eli5 why wouldn’t atronauts survive a fall from the ISS into the pacific?
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There are two main reasons.
The most important is that objects in space are not just floating up there like a hot air balloon. It’s a common mistake to think that there is no gravity in space. But that is not true. If you were 250 miles off the ground and dropped a ball, it would fall all the way back to the ground. But if you are moving fast enough the speed you fall is slower than the speed you are moving forward at so you never hit the ground. You just keep going around in a circle. This is called orbiting.
For the ISS the speed it has to be moving at is around 17,000 miles per hour. That is really fast. Faster than bullets. it is so fast that it can make it all the way around the world in about an hour and half. If you want to get back to the ground you have to get rid of all that speed. The most common way to do that is to use the atmosphere. But if you have ever gotten a rug burn you know that friction can make heat. All the friction from the air would easily cook you. Spaceships handle this by covering part of the ship with materials that can handle a lot of heat. In theory though, you could make a suit that would keep you safe from the heat.
The second is that at high speeds water acts like a solid. It’s kind of like sand. If you put your hand in it slowly, the sand particles have time to move out of the way and your hand moves through it. If you hit it hard though the particles don’t have time to move so your hand only hits the surface. Water is made up of little particles too and the same principle applies. If you hit the water going really fast you are going to have a bad time. So you’d need a parachute to slow you down.
So while it wouldn’t be possible to just jump out and land in the ocean, if you had the right suit, a parachute, and were initially slowed enough to get deep enough into the atmosphere it might be doable. We might in the future see the first orbital skydive. But it won’t be soon.
It isn’t possible to fall from ISS.
Being in orbit means they are already falling bit their horizontal speed keeps them in the same level. If they just walk out the airlock and push themselves towards the Earth nothing will happen – they will stay in roughly the same orbit. Forever.
So, first they need to slow down so they need a rocket. Usually rockets are only used to lose enough speed to touch the atmosphere, then the air drag does the rest. However, hitting atmosphere at such high speed means a lot of heat so they need a heat shield. In just a space suit they would evaporate.
It is possible to slow down enough that the horizontal speed becomes negligible but it would require a massive rocket – roughly as large as the one they used to launch, with all the boosters and thousand tonnes of propellant. But it is possible. You could even add a bit more fuel to slow them down vertically and eliminate the air drag burn until they hit the denser atmosphere.
If you could do all of the above then jumping from ISS would be no different than jumping from a tall building because air resistance creates a stable maximum speed, no matter how high you start the fall.
Then they would just die hitting the water.
Basically it is the same as leaving a bullet train that goes on water surface. But ISS goes almost 8 km/s. So you will be evenly smeared on water surface.
This question is really too generic to actually have a single answer.
But I’ll give you the most probable one. If an astronaut would get out of the ISS and “jump” they would not reach earth. Without a way to slow down the astronaut would just be going around the earth in their own orbit. Death by asphyxiation is my guess for the result.
As many people have said, you are at orbital velocity, and it would take years for the minimal amount of drag in low earth orbit to bring you down. But even then, you would simply burn up in the atmosphere because of how fast you where going. You are going 29KM a sec. The only way you could survive (and this is practically impossible) is to cancel out your relative velocity with a retrograde burn, at which time you would just fall back to earth at a reasonable speed. I dont believe you would gain enough velocity before you hit the atmosphere to cause any burning effect due to atmospheric drag. Once you hit the atmosphere, you wont go faster than terminal velocity, and then a parachute would be all you need to get safely back to the earth’s surface. The reason we rely on the atmosphere to slow us down is because you would need a tremendous amount of fuel in your spaceship to slow you down to a relative speed of zero. That would mean a much larger rocket to get into orbit in the first place, and the price per launch would increase exponentially. Go play Kerbal Space Program for about 100 hours. You wont ever have a question concerning orbital mechanics ever again.
The [ISS travels about 17,500 miles per hour (28,000 km/hr).](https://www.kennedyspacecenter.com/blog/the-20-most-frequently-asked-questions-about-the-international-space-station) It orbits the earth every 90 minutes. Anyone jumping off is going to have that same velocity. Upon hitting the earths atmosphere they will most likely burn up and not survive.
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