aerospace power know the basic facts and general operating principle of rocket engines. 1. outline...

Aerospace Power

Know the basic facts and general operating principle of rocket engines.

1. Outline the history of rocket engines.

2. Describe how rocket engines operate.

3. List the types of rocket engines.

4. Describe advanced propulsion systems.

Overview

1. History of Rocket Engines

2. How Rocket Engines Operate

3. Types of Rocket Engines

4. Advanced Propulsion Systems

Warm Up Questions

CPS Questions

(1-2)

History of Rocket Engines

• The Chinese used rockets as early as A.D. 1200. In A.D. 1232 they used “fire arrows” in a battle known as Kai-Feng-Fu.


• In 1405, Von Eichsteadt, a German engineer, devised a rocket that was propelled by gunpowder, and in 1429 the French used rockets to defend Orleans against the British.


• By 1630 rockets that exploded and sent small pieces of metal in all directions were developed for military use.

• Rockets were used in 1807 at the battle of Copenhagen, and in 1812, the British formed a rocket brigade.


• During the end of the 18th century and early into the 19th century, rockets experienced a brief revival as a weapon of war. • Col. William Congreve, a British artillery

expert, developed a rocket with fins for more controlled flight through better stabilization.

• Congreve’s rockets were successful in the bombing of Fort McHenry in the War of 1812. They inspired Francis Scott Key to write “the rockets’ red glare,” in his poem that later became The Star Spangled Banner.


• In the mid 1900’s, William Hale, a British subject, used spin stabilization for his rockets.

• Rockets were used to carry lifelines to ships wrecked along coastlines, and in World War I, troops used rockets to carry signal flares to light up the battlefield at night and to carry messages during battle.


• Dr. Robert H. Goddard in the United States and Dr. Hermann Oberth in Germany brought increasing interest in rocketry.• Dr. Goddard, known as the “Father of Modern

Rocketry,” was the first scientist to use liquid fuels (liquid oxygen and gasoline) in rockets.

• Dr. Oberth’s work with liquid oxygen and alcohol fuels closely followed that of Dr. Goddard. These “firsts” in the use of liquid fuels occurred in the late 1920’s.


• After World War II, both the United States and the Soviet Union acquired German personnel with rocketry expertise.• The United States began a program with high-

altitude atmospheric sounding rockets, one of Goddard’s early ideas.

• These became the starting point of the U.S. space program.

Learning Check #1

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How Rocket Engines Operate

• Rocket propulsion, flight, and control are achieved applying certain laws of science that Galileo Galilei and Sir Isaac Newton discovered.


• Physical laws are based on gravitation, the force of attraction that exists between all matter within the universe.• A body of small mass attracts a body of large

mass just as the large mass attracts the small mass.

• Mutual gravitation exists between all bodies regardless of size.


• Galileo experimented with gravitation by dropping a solid iron ball from the Leaning Tower of Pisa.


• Sir Isaac Newton concluded that bodies in space, such as planets and their moons, are attracted toward each other in a special way.


• Rocket propulsion is based on Sir Isaac Newton’s three laws of motion. The third law is the heart of rocketry because the action of the rocket engine produces the forward motion of the rocket.


• The relationship of force, weight, and mass is defined by Newton’s law of universal gravitation. • It states that,“Every object in the Universe

attracts every other object with a force directly along the line of centers for the two objects that is proportional to the product of their mass and inversely proportional to the square of the separation between the two objects.”

• Expressed by the equation F = M1M2/r2.


• The weight of a body, the Earth’s gravitational attraction to it, may be measured by using a spring scale. • The obvious weight of a body depends upon the

force exerted upon it by another larger body in close proximity.

• The degree of force exerted depends upon the masses of both bodies. However, the mass of a body, the quantity of matter it contains, never changes. It is the property of matter that enables a body to occupy space.


• Momentum is the product of mass and velocity.• Newton found that the action of force on a body

changes the body’s momentum at a rate proportional to the force and the direction of force.

• If the mass of a body remains constant, any change in momentum is reflected in a change in velocity.


• Newton’s three laws of motion as they apply to rocketry.• The first law states that when launching a

rocket vertically, the propulsion system must produce enough thrust to overcome the inertia of the launch vehicle. The thrust, in pounds, must be greater than the weight of the rocket.

• Newton’s second law states that the amount of force required to accelerate a body depends on the mass of the body.


• Newton’s third law of motion relates to what occurs in a rocket engine prior to launch.


• Airframe• The airframe and propulsion system of a rocket

engine exists to deliver whatever cargo the rocket is carrying.

• Provides the rocket with the streamlined shape. • It must be as lightweight as possible.• The Atlas rocket was a prime example of how

engineers designed airframes that were both strong and lightweight.


• The most spectacular airframe ever constructed for a rocket was the Saturn V launch vehicle.


• Propulsion System• The rocket’s propulsion system includes the

propellant used, the containers for the propellant, all the plumbing that may be required to get the propellant from the containers to the engine and the rocket engine itself.


• Propulsion System• Chemical systems usually involve the mixing

and burning of a chemical fuel and a chemical oxidizer.

• The gas-heating system design would use an “external” heat source to heat the propellant and build the pressure.

• Electric systems use magnetic fields and currents to propel matter in small amounts.

Types of Rocket Engines

• Liquid Propellant• Liquid-propellant rockets can operate on most

of the combustion fuels plus an oxidizer. • In some cases, liquid propellants permit

intermittent operations. Combustion can be stopped and started by controlling propellant flow.


• Liquid Propellant Classifications• Monopropellants

• Contains its oxidizer and fuel in one solution.

• May be a single chemical compound.

• The compounds are stable at ordinary temperatures and pressures, but break down when heated and pressurized, or when the breaking down process is started by a catalyst.

• Monopropellant rockets are simple since they need only one propellant tank and associated equipment.


• Liquid Propellant Classification• Bipropellant

• A combination of fuel and oxidizer, which is not mixed until after they have been injected into the combustion chamber.

• More stable and capable of better performance than monopropellants.

• In addition to a fuel and oxidizer, a liquid bipropellant may include a catalyst to increase the speed of the reaction, or other additives to improve the physical, handling, or storage properties.


• Bipropellant


• Liquid Propellant Classification• Tripropellant

• A combination of three compounds. The third compound is added to improve the basic bipropellant’s ability to increase the vehicle’s velocity.

• All liquid-propellant systems have propellant tanks; a propellant feed system, a thrust chamber, and controls such as regulators, valves, and sequencing and sensing equipment.


• Solid Propellant• In a solid propellant rocket system the fuel and

oxidizer are mixed together from the start.• The rocket case is the combustion chamber and

holds the propellants. There are no valves, pumps, or sensors. Additives, if needed to increase temperature or to control burning, are simply mixed with propellant grains.


• Hybrid Propellant• Hybrid propellants use a combination of both

liquid and solid propellants within the same engine.

• When solid fuel is used, it is packed into the rocket engine as an inactive material, without its oxidizer.

• The gases, approaching each other from opposite directions, unite and burn just above the face of the fuel grain.


• Hybrid Propellant• Hybrid propellants combine in a single rocket

engine many of the advantages of both liquid and solid propellant rockets.

• Flexibility gives the hybrid rocket its biggest operational advantage. It can be throttled from zero to full thrust and can be stopped and started in flight.

Learning Check #2

CPS Questions

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Advanced Propulsion Systems

• Electric Propulsion• Electric propulsion systems use power

generated by an on-board source to apply electric currents to matter that exits the engine at high velocity.

• The primary drawback to electric propulsion is that comparatively little thrust is produced.

• Depending on the space vehicle, batteries may be the backup or intermediate source of power.


• Electric Propulsion• Batteries for spacecraft operations are

recharged by an arrangement of solar cells called an array or a paddle. The Sun radiates the equivalent of 130 watts of electrical energy per square foot on any surface that is perpendicular to the Sun’s rays.


• Electric Propulsion• Another device that provides electricity from a

chemical reaction is the fuel cell. Fuel cells, unlike batteries, use chemical fuels and oxidizers that are stored outside the cell. Two porous nickel electrodes are submerged in a solution of sodium or potassium hydroxide. Pressurized hydrogen and oxygen are fed to these electrodes and spread throughout them.


• Electric Propulsion• Nuclear energy is a fourth means of generating

electricity. Basically there are two ways of using nuclear energy to generate electricity: the radioisotope method and the nuclear fission method.

• Nuclear fission is the splitting of atoms as in the process that takes place in an atomic bomb.


• Unit of Electric Propulsion• Electric propulsion techniques produce very

little total thrust, but the amount of thrust is extended over a very long time.

• No propulsion system, electric or otherwise, can work without a propellant mass.

• In space, sustaining thrust is more desirable than the intensity of thrust.

• Electric engines are expected to yield specific impulses of 2,000 to 30,000 seconds or more.


• Types of Electric Engines• Resistojet Engines

• Resitojet is the name given to miniature thrusters designed to deliver precisely controlled thrust for spacecraft attitude control and station keeping (keeping satellite in required position).

• Heat is generated by passing an electric current through a special wire or tube.

• A stream of hydrogen or ammonia is passed over the heating element and energized to high velocity as it travels out an exhaust nozzle similar to that of a conventional chemical rocket.


• Types of Electric Engines• Arc Jet Engines

• Electricity jumping this gap or “arcing” creates very high temperatures.

• As with the resistojet, the operating time is limited more by the fuel supply than by the duration of the power source.

• Teamed with a nuclear reactor, the arc jet might some day compete with more direct means of nuclear propulsions.


• Types of Electric Engines• Ion Engines

• Ion or electrostatic engines are in use as supplementary propulsion sources for north-south satellite station keeping and attitude control.

• Rate of fuel consumption is low and they can sustain thrust over long periods.

• The ion rocket is the first example of propulsion by some means other than gaseous heating.


• Types of Electric Engines• Plasma Engines

• A plasma is made up of ions, free electrons, neutrons, and other subatomic particles; they are not made up of molecules.

• Plasma engines first employ electric power to heat a gas and break it down into plasma.

• Specific impulse is directly proportional to exhaust velocity.

• Pulsed plasma thrusters have a number of advantages in missions requiring precise maneuvers.


• Nuclear Propulsion• Nuclear Energy for Rocket Application

• Nuclear Energy for Rocket Vehicle Application (NERVA) is a project started in 1961 to develop a nuclear propulsion unit.

• The NERVA could develop 75,000 pounds of thrust with a specific impulse of 825 seconds.

• The NERVA engine’s capability for easy stopping, restarting, and thrust regulation plus high specific impulse give it the means of using a propellant supply with efficiency.


• Nuclear Propulsion• Gas Core Nuclear Engines

• Gas core nuclear rockets, include the coaxial flow reactor and the light bulb reactor, have a specific impulse as high as 5,000 seconds compared to around a 1,000 seconds with the NERVA rocket.

• The nuclear light bulb (NLB) reactor system would consist of several cylindrical cavities.

• Thermal radiation would pass through the transparent wall to heat the hydrogen to desired temperatures.


• Nuclear Propulsion• Fusion and Photo Engines

• A fusion engine is a concept that goes far back beyond NERVA and NLB in that it proposes use of a reactor for controlled thermonuclear energy.

• A photon system is a futuristic concept that would convert matter into radiation or light energy.

• Another system is a passive one, which involves photons.

Learning Check #3

CPS Questions

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Review Questions

CPS Questions

(9-10)

Summary

1. History of Rocket Engines

2. How Rocket Engines Operate

3. Types of Rocket Engines

4. Advanced Propulsion Systems

aerospace power know the basic facts and general operating principle of rocket engines. 1. outline...

Documents

history of rocket engines

types of rocket engines

rocket propulsion

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body of large mass

french used rockets

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