Exploring Space: Journey Through Rocket Science

1. CHAPTER 5 EXPLORING SPACE

2. Chapter 5 Exploring Space Table of Contents Section 1 Rocket Science Section 2 Artificial Satellites Section 3 Space Probes Section 4 People in Space

3. Section1 Rocket Science Bellringer Why can’t a commercial airplane be used for space exploration?

4. Section1 Rocket Science Objectives • Outline the development of rocket technology. • Describe how a rocket accelerates. • Explain the difference between orbital velocity and escape velocity.

5. Section1 Rocket Science The Beginnings of Rocket Science • About 100 years ago, Russian high school teacher Konstantin Tsiolkovsky proposed that machines called rockets could take people to outer space. • A rocket is a machine that uses escaping gas from burning fuel to move.

6. Section1 Rocket Science Beginnings of Rocket Science, continued • Tsiolkovsky’s inspiration came from the stories of Jules Verne. In Verne’s book From the Earth to the Moon, characters reached the moon in a capsule shot from an enormous cannon. • Although this idea would not work, Tsiolkovsky proved—in theory—that rockets could generate enough force to reach outer space. • For his vision and careful work, Tsiolkovsky is known as the father of rocket theory.

7. Section1 Rocket Science Beginnings of Rocket Science, continued • A Boost for Modern Rocketry While Tsiolkovsky proved scientifically that rockets could reach outer space, he never built any rockets himself. • American physicist and inventor Robert Goddard launched the first successful liquid-fuel rocket in 1926.

8. Section1 Rocket Science Beginnings of Rocket Science, continued • Goddard tested more than 150 rocket engines, and by the time of World War II, Goddard’s work began to interest the Unites States military. • Goddard’s work drew much attention because of a terrifying new weapon that the German army had developed.

9. Section1 Rocket Science From Rocket Bombs to Rocket Ships • Toward the end of World War II, Nazi Germany developed a new weapon known as the V-2 rocket • The V-2 rocket could deliver explosives from German military bases to London—a distance of about 350 km. • The V-2 rocket was developed by a team led by Wernher von Braun, a young Ph.D. student whose research was supported by the German military.

10. Section1 Rocket Science Rocket Bombs to Rocket Ships, continued • In 1945, near the end of the war, von Braun and his entire research team surrendered to the advancing America army. The United States thus gained 127 of the best German rocket scientists. • With this gain, rocket research in the United States boomed in the 1950s.

11. Section1 Rocket Science Rocket Bombs to Rocket Ships, continued • The Birth of NASA The end of World War II marked the beginning of the Cold War, a long period of political tension between the United States and the Soviet Union. • The Cold War was marked by an arms race and by competition in space technology.

12. Section1 Rocket Science Rocket Bombs to Rocket Ships, continued • In response to Soviet advances in space, the U.S. government formed the National Aeronautics and Space Administration, or NASA, in 1958. • NASA combined all of the rocket-development teams in the United States. Their cooperation led to the development of many rockets, including those shown on the next slide.

13. Section1 Rocket Science

14. Section1 Rocket Science How Rockets Work • For Every Action . . . Newton’s third law of motion states that for every action there is an equal and opposite reaction. • This can be demonstrated if you blow up a balloon and let it go. Air rushing backward from the balloon (the action) results in the forward motion of the balloon (the reaction).

15. Section1 Rocket Science How Rockets Work, continued • Rockets work in the same way. In fact, rockets were once called reaction devices. • The following slide goes into further detail as to how rockets work.

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17. Section1 Rocket Science How Rockets Work, continued • In the case of rockets, the action and the reaction may not be obvious. • The mass of a rocket—including all of the fuel it carries—is much greater than the mass of the hot gases that come out of the bottom of the rocket.

18. Section1 Rocket Science How Rockets Work, continued • Because the exhaust gases are under extreme pressure, they exert a huge amount of force. The force that accelerates a rocket is called thrust. • Thrust is the pushing or pulling force exerted by the engine of an aircraft or rocket.

19. Section1 Rocket Science Thrust Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

20. Section1 Rocket Science How Rockets Work, continued • You Need More Than Rocket Fuel Rockets burn fuel to provide the thrust that propels them. In order for something to burn, oxygen must be present. • Although oxygen is plentiful at the Earth’s surface, there is little or no oxygen in the upper atmosphere and in outer space.

21. Section1 Rocket Science How Rockets Work, continued • For this reason, rockets that go into outer space must carry enough oxygen with them to be able to burn their fuel. • The space shuttles, for example, carry hundreds of thousands of gallons of liquid oxygen. This oxygen is needed to burn the shuttle’s rocket fuel.

22. Section1 Rocket Science How to Leave the Earth • The gravitational pull of the Earth is the main factor a rocket must overcome. A rocket must reach a certain velocity, or speed and direction, to orbit or escape the Earth.

23. Section1 Rocket Science How to Leave the Earth, continued • Orbital Velocity and Escape Velocity For a rocket to orbit the Earth, it must have enough thrust to reach orbital velocity. • Orbitalvelocity is the speed and direction a rocket must travel in order to orbit a planet or moon. • The lowest possible speed a rocket may go and still orbit the Earth is about 8 km/s (17,927 mi/h). If the rocket goes any slower, it will fall back to Earth.

24. Section1 Rocket Science How to Leave the Earth, continued • For a rocket to travel beyond Earth orbit, the rocket must achieve escape velocity. • Escapevelocity is the speed and direction a rocket must travel to completely break away from a planet’s gravitational pull. • The speed a rocket must reach to escape the Earth is about 11 km/s (24,606 mi/h).

25. Section1 Rocket Science Orbital, Suborbital, and Escape Velocities Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

26. Section2 Artificial Satellites Objectives • Identify the first satellites. • Compare low Earth orbits with geostationary orbits. • Explain the functions of military, communications, and weather satellites. • Explain how remote sensing from satellites has helped us study Earth as a global system.

27. Section2 Artificial Satellites The First Satellites • An artificialsatellite is any human-made object placed in orbit around a body in space. • There are many kinds of artificial satellites, including weather satellites, communications satellites, and remote-sensing satellites.

28. Section2 Artificial Satellites The First Satellites, continued • In 1957, the Soviets launched the first artificial satellite, Sputnik 1. It orbited for 57 days before it fell back to Earth and burned up in the atmosphere. • Two months later, Sputnik 2 carried the first living being into space—a dog named Laika.

29. Section2 Artificial Satellites The First Satellites, continued • The United States launched its first satellite, Explorer 1, in 1958. • The development of new satellites increased quickly. By 1964, communications satellite networks were able to send messages around the world. • Today, thousands of satellites orbit the Earth, and more are launched every year.

30. Section2 Artificial Satellites Choosing Your Orbit • Satellites are placed in different types of orbits. All of the early satellites were placed in low Earth orbit. • Low Earth orbit (LEO) is an orbit less than 1,500 km above the Earth’s surface. • A satellite in LEO moves around the Earth very quickly and can provide clear images of the Earth. However, this motion can place a satellite out of contact much of the time.

31. Section2 Artificial Satellites Choosing Your Orbit, continued • Most communications and weather satellites circle the Earth in geostationary orbit. • Geostationary orbit (GEO) is an orbit that is about 36,000 km above the Earth’s surface and in which a satellite is above a fixed spot on the equator. • A satellite in GEO is always above the same spot on Earth. Ground stations are in continuous contact with these satellites so that communications will not be interrupted.

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33. Section2 Artificial Satellites Military Satellites • Some satellites placed in LEO are equipped with cameras that can photograph the Earth’s surface in amazing detail. It is possible to photograph objects as small as a book from LEO. • While satellite photographs are now used for everything from developing real estate to tracking movements of dolphins, the technology was first developed by the military.

34. Section2 Artificial Satellites Military Satellites, continued • Because satellites can take very detailed photos from hundreds of kilometers above the Earth’s surface, they are ideal for defense purposes. • The United States and the Soviet Union developed satellites to spy on each other right up to the end of the Cold War. • Even though the Cold War is over, spy satellites continue to play an important role in the military defense of many countries.

35. Section2 Artificial Satellites Military Satellites, continued • The Global Positioning System In the past, people invented very complicated ways to keep from getting lost. • Now, for less than $100, people can determine their exact location on Earth by using a Global Positioning System (GPS) receiver. • GPS is another example of military satellite technology that has become a part of everyday life.

36. Section2 Artificial Satellites Military Satellites, continued • The GPS consists of 27 solar-powered satellites that continuously send radio signals to Earth. • From the amount of time it takes the signals to reach Earth, the hand-held receiver can calculate its distance from the satellites. • Using the distance from three or four satellites, a GPS receiver can determine a person’s location with great accuracy.

37. Section2 Artificial Satellites Global Positioning System (GPS) Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

38. Section2 Artificial Satellites Weather Satellites • Every day, millions of people make decisions based on information provided by weather satellites. • Weather satellites in GEO provide a big-picture view of the Earth’s atmosphere. These satellites constantly monitor the atmosphere for the “triggers” that lead to severe weather conditions.

39. Section2 Artificial Satellites Weather Satellites, continued • Weather satellites in LEO are usually placed in polar orbits. Satellites in polar orbits revolve around the Earth in a north or south direction as the Earth rotates beneath them. • These satellites, which orbit between 830 km and 870 km above the Earth, provide a much closer look at weather patterns.

40. Section2 Artificial Satellites Communications Satellites • Many types of modern communications use radio waves or microwaves to relay messages. Radio waves and microwaves are ideal for communications because they can travel through the air. • The problem is that the Earth is round, but the waves travel in a straight line.

41. Section2 Artificial Satellites Communications Satellites, continued • Communications satellites in GEO solve this problem by relaying information from one point on Earth’s surface to another. • The signals are transmitted to a satellite and then sent to receivers around the world. • Communications satellites relay computer data, and some television and radio broadcasts.

42. Section2 Artificial Satellites Remote Sensing and Environmental Change • Satellites gather information by remotesensing. Remote sensing is the gathering of images and data from a distance. • Remote sensing satellites measure light and other forms of energy that are reflected from Earth. • Some satellites use radar, which bounces high-frequency radio waves off the Earth and measure the returned signal.

43. Section2 Artificial Satellites Remote Sensing, continued • Landsat: Monitoring the Earth from Orbit One of the most successful remote-sensing projects is the Landsat program, which began in 1972 and continues today. • Landsat satellites gather images in several different wavelengths—from visible light to infrared. • The next slide shows two Landsat images of the Mississippi Delta.

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45. Section2 Artificial Satellites Remote Sensing, continued • One image was taken in 1973, and the other was taken in 2003. The two images reveal a pattern of environmental change over a 30-year period. • The main change is a dramatic reduction in the amount of silt that is reaching the delta. A comparison of the images also reveals a large-scale loss of wetlands in the bottom left of the delta in 2003.

46. Section2 Artificial Satellites Remote Sensing, continued • A New Generation of Remote-Sensing Satellites The Landsat program has produced millions of images that are used to identify and track environmental changes on Earth. • Satellite remote sensing allows scientists to perform large-scale mapping, look at changes in patterns of vegetation growth, map the spread of urban development, and study the effect of humans on the global environment.

47. Section2 Artificial Satellites Remote Sensing, continued • In 1999, NASA launched Terra 1, the first satellite in NASA’s Earth Observing System (EOS) program. • Satellites in the EOS program are designed to work together so that they can gather integrated data on environmental change on the land, in the oceans, in the atmosphere, and on the icecaps.

48. Section3 Space Probes Bellringer Does exploring other planets benefit us here on Earth? Why or why not?

49. Section3 Space Probes Objectives • Describe five discoveries made by space probes. • Explain how space-probe missions help us better understand the Earth. • Describe how NASA’s new strategy of “faster, cheaper, and better” relates to space probes.

50. Section3 Space Probes Visits to the Inner Solar System • A spaceprobe is an uncrewed vehicle that carries scientific instruments to planets or other bodies in space. Scientists have launched several space probes to explore the solar system. • Unlike satellites, which stay in Earth orbit, space probes travel away from the Earth.