A lot can go wrong during spaceflights. Astronauts must be prepared to confront the worst—to deal with emergencies so pressing that it's hard to imagine how one might keep one's cool in responding to them:

The SpaceX Crew Dragon spacecraft's systems were warning the crew of a "significant" issue, Isaacman said. They'd spent months poring over SpaceX manuals and training to respond to in-space emergencies, so they leaped into action, working with SpaceX ground controllers to pinpoint the cause of the error.

As it turned out, the Crew Dragon wasn't in jeopardy. But the on board toilet was.

Nothing in space is easy, including going to the bathroom. In a healthy human on Earth, making sure everything ends up in the toilet is usually a matter of simple aim. But in space, there is no feeling of gravity. There's no guarantee that what comes out will go...where it's supposed to. Waste can — and does — go in every possible direction.

To solve that problem, space toilets have fans inside them, which are used to create suction. Essentially they pull waste out of the human body and keep it stored away.

And the Crew Dragon's "waste management system" fans were experiencing mechanical problems. That is what tripped the alarm the crew heard.

The spaceship "wasn't in jeopardy"? I'm sorry, but if your toilet's not working, then the whole freakin' mission itself is in danger of being scrapped.

That's what you call mission critical.

I mean, if the toilet in space is broken—you've got nowhere to go. It's not like you can just pop out on the shuttle roof and go over the side.

Next time, make sure Elon Musk checks the fan's working before he sends people into the stratosphere!