Why study rockets?• One could argue that the greatest form of

human communication will be with extra-terrestrial life forms.

• Through space exploration, this form of communication may become a reality.

What every good rocket scientist should know

1. Center of Mass

2. Center of Pressure

3. Rocket Stability

Center of Mass

• The spot on a rocket that is balanced

Measuring the Center of Mass

1. Using a ruler or pencil, find where your rocket is balanced

2. Mark the COM on your rocket

Center of Pressure

• The spot on a rocket where the surface area above and below is the same

Measuring the Center of Pressure

1. Trace your rocket onto a piece of cardboard

2. Cut out the flat picture of your rocket3. Find and mark the COM of the cardboard4. The COM of the cardboard cutout is the

same as the COP of the rocket5. Place the rocket next to the cardboard and

mark the COP on your rocket

What’s up with COM and COP?

1. Rockets rotate around the Center of Mass

2. Force from the air (air resistance) is exerted at the Center of Pressure

When a rocket turns off path

When a rocket turns off path

The COM should be near the nose; the COP should be near the tail

• That was the point of the last two slides!

Why the COM should be far from the COP

1 because you are exerting a force farther from the pivot point

Why the COM should be far from the COP

Long handled wrenches

B because you are pushing farther from the pivot point (the red hex nut). This is why a long handled wrench can turn a really tight hex nut.

Another example

• Fat handled screwdrivers

A because you are exerting the force farther from the middle (the pivot point). So fat handled screwdrivers are good for screws that are hard to loosen.

Achieving Stability• Distance between COM and COP should be

at least one diameter

Add weight here to change the COM

If the COP is far from the COM, the same force will twist the rocket back on line better.

Brief History of the Space Program

• In 1957, the Soviet Union launched the first man made satellite (Sputnik) into orbit around the Earth.

• In 1961, the Soviet Union put the first man in space (Yury Gagarin).

• Gagarin made one orbit of the Earth in 1 hour, 29 minutes, reaching a max. altitude of 187 miles.

• Food for thought: What was Yury thinking about while on the launch pad?

Brief History of the Space Program

• The Soviets winning the race to space triggered panic in the U.S., as people worried that the Soviet Union held military advantage over the U.S.

• John F. Kennedy, president of the United States, made putting a man on the moon a national priority.

John F. Kennedy (1917 – 1963)35th president of the United States

“We choose to go to the moon in this decade, and do the other things, not because they are easy, but because they are hard. Because that goal will serve to organize and measure the best of our energies and skills. Because that challenge is one that we’re willing to accept. One we are unwilling to postpone. And one we intend to win, and the others too.”