84 Spaceship Motions and Deep, Deep Oceans-High

Spaceship Motions and Deep, Deep Oceans FOCUS Question How do machines help people explore outer space and the deepest oceans?

Extreme Travelers Think about traveling to the bottom of an ocean. It is dark and cold. The water above you is very heavy. The pressure is more than 1,000 times greater than on land. Now think about traveling into space. It takes a lot of fuel to escape the pull of Earth's gravity. Then, once you are there, you have to deal with feeling weightless. We have designed machines that can go to these extreme places. We have explored our solar system and the deep ocean. Which machines do we use? What makes them work?

Fighting Gravity Blow up a balloon and let it go. What happens? It flies! The balloon pushes away air. The air pushes the balloon in the opposite direction. This is similar to how a rocket engine works. When you blow up and release a balloon, it goes only a short distance. Rockets go all the way to outer space! This takes a lot of fuel. When rocket fuel burns, some of its energy changes into heat, light, and sound. The rest changes into motion. Gases rush from the bottom of the rocket, toward the ground. The rocket flies in the opposite direction, up into the sky. This force is called thrust. The upward thrust must be stronger than the downward pull of gravity for the rocket to fly.

Rockets and Shuttles Between 1969 and 1972, people went to the Moon! They flew in Saturn rockets. These rockets had three parts, called stages. The bottom stage was the biggest and produced the most thrust. It pushed the rocket up very high and then dropped away when it ran out of fuel. The second stage pushed the rocket higher. The third stage carried the spacecraft and people the rest of the way to the Moon. Later, engineers designed spaceships that were shaped more like airplanes. They could be used more than once. These were called space shuttles.

Over the years, people have made rockets that go higher and higher. V-2 Rocket The V-2 rocket was the first rocket to go into space. It was only 14 meters (45 ft.) tall, but it had a lot of thrust. Saturn V Rockets Saturn V rockets were the tallest and heaviest rockets ever built. They were 110 meters (363 ft.) tall. Space Shuttles Only six space shuttles were made. They were used to transport humans and tools into space and back. Scientists conducted experiments on the space shuttles. Wowser! Space shuttles orbited Earth quickly. The astronauts on board saw a sunrise or sunset every 45 minutes!

Fighting Buoyancy Submarines have the opposite problem of rockets. They need to go down instead of up! While rockets fight gravity, submarines must work against buoyancy (BOY-un-see). Buoyancy is the upward push of a liquid or gas. It is what makes things float in water— or on air. To submerge, or go underwater, submarines must overcome buoyancy. They do this by becoming denser. Density is the amount of material in a certain space. Think of a piece of cork and a solid rock that are the same size. The rock has more material in it. The rock is denser than the cork. A cork floats in water, while most rocks sink. Think About It Which is denser: this rubber ball or the bowling ball? Why? How could you test your answer?