5 ms·

Expecting the unexpected is a necessity in space exploration. Murphy’s Law: "Anything that can go wrong will go wrong"!

pavlov 2y ago
On the other hand, isn’t there a lot less things that could happen in space compared to Earth? The atmosphere is unpredictable. The ecosystem is teeming with life and a lot of it is animals with their own agency. Then there’s the whole human factor. If you’re making a vehicle that operates on Earth, you have to be prepared for drunk people and terrorists and all sorts of human contingencies. They’re not causing havoc in deep space. For better and worse, space is dead.
- rachofsunshine 2y ago
  On the other hand, you don't usually get hit by random pieces of debris traveling at mach 25 [1] on Earth. And on the other-other hand, the things that go wrong in spaceflight usually go wrong on launch or reentry - the parts where you combine the extreme conditions of space with the unpredictable extra nonsense of Earth. Like, say, a cold morning making an O-ring brittle or aerodynamic stresses ripping you apart on reentry. Only three deaths - the crew of Soyuz 11 [2] - have actually occurred in space proper; all other deaths have occurred within the Earth's atmosphere. (Although Apollo 13 came close to adding to that list.) [1] LEO orbital velocity is ~8 km/s, mach 1 is ~300 m/s, although meteoroids necessarily strike at much higher velocities than that because they're accelerated to at least Earth's escape velocity on descent. [2] https://en.wikipedia.org/wiki/Soyuz_11 https://en.wikipedia.org/wiki/Soyuz_11
- puzzledobserver 2y ago
  I suspect that it isn't the unpredictability, rather it is the acceptable margin of error. Say you have a 1500 kg car with a 100 hp engine, which starts from a standstill and runs for 5 seconds. How fast will the car be moving at the end of this run? This depends on how much friction the vehicle experiences, and is difficult to accurately predict. Try a similar calculation with a rocket in space, and you can calculate its final speed with a very high degree of certainty. But now consider the potential impact of a malfunction: if the car engine fails to start, you might be inconvenienced, but you will be fine. On the other hand, if the rocket engine fails to ignite in space, you can't perform necessary orbital maneuvers and you might be in deep trouble. It's something about environment on Earth being fundamentally hospitable to human life, and environment in space being similarly inhospitable. Because of this, malfunctions and unpredictable system dynamics on Earth are most often just minor inconveniences, while malfunctions in space / underwater / deep underground are disastrous events.
  - cesarb 2y ago
    > But now consider the potential impact of a malfunction: if the car engine fails to start, you might be inconvenienced, but you will be fine. On the other hand, if the rocket engine fails to ignite in space, you can't perform necessary orbital maneuvers and you might be in deep trouble. On a smaller but more relatable scale: it's like the difference between a car or a train, and an airplane. When you have a malfunction on a car or a train, an appropriate response is just to stop; when you have a malfunction on an airplane, you can't just stop, you have to keep things working long enough to get to land before you can stop.
- nkrisc 2y ago
  Think about it this way: what happens if your car won’t start in the grocery store parking lot? What happens if your lunar ascent module’s main engine doesn’t ignite on the moon’s surface? One is mildly inconvenient, the other is deathly inconvenient. Yes, many aspects of the extraterrestrial environment are predictable, but the consequences for being wrong are far greater. And as another has noted, most deaths during space flight actually occurred in the atmosphere anyway.
  - marcosdumay 2y ago
    > Think about it this way: what happens if your car won’t start in the grocery store parking lot? What happens if your lunar ascent module’s main engine doesn’t ignite on the moon’s surface? Is this a pitch for a near-Earth Uber service?
    - nkrisc 2y ago
      Yeah, just open up the Lünr app and get an available seat on the next manned mission.
- akira2501 2y ago
  The toilet on the shuttle dumps urine overboard but keeps feces in a tank. They just float around in there. There is a mechanism that gets actuated once or twice during flight which spins a net attached to an arm through the tank, to catch all the feces, and then smashes them up against a wall of the tank. The mechanism to run the net can break. It has broken during flight before. At that point you have to put on an arm-length glove, stick your hand in the tank, then smash all the feces up against the wall of the tank manually. You need to do this because at a certain point if you open the toilet to use it there's a very good chance you'll get something floating _out_ of the toilet. Free floating zero-g human waste is an absolute nightmare.
aaron695 2y ago
> "Anything that can go wrong will go wrong" The proper version of Murphy Law, which seems missing on Wikipedia is ~ "If a part can be installed in more than one position, it will be incorrectly installed in the field given enough time" It is almost last on the mitigating risk pyramid, training people to do things properly. PPE is the only one lower. To apply it here, would be "inadvertently stepping on it". They chose to train staff not to step on it. You can't mitigate all risk, maybe it was the best choice.
mulmen 2y ago
If that was true then spaceflight would be impossible. In reality risk is managed, not eliminated.

On the other hand, isn’t there a lot less things that could happen in space compared to Earth? The atmosphere is unpredictable. The ecosystem is teeming with life and a lot of it is animals with their own agency. Then there’s the whole human factor. If you’re making a vehicle that operates on Earth, you have to be prepared for drunk people and terrorists and all sorts of human contingencies. They’re not causing havoc in deep space. For better and worse, space is dead.

rachofsunshine 2y ago
On the other hand, you don't usually get hit by random pieces of debris traveling at mach 25 [1] on Earth. And on the other-other hand, the things that go wrong in spaceflight usually go wrong on launch or reentry - the parts where you combine the extreme conditions of space with the unpredictable extra nonsense of Earth. Like, say, a cold morning making an O-ring brittle or aerodynamic stresses ripping you apart on reentry. Only three deaths - the crew of Soyuz 11 [2] - have actually occurred in space proper; all other deaths have occurred within the Earth's atmosphere. (Although Apollo 13 came close to adding to that list.) [1] LEO orbital velocity is ~8 km/s, mach 1 is ~300 m/s, although meteoroids necessarily strike at much higher velocities than that because they're accelerated to at least Earth's escape velocity on descent. [2] https://en.wikipedia.org/wiki/Soyuz_11 https://en.wikipedia.org/wiki/Soyuz_11
puzzledobserver 2y ago
I suspect that it isn't the unpredictability, rather it is the acceptable margin of error. Say you have a 1500 kg car with a 100 hp engine, which starts from a standstill and runs for 5 seconds. How fast will the car be moving at the end of this run? This depends on how much friction the vehicle experiences, and is difficult to accurately predict. Try a similar calculation with a rocket in space, and you can calculate its final speed with a very high degree of certainty. But now consider the potential impact of a malfunction: if the car engine fails to start, you might be inconvenienced, but you will be fine. On the other hand, if the rocket engine fails to ignite in space, you can't perform necessary orbital maneuvers and you might be in deep trouble. It's something about environment on Earth being fundamentally hospitable to human life, and environment in space being similarly inhospitable. Because of this, malfunctions and unpredictable system dynamics on Earth are most often just minor inconveniences, while malfunctions in space / underwater / deep underground are disastrous events.
- cesarb 2y ago
  > But now consider the potential impact of a malfunction: if the car engine fails to start, you might be inconvenienced, but you will be fine. On the other hand, if the rocket engine fails to ignite in space, you can't perform necessary orbital maneuvers and you might be in deep trouble. On a smaller but more relatable scale: it's like the difference between a car or a train, and an airplane. When you have a malfunction on a car or a train, an appropriate response is just to stop; when you have a malfunction on an airplane, you can't just stop, you have to keep things working long enough to get to land before you can stop.
nkrisc 2y ago
Think about it this way: what happens if your car won’t start in the grocery store parking lot? What happens if your lunar ascent module’s main engine doesn’t ignite on the moon’s surface? One is mildly inconvenient, the other is deathly inconvenient. Yes, many aspects of the extraterrestrial environment are predictable, but the consequences for being wrong are far greater. And as another has noted, most deaths during space flight actually occurred in the atmosphere anyway.
- marcosdumay 2y ago
  > Think about it this way: what happens if your car won’t start in the grocery store parking lot? What happens if your lunar ascent module’s main engine doesn’t ignite on the moon’s surface? Is this a pitch for a near-Earth Uber service?
  - nkrisc 2y ago
    Yeah, just open up the Lünr app and get an available seat on the next manned mission.
akira2501 2y ago
The toilet on the shuttle dumps urine overboard but keeps feces in a tank. They just float around in there. There is a mechanism that gets actuated once or twice during flight which spins a net attached to an arm through the tank, to catch all the feces, and then smashes them up against a wall of the tank. The mechanism to run the net can break. It has broken during flight before. At that point you have to put on an arm-length glove, stick your hand in the tank, then smash all the feces up against the wall of the tank manually. You need to do this because at a certain point if you open the toilet to use it there's a very good chance you'll get something floating _out_ of the toilet. Free floating zero-g human waste is an absolute nightmare.

aaron695 2y ago

> "Anything that can go wrong will go wrong" The proper version of Murphy Law, which seems missing on Wikipedia is ~ "If a part can be installed in more than one position, it will be incorrectly installed in the field given enough time" It is almost last on the mitigating risk pyramid, training people to do things properly. PPE is the only one lower. To apply it here, would be "inadvertently stepping on it". They chose to train staff not to step on it. You can't mitigate all risk, maybe it was the best choice.

mulmen 2y ago

If that was true then spaceflight would be impossible. In reality risk is managed, not eliminated.