Weapon Propulsion and Architecture

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Weapon Propulsion and Architecture

• Naval Weapons Systems

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Learning Objectives

• Comprehend gravity, impulse, and reaction
  propulsion.
• Comprehend the factors involved in impulse
  propulsion, including the explosive propellant
  train, the factors controlling burn rate, and
  interior ballistics.
• Know the different types of reaction propulsion
  systems.

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Learning Objectives

• Comprehend the basic principles of fluid dynamics
  and be able to apply them in shipboard
  situations.
• Know the concepts of lift and drag, atmospheric
  properties and effect, subsonic and supersonic
  flow characteristics, and high speed
  aerodynamics.
• Know aerodynamic and hydrodynamic controls.
• Comprehend basic weapons architecture.

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Introduction

• Every weapon requires some form of propulsion to
  deliver it to its intended target.
• Propulsion systems are based on Newtons Third
  Law To every action there is an equal and
  opposite reaction.

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I. Types of Propulsion

• A) Propulsion Types can be divided into two
  categories
• 1) Energy Source
• Chemical Reaction
• Compression of Liquids
• Effect of Gravity
• 2) Method of Launch
• Impulse - a projectile
• Reaction- a missile
• Gravity - a bomb

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B. Gravity Propulsion
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C. Impulse Propulsion

• Impulse propulsion systems include all weapons
  systems in which a projectile is ejected from a
  container by means of an initial impulse.
• Explosive Propellant Train1) 2) 3)

Igniter
Primer
Propellant Powder
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C.1 . Propellants(2 types)

• a. Smokeless Powders or Gunpowders
• Can be single or multi-based, depending on the
  number of components used to make it up. Powders
  are produced in a granular form.
• All are designed to produce large volumes of
  gases at a controlled rate. This rate is based
  on the maximum pressure that can be withstood by
  the gun barrel, rocket casing, etc.

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(a.1) Burn Rate Controlling FactorsThe burn
rate, which controls the pressure generated by
the propellant is controlled by variances in the
following factors

• Size and shape of the powder grain
• Web thickness amount of propellant between
  burning surfaces of the grain.
• Chemical burn rate constant of the propellant
  material
• Percentage of volatile material present.

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(a.2) Burning Rates

• The Burn Rate increases as both the pressure and
  temperature rise.
• Propellants can also be classified by variations
  in their burning rates
• Degressive As it burns, the burning surface area
  decreases
• Neutral The burning surface area remains
  constant
• Progressive Burning surface area increases as
  it burns.

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Propulsion Propellent Burning Grains

• Degressive burning Grains
• Ball Pellet Sheet
• Strip Cord

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Propulsion Propellent Burning Grains

• Neutral Burning Grains
• Single Perforated
• Star Perforated

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Propulsion Propellant Burning Grains

• Progressive Burning Grains
• Multi-Perforated
• Rosette

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Propellants(2 types)

• b. Compressed Air / Gas
• Used to eject missiles or torpedoes from
  submarines.
• Easily controllable doesn't harm weapons
• However, requires loud compressor machinery to
  maintain a supply of compressed gas.

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C.2. Interior Ballistics

• Action Inside a Gun.
• Ignited propellant creates pressure within the
  chamber that forces the projectile down the
  barrel.

Degressive
Neutral
Pressure
Progressive
Gun Barrel
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D. Reaction Propulsion

• Weapons employing reaction-type propulsion obtain
  thrust by creating a pressure differential in the
  medium they operate in, i.e. air or water.
• Examples include
• Rockets, Missiles
• Turbo-jet, and Ram Jet engined Cruise Missiles

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D.1. Development of Thrust in a Rocket Motor

Burning Propellant along the inside of the casing
exerts pressure in all directions at once, until
a nozzle is fitted a one end.
US weapons use solid fuel Russian Liquid- Loss of
subs
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D.2. Types of Jets

• Ramjet
• Scramjet
• Turbojet
• Turbofan
• Turboprop

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Jets
D.2.a. Bernoullis Theory
Divergent
Convergent
Pressure lt Velocity gt
Pressure gt Velocity lt
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D.2.b. Ramjet / Scramjet
Low-Supersonic Mach 3 to Mach 5
JP-4
Hydrogen
Hypersonic Mach 5 to Mach 20
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D.2.c. Turbojet / Turbofan
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D.2.d. Turboprop
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II. Fluid dynamics

• Aerodynamics The study of the motion of gaseous
  fluid flows, and of their actions against and
  around bodies in motion in that fluid.
• There are four forces that act upon a missile in
  flight.
• Thrust Due to the force from the engine
• Weight Due to the force of gravity
• Lift Due to the difference of air pressure
  above and below the airfoils, perpendicular to
  the direction of flight
• Drag Due to the friction caused by air in front
  of and along the missile, opposes missile motion

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Fluid dynamics
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Fluid dynamics

• Bernoulli's Principle Air flow on the top of an
  airfoil is faster than that on the bottom, thus
  the density of the air is less on the top of the
  airfoil, causing the missile to rise.

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Fluid dynamics

• Aerodynamic forces are greatly due to atmospheric
  properties.
• Static pressure
• Caused by the weight of the air upon an object
• Static pressure decreases with an increase in
  altitude.
• Density
• Mass of air per unit volume
• Density decreases with an increase in altitude.
• Temperature Temperature decreases with an
  increase in altitude.
• Humidity As humidity increases, air density
  decreases (less air molecules and more water
  molecules per unit volume).
• Viscosity
• Air's resistance to flow
• Viscosity increases as temperature increases.

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Fluid dynamics

• Atmospheric conditions change with altitude,
  season, weather, location, and time of day.
• Lift is directly related to the density of the
  air and the missile's velocity and angle of
  attack.
• As static pressure decreases, lift decreases.
• As density decreases, lift decreases.
• As humidity increases, lift decreases.
• As altitude increases, the combination of
  atmospheric effects reduces lift and the angle of
  attack must be adjusted.

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Fluid dynamics

• Drag is affected by atmospheric conditions.
• As temperature increases, viscosity increases.
• As viscosity increases, friction and drag
  increase.
• At high speeds, the effects of aerodynamic forces
  and atmospheric forces are amplified.
• Subsonic and supersonic flow characteristics
• At supersonic speeds, air is compressed and the
  density of the air changes.
• At subsonic speeds, density changes are minimal
  and can be ignored. As area decreases, velocity
  increases.

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Fluid dynamics

• Hydrodynamics The study of the motion of
  fluids, and of their actions against and around
  bodies in motion in that fluid.
• Air and water are both fluids and act similarly.
• There are differences due to differences in
  density and mass, and the lack of compressibility
  of water.
• Torpedoes, like missiles, are affected by lift
  and drag, and pitch, roll, and yaw.
• Torpedoes, unlike missiles, are affected by
  buoyancy.

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III. Control surfaces

• Missiles
• Canard control
• Small control surfaces are forward.
• Lifting surfaces are aft.
• Wing control
• Control surfaces are near the center of the
  airframe.
• Control surfaces also provide lift.
• Tail control
• Control surfaces are aft.
• Lift surfaces are near the center of the airframe.

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Control surfaces

• Torpedoes
• Upper and lower fins control roll and pitch.
• Port and starboard fins control pitch.

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IV. Basic missile architecture

• Guidance system
• Warhead and fuze
• Autopilot

• Propulsion system
• Control surfaces

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Basic torpedo architecture

• Propulsion system
• Control and guidance system
• Warhead and fuze

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Gun ammunition architecture

• Penetrating

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Gun ammunition architecture
Gun ammunition architecture

• Penetrating
• Fragmentation

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Gun ammunition architecture

• Penetrating
• Fragmentation

• Special purpose

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Assignment 12

• Workbook
• Ch. 16 2,4,5,12,13,14,15
• Describe how thrust in a rocket motor is
  developed
• Descibe how a subsonic nozzel works.
• What are the 4 forces acting on a missile during
  flight?
• Read Ch. 17 Launching Systems