Appunti di Human Factor

28/02/22 (Torchia—S)

Atmosphere

The atmosphere is a tiny envelope which surrounds Earth and protects life. This protection regards radiation, thermal and meteoric, and the atmosphere is made of some gases which support life, such as H₂O, O₂ and CO₂, but were of:

• nitrogen 78% which doesn’t reach in our lungs;
• oxygen 21% at sea level;
• other gases 1%, such as argon or CO₂.

At sea level the weight of the atmosphere (or pressure) is exactly the same of a column of mercury of the height of 760 mm (mmHg), and the pressure mostly decreases from sea level (s.l) to n 5000 feet so the altitude can be measured in many ways:

• true altitude with respect to the s.l no matter where we are;
• absolute altitude with respect to the ground, so it depends from the place;
• pressure altitude, very weak in variation and such that it depends from the temperature the place and the altitude because it is measured with respect to the standard 760 mmHg. This means that planes flying at the same true altitude but in different places will have different pressure altitudes.

In general, the relation between pressure and altitude is very different from the one between temperature and altitude.

The atmosphere is so divided in:

• troposphere, where all the climate phenomena happen;
• stratosphere → ionosphere → exosphere → space

In particular ionosphere is such that it goes from s.l to 60000 ft and the temperature rate of drop is 2°C per 1000 ft and in this layer wind, rain ecc is very important.

Another important dimension the one of 10000 ft, which is the altitude over which we don’t have enough oxygen and so staying there for a very long causes the hypoxia. Over 40000 ft we need an extra source of oxygen because the pressure is so low that we don’t have enough air to breath!

Atmosphere

The atmosphere is a tiny envelope which surrounds Earth and protects life. This protection regards radiation, thermal and meteoric, and the atmosphere is made of some gases which support life, such as H₂O, O₂ and CO₂, but more of:

• nitrogen 78%, which doesn't reach in our lungs;
• oxygen 21% at sea level;
• other gases 1%, such as argon or CO₂.

Constant percentage up to 50-60 miles altitude but going higher the density decreases, and so does the pressure.

At sea level the weight of the atmosphere (or pressure) is exactly the same of a column of mercury of the height of 760 mm (mmHg), and the pressure mostly decreases from sea level (s.l.) to n 5000 feet, so the altitude can be measured in many ways:

• true altitude with respect to the s.l. no matter where we are;
• absolute altitude with respect to the ground, so it depends from the place;
• pressure altitude, very used in aviation and such that it depends from the temperature the place and the altitude because it is measured with respect to the standard: 760 mmHg. This means that planes flying at the same true altitude but in different places will have different pressure altitude. In general, the relation between pressure and altitude is very different from the one between temperature and altitude.

The atmosphere is so divided in:

• troposphere, where all the climate phenomena happen;
• stratosphere → ionosphere → exosphere → space

In particular, ionosphere is such that it goes from s l to 60000 ft and the temperature rate of drop is 2°C per 1000 ft and in this layer wind, rain etc. is very important.

Another important dimension is the one of 10000 ft, which is the altitude over which we don't have enough oxygen and so staying there for a very long time can be injurious. Over 40000 ft we need an extra source of oxygen because the pressure is so low that we don't have enough air to breath!

...here we need to pressurize both the cabin and a pressure suit to let workers...

...breathe because of the very very low pressure. ...Going up to 63500 ft the _{armstrong line} is reached and here no life is...

...possible...physiological division of the atmosphere is such that...

...physiological zone is up to 10000 ft (523 mmHg) and we don’t need any...

...oxygen from an extra sources;...

...physiologically deficient zone from 10K to 50K ft (87 mmHg) were we need...

...artificial help from the right pressure and extra sources of oxygen;...

...space equivalent zone were life can be sustained instead of creating an...

...artificial atmosphere...The definition of the Armstrong line is related to the fact that at that alti...

...tude the pressure is 47 mmHg and at that pressure, the boiling temperature...

...of body fluids is ~37°C which is exactly the body temperature...

...let's now see some gas laws to understand how gasses affect our body;...

- Boyle’s law which is related to a barotrauma which means a trauma..