What would happen if the ISS made an uncontrolled re-entry through Earth's atmosphere? [closed]

Question

Total annihilation? Global impact? Localised consequences?

To give my question a little more context: the International Space Station (ISS) is supposed to be retired sometime in 2020 due to having reached the end of its operational life. This means they will have it fall with style into the Pacific when the time comes.

This, of course, has made me wonder what would happen if they decided to extend the life of the outpost and things went wrong. Mainly, I'm curious if there would be a complete obliteration like in Seeking a Friend for the End of the World, if there would be less devastating but still severe worldwide consequences, or if it would just impact the area where it fell (be it land or sea).

Some info on the ISS that might be useful:

The orbital outpost, which flies about 220 miles (354 kilometers) above Earth, consists of 13 rooms and is typically home to a six-person crew. The space station weighs nearly 1 million pounds, which is roughly equivalent to 320 cars. [source]

Thank you in advance!

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EDIT: Thanks to everyone who answered. I posted this question in the Worldbuidling Stack because I was thinking of using the premise for a story. I will remember there are other Stacks in the future to avoid being off-topic.

Answer 1

To get a clue, we can look at the fate of space station Mir, which deorbited (in a controlled fashion) in 2001. At 130,000 kg, it was roughly one-third the mass of ISS, but more compactly built.

Mir broke up in orbit 8 minutes after entering the atmosphere, and most of the fragments burned up in the atmosphere. Most of the unburned fragments fell into the South Pacific about 8 minutes after breakup.

The same thing will happen with ISS, should it deorbit (and it will likely be forcibly deorbited when it is decommissioned). If fragments were to hit land, they would do some damage, but nothing catastrophic unless they hit a dense population centre. Most likely, they will land in water, since 70 percent of the Earth'surface is water. The orbit of ISS has an inclination of 51.64 degrees, so it could land anywhere between 51.64 degrees south and 51.64 degrees north.

Mir breaking up on re-entry.

Answer 2

The space station while very heavy and large is essentially built like a "tin can" with walls as thin as they possibly can be to contain the volume inside. On reentry, it would reach a maximum terminal velocity of a few hundred km/h, which is devastating if it lands on your head, but otherwise not so much.

Think of it like a plane crash except without all that burning jetfuel. 1 million pounds is equivalent to a fully loaded Boeing 747, so it may smash a building but otherwise it won't cause "global devastation"

Example of what happens when a large plane lands in your neighborhood:

Related: https://space.stackexchange.com/questions/9464/what-are-the-requirements-of-a-suborbital-trajectory-to-ensure-that-a-small-pay

Answer 3

As with all these questions, perhaps the best place to start is by comparison to the Chicxulub Asteroid. This is the event that effectively wiped out the dinosaurs. That was an asteroid generally thought to be 10¹⁵ Kg in mass at a minimum. The ISS is closer to 4.5 x 10⁵ Kg in mass, so it's at least 10 orders of magnitude less mass than the asteroid that wiped out the dinosaurs, but not life, off the face of the Earth.

The fact that its planned decommission involves dumping it in the middle of the Pacific tells you that it could do some local damage, but not global damage. Putting it down in the ocean would not help matters and might actually make things worse, with global tsunamis and the like very probable.

On Wikipedia, they have a handy reference chart that, while not directly relevant to your needs, does go some way to explaining what the kinetic energy might be and how often that already happens. Given that the ISS is not solid rock, the likelihood is that it will break up long before it hits the surface and spread the debris over a very large area is high, hence using the Pacific as a target makes it easier to contain damage. There is a far better chance of hittinging the basket if the basket is bigger. But, I digress.

For what it's worth, this is not the first time that we've had to worry about such things. Us older folk still remember Skylab being decommissioned and falling into the Pacific - Taco Bell even made a bet for free tacos with the entire population of USA that a part of it would hit a target they put off the cost of California somewhere.

Bottom line is that I don't want it falling down on the city in which I live, but it's not about to end life on the Earth either.

Answer 4

Consider the implausible worst case. The ISS keeps its current velocity (7.66km/s) whilst passing through the atmosphere, somehow. It retains full structural integrity, and hits the ground entirely intact. It weighs 417289 kg, giving it a kinetic energy of ~12TJ, or the equivalent of about 3 kilotonnes of TNT. Consider that the largest nuclear tests were in excess of 50 megatonnes, you'll see that this is very much small beans by the by scale of human-triggered explosions, and is pretty miniscule compared to the energy released by, say, a hurricane or reasonable-sized volcanic eruption.

So, with a nod to Betjeman, lets have it crash into Slough. At 51.5105° N, it is right on the edge of the plausible debris track, but close enough for handwaving. Using good old NUKEMAP, we get this sort of thing:

The 1psi overpressure line (enough force to break glass, but not much more than that) doesn't even reach as far as Eton, alas.

In practise, even if it does hit the ground, it will not hit it at orbital speeds. A deorbit burn will slightly reduce the speed of a satellite, dropping its orbit into the outer fringes of the atmosphere which will slow it down further til its path intersects the earth. As it falls deeper into the atmosphere, air resistance increases and will slow it down even further. Not being intended to survive re-entry, it will break up and largely burn away, so the chances of very much of it hitting the surface at all are pretty small.

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By way of ridiculous extrapolation, how fast would the ISS have to be travelling (if it hit the ground intact) to release as much energy as the Chixulub impactor, a good model for a global catastrophe?

Relativistic kinetic energy equation: $KE = mc^2\left[ \frac{1}{\sqrt{v^2/c^2} }- 1 \right]$. With a bit of deft rearranging, you can throw in a guess at the Chixulub impact energy (say, 1x10²⁵J) and get out a velocity of a brisk .999993c. It is left as an exercise to the reader to work out how you could accelerate a few thousand kilos of space station to that velocity in a short period of time. In any case, it seems unlikely to happen to the ISS.