Rockets

The first time true rockets were used was by the Chinese in 1232 AD.  At this time the Chinese and the Mongols were at war with each other.  The Chinese had manufactured “arrows of flying fire” to use as weapons to fight the Mongols.  These simple rockets were really a tube, capped at one end that contained gunpowder.  The other end was left open and the tube was attached to a long stick.  When the gunpowder was lit, the powder produced fire, smoke, and gas that escaped out the open end and created the thrust that launched the rocket.  The stick kept the rocket headed in one general direction as it flew through the air.    

          Understanding gravity and mass is critical to the study of rocketry.  Every time you jump, you experience gravity. Gravity pulls you back down to the ground.  Without gravity, you'd float off into the atmosphere, thus pulling you out into space.  You see gravity at work any time you drop a book, or toss a ball up into the air. The fact that these objects fall to the ground rather than float in the air is the product of gravity. 

The definition of gravity is “the force that attracts a body toward the center of the earth or toward any other physical body having mass”.  Even in space, gravity keeps the moon in orbit.  We know that objects with a greater mass have a higher gravitational force, but we simply don’t know why gravity exists. 

            As far as mass is concerned, it is easy to understand that moving objects with a larger mass is harder than moving smaller objects. For example, in the playground it is harder to get a bigger person moving on the swings than a smaller person.  This has an effect on the mass of a rocket as well.  In a more literal way, when a rocket is lighter, it flies farther because there is less mass, and mass brings objects to the ground.  In this situation gravity cannot control the rocket from dropping to the ground.   If objects with a greater mass have a higher gravitational force, then changing the dependent variables, length of the rocket and nose cone, will result in different distances that the rocket will travel. Smaller mass rocket components will result in longer distances travelled.