Here's the situation: The ISS suffered from some kind of catastrophic failure. The crew is unharmed, but the nature of the failure includes:

  1. The destruction of any present vehicles capable of returning safely to Earth.
  2. The crew has to be extracted immediately. The nature of the damage does not mean that any unusual procedures have to be performed once a spaceship gets to the ISS to get the crew out and back home safe.

So in order to get the crew out, a spaceship has to be sent up to rescue them. How quickly could one be ready to launch to retrieve them? They'd need to prepare a ship, brief the crew, wrangle the press monkeys and all the myriad things that come with launching a ship. Luckily all the world's space agencies are willing to contribute to this heroic mission (though likely it's because of the goodwill it would curry them if they succeeded), so it's not just up to the ones running the ISS.

Thus I am wondering:

What is the smallest possible time frame we could get a spaceship to the ISS to retrieve the crew without seriously endangering the crew of either the ISS or the rescue vessel?

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    $\begingroup$ Why would the rescue vessel need a crew? $\endgroup$
    – gerrit
    Sep 8, 2015 at 10:53
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    $\begingroup$ If the crew needs to leave immediately, the mostly likely answer is that an automatic scuttling payload will be launched some months/years later to conduct a controlled deorbit of the station/cremation of the remains on board. None of the currently available launch systems are capable of an immediate unscheduled launch; and after several months of decomposition of the crews bodies the station is unlikely to be able to be restored to a habitable condition. $\endgroup$ Sep 8, 2015 at 16:14
  • 3
    $\begingroup$ Simples: Use the secret military shuttle from the 'stranded astronauts' episode of The West Wing. $\endgroup$
    – A E
    Sep 8, 2015 at 18:58
  • 1
    $\begingroup$ Related question. $\endgroup$
    – dotancohen
    Sep 9, 2015 at 14:35
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    $\begingroup$ I don't know the protocols at all, but I would imagine in a severe situation like this, wrangling the "media monkeys" would be relegated to an afterthought, and wouldn't factor in. First priority is getting them back to Earth safely. $\endgroup$
    – loneboat
    Sep 9, 2015 at 16:31

4 Answers 4


There is a Soyuz capsule (source1) docked to the ISS at all times, allowing for immediate evacuation in an emergency. This limits the ISS to 3 people when it is the only capsule available. For Expidition 20, they docked 2 capsules, allowing for six astronauts at a time.

Your scenario involves the destruction of these vessels and simultaneously jeopardizing the safety of the astronauts sufficiently to demand an emergency return. Given the redundancy of the systems, this would be an impressive set of failures. At such a point, evac is no longer a simple issue. Questions like "can we even dock another craft" begin to come into play due to the unknown-but-catastrophic damage. Accordingly, plans for such an evacuation will be like those of combat plans. Then again, I fully expect the planning to have been done, if nothing else along Winston Churchil's line "Plans are useless, planning is essential."

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    $\begingroup$ I would tend to agree with this. I do think a 1 Soyuz unusuable is a realistic scenario, but 2 isn't. $\endgroup$
    – PearsonArtPhoto
    Sep 8, 2015 at 22:40
  • $\begingroup$ Couldn't they put on their spacewalking gear and huddle up in a Shuttle bay until it lands? $\endgroup$ Sep 9, 2015 at 14:09
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    $\begingroup$ @CeesTimmerman : The NASA Space Shuttles? Those would require "several years" to bring back into service. $\endgroup$ Sep 9, 2015 at 14:33
  • $\begingroup$ @ceestimmerman One bit of turbulence at the wrong time and you'd have to scrape them from the interior walls. $\endgroup$ Sep 9, 2015 at 16:02
  • $\begingroup$ @Shadur Then weld some of them fancy cockpit seats in there. $\endgroup$ Sep 9, 2015 at 17:05

Not very quickly, for a number of reasons. Here's a list of some of the reasons:

  • Soyuz requires 2 astronauts just to fly it (Under nominal operations) It can only take down 3. Thus, 6 Soyuz launches would be required. (Note, this might be a reference to manned flight, Soyuz does have remote capabilities). Some work could probably be done to reduce that to 1 person, thus only requiring 3 launches. This is probably the quickest pathway to rescue. In theory, Soyuz can be flown completely unmanned, but this hasn't been done for an ISS mission (Although it is similar to Progress).
  • If there was a true emergency, I would imaging a Dragon capsule could have restraints placed inside, allowing it to land. Most of the upgrades to man rate Dragon require changes for going up, not coming back down. I think there's a Dragon that's ready to go.
  • China's ability to launch people into space is rather limited. They might be able to do one of the rescue missions, but certainly not all of them.

The only 3 vehicles currently capable of reentry and contain pressurized compartments are the ones listed. Anything else would take a huge amount of time. I suspect the quickest that any such launches could be attempted would be on the order of weeks to months, especially considering the large number of launches that would be required to make this happen.

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    $\begingroup$ Does Soyuz really need crew to fly? I thought the Russians had another philosophy, they flew their Buran space shuttle unmanned, NASA couldn't do that. Progress is Soyuz derived and flies on remote control. It would still take months to get two Soyuz up there even if they launch empty. But wouldn't they be able to save at least the three astroladies on the space Titanic first? $\endgroup$
    – LocalFluff
    Sep 8, 2015 at 15:58
  • $\begingroup$ That's a good question. I know I've seen somewhere it requires 2 pilots, but that might be for a specific type of mission. I know I've seen that it would be relatively easy to change that to 1. Maybe the issue is that if it's manned, it requires two pilots, but it can launch unmanned. Hmmm... $\endgroup$
    – PearsonArtPhoto
    Sep 8, 2015 at 16:55
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    $\begingroup$ What about send up a couple of MOOSE. You only need to really strap the astronauts to a heat shield and a parachute. $\endgroup$
    – Aron
    Sep 8, 2015 at 17:11
  • $\begingroup$ I wonder if Dragon 2 could change that in a few years. It has the capacity for 7 people, and presumably, it could launch and dock with ISS autonomously. If a spare rocket and a Dragon 2 were available, it would presumably be rather straightforward to launch it and take the whole crew at once. $\endgroup$
    – radex
    Sep 8, 2015 at 17:14
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    $\begingroup$ @Aron: While interesting, it's not developed yet. Any existing system with some modifications would be easier than launching a system like MOOSE. $\endgroup$
    – PearsonArtPhoto
    Sep 8, 2015 at 17:15

Types of Emergency

The most probable causes of an emergency are Fire aboard, leak aboard, or life threatening illness aboard. A failure of Life Support is also a dire emergency...

Fire and leak are the two most emergent of these.

In order to render the need for a rescue flight, you would need to damage a Soyuz, possibly two.

Self Rescue via Soyuz

At any point, the station is to have no more persons aboard than it has return capsules for.

This means, most of the time, there are two soyuz capsules docked.

The Emergency Ops Plan is pretty clear that plan 1 in an emergency is "Tell NASA", priority 2 is Stay alive, and priorty 3 is "Fix it if you can, come home if you can't fix it." Most of the outcomes on the flow chart on page 7-1 involve leaving the station in a Soyuz capsule.

Self-Rescue via cargo ship.

At times, there is also a cargo capsule docked - either the Dragon, a Cygnus, or Progress capsule. In a pinch, any of these three could be used as a lifeboat, as well... but more drastic, because it would require (1) travel in a space suit, and (2) inadequate cushioning of note for the astronauts. The cargo units are pressurized, but don't have the same atmospheric processing as manned capsules. They have several person-hours of breathable air, presuming, of course, that the air aboard isn't contaminated by the emergency.

SpaceX to the Rescue

At KSC, SpaceX has rented a hangar. At KSC, SpaceX is testing the Dragon Manned Capsule.

At any given point, SpaceX seems to have a Falcon rocket nearly ready to launch. By the time they roll one out, the next one is already in assembly. In a pinch, a dragon cargo capsule can be fitted with straps and foam, loaded with PLSS packs, and on the pad in about 2 days (It takes a day to move the crawler each way). Finishing up the rocket could be a week or two. Current production is a Falcon 9 every month... (cite).

Rescue by Russians or Chinese

The Soyuz program launches about once every two months, with the capability to push to one every 3 weeks, as I recall. So, a Progress with seats installed could be sent up for emergency rescue in probably a month, along with extra PLSS packs and suits.

The Chinese are much slower - about 1 per quarter is what I've seen guessed for them. In an emergency on the ISS, they are quite likely to sent a ship within a window of 3 weeks, if they have a launcher far enough along.


Since the scenario includes no soyuz available at station, and immediate extraction the failure mode is "death."

The best possibility would be if a CRS mission was waiting to launch. in which case, unloading time, and charging time for the needed PLSS packs. Which would mean, assuming they simply write off the cargo, about 6 hours, leaving the cargo in the launch gantry.

If a Cargo mission or a personnel swap isn't scheduled, then "immediate" would be at least 2 days, if not a week or two, for the next available launcher.


It depends: if there's a mission already being prepared that you could use, you'd be in luck. Otherwise, you'd have to wait for a rocket and capsule to come off the production line. Your best chance of that happening soon is with a rocket that has a high rate of production.

In 2014, 23 R-7 rockets were launched. 4 of these were Soyuz manned capsules, and 4 were Progress. The others were satellite launches. This is one launch every 2.2 weeks.
If they had a Soyuz capsule lying around, it might be possible to swap the planned payload for the Soyuz. So that gives a ballpark figure of 2 weeks. Maybe a little less by cutting corners and/or going to a 24/7 schedule.
The main constraint would be the production rate of the capsules. A rate of 4 per year means on average, the next one will be delivered in 3 months.
Other countries have fewer launches, so it'd tend to take longer for them to mount a rescue mission.


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