Let's say it's NASA. What could happen if after takeoff, when there's no turn around, the astronauts found a human stowaway?

Some things to look at; It takes millions of dollars to carry out a space mission, possibly more depending on how far they're going. The person who is a stowaway is 120 pounds and is a complete stranger to the astronauts or anyone at NASA.

Also: (curious but don't need to be answered, the question in the title is most important so just overlook these if you want)

  • The plausibility of the astronauts deciding not to report the
    stowaway until they returned,

  • the possibility of them surviving if it's a long term/permanent (as
    in going to Mars or something to colonise)/ or short term mission,

  • and the overall possibility of it happening in the first place.

  • 2
    $\begingroup$ NASA don't be stingy, can't u offer that poor man a potato or 2? $\endgroup$
    – user6760
    Commented Oct 12, 2017 at 4:37
  • $\begingroup$ He or she will be reported immediately. If astronauts wouldn't do it, they'll have a lot of explanation to do later and they will lose their jobs at the very least. NASA is an extreme secure organisation because each mistake might cause billions of dollars to vanish. $\endgroup$ Commented Oct 12, 2017 at 7:57
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    $\begingroup$ @user2851843 And people. Adding 120 lb. to a rocket without compensating with more fuel means the rocket may not reach orbit and end up crashing back to Earth. It could also throw off the careful calculations and calibrations necessary for a launch, meaning the rocket wavers and explodes midflight. In both cases, people die. $\endgroup$
    – Frostfyre
    Commented Oct 12, 2017 at 12:07
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    $\begingroup$ @anon yes sure - but only after the vogon poetry reading $\endgroup$
    – Slarty
    Commented Oct 12, 2017 at 22:07
  • 2
    $\begingroup$ @JustinThyme: Stack Exchange has never been anything but a deliberate merit- and involvement-based oligarchy. This is fundamental to the intended design of the system. If you don't like that I suggest reading this old blog post that explains why closing upvoted questions is often necessary. $\endgroup$ Commented Oct 13, 2017 at 3:56

8 Answers 8


It really depends on when the crew discover the stowaway. I would bet, though, that they'll choose to restrain the person, report the incident to Mission Control, and then, after talking with Mission Control, abort the mission.

Reasons for aborting:

  • The person could be trying to sabotage the mission and/or hijack the shuttle. This could be especially worrisome if the payload includes a military satellite.
  • The person could have already sabotaged the shuttle or placed a bomb on board; if possible, the crew (and the payload!) need to be gotten somewhere safe.
  • Having another person on board means that the crew may have fewer resources.
  • Doing otherwise could have a negative psychological impact on the crew members.

Shuttle security breach

The plausibility of a stowaway, as others have said, is doubtful. It would very difficult for the person to board the shuttle at all; it's a few orders of magnitude harder than breaking into a car, for example. Post-9/11, public access to Kennedy Space Center was restricted around the time of shuttle launches. In the first mission or two after the attacks, even the planned launch time was kept secret, meaning that this would-be stowaway would have to either be on the inside (which would help with other aspects of the plot) or be a very good guesser. Even then, the launch could be scrubbed and moved back because of things like inclement weather. The person could be kept hiding for days, likely with minimal provisions and supplies.

Military personnel have often been used for security (for instance, before Columbia's final mission, because Israeli astronaut Col. Ilan Ramon was one of the members). We're not talking about a few security guards with nightsticks; we're talking about military-grade weapons used by the actual military.

1. T-0 to T+8:30

In this case, you probably want to abort the mission as soon as possible. Someone unknown is in a spaceship and could have a weapon, bomb or other harmful device. They could hijack the mission and cause serious problems. There's very little this person can do in the early stages of the launch, so that's when the crew need to act.

Once the solid rocket boosters (SRBs) were ignited, no abort could be performed before SRB separation, roughly two minutes into the flight. After that, there were several abort options[1], [2]:

  • Return to Launch Site (RTLS), involving jettisoning the external tank and landing at Kennedy Space Center.
  • Trans-Atlantic Abort (TAL), involving jettisoning the external tank and landing at one of a number of sites in Europe and Africa.
  • Abort Once-Around (AOA), involving a modified flight pattern circling Earth once before landing somewhere.
  • Abort To Orbit (ATO), involving reaching a lower orbit than intended.

The optimal options here are RTLS and TAL. AOA only had a very tiny window in which to initiate, and ATO meant that a modified mission will still go on. RTLS and TAL meant that the Shuttle could land very quickly and stop the mission.

2. T+8:30 onward

Main Engine Cutoff (MECO) occurs at T+8:30. After this point, the crew likely can no longer perform an RTLS or TAL abort. An AOA abort would get them back to Earth, but again, that might be hard to do. What the crew can do is go into a modified orbit, using an ATO abort. If they're already in orbit when they discover the stowaway, of course, then they'll stay where they are.

So, they're now stuck in a spacecraft with an unknown person - again, potentially harmful. Their course of action depends on what the mission is. It could be any of a number of things, including

  • Going to the ISS or another space station.
  • Launching a civilian satellite.
  • Launching a military satellite.
  • Repairing a satellite or telescope (such as Hubble).

All of this takes time. If the crew has performed an ATO abort, though - which they likely have - then the mission is compromised. They could move to a different orbit, yeah, but there's already a wrench thrown into things. Who wants to launch a satellite with a potential psychopath in close quarters with you?

The point is, the best thing to do is go into a lower orbit and do a final consultation with Mission Control before returning to Earth with the mission incomplete. Better safe than sorry.

  • $\begingroup$ On some missions, the safest abort is completion, particularly after leaving low earth orbit. $\endgroup$
    – pojo-guy
    Commented Oct 13, 2017 at 5:00
  • $\begingroup$ @pojo-guy Depends on what you mean by "completion". Go through with the mission exactly as planned and ignore the stowaway, not very likely. Execute an immediate deorbit burn to get back onto the ground, also not necessarily the best course of action, but may be an option. Even Apollo 13 completed its mission, just not its original mission; it changed some time around MET 60h when the full impact of the disaster became clear. And even Apollo 13 had data (onboard!) on how to perform a mid-coast direct abort; they just opted not to use it; for one, the state of the main SPS engine was unknown. $\endgroup$
    – user
    Commented Oct 13, 2017 at 7:19
  • $\begingroup$ MECO is far too late for a RTLS about, and very likely too late for a TAL abort. By MECO you are basically in your final orbit (just a few nudges still needed), and you're ditching the all-but-empty ET. For example, quoting from space.stackexchange.com/a/10605/415 which you linked: "For example, the last possible time to select RTLS ocurred when the vehicle did not have enough propellant remaining to burn its velocity down to zero and then back up high enough to make it to Kennedy Space Center." $\endgroup$
    – user
    Commented Oct 13, 2017 at 8:58

It wouldn't compromise the mission, since these systems are engineered with a lot of "excess capacity" in case something goes wrong.

The big issues would be regarding room in the "cabin": it's going to be pretty darned small to begin with, so the possibility of there being a place for the stowaway to hide is somewhere between zero and none.

EDIT: the stowaway might actually compromise the mission if the extra mass causes the vehicle to be placed into slightly the wrong orbit. That's because -- even now -- if a rocket's second stage engine cuts off just a couple of seconds too early, the satellite can be placed in a wrong orbit. If the on-board computers were to chat with ground radar and discover that it's not going as fast as it should, then it could burn the engines longer, but I don't know if that's what happens now.

EDIT 2: Space Shuttle missions had Safe Haven Food, which was an extra 22 day supply of food/water, and the ISS has much redundancy (including food/water).



  • $\begingroup$ +1 for the size of the crew compartment. I actually wrote the start of a novel based on OP's premise. The lockers on the (now retired) shuttles were just the right size for a smallish 10 year old to squeeze into and hide. Odds are that the stress of launch would cause them to wet themselves, the force and vibration of launch without a fitted and padded seat would leave them bruised and sore, and there is a probability of them getting motion sick with the sudden transition from high to zero G. $\endgroup$
    – pojo-guy
    Commented Oct 12, 2017 at 5:17
  • $\begingroup$ these systems are engineered with a lot of "excess capacity" I think this needs a citation. If anything, space travel is all about shedding every little bit of excess weight you can, everywhere. They might be engineered to have excess capacity, but that doesn't mean that said "excess" capacity is available. If a particular mission doesn't require the full MTOW of the spacecraft and booster, they aren't going to load up the extra fuel to get the ability to fulfill the mission at MTOW just in case. $\endgroup$
    – user
    Commented Oct 12, 2017 at 14:22
  • $\begingroup$ @MichaelKjörling I added justification on extra food/water, but can't find anything on whether or not liquid fueled rockets are loaded with a few percent extra fuel. $\endgroup$
    – RonJohn
    Commented Oct 12, 2017 at 14:43
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    $\begingroup$ @JustinThyme the cargo bay on the old shuttles is not sealed. Suffocation and explosive decompression could be a minor issue. $\endgroup$
    – pojo-guy
    Commented Oct 12, 2017 at 18:51
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    $\begingroup$ @RonJohn a weight variance of a couple of hundred pounds is not unusual - the layer of frost that forms on the liquid fuel tanks can weigh more than that. $\endgroup$
    – pojo-guy
    Commented Oct 12, 2017 at 18:52

The most probable outcome is that the astronauts would still report the stowaway. Since this is NASA, it should already be highly unlikely that there are any stowaways in the first place, as protocol and procedures are very strict and should always be followed. Unauthorized personnel should never be allowed in the first place.

What would happen if there was however, and the craft had passed the point of no return, it would be by circumstance that the staff in the craft will have to take the stowaway in. Every pound in a space craft is important because the amount of fuel needed to get the craft to lift off is perfectly calculated though, so there would be a chance that the craft failed to take off in the first place. But since the craft got into orbit anyway, I'm assuming weight is not a problem in this scenario.

What would be a problem though is training. It takes years for one astronaut to be trained well enough to even get in a space craft, and since this stowaway is a complete stranger and is not used to a zero gravity environment, the most probable outcome other than the stowaway being taken in is that they will die during the trip or in any other point in time due to the body not being used to the environment.


One thing that will be difficult in getting a stowaway onto the shuttle is getting to the shuttle in the first place... Once on the Launch Padd, it's monitored extensively and the shuttle is normally out there for 48 hours before the launch... plus the time on the crawler where it is pretty much inaccessible. Access into the shuttle is very restricted once on the launch padd for a number of reasons, among them, the fact that the slightest bit of dust or hair could float into equipment and cause problems means that they are pretty clean room environments before the orbiter (the white plane like component of the shuttle) is fitted to the entire launch assembley (called the Shuttle. The rest are the two Solid Fuel Rocket Boosters (SRBs) and the External Tank (ET).) And it takes about two days to get from the assembly building to the launch pad by crawler... during this time, you can't get in, because there is no access to the door.

Again, once there, it's fueled for 48 hours and again, the door isn't opened or closed at this time, to preserve the clean room... Any unknown opening would probably trigger some alarm as the door of a space craft can't just open because of the breeze... and any alarm will shut down the launch clock until it's figured out what is going on. Astronauts only enter the craft about 2.5 hours from launch, and that close, the shuttle is monitored even more closely.

The total launch assembly has theoretical yield comparable to that of the Hiroshima Bomb when fully fueled and for that reason, NASA has a 3 mile radius ground clearance from any critical facility and a further area that is controlled to public access (you can tour facilities inside this area, but they are controlled more than the main visitor facility and they do close them off to the public during the launch). So in essense, to stowaway, you must make a three mile run through highly controlled access area, get into a sealed vehicle without tripping any doors, do so before the astronauts board, remain hidden for that time until they do board, and remain hidden for a further 2.5 hours plus the additional 8.5 minutes before main engine cut off to pull this off. Unless you have a NASA reason to be that close to the shuttle, you can't get that close at all.

  • $\begingroup$ You forgot the natural barriers. KSC is the world's largest alligator preserve. That last three miles is mostly alligator infested swamp. $\endgroup$
    – pojo-guy
    Commented Oct 13, 2017 at 0:36
  • $\begingroup$ @pojo-guy: Valid point, though the only time alligator's seemed to affect NASA operations at the cape was that they would have to clear gators from the orbiter landing strip on more than one occasion. That said, Alligators are an Ambush predator, meaning that if they are on land, they won't go for you unless you get too close... they typically wait in the water for something to come close. Not sure about the Cape, but nearby Orlando International has no fencing separating public roads and the airfield... just alligator infested motes. Like the good ol' days. $\endgroup$
    – hszmv
    Commented Oct 13, 2017 at 13:11
  • $\begingroup$ From my tour information, every launch at KSC triggers an alligator mating frenzy. Apparently the males think they just chased off the world's biggest gator and want to celebrate. $\endgroup$
    – pojo-guy
    Commented Oct 13, 2017 at 13:54
  • $\begingroup$ @pojo-guy: I have never heard that but it sounds so hilarious. Last tour I was on, I was not old enough that our guide would probably not tell me that information. Most of my stuff was because I went through a hard NASA phase as a kid followed by living close enough to see launches from the ground. $\endgroup$
    – hszmv
    Commented Oct 13, 2017 at 14:25

The stowaway is not going to die. The astronauts are not monsters. If they have to throw stuff off the craft to meet the weight limit, they will throw away the least vital equipment.

The stowaway is unlikely to die simply because they aren't as fit as the astronauts. The maximum amount of force due to acceleration is 3G (three times earth's gravity) at take off. https://www.physicsforums.com/threads/acceleration-of-space-shuttle-at-liftoff.224305/

That's easily survivable by most people without medical conditions. The stowaway will have more muscular degeneration problems when they return to earth because they aren't as fit.

There probably isn't an extra empty chair for the stowaway to strap into when they re-enter the earth's atmosphere. However, there is always extra oxygen in case a problem develops with an oxygen tank. Food can be rationed.

The stowaway isn't going to have any fun. The astronauts are DEFINITELY going to report the stowaway. The stowaway might initially think along the lines of: "Look at me. How cute and funny I am being." The astronauts, by contrast, belong there. It isn't funny or cute for the astronauts. Who knows if this stranger messed with important equipment? Did the stowaway bring anything dangerous on board? What if this person gets injured or injures someone else?

Imagine if you worked at an amusement park and if you caught some random person wandering around the amusement park after it closed. You'd not find their antics very funny. You'd be alarmed.

NASA has protocols for dealing with crazy astronauts in space. The other crewmembers use duct tape on the wrists and ankles. They then tie the person down with bungee cords and give them tranquilizers. https://www.cbsnews.com/news/nasa-has-plan-if-astronauts-lose-it/

That's probably what they would do if they didn't trust the stowaway not to press buttons. At best, the stowaway would be forced just to sit quietly and not touch anything. This defeats the purpose of going into space.

It's unlikely that someone would be able to stowaway. There isn't a lot of space (and certainly not extra human sized cavities of unused space.) Also, part of the pre-flight checklist is to check all the hardware system on board. https://www.wired.com/2010/05/process_shuttle/ It would be difficult for engineers to somehow miss a hidden person when they are checking every piece of equipment on board.

Finally, the stowaway is going to be arrested and charged with criminal trespassing when they return to earth.

  • 1
    $\begingroup$ To "just [] sit quietly and not touch anything" likely isn't going to be all that easy for an untrained person in a freefall environment, no matter how well the stowaway individual wants to behave. $\endgroup$
    – user
    Commented Oct 12, 2017 at 14:19
  • $\begingroup$ Let me clarify then. "Float there and don't touch anything." $\endgroup$
    – emawerna
    Commented Oct 12, 2017 at 23:55

Most probably the astronauts will have to deal with someone has the worst case of space sickness. The sheer delight of having the stowaway vomiting copiously and regularly. If everybody is exceptionally lucky, the stowaway won't be affected by weightlessness, but that seems very, very improbable.

The astronauts will report the stowaway. The mission will continue under severe constraints. It won't go to Mars or anywhere in the solar system (except back home to planet Earth). Stowaways on the space shuttle are extremely unlikely. Strangely, NASA isn't stupid. They make access to the space shuttle extremely difficult unless you have an authorized reason for being there. Therefore, an unknown person won't have a chance of getting on board.

Oh yes, there is the distinct possibility the stowaway will be injured during lift-off. Experiencing high g-forces, while not properly seated or secured, has a definite risk factor.

In summary, the astronauts should be delighted to find they have a vomiting medical emergency in the form of a stowaway. A person who has no training or expertise in space travel or the requirements of a space shuttle. Just the thing to ruin a good space mission. To say nothing of all the extra cleaning up they will have to do. Provided they don't succumb to the temptation of pushing the stowaway out of the airlock. :)

  • $\begingroup$ "NASA isn't stupid"... but they lost a Shuttle and 5 astronauts to spare a 10k $ redesign of an O-ring... $\endgroup$
    – L.Dutch
    Commented Oct 12, 2017 at 5:49
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    $\begingroup$ @L.Dutch That is a different context. Every institution has its different levels of stupidity. I was referring to their capacity to prevent unauthorized personnel sneaking on board. The managerial failures for the Challenger were more than the simplistic cost cutting. With hindsight it was an avoidable accident, but that's not uncommon. $\endgroup$
    – a4android
    Commented Oct 12, 2017 at 11:46
  • $\begingroup$ @a4android Heck, lots and lots of plain old commercial aviation accidents are plenty avoidable in hindsight. Those very often, but certainly not always, boil down to that someone didn't do what they were supposed to do. $\endgroup$
    – user
    Commented Oct 13, 2017 at 9:14
  • $\begingroup$ @MichaelKjörling Not only in aviation, but with all too many accidents and that's why It's uncommon. $\endgroup$
    – a4android
    Commented Oct 13, 2017 at 11:54

They would abort the mission. Current spacecraft carry supplies sufficient to support the crew on board with a safety reserve. These include the lithium canisters needed to remove CO2 from the air inside the spacecraft, without which the astronauts would pass out and die from too much CO2. An extra person would pose a problem for CO2 removal, as there would now be more CO2 to deal with, meaning the lithium scrubber canisters would be saturated sooner.

This problem was encountered on the Apollo 13 mission, when three astronauts were packed into the LEM, whose lithium canisters were only planned for two people. They did manage to adapt the CSM lithium canisters when the LEM canisters were exhausted, but this does illustrate how carefully keeping people alive in space is planned.


Unfortunately, there is precedent. See "The Cold Equations" by Tom Godwin. Story has to do with a girl stowing away on a medical transport moving emergency supplies to an outpost threatened by disease. Fuel and time are at a premium, and the longer the extra weight throws the ship's trajectory off, the harder it'll be to get to the planet on time...

You can see the story here: https://photos.state.gov/libraries/hochiminh/646441/vantt/The%20Cold%20Equations.pdf

  • $\begingroup$ I assumed the question was based on this premise with the serial numbers filed off, honestly. Isn't this required reading for anyone wanting to write about stowaways IN SPACE? $\endgroup$ Commented Oct 13, 2017 at 4:00
  • $\begingroup$ The Cold Equations has come under a lot of criticism since its writing. Many man-rated spacecraft large enough to stow away on, will likely have enough safety factor and/or enough not-totally-essential equipment to jettison. $\endgroup$
    – ikrase
    Commented Feb 28, 2020 at 9:00

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