1. The Science of Rockets
Chapter 2, Section 1
P40-45

2. A History of Rockets
Rocket: device that expels gas in one direction and moves in the opposite direction
Rocket technology originated in China hundreds of years ago and gradually spread to other parts of the world
Rockets were developed for military use and for fireworks

3. A History of Rockets Origins of Rockets
First rockets made in China in 1100’s
Arrows coated with flammable powder
Lit and shot with bows
Chinese used gunpowder around 1200
British greatly improved rockets in 1800’s
War of 1812, Fort McHenry in Baltimore
“Rocket’s red glare” British rockets used against US

4. A History of Rockets Development of Modern Rockets
Modern rockets developed in early 1900’s
Scientists involved:
Tsiolkovsky – Russian
Goddard – American
von Braun – German

5. A History of Rockets Tsiolkovsky – Russian Goddard - American
Described how rockets work
Proposed designs for advanced rockets
Goddard - American
Built rockets to test his designs
von Braun – German
Designed V2 rocket carried explosives
Major advances during WW II
Brought to US after war
Directed development of rockets used in US space program

6. How Do Rockets Work? How do rockets work
A rocket moves forward when gases shooting out the back of the rocket push it in the opposite direction
Similar to balloon propelled through air releasing gas
Fuel is burned in most rockets produces hot gas
Gas pushes outward in every direction
Gases only leave out opening in back
Gases moving out openings moves rocket forward

7. How Do Rockets Work? How do rockets work Figure 3: Action Force
Hot gases pushed out of the engine
Reaction Force
Hot gases push rocket forward / upward

8. How Do Rockets Work? Action and Reaction Forces
Newton’s 3rd Law of Motion:
For every force, or action, there is an equal and opposite force, or reaction
Balloon
Air moves out of the balloon - Action
Balloon moves forward – Reaction

9. How Do Rockets Work? Action and Reaction Forces
Thrust: reaction force that propels rocket forward
Depends on mass & speed of propelled gases
Greater thrust – greater rocket’s velocity
Velocity: speed in a given direction

10. How Do Rockets Work? Orbital and Escape Velocity
Rocket must have more upward thrust than downward force to liftoff
Orbital velocity: velocity rocket must reach to establish orbit around Earth
Rockets slower than orbital velocity fall back to Earth
Rockets faster than orbital velocity flies into space
Escape velocity: velocity rocket must reach to fly beyond planet’s gravitational pull

11. How Do Rockets Work? Rocket Fuels
Rockets create thrust by ejecting gas
3 types of fuel used in modern spacecraft
Solid fuel
Liquid fuel
Electrically charged gas particles (ion)

12. How Do Rockets Work? Rocket Fuels Solid fuel Liquid fuel
Oxygen mixed with solid, dry explosive chemical
Example: firework
Disadvantage: once fuel ignites it burns until gone
Liquid fuel
Carry liquid oxygen & liquid fuel in separate compartments
Pumped into chamber and ignited
Advantage: fuel burning can be controlled
Electrically charged gas particles (ion)
Expel gas ions
Create less thrust
Very fuel efficient

13. Multistage Rockets
Idea: What if empty part of rocket could be discarded so you didn’t have to continue carrying it?
Main advantage of multistage rockets:
Total weight of rocket is greatly reduced as rocket rises

14. Multistage Rockets
Total weight of rocket is greatly reduced as rocket rises
Idea proposed by Tsiolkovsky in 1903
Smaller rockets (stages) stacked on larger rockets
When fuel is used up, that container falls away
The next rocket (stage) ignites
Left with single rocket (stage) left at end

15. Multistage Rockets
Total weight of rocket is greatly reduced as rocket rises
Uses
Saturn V sent spacecraft to the moon 1960’s
Used to launch satellites and space probes today
Multistage Rocket Active Art
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16. Homework Read Section 1, p40-45
Answer ?s 1-3 p45 AND Analyzing Data ?s 1-4 p43
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