Rockets 101 AIAA – March 2009

Theory of Rockets

Dr. Eric Besnard

California State University, Long Beach

Project Director, California Launch Vehicle Education Initiativehttp://www.csulb.edu/rockets/

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Rockets 101 AIAA – March 2009

How does a rocket work?

• Exercise 1: – Take a balloon and blow it up – Do not tie it– Release the balloon– What happens? Why?

• Exercise 2:– Take a cart with a pile of bricks on it– Stand on the cart and throw bricks backward– If there is no friction on the wheel, what happens? Why?

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Rockets 101 AIAA – March 2009

Thrust

• This effect comes from conservation of momentum– Momentum:

• Definition: mass x velocity (speed)

• A truck at 40 miles per hour has more momentum than a car at 40 miles per hour

• A car at 40 miles per hour has more momentum than a car at 20 miles per hour

– Newton’s first law of motion: When no external forces are applied on the object, momentum is conserved

– Mass exits backwards at a certain speed or velocity

– Therefore object moves forward at a speed which will conserve momentum:

→ THRUST is generated

Rocket

(large mass, “small” velocity)

Gas

(small mass, large velocity)

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Rockets 101 AIAA – March 2009

Rocket flight

• Newton’s second law of motion: forces acting on the object will change the momentum of the object:

F = m a– F: Sum of all forces

– m: mass of object

– A: acceleration of object

• Forces on our rocket:– Drag (air)

– Weight (gravity)

– Thrust (engine)

• Fins are added for stability of the rocket

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Rockets 101 AIAA – March 2009

Rocket engines

• Generate high velocity gas by chemical reaction (burning) of propellants:

– Something which burns: fuel– Something which carries oxygen: oxidizer

• Unlike aircraft engines which take the oxygen from the atmosphere (“air-breathing” engines), rocket engines carry their own oxygen so they can fly in space (where there is no atmosphere)

LOX tank

LH2

tank

Solid Rocket Booster

Orbiter

• Types of propellants:– Solids. Ex: gun powder, Estes rockets– Liquids. Examples:

• Oxidizer: liquid oxygen, LOX (≈ -320 F)

• Fuel: liquid hydrogen, LH2 (≈ -425 F) or kerosene

– Hybrids: nitrous oxide (laughing gas) & rubber

• Propellant is burnt and accelerated with a nozzle

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Rockets 101 AIAA – March 2009

A Really BIG rocket engine

• 5 F-1 engines were used on the Saturn V on its way to the Moon

• 1.5 million pounds each!

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Rockets 101 AIAA – March 2009

Smaller rockets, same technology…

Designed and integrated by Long Beach State students

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Rockets 101 AIAA – March 2009

Aerospike rocket engine static fire test

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Rockets 101 AIAA – March 2009

When something goes wrong…

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Rockets 101 AIAA – March 2009

Prospector-4 flight

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Rockets 101 AIAA – March 2009

A slightly bigger rocket: size for 20 lb to orbit!

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Rockets 101 AIAA – March 2009

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Rockets 101 AIAA – March 2009

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Rockets 101 AIAA – March 2009

Your rocket

Nozzle

Solid propellant

Ejection charge for deployment of recovery system

Non-thrust delay and smoke tracking charge

High thrust charge for lift-off and acceleration