So if your character breaks their tether during a space walk here's what will happen

[Snicklefritz]

The Vacuum of Space Won’t Make You Explode, But It Will Kill You Like This…

Plus, what your body’s journey looks like over the next billion years.

www.popularmechanics.com

 

[Swank]

There's a paywall.

 

[Snicklefritz]

There's a paywall.

Sorry. Thought I'd used a free-access link.

 

[StilLearning]

Ahem, as there's a firewall: Assuming the airlock door just pops open: IIRC you need to prep: Hyperventilate to load your blood with oxygen, then blow all the air out of your lungs. Also fart and pee and poo if you can - everything will try to exit: If you hold your breath the suction will rip the are out and destroy your alveoli, and you're f###ed even if you get rescued. You will pass out after 15 - 20 seconds. 20 being if you're in good shape and air used to high altitude and low pressure. You wont explode - your skin is tough enough to stand the pressure difference, though you will get swelling. About 10 of those 15 sec will be useful consciousness, then a few seconds of confusion. This is due to how long it takes de-oxygenated blood to go from lungs to brain. If you can keep your heart rate as low as possible it will buy you a little bit extra - a zen master's meditation may be needed to do this, but it would help. So you have 10 sec to get to an external window or surface and bang on it to signal someone. Once you pass out, experiments on animals (I never said this was nice) suggest that as long as you're got back inside before your heart stops you'll recover (probably) with superficial injuries, including extreme sun burn at Earth's orbit. That means you've got 2-4 minutes or so. You will suffer both oxygen deprevation and the bends, but these will pass if and when you get back inside. Vacuum is a good insulator - so while you will freeze this wont be what kills you, as it takes hours at least.

That's what's in my memory, how'd I do?