How could depressurizing air generate light?
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Last week the world was treated to an unexpected spectacle - the sight of an airplane cabin with a big hole in it open to the sky. We can imagine that this spectacle was even more unexpected to people who were on the flight. If you saw photos or video of the hole, you may have also been struck by how little there is between "inside" and "outside" in an airplane. There is a piece of plastic headliner on the inside of the plane, some insulation and then a thin aluminum skin on the exterior of the plane. That's it.
It brings up an interesting question - what is going on inside an airplane cabin when it is cruising at 33,000 feet? It turns out that passengers are flying in something that vaguely resembles a space capsule. Let's take a look at how the space capsule works.
The first thing to understand is that people dressed in normal clothing definitely cannot survive at 33,000. This altitude is roughly the equivalent to standing at the summit of Mount Everest. If there were some way you could stick your arm out the window at 33,000 feet, the first thing you would notice is that it is incredibly cold - minus 40 degrees F or colder. The second problem is incredibly low air pressure. The pressure is so low that people would pass out very quickly from lack of oxygen. The air at that altitude and temperature is also extremely dry.
So how are we able to sit in an airplane's comfy chairs at 33,000 feet feeling like we are sitting in someone's living room?
The first thing that has to happen is pressurization. The air at sea level is about 14.7 PSI (pounds per square inch). The pressure at 33,000 feet (roughly 6 miles up) is approximately 4 PSI. Something has to be done to increase the pressure, or people would quickly pass out from lack of oxygen at 4 PSI. Fortunately, the jet engines on the aircraft act like big air compressors.
If you take apart a jet engine and look at it, it has four main sections. At the front, where the air is coming in, there is the compressor stage. Blades suck in air and compress it. The fuel is injected into the compressed air and ignited in the combustion stage. The air expands greatly from the heat of combustion, and flows through another set of blades, turning them as it passes through. And then the exhaust gases flow out of the engine to create thrust to keep the airplane in the air.
It brings up an interesting question - what is going on inside an airplane cabin when it is cruising at 33,000 feet? It turns out that passengers are flying in something that vaguely resembles a space capsule. Let's take a look at how the space capsule works.
The first thing to understand is that people dressed in normal clothing definitely cannot survive at 33,000. This altitude is roughly the equivalent to standing at the summit of Mount Everest. If there were some way you could stick your arm out the window at 33,000 feet, the first thing you would notice is that it is incredibly cold - minus 40 degrees F or colder. The second problem is incredibly low air pressure. The pressure is so low that people would pass out very quickly from lack of oxygen. The air at that altitude and temperature is also extremely dry.
So how are we able to sit in an airplane's comfy chairs at 33,000 feet feeling like we are sitting in someone's living room?
The first thing that has to happen is pressurization. The air at sea level is about 14.7 PSI (pounds per square inch). The pressure at 33,000 feet (roughly 6 miles up) is approximately 4 PSI. Something has to be done to increase the pressure, or people would quickly pass out from lack of oxygen at 4 PSI. Fortunately, the jet engines on the aircraft act like big air compressors.
If you take apart a jet engine and look at it, it has four main sections. At the front, where the air is coming in, there is the compressor stage. Blades suck in air and compress it. The fuel is injected into the compressed air and ignited in the combustion stage. The air expands greatly from the heat of combustion, and flows through another set of blades, turning them as it passes through. And then the exhaust gases flow out of the engine to create thrust to keep the airplane in the air.
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Light aircraft – approx. 3-5 psi ... pressurizing cabin air varies between ... amount of pressurized air that is allowed to exit the cabin ..... The chemical oxygen generator differs from
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