Introduction to Aerospace Atmoshere.pptx

Understanding Atmosphere around us. Critical for Aviation industry.

1. 1 ATMOSPHERE

2. 2 ATMOSPHERE 1.The gaseous envelope surrounding  the   earth ;  the air. 2.This medium at a given place. 3.Astronomy . the gaseous envelope surrounding a heavenly body. 4.Chemistry . any gaseous envelope or medium 5.A conventional unit of pressure, the normal pressure of the  air at sea level, about 14.7 pounds per square inch (101.3kilopascals), equal to the pressure exerted by a column of mercury   29.92 inches  (760 mm) high. Abbreviation:  atm.

3. 3 ATMOSPHERE 6.a surrounding or pervading mood,  environment,or   influence:an  atmosphere of impending war;  a very tense atmosphere. 7.the dominant mood or emotional  tone  of a work of  art , as of  play or novel: the chilly atmosphere  of a ghost story. 8.a distinctive quality, as of a place; character: The old part of town has lots of atmosphere.

4. 4 ATMOSPHERE Troposphere (8 – 14.5 km) Stratosphere ( up to 50 km) Mesosphere (up to 85 km) Thermosphere (up to 600 km)

5. 5

6. 6

7. 7 Composition Of the Air The atmosphere is composed of a mixture of gases: Nitrogen is by far the largest component of air, accounting for 78 percent. Next largest component is oxygen, which consists of 21 percent. The remainder consists of small portions of other gases.

8. 8 Composition of the Atmosphere The atmosphere is primarily composed of Nitrogen (N 2 , 78%), Oxygen (O 2 , 21%), and Argon ( Ar , 1%). A myriad of other very influential components are also present which include the water (H 2 O, 0 - 7%), "greenhouse" gases or Ozone (0 - 0.01%), Carbon Dioxide (CO 2 , 0.01-0.1%),

9. 9 Composition of the Atmosphere

10. 10 Beyond the Atmosphere The exosphere starts at the top to the thermosphere and continues until it merges with interplanetary gases, or space. In this region of the atmosphere, Hydrogen and Helium are the prime components and are only present at extremely low densities.

11. 11 Standard Sea Level Conditions The standard atmosphere approximates the average conditions existing at 40° latitude, and is determined on the basis of the following assumptions. The standard sea level conditions are: Pressure at 0 altitude (P ) = 29.92 inches of mercury. Temperature at 0 altitude (T ) = 15° C 59° F . Gravity at 0 altitude (g ) = 32.174 ft/sec2 Density at 0 altitude (  ) = .0024 slugs/ cu.ft =1.1338kg/cu meter =0.0709 lb/cu ft

12. 12 Pressure The atmosphere extends upward for hundreds of miles. The pull of the Earth's gravity on air molecules creates a pressure that pushes in all directions and amounts to about 14.7 pounds per square inch (psi) at sea level.

13. 13 Pressure (Cont’) 14.7 psi is air pressure on a standard day at sea level. In other words, the pressure, which the atmosphere applies to a square inch of area, is equal to the weight of a column of air one square inch in cross section, which extends from that area to the "top" of the atmosphere.

14. 14 Standard Sea Level Conditions

15. 15 Pressure Measurement Mercury barometer The mercury barometer works on the principle of balancing the weight of a column of air by the weight of a column of mercury . Simple relationship exists between pressure measure- ments in ‘psi’ and in inches Hg. One cu in of mercury weighs 0.491 pound. Therefore, a pressure of 30 inches of mercury would be the equivalent of: 0.491 x 30 = 14.73 psi

16. 16

17. 17 Pressure Measurement Aneroid barometer The aneroid barometer was developed because of the difficulty in using a mercury barometer. Aneroid means "without fluid" The aneroid barometer consists of four basic parts.

18. 18

19. 19 Aneroid barometer The first part is a closed chamber (the aneroid chamber-#1) of thin, pliable metal, partly evacuated. Thus, it is not " truely " aneroid. This chamber expands as the atmospheric pressure pressing on the chamber decreases in magnitude. The chamber compresses as the atmospheric pressure increases in magnitude. The second part , a spring, #2, either within the chamber or external to the chamber, as in the image to the right, is used to keep the chamber from collapsing. One side of the chamber is usually stationary and the other side is allowed to move under changing air pressure The third part transfers movement of the chamber and is a linking mechanism, #3 - #9, to the fourth part , a pointer on the face of the aneroid barometer or to a pen to record on a moving graph the atmospheric pressure.

20. 20 Aneroid barometer The calibrations are made in thousands of feet rather than in psi. For example, the standard pressure at sea level is 29.92 in Hg, or 14.69 psi. At 10,000 feet above sea level, standard pressure is 20.58 in Hg, or 10.10 psi. Altimeters are calibrated so that if the pressure exerted by the atmosphere were 20.58 in Hg, the altimeter would point to 10,000 feet. In other words, the altimeter is calibrated so that it indicates the altitude at which the prevailing atmospheric pressure would be considered standard pressure. Thus, the altitude read from the altimeter, being dependent upon atmospheric pressure, is called pressure altitude (Hp). Actually, an altimeter will read pressure altitude only when the altimeter adjustment is set at 29.92 inches Hg.

21. 21

22. 22 Temperature the degree of hotness or coldness of a body or environment (corresponding to its molecular activity) the somatic sensation of cold or heat Temperature is the physical property of a system which underlies the common notions of "hot" and "cold"; the material with the higher temperature is said to be hotter. Temperature is a measure of the average kinetic energy of the particles in a sample of matter.

23. 23 Temperature To convert from Fahrenheit to Celsius or centi -grade you need to subtract 32 degrees from the Fahrenheit temperature and then multiply the difference by five. Finally divide the product by nine. See the formula :

24. 24 Temperature To convert centigrade or Celsius to Fahrenheit, multiply the centigrade temperature by nine and then divide the product by five. After you do that add 32 degrees to the total. See the formula below:

25. 25 Temperature Vertical Structure of Earth's Temperature

26. 26 Horizontal Structure of Earth's Temperature

27. 27 1(x 1 , y 1 ) 2(x 2 , y 2 ) x y 1(C 1 , F 1 ) 2(C 2 , F 2 ) C F

28. 28 1(0, 32) 2(100, 212) C F 1(C 1 , F 1 ) 2(C 2 , F 2 )

29. 29 Density Density is the amount of material (mass) contained in a unit of volume Density is constant in solids Factors affecting air density are: Barometric pressure Altitude Temperature Humidity

30. 30 Effect Of Pressure/Temp On Density The air becomes rare or less dense as the altitude is increased due to drop in pressure. As we reduce the pressure density also reduces. Therefore, the density is directly proportional to the pressure. When the temperature is increased the density will decrease, hence, density is inversely proportional to the temperature .

31. 31 "Substance, Air, Mass Density (kg/m 3 ), 1.29, *Unless otherwise noted, densities are given at 0 °C and 1  atm pressure." The density of moist air may be determined by a similar relation: D = 1.2929 (273.13/T) [(B – 0.3783e)/760] where T is the absolute temperature; B, the barometric pressure in mm, and e the vapor pressure of the moisture in the air in mm.

32. 32 Density altitude is the altitude corrected for non-ISA International Standard Atmosphere (ISA) conditions at which the air density is unequal to ISA conditions. Aircraft performance depends on density altitude, which is affected by barometric pressure and temperature. On a very hot day, density altitude at an airport may be so high as to preclude takeoff, particularly for helicopters or a heavily loaded aircraft. Density Altitude

33. 33 Humidity Humidity is a measure of the amount of water vapour that is in the atmosphere . Relative Humidity is the ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature It is expressed as a percentage.

34. 34

35. 35

36. 36 Speed Of Sound The speed of "sound" is actually the speed of transmission of a small disturbance through a medium . The speed at which sound travels depends on the medium through which the waves are passing, and is often quoted as a fundamental property of the material. In general, the speed of sound is proportional to the square root of the ratio of the elastic modulus (stiffness) of the medium and its density. Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on temperature . In air at sea level, the speed of sound is approximately 769.5 mph (1,238.3 km/h) at 68 °F (20 °C), in water 3,315.1 mph (5,335.1 km/h) at 20 °C (68 °F), and in steel 13,332.1 mph (21,446 km/h). The speed of sound is also slightly sensitive (a second order effect) to the sound amplitude, which means that there are nonlinear propagation effects, such as the production of harmonics and mixed tones not present in the original sound.

37. 37 Speed Of Sound The speed of sound depends on the state of the gas-more specifically, the square root of the temperature of the gas. The equation for the speed of sound is given as a= ( γ RT) 1/2 where,  = ratio of specific heats (1.4 for air at STP) R = gas constant (286 m 2 /s 2 /K o for air T = absolute temperature (273.15 + o C )

38. 38 The speed of sound varies with altitude. It is affected by the density, temperature, and chemical composition of the surrounding air. Generally, below 40,000 feet, the speed of sound decreases as altitude increases . Sea level 1,116.45 ft/sec 10,000 feet 1,077.40 ft/sec 20,000 feet 1,036.93 ft/sec 30,000 feet 994.85 ft/sec 40,000 feet 968.08 ft/sec 50,000 feet 968.08 ft/sec 60,000 feet 968.08 ft/sec 70,000 feet 970.90 ft/sec 80,000 feet 977.62 ft/sec 100,000 feet 990.90 ft/sec