1. Part 2: Rocket Principles
Module 4 .
Rocketry
Part 2: Rocket Principles
Rev 1, 17 Nov Steven Esh

2. What We Will Learn Newton’s three laws Rocket vocabulary
Thrust in rockets
Rocket stability
Page 2, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

3. Vocabulary
Inertia: the tendency of a body to maintain its same motion if no force is applied to change it
Velocity: how fast something moves
Acceleration: how fast a body’s speed changes
Mass: the amount of substance in a thing
Thrust: a “pushing” force
momentum: mass x velocity
Page 3, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

4. Newton’s Laws 1st Law: inertia
A body at rest tends to stay at rest. A body in motion tends to maintain that same motion
2nd Law: conservation of momentum
The force on a body = change in momentum (momentum = mass x velocity)
3rd Law: balance of forces
For every action, there is an equal and opposite reaction
Page 4, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

5. Rocket Thrust
Depends upon how fast momentum is changing (Newton’s 2nd Law)
Comes from mass of fuel being pushed out at high velocity
Needs nothing to “push against”, so it can work in outer space
Page 5, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

6. Stability
Is the tendency to return to its original flight path after an upsetting disturbance
Is Positive (stable) if the rocket tries to stay on its intended path
Is Negative (unstable) if the rocket tends to go out of control
Page 6, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

7. Stability
A stable rocket must have it’s Center of Gravity (CG) ahead of it’s Center of Pressure (CP)
The distance from the CP to the CG determines how stable it is
The fins provide stability through a “weather vane” effect (the CP moves toward the fins)
Page 7, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

8. The future? The ion engine - for space flight .
Page 8, Module 4, Part 2
Rev 1, 17 Nov Steven Esh

9. Review What are the properties of rocket thrust?.
What are Newton’s three laws?
What is required for a stable rocket?
Page 9, Module 4, Part 2
Rev 1, 17 Nov Steven Esh