I found this question, and I was wondering why the ISS is constantly manned (Except for some hours during particular situations). Is that a technical problem? Is it to guarantee safety? Or just because it would be a waste of money to leave it empty?

  • 14
    $\begingroup$ Why? What benefit could it possible have to leave it uncrewed?? A crewed spacecraft docks with it to leave a crew and take a crew back. It's like why should a passenger ship go empty across the sea. $\endgroup$
    – LocalFluff
    Apr 12, 2017 at 15:40
  • 2
    $\begingroup$ It is an ego thing, "continuously manned", I would think by now it has exceeded the Mir Space Station record. $\endgroup$ Apr 12, 2017 at 15:47
  • 4
    $\begingroup$ The station was costly enough to shoot up into orbit, having it unmanned is a waste of resources. The station will not work forever, especially (but not only) electronic components might wear out quite fast up there. So use the station for as long as possible is a prudent approach. $\endgroup$
    – Adwaenyth
    Apr 13, 2017 at 6:28
  • 11
    $\begingroup$ Why on earth (lol) would you leave the ISS unmanned? It has nothing whatsoever to do with "ego". This is kind of a silly question. I'm curious what you think actually happens on the ISS; they're not just playing Candy Crush and waiting out their flight period. $\endgroup$ Apr 13, 2017 at 11:25
  • 5
    $\begingroup$ It would be pointless to build a space stations whose sole purpose is to provide habitable environments for manned experiments/work, and then leave it unmanned. Its an extremely costly endevour, and thus its just common sense to use it as much as possible. $\endgroup$
    – Polygnome
    Apr 13, 2017 at 21:00

4 Answers 4


The ISS is a science laboratory -- a National Lab in fact. Leaving it uncrewed would take away a huge portion of the science productivity without substantially impacting the cost to operate it.

Why is it constantly crewed? Because anything else would be a phenomenal waste of resources.

  • 2
    $\begingroup$ Your assertion that it would not substantially impact the cost is without basis. If you have evidence for this, please provide a new answer to this question: space.stackexchange.com/q/5494/58 $\endgroup$
    – called2voyage
    Apr 12, 2017 at 17:35
  • 26
    $\begingroup$ Unless you leave it uncrewed for long enough to effectively furlough everyone not absolutely necessary to keep it from falling out of the sky, the basis should be obvious. There is a standing army that makes the ISS run, and unless the program decides to lay them off or furlough them, they're getting paid whether station is crewed or not. $\endgroup$
    – Tristan
    Apr 12, 2017 at 17:37
  • 9
    $\begingroup$ At that point, you would probably have to consider the program effectively canceled. There's no way you could shed that much cost without permanently losing a huge amount of tribal knowledge. As a WAG, I would spitball the length of furlough necessary to outweigh the workforce recovery cost to be able to bring station back to operational status to be in the neighborhood of 1 to 2 years. Given that the premise of this question seems to suggest decrewing for weeks-ish, I won't provide carveouts in my answer for utterly nonsensical situations. $\endgroup$
    – Tristan
    Apr 12, 2017 at 17:46
  • 5
    $\begingroup$ @Tristan, I think a lot of folks don't realize the incredible amount of commanding that is done by MCC every day to keep the ISS going. $\endgroup$ Apr 12, 2017 at 17:49
  • 16
    $\begingroup$ @OrganicMarble Not to mention the literally thousands of largely-unsung engineers working daily to provide the MCC and MER folks the answers they need to continue to operate the vehicle (let alone the technical work that goes into long term planning). The overwhelming majority of them would be working whether there are people on board or not. It takes the population of a small city to make ISS work. $\endgroup$
    – Tristan
    Apr 12, 2017 at 17:54

Because the official United States Government policy reason for funding the International Space Station is to (bold-facing mine):

Develop and operate the International Space Station to support activities requiring the unique attributes of humans in space and establish a permanent human presence in Earth orbit. The International Space Station will support future decisions on the feasibility and desir­ability of conducting further human exploration activities.

(Presidential Decision Directive I National Security Council 49, "Fact Sheet: National Space Policy," White House National Science and Technology Council, 19 September 1996.) quoted in The Changing Purpose of the Space Station

Note that the entire rationale for US involvement in the project is directly linked to humans in space. If the station were to be operated unmanned, the entire reason for its existence would be null and void.

  • 7
    $\begingroup$ Also this. Crewed flight is its raison d'être. (Only commenting because I wanted an excuse to say "raison d'être") $\endgroup$
    – Tristan
    Apr 13, 2017 at 1:10
  • 15
    $\begingroup$ @Tristan - so...raison d'être is that comment's raison d'être? $\endgroup$ Apr 13, 2017 at 17:19
  • $\begingroup$ Great minds....see my comment to this question from a couple of years ago. space.stackexchange.com/questions/5494/… $\endgroup$ Apr 13, 2017 at 17:31

Because it might be more costly not to have people in it.

The experience from previous space stations was that when a minor issue occur on a space station, it can be easily fixed and detected.

If nobody's here, it can in turn become more expensive to fix.

Salyut had such kind of issues: something broke down that prevented the batteries to be charged. It caused the whole station to freeze over, prompting more difficult and extensive repairs that what could've been done if the station was manned at that time.

  • 1
    $\begingroup$ A shutdown nuclear reactor is in the same boat, but I don't know if such information is pertinent. I don't remember how operator watches are stationed when a plant is cooled down, but all the maintenance work being down would probably override that. $\endgroup$ Apr 13, 2017 at 18:43

I see a few people have answered that it would be wasteful to have it empty, and that is why. However both the Skylab and Mir space stations had vacant periods between expeditions to them. So, that can't be the only reason.

So, I think that the reason it has been manned continuously is that it has been possible to do so. There have been more regular manned flights and supply launches since both the USA and Russia have been launching them. (though manned launches have only been from Russia since the shuttle flights stopped).

  • 1
    $\begingroup$ Can I add the informations about SkyLab and Mir to my question ? In order to give it a little more legitimacy ? $\endgroup$ Apr 17, 2017 at 13:54
  • $\begingroup$ The Skylab couldn't make crew exchanges because it had only one docking port. Another Apollo wouldn't be able to dock to it as long as the former Apollo was docked. $\endgroup$ Feb 23 at 14:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.