Whenever something breaks on the International Space Station it’s a pretty big deal for the astronauts on board.
Consider this: your toilet leaks in places where it really shouldn’t. What do you do? You call a plumber. Some guy or gal shows up with a toolbox, spills some red tracer dye, says something about ball cocks and flapper valves, wrestles with a big wrench, makes a mess on your bathroom floor and then charges you a ridiculous amount of money. But you pay up because you don’t have a clue what they’re talking about and the problem is solved, besides, what are you gonna say anyway?
Now imagine the same thing happens to you while you’re working up there in earth orbit.
Nope, can’t call a plumber. You ARE the plumber. No big deal, you think; you’ve done all of it during your extensive multi-year training. Mission Control will go over the details with you; you don your spacesuit and get ready to head out the airlock into the void of outer space.
Being an astronaut is often glamorized by the media. It’s the most awesome job in the world, right?
The truth is that you have to do everything that you would normally call in help for, back on earth. So when recently a valve went bad in one of the ammonia cooling pumps on the ISS, it was up to astronauts themselves to fix it.
Lucky for them, they actually didn’t have to take the entire thing apart just to replace the faulty valve (which may not have fixed the problem, anyway). Instead, they replaced the entire pump module. It’s a refrigerator-sized box located on the outside of the ISS, and fortunately there are several spare modules on board.