Rockets

Humans did not reach space until the second half of the 20th century. However, the main technology that makes space exploration possible, the rocket, has been around for a long time. A rocket is propelled by particles flying out of one end at high speed. We do not know who built the first rocket, or when, but there are records of the Chinese using rockets in war against the Mongols as early as the 13th century. The Mongols then spread rocket technology in their attacks on Eastern Europe. Early rockets were also used to launch fireworks and for other ceremonial purposes.

How Rockets Work

Rockets were used for centuries before anyone could explain exactly how they worked. The theory to explain rockets did not arrive until 1687, when Isaac Newton (1643–1727) described the three basic laws of motion, now referred to as Newton’s Laws of Motion:

1. An object in motion will remain in motion unless acted upon by a net force.

2. Force equals mass multiplied by acceleration.

3. To every action, there is an equal and opposite reaction.

Newton’s third law of motion is particularly useful in explaining how a rocket works.

Assignment 1: Newton's 3rd Law - Hero's Engine:

Hero's Engine: Example of Newton's Third Law Sir Isaac Newton, a scientist and philosopher of the late 1600’s, spent many years trying to come up with codified rules that describe how all stuff in the universe behaves.

• In the experiment below, we will explore Newton’s third law, which states that “for every action there is an equal and opposite reaction”—but what does this mean, exactly?

Imagine dropping a tennis ball to the ground. What happens in response to the action of the ball striking the ground? It bounces back up towards you.

This is due to the reactionary force of the floor acting against the ball, which pushes it upwards into the air.

To explore this idea more fully, you can easily construct your very own device called an aeolipile (sometimes referred to as Hero’s Engine or a Hero engine). Created by an engineer named Hero of Alexandria about 2000 years ago, this invention was able to show one way in which an action can lead to an equal and opposite reaction: an example of Newton's third law.

* Problem: how does a Hero engine demonstrate Newton’s 3 rd law?

Materials:

• • Plastic cup

  • 2 plastic bendable straws

  • String Craft knife

  • Water and sink

  • Modeling clay

  • Procedure

    • 1. Take plastic cup and have an adult help you poke two small holes near the top rim on opposite sides from one another.

    • 2. Thread string through the holes and tie a knot so that the cup can be suspended from the string.

    • 3. Have an adult make two slightly larger holes near the bottom of the cup as seen in the picture below (make sure these holes are just large enough for the straws to fit through)

    • 4. Cut each straw about 1.5 inches below its bendable portion.

    • 5. Slide the straws into the holes. Make sure that they both point in a clockwise direction.

    • 6. Use your modeling clay to seal the space between the cup and the straw so that no water leaks

Explain: What happened? Why?

Assignment 2: Complete the reading on satellites, shuttles and space stations. Complete the review and Explore more questions.

Satellites, Shuttles, and Space Stations