LEARN MORE ABOUT: THE ATMOSPHERE

LEARN MORE ABOUT: 

THE ATMOSPHERE

An atmosphere (from Greek ατμός - atmos, "vapor" + σφαίρα - sphaira, "sphere") is a layer of gases that may surround a material body of sufficient mass,^[1] by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low. Some planets consist mainly of various gases, and therefore have very deep atmospheres (see gas giants).

The term stellar atmosphere is used for the outer region of a star, and typically includes the portion starting from the opaque photosphere outwards. Relatively low-temperature stars may form compound molecules in their outer atmosphere. Earth's atmosphere, which contains oxygen used by most organisms for respiration and carbon dioxide used by plants, algae and cyanobacteria for photosynthesis, also protects living organisms from genetic damage by solar ultraviolet radiation. Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.

What Is Atmosphere?

The atmosphere is the mixture of gases and other materials that surround the Earth in a thin, mostly transparent shell. It is held in place by the Earth's gravity. The main components are nitrogen (78.09%), oxygen (20.95%), argon (0.93%), and carbon dioxide (0.03%). The atmosphere also contains small amounts, or traces, of water (in local concentrations ranging from 0% to 4%), solid particles, neon, helium, methane, krypton, hydrogen, xenon and ozone. The study of the atmosphere is called meteorology.

 

Life on Earth would not be possible without the atmosphere. Obviously, it provides the oxygen we need to breath. But it also serves other important functions. It moderates the planet's temperature, reducing the extremes that occur on airless worlds. For example, temperatures on the moon range from 120 °C (about 250 °F) in the day to -170 °C (about -275 °F) at night. The atmosphere also protects us by absorbing and scattering harmful radiation from the sun and space. 

Of the total amount of the sun's energy that reaches the Earth, 30% is reflected back into space by clouds and the Earth's surface. The atmosphere absorbs 19%. Only 51% is absorbed by the Earth's surface. 

We are not normally aware of it but air does have weight. The column of air above us exerts pressure on us. This pressure at sea level is defined as one atmosphere. Other equivalent measurements you may hear used are 1,013 millibars, 760 mm Hg (mercury), 29.92 inches of Hg, or 14.7 pounds/square inch (psi). Atmospheric pressure decreases rapidly with height. Pressure drops by a factor of 10 for every 16 km (10 miles) increase in altitude. This means that the pressure is 1 atmosphere at sea level, but 0.1 atmosphere at 16 km and only 0.01 atmosphere at 32 km. 

The density of the lower atmosphere is about 1 kg/cubic meter (1 oz./cubic foot). There are approximately 300 billion billion (3 x 10**20, or a 3 followed by 20 zeros) molecules per cubic inch (16.4 cubic centimeters). At ground level, each molecule is moving at about 1600 km/hr (1000 miles/hr), and collides with other molecules 5 billion times per second. 

The density of air also decreases rapidly with altitude. At 3 km (2 miles) air density has decreased by 30%. People who normally live closer to sea level experience temporary breathing difficulties when traveling to these altitudes. The highest permanent human settlements are at about 4 km (3 miles).

Layers of The Atmosphere

The atmosphere is divided into layers based on temperature, composition and electrical properties. These layers are approximate and the boundaries vary, depending on the seasons and latitude. (The boundaries also depend on which "authority" is defining them.)

Layers Based On Composition

Hemispheres

· The lowest 100 km (60 miles), including the Troposphere, Stratosphere and Mesosphere.

· Contains 99% of the atmosphere's mass. 

· Molecules do not stratify by molecular weight. 

· Although small local variations exist, it has a relatively uniform composition, due to continuous mixing, turbulence and eddy diffusion. 

· Water is one of two components that is not equally distributed. As water vapor rises, it cools and condenses, returning to earth as rain and snow. The Stratosphere is extremely dry.

· Ozone is another molecule not equally distributed. (Read about the ozone layer in the Stratosphere section below.) 

Heterosphere

· Extends above homosphere, including the Thermosphere and Exosphere. 

·Stratified (components are separated in layers) based on molecular weight. The heavier molecules, like nitrogen and oxygen, are concentrated in the lowest levels. The lighter ones, helium and hydrogen, predominate higher up.

Layers based On Electrical Properties

Neutral atmosphere

 

· Below about 100 km (60 miles) 

Ionosphere

 

· Above about 100 km

· Contains electrically charged particles or ions, created by the absorption of UV (ultraviolet) light.

· The degree of ionization varies with altitude.

· Different layers reflect long and short radio waves. This allows radio signals to be sent around the curved surface of the earth.

· The Aurora Borealis and Aurora Australis (the Northern and Southern Lights) occur in this layer.

The Magnetosphere is the upper part of the ionosphere, extending out to 64,000 km (40,000 miles.) It protects us from the high energy, electrically charged particles of the solar wind, which are trapped by the Earth's magnetic field.

Layers Based On Temperature

Troposphere - Height depends on the seasons and latitude. It extends from ground level up to about 16 km (10 miles) at the equator, and to 9 km (5 miles) at the North and South Poles.

· The prefix "tropo" means change. Changing conditions in the Troposphere result in our weather.

· Temperature decreases with increasing altitude. Warm air rises, then cools and falls back to Earth. This process is called convection, and results in huge movements of air. Winds in this layer are mostly vertical.

· Contains more air molecules than all the other layers combined. 

Stratosphere - Extends out to about 50 km (30 miles)

· The air is very thin.

· The prefix "strato" is related to layers, or stratification.

· The bottom of this layer is calm. Jet planes often fly in the lower Stratosphere to avoid bad weather in the Troposphere.

· The upper part of the Stratosphere holds the high winds known as the jet streams. These blow horizontally at speeds up to 480 km/hour (300 miles/hour)

· Contains the "ozone layer" located between 15 - 40 km ( 10 - 25 miles) above the surface. Although the concentration of ozone is at most 12 parts per million (ppm), it is very effective at absorbing the harmful ultraviolet (UV) rays of the sun and protecting life on Earth. Ozone is a molecule made of three oxygen atoms. The oxygen molecule we need to breathe contains two oxygen atoms.

· The temperature is cold, about -55 °C (-67 °F) in the lower part, and increases with increasing altitude. The increase is caused by the absorption of UV radiation by the oxygen and ozone.

· The temperature increase with altitude results in a layering effect. It creates a global "inversion layer", and reduces vertical convection. 

Mesosphere - Extends out to about 100 km (65 miles)

· Temperature decreases rapidly with increasing altitude. 

Thermosphere - Extends out to about 400 km ( 250 miles)

· Temperature increases rapidly with increasing altitude, due to absorption of extremely short wavelength UV radiation.

· Meteors, or "shooting stars," start to burn up around 110-130 km (70-80 miles) above the earth. 

Exosphere -Extends beyond the Thermosphere hundreds of kilometers, gradually fading into interstellar space.

· Density of the air is so low that the normal concept of temperature loses its meaning.

· Molecules often escape into space after colliding with one another.

 

Space Math V Educator Guide

Audience: Educators
Grades: 9-12

These activities comprise a series of 87 practical mathematics applications in space science. This collection of activities is based on a weekly series of problems distributed to teachers during the 2008-2009 school year. The problems in this booklet investigate space phenomena, space travel and mathematics applications such as planetary nebulae, collapsing gas clouds, space shuttle launch trajectory, evaluating functions, and differentiation. The problems are authentic glimpses of modern science and engineering issues, often involving actual research data. Each word problem includes background information. The one-page assignments are accompanied by one-page teachers answer keys.

Space Math V  [9MB PDF file]

More booklets in this series:
Space Math I
Space Math II
Space Math III
Space Math IV
Space Math VI
Space Math VII
Astrobiology Math
Black Hole Math
Earth Math
Electromagnetic Math
Image Scale Math
Lunar Math
Magnetic Math
Radiation Math
Remote Sensing Math
Solar Math
Space Weather Math
Transit Math

Source: NASA

Teknik Penerbangan Luar Angkasa dan Astrofisika

Astrophysics and Aerospace Engineering

(Teknik Penerbangan Luar Angkasa dan Astrofisika)

Add & Edited By:

Arip Nurahman

Department of Physics,
Faculty of Sciences and Mathematics
Indonesia University of Education
and
Follower Open Course Ware at Massachusetts Institute of Technology, Cambridge.
USA

Aerospace engineering is the branch of engineering behind the design, construction and science of aircraft and spacecraft. Aerospace engineering has broken into two major and overlapping branches: aeronautical engineering and astronautical engineering. The former deals with craft that stay within Earth's atmosphere, and the latter deals with craft that operate outside of Earth's atmosphere. While "aeronautical" was the original term, the broader "aerospace" has superseded it in usage, as flight technology advanced to include craft operating in outer space.^[1] Aerospace engineering is often informally called rocket science.

Contents 1 Overview 2 History 3 Elements 4 Aerospace engineering degrees 5 Popular culture 6 See also 7 References

Overview

Modern flight vehicles undergo severe conditions such as differences in atmospheric pressure and temperature, or heavy structural load applied upon vehicle components. Consequently, they are usually the products of various technologies including aerodynamics, avionics, materials science and propulsion. These technologies are collectively known as aerospace engineering. Because of the complexity of the field, aerospace engineering is conducted by a team of engineers, each specializing in their own branches of science.,^[2] The development and manufacturing of a flight vehicle demands careful balance and compromise between abilities, design, available technology and costs.

Elements

See also: List of aerospace engineering topics

Some of the elements of aerospace engineering are:^[5][6]

• Fluid mechanics - the study of fluid flow around objects. Specifically aerodynamics concerning the flow of air over bodies such as wings or through objects such as wind tunnels (see also lift and aeronautics).
• Astrodynamics - the study of orbital mechanics including prediction of orbital elements when given a select few variables. While few schools in the United States teach this at the undergraduate level, several have graduate programs covering this topic (usually in conjunction with the Physics department of said college or university).
• Statics and Dynamics (engineering mechanics) - the study of movement, forces, moments in mechanical systems.
• Mathematics - because aerospace engineering heavily involves mathematics.
• Electrotechnology - the study of electronics within engineering.
• Propulsion - the energy to move a vehicle through the air (or in outer space) is provided by internal combustion engines, jet engines and turbomachinery, or rockets (see also propeller and spacecraft propulsion). A more recent addition to this module is electric propulsion and ion propulsion.
• Control engineering - the study of mathematical modeling of the dynamic behavior of systems and designing them, usually using feedback signals, so that their dynamic behavior is desirable (stable, without large excursions, with minimum error). This applies to the dynamic behavior of aircraft, spacecraft, propulsion systems, and subsystems that exist on aerospace vehicles.
• Aircraft structures - design of the physical configuration of the craft to withstand the forces encountered during flight. Aerospace engineering aims to keep structures lightweight.
• Materials science - related to structures, aerospace engineering also studies the materials of which the aerospace structures are to be built. New materials with very specific properties are invented, or existing ones are modified to improve their performance.
• Solid mechanics - Closely related to material science is solid mechanics which deals with stress and strain analysis of the components of the vehicle. Nowadays there are several Finite Element programs such as MSC Patran/Nastran which aid engineers in the analytical process.
• Aeroelasticity - the interaction of aerodynamic forces and structural flexibility, potentially causing flutter, divergence, etc.
• Avionics - the design and programming of computer systems on board an aircraft or spacecraft and the simulation of systems.
• Risk and reliability - the study of risk and reliability assessment techniques and the mathematics involved in the quantitative methods.
• Noise control - the study of the mechanics of sound transfer.
• Flight test - designing and executing flight test programs in order to gather and analyze performance and handling qualities data in order to determine if an aircraft meets its design and performance goals and certification requirements.

The basis of most of these elements lies in theoretical mathematics, such as fluid dynamics for aerodynamics or the equations of motion for flight dynamics. However, there is also a large empirical component. Historically, this empirical component was derived from testing of scale models and prototypes, either in wind tunnels or in the free atmosphere. More recently, advances in computing have enabled the use of computational fluid dynamics to simulate the behavior of fluid, reducing time and expense spent on wind-tunnel testing.

Additionally, aerospace engineering addresses the integration of all components that constitute an aerospace vehicle (subsystems including power, communications, thermal control, life support, etc.) and its life cycle (design, temperature, pressure, radiation, velocity, life time).

See also

At Wikiversity you can learn more and teach others about Aerospace engineering

at:

The Department of Aerospace engineering

• Aerospace
• List of aerospace engineering topics
• List of aerospace engineers
• List of aerospace engineering schools
• American Institute of Aeronautics and Astronautics
• Flight test

References

1. ^ ^{a b} Stanzione, Kaydon Al (1989). "Engineering". Encyclopædia Britannica (15) 18. 563–563.
2. ^ "Career: Aerospace Engineer". Career Profiles. The Princeton Review. Retrieved on 2006-10-08. "Due to the complexity of the final product, an intricate and rigid organizational structure for production has to be maintained, severely curtailing any single engineer's ability to understand his role as it relates to the final project."
3. ^ Kermit Van Every (1988). "Aeronautical engineering". Encyclopedia Americana 1. Grolier Incorporated.
4. ^ A Brief History of NASA
5. ^ "Science: Engineering: Aerospace". Open Site. Retrieved on 2006-10-08.
6. ^ ^{a b} Gruntman, Mike (September 19, 2007). "The Time for Academic Departments in Astronautical Engineering" in AIAA SPACE 2007 Conference & Exposition. AIAA SPACE 2007 Conference & Exposition Agenda, AIAA.
7. ^ USNews.com: America's Best Colleges 2008: Aerospace / Aeronautical / Astronautical
8. ^ USNews.com: America's Best Colleges 2008: Aerospace / Aeronautical / Astronautical