Rocket Science for Kids

Dr. Goddard was the first modern scientist to have a vision for space travel and also the ingenuity to formulate solutions to rocket propulsion. He was the first to make mathematical calculations that showed how rocket propulsion could be used to travel to the moon. At first he was not taken seriously by many but his research was documented and many scientists in Europe studied what he had reported. Several years later the German Rocket Society was formed and the German Army began its rocket program. From these efforts, the Germans developed the V-2 rocket which was used in World War II.

In 1926 Dr. Goddard was the first to demonstrate the use of a liquid fuel powered rocket. His work on liquid-propellant rocket engines laid the groundwork for development of the large rocket engines that propelled the first astronauts to the moon in 1969 aboard the Saturn V rocket. The Space Shuttle main engines are also liquid-propellant rocket engines.

Today Dr. Goddard is highly respected as a pioneer of modern rocketry. The Goddard Space Flight Center (GSFC) in Maryland was named after him and is NASA's lead center for space exploration programs that focus on studies of the Earth. Much of the research done here is trying to better understand our Earth as a global environment system. One program is using data from a series of satellites orbiting the earth to study Earth's atmosphere, land surface, and oceans. GSFC is also the home of the Hubble Space Telescope's control center.

Aerodynamics - the study of the motion of air and other gases and how they affect the motion of objects moving through them.

Propulsion System - the engine used to power a rocket. There are many different types of engines so we refer to the engine systems as propulsion systems because they propel the vehicle.

Thrust - the force that acts on rockets or airplanes to make them move forward. This force is created by the rocket or airplane engine, also known as the propulsion system.

Drag - the force that acts on the surface of an object moving through a gas or liquid that slows it down. It acts in the line of motion but in the opposite direction. This force is caused by the fluid resisting the movement of the object. Drag is one of the aerodynamic forces.

Lift - the force that acts on the surface of an object moving through a gas or liquid that acts perpendicular to the direction of motion. This is the force that acts on an airplane's wings to push it upward. Lift is one of the aerodynamic forces.

Velocity - the speed of an object. When you talk about the speed of your car in miles per hour you are talking about the car's velocity.

Mass - an object's quantity of matter. The mass of an object is multiplied by the gravitational acceleration to determine its weight.

Acceleration - the change of velocity. If you are speeding up your velocity is changing and we say you are accelerating. Deceleration is when you are slowing down. If you are not moving or are traveling at a constant speed your velocity is not changing and we say you are not accelerating, or your acceleration equals zero.

Gravitational force - the force that gravity exerts on a mass. When we refer to our weight we are actually talking about the force of the earth's gravity on our body mass. We would have a different "weight" on the moon since the moon's gravity is different than the earth's, but the mass of our body would be the same. In space, astronauts are far from gravitational forces of the earth and moon so the force is weaker. That's why they float and feel weightless.

Inertia - refers to the property of an object to resist change in motion.

You've probably heard the story we like to tell about Sir Isaac Newton sitting under the apple tree. He supposedly got hit on the head by a falling apple and discovered the laws of gravity. Well, even if it didn't happen exactly that way, Newton did develop the theories about motion and gravitational forces. He developed these theories in 1666 when he was only 23 years old and later presented his three laws of motion in a book. We continue to use these laws today and they explain the motion of everything from apples to rockets. Let's take a look at Newton's three laws and learn how we represent them in math equations.

Newton's First Law of Motion - " Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it."

This means that an object won't move unless a force makes it move. If an object is moving it will continue to go the same speed unless a force makes it slow down or speed up. This is also considered to be the definition of inertia.

Newton's Second Law of Motion - "Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration"

This means that the force on a body is dependent on the body's mass and how much it is accelerating. If the body is not moving it's acceleration is zero. The force would be equal to zero times the mass which is zero. If the body is moving and you know it's acceleration you could find out how much force is acting on it by multiplying the acceleration by the mass. If the body is traveling at a constant velocity then the acceleration is equal to zero. Just as the body that is not moving, the force would be equal to zero.

Newton's Third Law of Motion - "For every action, there is an equal and opposite re-action."

This is the law of action and reaction. Think of blowing a balloon up and then letting it go? You know what happens, it flies all over the place! The air inside the balloon rushes out of the small opening (the action). This causes the balloon to move in the opposite direction (the reaction). This is similar to what happens in a rocket engine.
Newton's Third Law can be used to show how the thrust of a rocket engine makes the rocket go forward.

Liquid rocket engines use a liquid oxidizer and a liquid fuel. Theses propellants are usually pumped up then mixed together and burned in the engine's combustion chamber. There are many different fuels and oxidizers that can be used. Oxygen is the most commonly used oxidizer. Some of the fuels used are hydrogen, kerosene, and hydrazine.

Using liquid propellants allows a greater mass to be carried than if gas were used. Liquid rockets can also be throttled. This means that the power level of operation can be changed. Solid rocket motors cannot be throttled.

Some liquid rocket engines in use today include the Space Shuttle main engines, the RL10 engine, the RS-68 engine, and the AJ26-58 engine.

Solid rockets burn a solid that is made up of the fuel and the oxidizer. This rubbery or plastic-like solid is called the grain. This solid is packed into a cylindrical casing with a passage through the middle. The solid fuel and oxidizer are ignited by an electric charge. Solid rockets don't require pumps so they are less complex than liquid rockets, however, once a solid is ignited, there's no turning back! Solid rockets cannot easily be stopped and usually stop only when the fuel is depleted.

Solid rockets are used for missiles and as boosters for launch vehicles. They are also used in fireworks. Probably the most famous solid rockets are those used for the Space Shuttle. Two Solid Rocket Boosters (SRB) are used for the Space Shuttle.

The Space Shuttle has three liquid-fueled main engines in addition to the two large solid rocket boosters. The liquid-fueled main engines use liquid hydrogen and oxygen. Here are a few facts about the main engines:

The turbopump is so powerful that it could drain an average family-sized swimming pool in 25 seconds.

The liquid hydrogen in the engine is -423 degrees Fahrenheit (-253 degrees Centigrade) and when it is burned with the liquid oxygen the temperature is over 6,000 degrees F (3,316 degrees C). That is about 2/3 the temperature of the surface of the sun.

The energy released by the three main engines is about the same as delivered by 23 Hoover Dams.

If you could convert the heat energy to electric power, the two solid rocket motors (SRM) burning for two minutes could supply all the power needed by 87,000 homes for one full day.

Read more fascinating facts on NASA's Kennedy Space Center website: Shuttle Fun Facts

Marvin the Martian is a Looney Tunes character that only appeared in a few cartoons but has many fans! The launch patch for the Mars Rover, Spirit, features Marvin.

James Isaac Neutron, aka Jimmy Neutron, is the main character in a Nickelodeon cartoon by the same name. Jimmy is a boy-genius who often gets himself in trouble with his brilliant ideas. Solving the problems he creates is always fun to watch. His name, in case you didn't guess, is a spoof on the name of the famous scientist Sir Isaac Newton. Even Jimmy's dog, Goddard, is named after a famous rocket scientist.

The Jetsons was a cartoon from the early 1960's about a family living in the 21st century. It took place in Orbit City. The family members were George and Jane, the father and mother, Judy and Elroy, the daughter and son, and their pet dog Astro. Rosie the Robot was also an important member of the family who cooked their meals, cleaned their house and served them in many other ways. Mr. Spacely was George's grumpy boss. The Jetsons flew around in their own personal space vehicles and lived in houses suspended in space.