The ISS is a huge (relatively) satellite which, according to NASA, is longer than a football field. I am curious about what would happen if the station's skin was punctured - perhaps by a careless astronaut, by a small object flying through space, or a monkey.

If this were to happen, I would imagine that air would start to leak out of the station, eventually depriving the crew of breathable air.

What would the crew do? Are there ways to block off parts of the station? Would you just float up to it and patch it?


4 Answers 4


There are two kinds of depressurization alarm:

  • ΔP/ΔT (rapid depressurization)
  • ATM PRESS (slow leak, or pressure hitting the thresholds)

Main steps that are taken:

  • Record incident and contact mission control
  • Take pressure gauge
  • Evacuate into the Soyuz
  • Check if Soyuz descent module is leaking
  • If time remaining (T.res) is less than X minutes, say "Bye-bye" to the station, prepare the Soyuz for flight and undocking. Contact Mission control
  • If T.res is more than X minutes and the Descent module is leaking, return to the ISS, and deactivate the station orderly
  • If T.res is more than X minutes and the Descent module is safe, return to the ISS, close vacuum valves through the laptop and pinpoint leak
  • Isolate the leaking compartment

Roughly speaking, X is the time to deactivate the station.

How to spot the leak:

  • Use the ISS computer to find the leaking compartment
  • If fails, use pressure gauge in each compartment with closed hatches to determine the culprit.

Any steps to patch leaks are taken only after consulting Mission Control



Note: if anybody knows where to find an up-to-date SODF please let me know.

  • $\begingroup$ Aren't your steps number 6 and 7... confused? If the descent module is leaking, why do they return to the station to shut it down? $\endgroup$ May 10, 2017 at 9:25
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    $\begingroup$ Indeed, I think there may be a mistake here: "If T.res is more than X minutes and the Descent module is leaking, return to the ISS, and deactivate the station orderly". Because if it is the descent module that is leaking, why is the station being deactivated, rather than sealing off the descent module? $\endgroup$ Jul 14, 2017 at 13:54

Quoth Robert Frost, self-described as "instructor/engineer in the NASA Mission Operations Directorate":

If the object is in LEO and larger than around 10 cm, the ISS can be warned and moved, a few orbits in advance of the potential impact. For smaller objects, they just accept the risk.

The ISS has shields called Whipple bumpers. They are multi-layered with spaces between the layers. The intent is that impact with a layer will both slow and hopefully break apart the projectile, so that by the time it gets to the bottom layer it is no longer harmful. That shielding is heaviest near the front of the vehicle, since that is where impacts of the greatest velocity would likely happen.

Should a projectile puncture the hull into the pressurized cabin, the crew have patch kits that they can use to plug the hole.

The cabin has not been penetrated, but there are several punctures on the vehicle. The solar arrays, radiators, and some truss have scars from hits. The crew have occasionally been made aware of a hit by hearing a loud banging noise.

  • $\begingroup$ the problem is to find the tiny tiny hole in such an event $\endgroup$
    – Quonux
    Jul 31, 2013 at 16:34
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    $\begingroup$ Also, the exterior walls of most modules are buried with equipment. I.e. Inside of the ISS modules, often look cubical/rectangular, as opposed to round, since the equipment racks are against the walls, and make the boxy shapes. So you probably would have terrible time finding the leak location. $\endgroup$
    – geoffc
    Aug 2, 2013 at 1:41
  • $\begingroup$ @Quonux The crew has an ultrasonic leak detector to aid in finding the source of the leak. $\endgroup$
    – Doresoom
    Feb 6 at 22:32

This has happened in space before, as a matter of fact, on Mir.

During tests of a new manual control system for cargo ships, the cosmonaut piloting the ship managed to crash it into the Spektr module. The crew determined the location of the leak, and after some tense moments trying to sever the various hoses and cables leading into the module, they managed to close the hatch.


Unfortunately, that module was unusable for the rest of Mir's life. After some time, engineers were able to send up a modified hatch that allowed the power from Spetkr's solar panels to flow to the rest of the station, gaining some use from it. There was an attempt to find the hole and seal it via an Internal Vehicular Activity (IVA, wearing a spacesuit inside the station as opposed to outside), but it was unsuccessful.


TsSKB Progress has released the unclassified 1979 educational film Razgermetizatsiya Stantsii (that is Depressurization of the Station) created for Salyut stations. The films shows mandatory procedures step by step.

Of course the ISS is bigger and the crew can be larger than just the commander and the flight engineer, but it can be assumed that while the Soyuz is used as a lifeboat, the crew still follows a similar set of procedures.

The cosmonauts have 5 minutes to perform necessary actions and get to Soyuz landing module.

In the case of pressure going down in Soyuz after the hatch has been closed, the problem is in Soyuz itself. They need to get back to the station and isolate the station from the leaking spacecraft.

  • $\begingroup$ Cool video. I just had some great fun with the automatic subtitle & translation feature of youtube. Anyway, is there a transcript or translation of the comments available somewhere? $\endgroup$
    – s-m-e
    Aug 1, 2013 at 12:47

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