Rocket Stability

Forces Acting on a Rocket Gravity Thrust Air Drag

Inertia The tendency of all bodies to resist any change in motion

Newton’s Laws Law of Inertia: A body at rest stays at rest, a body in motion stays in motion unless there is another force acting on that body. Law of Acceleration:: Motion is proportional to the forces exerted Law of Reaction: For every action there is an opposite and equal reaction

Center of Gravity CG The Center of Gravity or CG is the balancing point of a free body that can rotate around all axis. It is an imaginary point at which all mass seems to be concentrated.

Center of Pressure CP Center of Pressure is a point where all air pressure forces converge or act.

CG -CP Relationship

Inherently Stable Rocket CG must be forward of CP or CP must be aft of CG

Changing CG to make a Stable Rocket Use Lighter Motor Add Weight to Nosecone Make rocket Longer

Changing CP to make the Rocket Stable Use Larger Fins Increase the number of Fins Make Nose Cone Longer

Stability Characteristics A positive stability rocket will have a stable flight A neutral stability rocket might have a stable flight a negative stability rocket will not have a stable flight

Flight paths