Why aren't the 'bedrooms' aboard the ISS also the escape pods?

Question

If ISS was designed this way, couldn't the astronauts have a quick escape if the ISS is destroyed (severe meteor shower, re-entry, uncontrollable fire, explosive decompression, etc.) while they are asleep.

The crew cabins are also centralized on the station, so they would be quick to access.

.. panicking and activating the eject functionality unnecessarily. — Andrew Thompson, May 08 '17 at 07:56
By admittedly loose analogy, why aren't cruise ship cabins also lifeboats? It's a question of disaster event type with associated crew risk, probability of occurrence, and cost effectiveness of the method of escape. Every added system brings its own life cycle costs, reliability issues, fitness/availability for use at any given moment, crew training requirements, maintenance requirements, and risks associated with its use (or potential inadvertent or mis-use) even if in perfectly working order. Sometimes adding additional systems for a given contingency isn't the best solution. — Anthony X, May 08 '17 at 16:16
Isn't this question basically the same as "Why don't the astronauts aboard the ISS sleep in the Soyuz capsule?" — vsz, May 09 '17 at 06:14
Plus, how much time is actually spent in one's cabins versus at work, at play, etc.? — Teacher KSHuang, May 09 '17 at 11:12

score 63 · Answer 1 · answered May 08 '17 at 07:57

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Primarily, because without a lot of extra equipment, they could at best be space coffins for the astronauts.

First, they share life support with the rest of the station. Air circulated through them is scrubbed of CO2 in the station's scrubbers. Heat is regulated through station's radiators. This all is powered by station's solar panels. And that's just for breathable atmosphere of reasonable temperature.

Now add to this:

airlock/hatch with undocking mechanism. That's not nearly as simple as it sounds, if you get into details of what that entails.
propulsion, to deorbit the pod (or it will float in space until the astronaut dies) - a launch to ISS takes months of planning at least, so no, "rescue mission" is not really an option.
attitude control, so that the propulsion deorbits the pod instead of sending it into a higher orbit or into a spin
heat shield for reentry. The power output during reentry is of order of gigawatts. Your typical heater for home is 1-2 kilowatts. This is a million times stronger. Shielding against this sort of heat is an enormous challenge
parachute
survival supplies, and a beacon for locating the landed capsule, because it can land pretty much anywhere on Earth, except polar regions.

...and probably a bunch of other stuff I missed.

From a simple box, this turns into a fully featured spacecraft. And you want a bunch of these, one per crew member. The cost becomes... astronomical.

answered May 08 '17 at 07:57

SF.

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Can it really "land pretty much anywhere on Earth"? What happens if it lands in North Korea or an active warzone? – Ordous May 08 '17 at 12:35
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If you check the IIS' ground track, you will see it passes over most of the world at some point, this is a deliberate choice so that multiple launch existing launch sites could be used without to much flight correction. So yes, something falling from the IIS' orbit could fall anywhere. It's unlikely as slight alterations of orbital trajectory have a dramatic impact on your landing site. But if it were to happen I'd imagine a very similar situation to what happens to foreign journalists or pilots who go down in these areas, if friendlies don't get there first, usually a hostage situation. – CyanAngel May 08 '17 at 13:09
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The ground track was set by the location of the launch site in Russia. – Organic Marble May 08 '17 at 13:26
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@Ordous: Then they are screwed. Simple as that. Given contact with ground station or even some time to perform calculations locally they can calculate the general region of landing. But read up on Voskhod 2 to see what happens if the planned window for landing is missed... – SF. May 08 '17 at 13:54
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You probably don't need the life support if you deorbit immediately. If it holds pressure it will have breathable air for at least some time. – Joshua May 08 '17 at 16:02
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@Joshua But the deorbiting and the heat shielding are by far the largest problems. It takes quite a bit of energy to deorbit something quickly. If you detach something from the ISS, it doesn't just fall to the planet. It would keep orbiting. And the faster you want to deorbit the more energy you're going to need. – Shufflepants May 08 '17 at 21:12
@Joshua: If you don't want to pack up a lot of propellant for the engine, you still need about an hour of life support, to get the periapsis into the atmosphere on the opposite side of Earth, wait until you get there, then aerobrake enough for reentry. If you want to deorbit sooner, fuel requirements grow rapidly. – SF. May 09 '17 at 00:20
@SF: I'm accustomed to accounting a small room as having an hour of breathable air before the partial pressure of CO2 gets too high, which is about the time I account for rapid reentry (as you did). – Joshua May 09 '17 at 01:56
@Joshua A Soyuz capsule is not a small room. – user May 09 '17 at 08:03
A rudimentary CO2 scrubber (non-reusable) would be simple enough to keep the air breathable for a couple hours. I'm more concerned about thermal control, that thing takes volume (and area!), is fault-prone and energy-hungry, and can't be cobbled together from a piece of filter and a simple fan. Plus propulsion, and attitude control. This being light, human body position would account for a considerable fraction of position of center of mass, so the engine would likely need to be gimballed, and a decent set of reaction wheels would be needed. – SF. May 09 '17 at 08:50
Plus all the infrastructure and fuel needed for deorbiting would add to station mass needed to be reboosted periodically, and the things would need to be maintained, checked, repaired... Upkeep costs would be quite high, not just design and construction costs. – SF. May 09 '17 at 08:51
"Attitude control" (point 3)? – Canadian Luke May 09 '17 at 17:01
(...) a launch to ISS takes months of planning at least (...) – until Elon tackles this and then it will be 3 days at most :) – Piotr Dobrogost May 09 '17 at 17:19
@CanadianLuke: In short, rotation of the craft. This is a serious problem in space, without friction, to keep the engine turned the right way for the burn, and during reentry where the craft entering a spin may literally rip the passenger (and craft) apart. While science of both problems is well understood, the engineering side... fails a bit too often currently. – SF. May 09 '17 at 18:58
@PiotrDobrogost: Even then the launch takes months - while launches could be performed every few days, preparation for each last well over half a year (work on multiple launches going in parallel.) - although with constant demand for launches, one of commercial launches could be "hijacked" / replacing the payload with a rescue craft. That's still a matter of weeks though, and assuming the rescue craft is just available for use, not, say, halfway disassembled for upgrades/refurbishing. – SF. May 09 '17 at 19:06

Graham · Answer 2 · 2017-05-08T16:19:29.777

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Firstly the ISS doesn't have dedicated "escape pods". The Crew Return Vehicle was intended as one, but it was cancelled, so instead the ISS keeps enough Soyuz capsules docked to allow its occupants to escape in an emergency. This is a case of expedience, not of design from a blank sheet of paper.

That aside though, all capsules are only big enough to contain the astronauts, and no bigger. The larger you make it, the more fuel it takes to get it into orbit. It also costs more with all the heat shielding and other stuff, but that's secondary. The major cost with getting anything into orbit is the fuel to get it there, and the lighter it is, the less fuel you need. Also the capsules are designed to safely contain the astronauts during the ridiculously rough rides between Earth and space, but not for comfort when they're up there. So a capsule resembles a race car, not an RV.

All of this means that a capsule is just not going to be a comfortable place to sleep. Conversely, in the main habitation areas you have plenty of space to velcro your sleeping bag to the wall wherever is most convenient.

For your list of risks:-

Meteor showers and other debris risks are known about days or weeks ahead, and the astronauts then do shelter in the Soyuz capsules for safety, even though it's uncomfortable.
ISS re-entry would be known about months in advance, and simply will not happen unexpectedly (because physics).
A leak could happen, but that's an all-hands-on-deck emergency, and there is enough reserve air to allow the occupants to don EVA suits for repairs, or if it's not fixable then they can still get to the Soyuz capsules in time. Contrary to the bad Hollywood films that most likely inform this question, even exposure to space is not immediately fatal, and they've got enough time to get there before that happens anyway. Related question for this and actual decision tree for what to do.
Explosive decompression needs more than one atmosphere of pressure difference.
A fire is an all-hands-on-deck emergency too, and again the crew bail for the Soyuz capsules. And when fire-fighting, as per the link above:

Crew actions should provide possible ingress into their spacecraft

edited May 08 '17 at 16:19

answered May 08 '17 at 10:58

Graham

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There is a night watch... down in the Mission Control. Also, rapid emergency re-entry with Soyuz (scale of hours) is possible, if unadvisable, due to random landing place which might turn out lethal (say, steep mountain slopes). A massive leak (linkage failure between modules?) might force evacuation. – SF. May 08 '17 at 12:27
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Too many errors of fact in this answer, and no references. Downvoted. – Organic Marble May 08 '17 at 12:54
@SF. Or you could get into the Soyuz and close the hatch until either the situation stabilizes, or you are in a good spot for reentry. If the situation requires, you could even undock and maintain an orbital position next to the space station for a while. I don't know how much oxygen is carried in a Soyuz, but if they are able to carry a crew up to the ISS, surely it would have the ability to wait a little while before carrying a crew back down to Earth. – user May 08 '17 at 13:18
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@MichaelKjörling: Soyuz can sustain the crew for weeks. Possible scenario for few days to reentry - MASSIVE coronal ejection. Possible scenario for hours: Kessler Syndrome. – SF. May 08 '17 at 13:50
@SF.: The answer's listing of "reentry" is meant as unplanned reentry of the ISS, not any of the capsules. It's correct: there's no way the ISS as a whole is going to just suddenly on a whim decide to reenter. – Nathan Tuggy May 08 '17 at 14:51
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@OrganicMarble Can you point out any errors of fact not yet mentioned by SF and Hobbes so they can be corrected? Also consider suggesting an edit. – Philipp May 08 '17 at 15:09
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@Hobbes My bad - I believed they did run a rotating sleep pattern, but I'm wrong. I've editted my answer accordingly. – Graham May 08 '17 at 15:12
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@SF As Nathan says, the question mentions re-entry as a threat to the ISS, not to the Soyuz. Given the mass of the ISS (400 tonnes), the only possible way that the ISS could be de-orbitted rapidly would be a direct impact by an extinction-level-event-sized meteorite, at which point there would be little left of the ISS, the astronauts, or (a few minutes later) Earth and every major species on it. – Graham May 08 '17 at 15:22
@OrganicMarble One error of fact, now fixed. – Graham May 08 '17 at 15:23
It's also incorrect to state that re-entry would be known months in advance (unless you mean the whole ISS, in which case you need to clarify). Fire, depressurization, medical emergency, and/or toxic leak could result in emergency evacuation via Soyuz. http://spaceref.com/iss/operations.html#emergency Also, you need to add some references to back up your claims. For example, are all possible leaks survivable, as you state? – Organic Marble May 08 '17 at 15:38
@OrganicMarble The original question clearly said that the risk was re-entry of the entire ISS, since they listed this as a way for the ISS to be destroyed. For complete lack of ambiguity, I've editted the answer. – Graham May 08 '17 at 16:13
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@OrganicMarble Also references. – Graham May 08 '17 at 16:19
@Graham Earth would likely be chugging along just fine in its orbit, thank you. The Moon, too. Earth has suffered through a handful of mass extinction events of various kinds over the last few billion years; you'd just be adding another to the pile. Now, had you said giant impact size, that might possibly have been different. – user May 08 '17 at 18:43
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"Explosive decompression needs more than one atmosphere of pressure difference." Err your source seems to contradict that statement, and even lists concrete examples. – NPSF3000 May 08 '17 at 21:58

Why aren't the 'bedrooms' aboard the ISS also the escape pods?

2 Answers2