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Risk Mitigation in Theory
Trying to deal with risk is a personal choice, but it’s also pretty well-documented. For example, what’s the risk of getting hit by lightning? It’s pretty low. I mean, do you know anybody that’s been hit by lightning? It only happens occasionally, but the consequences of getting hit by lightning are really high. If lightning hits you, you’re pretty much dead. Or if a meteorite comes smoking through the atmosphere and crashes into you, you’re toast. You’re done. So that balance between consequence and probability is what risk is all about, and that’s how we predict risk.
If it’s a thing that has no consequence, like the risk of a fly landing on my shoulder, well, it might happen, but there’s no consequence. Who cares if a fly lands on my shoulder? It doesn’t matter. So in that case it would be way down in the lower left side of a matrix of some probability and some consequence. There are some things that have extremely high consequence – a lightning strike – but very low probability. So how much do you actually have to prepare for those? It’s when you get the worst of both, where you get a high probability – this is actually probably going to happen – and it has a high consequence. Like having a car accident. In your life, sometime, you’re probably going to have an accident with your car and it can have very high consequence. Then, you need to deal with it – you need to somehow mitigate and change that risk. So you do. We have rules on how to drive a car. You have to get a license. In your car, it has crumple zones. We do crash tests. You have an airbag to protect you. You have your harness, your seat belt, strapping you in. You practice, you learn how to drive. All of those things are just structured to mitigate a risk that has high probability and high consequence.
You can approach anything that way. Just say, what’s the risk and what’s the chance that it’s going to happen? What’s the consequence of it happening? And then you can decide how much time you’re going to invest in preventing that event from happening in your own life. It’s just sort of engineering, and it’s the way we fly rocket ships, but maybe it’s not a bad thing to just analyze your own life with as well. What are my risks? What are my probabilities? What should I change? What should I get ready for?
Risk Mitigation in Practice
It’s fun to look up and see a shooting star. But of course, what a shooting star is is a rock coming in from the universe and burning up in the atmosphere. When you count up all those rocks, the Earth gets hit by 50 tons of rock a day. 50 tons of meteorite hit our Earth every day, and every ounce of those go by the space station – because it’s up there. So there’s a definite risk on board the space station of having a meteorite punch a hole in the wall of the spaceship. So that’s a risk. Now the question is: What are the consequences of that happening and what’s the probability of it happening? And how can we deal with both of those?
So the probability of a rock punching a hole, well you can just sort of do the math and think about it, and we realized that over a 30-year lifespan of a space station, there’s a certain fairly high percentage that a rock will at some point punch a hole in it. So we put armor on the outside of the space station. It has another whole protective layer of what we call Micrometeorite Orbital Debris protection – MMOD protection. And it’s not going to solve all problems, but it decreases the chances of one of those rocks coming through. We also, if we know something’s coming that’s big enough, we can actually fire the engines on the space station and get it out of the way – another way to avoid getting hit.
But there’s always going to be some chance of just something unplanned just punching a hole. So then we change inside. We recognize that if we get a hole punched in the ship, how do we react? How do we stop it from causing bodily harm to us and ruining the spaceship? And so we practice all the time. We have a bunch of sensors inside to measure a drop of pressure, including our eardrums – they’re a pretty good sensor. If you feel your ears starting to pop, then you know the pressure’s dropping. And then we have alarms that go off in the middle of the night, and you know ok, I need to go get the mask and I need this equipment, follow this procedure, do all of these things. And then we immediately have a long, carefully written and practiced sequence of procedures for how to deal with a pressure loss. And initially, we’re worried about saving our lives, but if the leak is slow enough then you run around the station in a logical sequence and start closing hatches, and try to lock off wherever the leak might be so that that portion might depressurize but the rest of everything’s going to be ok. And we practice that, and we constantly improve it and think about it, and we’re good at it.
And that combination of recognizing there’s a risk, figuring out the consequences, looking at the probability, and then working on how we’re going to respond and prevent, that drops the risk down to a level that we can go live on a spaceship. We know that that risk exists, but we’ve analyzed it and worked on it and mitigated it enough that we can safely live on a spaceship for decades. And between the Russian space station Mir, which was launched in 1986, and the International Space Station, which we started living on in 2000, we’ve had lots – thousands and thousands – of meteorites hit the ship, but never once has a meteorite punched a hole, and if it does, we’re ready to deal with it.