Transcript Weapon Propulsion and Architecture

Weapon Propulsion and
Architecture
Naval Weapons Systems
Learning Objectives
Comprehend gravity, impulse, and
reaction propulsion
Comprehend factors involved in impulse
propulsion (explosive propellant train, burn
rate, interior ballistics)
Know the different types of reaction
propulsion systems
Comprehend basic principles of fluid
dynamics
Comprehend basic weapons architecture
Why is this important?
Evolution of Warfare
– Fists, sticks, and stones
– Spears and Bow/Arrow
– 20th Century brought guns
Before fought in big formations (out mass enemy)
– Machine guns and cannons
Increased need for dispersion
– Grenades and explosive shells
In Desert Storm the allies decimated the
Iraqi ranks and infrastructure from the air
and sea before the troops ever entered the
scene. When troops did move in, the
Iraqi's were confused, hungry and
demoralized. Many surrendered and those
few that didn't were quickly killed.
Introduction
Every weapon requires some form of
propulsion to deliver it to its intended
target.
Propulsion systems are based on
Newton’s Third Law: For every action
there is an equal and opposite reaction.
Types of Propulsion
Propulsion Types can be divided into two
categories:
– 1) Energy Source
Compression of Liquids/Gasses
Chemical Reaction
Effect of Gravity
– 2) Method of Launch
Gravity - a bomb
Impulse - a projectile
Reaction - a missile
Gravity Propulsion
Simple: Uses the force of gravity
to get the weapon to the target.
Used in:
- All free fall and
glide bombs
- Torpedoes launched
from aircraft (until
it submerges)
Gravity Bombs
MK-20 Rockeye
– Free fall cluster bomb
– Over 27,000 dropped during
Desert stormTanks and
armored vehicles
AGM-62 Walleye
– Television guided glide bomb
– 2000’ version “Fat Albert”
– Used during Vietnam
MK-46 Torpedo
Impulse Launching
Chemical Reaction
Impulse Propulsion
Projectile is ejected from a container by
means of an initial impulse.
Explosive Propellant Train:
1
2
Primer
Igniter
3
Propellant Powder
Propellants
Smokeless Powders or Gunpowder's:
– All are designed to produce large volumes
of gases at a controlled rate.
– Rate is based on the maximum pressure
that can be withstood by the gun barrel,
casing, etc.
Burn Rate Controlling Factors
- controls the pressure generated by the
propellant
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.
Burning Rates
The Burn Rate increases as both the
pressure and temperature rise.
Classification by variation in burn rate:
– Degressive: As it burns, the burning surface area
decreases
– Neutral: The burning surface area remains
constant
– Progressive: Burning surface area increases as
it burns.
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
Propulsion Propellent Burning Grains
Degressive burning Grains:
Ball
Pellet
– Strip
Cord
Sheet
Propulsion Propellent Burning Grains
Neutral Burning Grains:
– Single Perforated
– Star Perforated
*
Propulsion Propellant Burning Grains
Progressive Burning Grains:
– Multi-Perforated
– Rosette
Reaction Launch
Compression of
Liquids/Gasses
Propellants
Compressed Air / Gas:
– Used to eject missiles or torpedoes from
submarines.
– Easily controllable; doesn't harm weapons
– Problem: Compressor machinery to maintain
a supply of compressed gas.
Liquid Fuels
More powerful than solid fuels
High volatility
Can’t be stored for long periods
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
– Cruise Missiles
– Turbo-jet, and Ram Jet engines
Reaction Propulsion
Development of Thrust in a Rocket
Motor:
Pressure is Balanced
Forward Velocity
Burning Propellant along the inside
of the casing exerts pressure in all
directions at once, until a nozzle is
fitted a one end.
Pressure is Un-Balanced
Thrust
Bernoulli’s Theory
Convergent
Pressure Increases
Velocity Decreases
Divergent
Pressure Decreases
Velocity Increases
Gas Turbine Engine
Turbojet
LM2500
DC 10
Turboprop
Ramjet
Low-Supersonic
Mach 3 to Mach 5
JP-4
Scramjet
Hydrogen
Hypersonic
Mach 5 to Mach 20
SOLID FUEL
Advantages
– Simple
– Reliable
– Unlimited Speed
– Any medium/vacuum
– Few moving parts
– Full thrust at takeoff
– Store fully fueled
– Ready to fire!
Disadvantages
– No booster
– Not restartable
LIQUID FUEL
Advantages
– Restartable
– Practically unlimited
speed
– Any medium/vacuum
– Full thrust on take-off
– Less need for booster
than air breather
– Staged with liquid/solid
rockets
Disadvantages
– Many moving parts
– Complex
– Cost and Safety
issues
– More Volatile
TURBOJET
Advantages
– Large static thrust
– Oxygen from air
– Common fuels (JP4,5,&8)
– Thrust independent of
speed
Disadvantages
– Basic design lacks
improvements in
efficiency and power
TURBOFAN
Advantages
– Quieter than turbojet
– More efficient at
subsonic airspeeds
than turbojet (typically
at higher altitudes)
Disadvantages
– More complex
– Large diameter engine
– More blades=more
susceptible to FOD
TURBOPROP
Advantages
– Very high fuel
efficiency at slow
speeds
– High shaft power to
weight ratio
Disadvantages
– Limited top speeds
– Noisy
– Complex prop
driveshaft
RAMJET/SCRAMJET
Advantages
–
–
–
–
–
–
–
–
–
Simple
No wearing parts
Oxygen from air
Lightweight
Inexpensive to build and
operate
Common fuels
Efficient at high
speeds/altitudes
Supersonic
Hydrogen fuel (for
SCRAMJET)
Disadvantages
–
–
–
–
In Developmental stages
Cooling/Intake difficulties
No thrust at rest
Must be combined with
another type of engine to
get up to speed.
– Minimum Mach Number
– Hydrogen fuel (for
SCRAMJET)
– EXPENSIVE fuel source
Questions?