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Launcher: How are Satellites Launched into Orbit Around the Earth?

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Author: Janice VanCleave

Problem

How are satellites launched into orbit around the Earth?

Materials

  • cardboard box
  • 2 plastic rulers with groove down center
  • modeling clay
  • marble

Procedure

  1. Turn the cardboard box upside down on top of a table.
  2. Place the edge of the box 10 inches (25 cm) from the edge of the table.
  3. Lay one ruler on top of the box with 4 inches (10 cm) of the ruler extending over the edge of the box.
  4. Launcher

  5. Hold the second ruler so that one end touches the end of the first ruler, with the grooves of the rulers lined up, and the second end is 2 inches (5 cm) above the box. Support that end by placing a piece of clay under it.
  6. Position a marble at the top of the raised ruler, and then release the marble.
  7. Observe the path of the marble.
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Results

The marble rolls down the ruler and off its end. The marble's path curves downward after it leaves the end of the "launcher" until it hits the floor.

Why?

The table represents the Earth, and the top of the box is a position above Earth's surface. The marble represents a satellite. A satellite is a body that moves in a curved path about a celestial body. The "marble satellite" is launched horizontally, parallel to the Earth's surface. All satellites are raised to a desired height above Earth by booster rockets, and then with additional rocket power the satellite is launched parallel to Earth's surface. Neither the "marble satellite" nor a space satellite continues to move forward in a straight line, because gravity pulls them toward Earth.

The marble moves in a curved path out over the tabletop and past the edge of the table because gravity pulls it down and its launching speed pushes it forward. A space satellite also moves in a curved path, but it continues to curve completely around Earth. This curved path of one body about another is called an orbit. The horizontal launching speed of any man-made satellite, like that of the marble, has to be great enough to balance the pull of gravity. Its forward speed, combined with the pull of gravity, keeps it away from the Earth's surface and moving in a curved path.

Let's Explore

  1. If the horizontal launching speed is too slow, gravity pulls the satellites back to Earth's surface. Demonstrate this by repeating the experiment with the end of one ruler raised less than 2 inches (5 cm) above the box.
  2. If the horizontal speed is too great, the craft breaks away from the Earth's gravitational pull and escapes into space. You cannot cause the marble to actually escape into space, but repeating the experiment with the raised end of the launcher higher than 2 inches (5 cm) will demonstrate the movement of the satellite away from the normal path produced in the original experiment. Science Fair Hint: The launcher and pictures of the launcher could be used as part of a project display.
  3. Does the weight of the marble affect its speed? Follow the procedure of the experiment, but use a larger, heavier marble. Record any difference in the path of the marble.

Show Time!

  1. A cartoon diagram similar to the one shown may help to demonstrate the effect that launching speed has on placing satellites into orbit.
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  3. Multistaged rockets are used to place satellites into orbit. How is this achieved? What happens to each part of the system? Balloons and a paper cup can be used to demonstrate rocket staging. The diagram gives a clue to the construction of a multistage rocket system. A diagram of this balloon model along with pictures of actual multistaged rockets would make a good project display.
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Check it Out!

  1. Weather satellites stay in the same place above the Earth's surface. They are said to be in a geosynchronous orbit. Read about geosynchronous orbits on pages 184 and 185 of Janice VanCleave's Astronomy for Every Kid (New York: Wiley, 1991). Write to NASA for information about satellites. Your parent or teacher can assist you in securing the address.
  2. Read about the space shuttle and how it launches satellites. What does it mean to say satellites "fall" into orbit? NASA can provide printed material about the space shuttle and satellites.
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