rate at which the bilge pumps can remove it.

The occupants will die in minutes as the air pressure decreases below the level needed to sustain oxygen flow across lung membranes.

If your submarine is being launched from the surface of an Earth-like planet, this will happen before it reaches space (100km up). Consider Helios 522 where people passed out and died somewhere under 10km up.


Short answer: NO.

It'll pop open almost instantly - not like a balloon, but split on a join or seal and leak air out. Submarines are designed to withstand compressive pressure, not de-compressive pressure.

Conversely, shuttles are designed for de-compressive pressure. This is why we don't fit propellers to our shuttles and send them underwater. :P

  • $\begingroup$ This will be the number one killer, even before guildsbounty's answer matters. As soon as the shuttle is in space it will blow explode from it's internal pressure and the question now becomes how long can an unprotected human last in space (hint, not long) $\endgroup$ – dsollen Aug 28 '15 at 16:49
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    $\begingroup$ Nah. One atmosphere of pressure isn't all that much. 1atm is 14psi. If 14psi coudld reupture the hull, sailors leaning on the inside would rupture the hull. $\endgroup$ – Shane Aug 28 '15 at 17:28
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    $\begingroup$ Unless you have a source showing the de-compressive abilities of subs (at < 1 atm), this isn't correct. Water exerts about 1 atm of pressure every 10m. It may be built stronger in one direction than the other, but not by a factor of 50-75 (nuclear sub). And certainly not by a factor of 1100 (deepest manned). There might be some valves or something that malfunction under decompressive forces though, but those should be easy enough to patch. $\endgroup$ – slicedtoad Aug 28 '15 at 18:07
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    $\begingroup$ Even a can of tuna can survive space vacuum! Let alone a submarine build for several atmospheres of pressure to dive- even if the force is in the opposite direction. Heck, my bicycle tires easily handle 5 or 6 times the pressure! $\endgroup$ – Daniel Jun 20 '18 at 14:41

Well, a submarine is primarily designed for pressures on the outside trying to crush it. However, I expect that the same seals that keep water out, will help keep the air inside. They of course will have no propulsion at all except for evacuating the ballast tanks.

Some of the subs are designed to survive six months under the ice caps on missions. So in theory the submariners could go for months. However, there are several things causing a problem. The first is weightlessness in a cramped place designed for gravity. The latrines will be almost useless, causing sanitary issues. People who aren't trained in freefall will be breaking bones, etc. in the confined spaces. On top of that even though the seals will do a decent job of keeping air in, there will be leaks because the they were designed for different things, air 'pushing' out is vastly different than water 'pushing' in. So if broken bones and sanitation don't kill them, likely asphyxiation will likely be the last killer.

  • $\begingroup$ Water and air are going to be a problem. Both are easy if you have lots of (electrical) power and water outside the hull, and subs are making use of that. $\endgroup$ – o.m. Aug 27 '15 at 18:38
  • $\begingroup$ Great point about the propulsion. $\endgroup$ – BrettFromLA Aug 27 '15 at 20:32
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    $\begingroup$ Don't count on a seal that's designed to keep water from coming in being just as effective as keeping air from going out -- ignoring the difference between sealing for water versus air, lots of seals rely on pressure in the intended direction to keep them tight, reverse the pressure differential and the seal may leak. $\endgroup$ – Johnny Aug 28 '15 at 0:19
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    $\begingroup$ I'm sure I mentioned that in my post $\endgroup$ – bowlturner Aug 28 '15 at 0:40
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    $\begingroup$ But you opened with I expect that the same seals that keep water out, will help keep the air inside $\endgroup$ – Johnny Aug 28 '15 at 1:01

Submarines do not have the same kind of insulation that space stations have, so the heating/cold might be an issue. Yes, both of the clips there are ships without power freezing, but they are space ships with space insulation and the submarine is designed to combat the constant ambient ocean temperatures.

Other than that, I would think the layers of metal would protect from most radiation for the duration that they are in space. They have no useful sensors or means of navigation. Perhaps the periscope for sighting and change with the ballast tanks (usable only once) could help them make a slight correction. They would have to be unusually precise on where their ballast vents are, not a common thought when in the ocean.

They should be safe from air leaks, because air leaks would make bubbles in the ocean and be a bad thing for a submarine. However, submarines are designed to hold up as the water pushes in on all sides. In space, the air inside is pushing out on all sides. Small things like this are assumptions engineers often make for the intended use, and often cause trouble when the thing is used in a different way. That insight is derived from my day job as a developer, working with other developers' code.

  • $\begingroup$ Regarding radiation: metal shielding is actually worse than nothing. Gamma rays such as Galactic Cosmic Rays you can't reasonably shield against, but solar radiation consists mostly of charged particles. These can be reduced by hydrogen-rich materials such as water, paraffin, or plastics, but when they hit metal shielding, the particle radiation energy is transformed into a shower of x-rays that are much more harmful to the crew. $\endgroup$ – amon Aug 27 '15 at 21:05
  • $\begingroup$ I think the cold will kill them before the radiation gets lethal And if they are turned to x-rays, by he outer hull, then the bulkheads would stop the x-rays like a dental filling, or like that metal apron the dentist used to put on me. I know submarines are not made of lead, but that is just an efficiency thing. $\endgroup$ – DeveloperWeeks Aug 27 '15 at 21:13
  • $\begingroup$ @amon - Cosmic Rays are energetic nuclei, not gamma rays, which are energetic photons. $\endgroup$ – Oldcat Aug 27 '15 at 22:51
  • $\begingroup$ @DeveloperWeeks Weight efficiency doesn't matter when it comes to absorption spectra. The reason the dentist used a lead apron instead of an aluminum one is because lead absorbs x-rays and aluminum doesn't. Your fillings on the other hand don't absorb all x-rays either, just slightly more than your teeth do. And anyways, freezing is the least of your concerns in this case, burning up is more of a problem thanks to that nuclear reactor not being able to vent its heat. $\endgroup$ – thanby Aug 29 '15 at 11:18
  • $\begingroup$ @thanby, that reactor simply cannot run in space. It will shut down long before burning up as you say might become a problem. $\endgroup$ – Sean Boddy Aug 29 '15 at 16:43

There is no way to launch something as heavy as a submarine into space.

A nuclear submarine weighs about 13 million pounds -- that's calculated because there is no way to weigh it in any conventional sense. There is also no way to tip it upright outside the support of water -- it's structure would not support its own weight.

The entire space shuttle weighed about 165 thousand pounds. That is to say, an average submarine is about 80 space shuttles!

The apparatus needed to launch a pound of payload into low earth orbit weighs between 25 and 40 pounds. [The Saturn-V that launched the moon shots had the best ratio, about 13.] The device needed to launch a submarine would weigh more than a skyscraper and no one could build such a thing.

Things designed to go into space are always as light as possible. Special materials (e.g. beryllium) are used and the layout of material is always just enough to stand the forces of launch. Some rockets are so flimsy that they cannot stand on their own (Soviet rockets had a tower that retracted just as the rocket motors started!). The LEM that landed on the moon was made of materials so thin that you could easily have kicked through it's walls with your foot.

Even the space station, which required weighs about 900,000 pounds -- about 1/14 of a submarine -- and it required 40 launches to get that much into orbit.

One cam imagine a submarine in orbit but why?

  • $\begingroup$ The question assumes that the submarine is already in space. $\endgroup$ – HDE 226868 Aug 30 '15 at 15:12
  • $\begingroup$ I didn't ask how to launch it. Sure, why would someone launch it ? That's non sense. (Just another stupid debate with my brother, if you want to know. We had a few ideas about the way this poor submarine could find himself floating in space, but that's even more non sense, does it deserve a question here ?) $\endgroup$ – Tyrabel Aug 30 '15 at 15:15
  • $\begingroup$ " that's calculated because there is no way to weigh it in any conventional sense." That sucks man! If only Archimedes was around, I'm sure he would have figured something out. $\endgroup$ – NPSF3000 Aug 31 '15 at 6:38

(from the dead)

Sean makes a great case why and why not an un-modified 688-class (or comparable design) would work.

My background: Sonar tech on a 688 Flight II boat, circa early 90's.

If you were a crew on a nuclear submarine and suddenly found your whole ship suddenly teleported into space, you would not be happy. Gravity, power, life support... all those things that work in the vacuum of space are now missing. You wouldn't instantly die, but life would be measure in no more than days, possibly hours. Leaking seals would let air out and the black hull would collect lots of heat through radiation.

If that's the core question, will a submarine make a good spaceship, the answer is no.

That said, me and some buddies played a thought experiment on how to convert a submarine to a space ship for RPG campaign. A few caveats...

1) Star Trek style technology is available... impulse drives, warp reactors, anti-gravity, etc...

2) Yamato style stealth engineering. We don't want to look like we're building space ships, so let's modify an existing naval vessel.

We basically replaced the fission reactor with a matter / antimatter warp core, and turned the entire after section into a Star Trek style warp nacelle. Added gravity control, sensors and propulsion / helm controls. For giggles, we left the interior layout as untouched as possible.

The funny thing is, our design for the control center (this was about 1992 as I recall) shares a lot with the publicly available images of the current Virginia-class subs.

It should go without saying that a submarine makes a better starting point than a surface vessel.

A submarine hull could be re-engineered into a spaceship, if you had sufficiently advanced technology. Under most economic models, it would be cheaper to build a purpose-built spaceship, but I'm sure a scenario could be made to compensate for that.

  • $\begingroup$ This looks more like and anecdote than a real answer. See help center and tour, please, to see what this site is about, and what it is not. $\endgroup$ – Mołot Apr 24 '18 at 17:52

The ordinary (not nuclear-powered) submarine cannot stay submerged for really long, as it uses battery power to run various required systems. It may also run out of other necessary resources like compressed air, and it may eventually loose some air being not completely airtight. Some devices may not run in the absence of gravity.

However I think that at least with the help of heroic attempts the crew may be able to survive for many hours if not days.


in real life, the crew might live for hours, more likely minutes as has been covered. In fiction, it's been done pretty well by John Ringo and Travis Taylor in http://www.baenebooks.com/p-613-vorpal-blade.aspx of course, his setup depends on an alien device.... but it's a fun read, a lot of the science is sound given the premises made in the name of a good story :)

Ranging in topics from the best gun to kill armored space monsters to particle physics to cosmology, Vorpal Blade is a return to the "good old days" of SF



Most unmodified would fail but it depends on the sub, not to mention the increasing heat warping metal. A hardy sub might survive with proper cooling and maintenance. They would definitely require hull modifications, sealing the propeller and replacing the propulsion system, removing and sealing the fins, and sealing the water containers. I would be safe and give another hull layer along with extra inner steel . Then the sub could survive but you need life support for the crew. Other than that I don't see why not.

Just make sure your devices work in free fall, and modify them if necessary.

  • $\begingroup$ welcome to Worldbuilding! you've provided an answer which disagrees with the top answers here, i suggest reading the accepted answer to see why your answer is incorrect $\endgroup$ – Cursed Apr 2 '17 at 19:39

A submarine would make a great spaceship. I don't know why the other answers say otherwise. The difference between a spaceship and a submarine aren't that large. Of course it isn't automatically ready to go to space, it would need a lot of improvements, but not as much as you would think. If the right precautions are taken and improvements are made, it would make a decent spaceship.

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    $\begingroup$ Hi Kyle. Do avoid rude language in posts, even if it is a subject that you feel strongly about and even if you feel other answers are wrong. See our be nice policy. $\endgroup$ – a CVn Sep 10 '17 at 12:09

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