1. Weapon Propulsion and Architecture
Naval Weapons Systems

2. 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

3. 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

4. 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.

5. 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.

6. 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
We have talked about the warhead itself, how the warhead knows when to detonate and principles of how the weapon finds the target. Now we will discuss how the warhead gets to the target.
We will discuss the propulsion systems used in weapons.
Propulsion systems are discussed from two viewpoints the
1. The propulsion system’s Energy Source
2. The method of launch
Energy Source
The energy source is normally from:
1. The effect of gravity
2. A compression of gases or liquids
3. A chemical reaction (explosion)
Method of Launch
Method of Launch is normally classified as:
1. Gravity (bomb)
2. Reaction (a missile or torpedo)
3. Impulse-propulsion or gun-type (projectile)

7. 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)
The first propulsion system is very simple. Let gravity take the weapon and deliver it to the target.
Obviously the launch platform must be higher than the target.
Gravity propulsion is used in:
- All free fall bombs and glide bombs
DESCRIBE the difference between a free fall and glide bomb.
include that a glide bomb can still have a guidance system
which can control it’s flight path within the limits of gravity.
- Torpedoes launched from an aircraft
- MIRV’s

8. Gravity Bombs MK-20 Rockeye AGM-62 Walleye MK-46 Torpedo
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

9. Impulse Launching Chemical Reaction

10. Impulse Propulsion
Projectile is ejected from a container by means of an initial impulse.
Explosive Propellant Train:
Primer 1
Igniter 2
Propellant Powder 3
Normally an explosion causes a gas to expand and eject the projectile.
To produce the gasses which eject the projectile we must produce an explosion.
The sequence of events that occurs is the Explosive Propellant Train.
1. The explosive train is similar to the high explosive "train“ that we
discussed when we talked about how the warhead works.
2. The difference is this train uses low explosives instead.
3. Although a low explosive, it still burns rapidly.
The propulsion train consist of the same steps
- Primer normally ignited by blows from a firing pin
- An igniter which is used to start the burning of the Propellant powder. Burns and produces the gases.

11. 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.
Propellant:
Single – Nitrocellulose only (nitric acid and cotton)
Multi-based – Nitroglycerine added – enhances explosive qualities
- Is usually a solid and a chemical.
- The first solid propellant was black powder
- Black powder not suitable for use because:
* High burning temperature
* Incomplete combustion (leaves residue causing high erosion of gun bore).
Solid propellants are designed to produce a large volume of gases at a controlled rate. (makes the performance standard and predictable.)

12. 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.
PRESSURE GENERATED CAN BE CONTROLLED BY THE BURNING RATE.
Gun barrels are designed to withstand a fixed maximum pressure.
- Propellants must produce gases within these pressure limits.
- Can control amount of gases and resulting pressure by controlling the
burn rate of the propellant.
Control propellant burn rate by:
1. Size and shape of the grain (propellant). Explain Grain.
Controls the amount of surface area available to burn.
(remember, only the surface burns)
2. The web thickness of the solid propellant between the burning surfaces.
The thicker the web the longer the burn time. Longer time gas is
produced.
3. The chemical composition of propellant controls the rate at which the
propellant burns.
4. Percentage of undesirable (non-burnable) material mixed in with the
propellant. Other material changes the burning rate.
Big science in designing the propellant grains to get the burn rate desired to get the desired gas production rate and amount and to control the resulting temperature and pressure.

13. 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.

14. Interior Ballistics Action Inside a Gun.
Ignited propellant creates pressure within the chamber that forces the projectile down the barrel.
Degressive
Neutral
Step 1: Degressive Burning
Step 2: Neutral Burning
Step 3: Progressive Burning
Pressure
Progressive
Gun Barrel

15. Propulsion Propellent Burning Grains
Degressive burning Grains:
Ball Pellet Sheet
Strip Cord
Digressive Burning Grains {Pg 459-Old Book}
- As burning proceeds, the total burning surface decreases
- Used in weapons with short tubes
- Pellets, Ball and sheet shapes are common

16. Propulsion Propellent Burning Grains
Neutral Burning Grains:
Single Perforated
Star Perforated
{pg 460 – Old Book}
Neutral Burning Grains
- Surface area stays the same as it burns
- Produces constant amount of gas production *

17. Propulsion Propellant Burning Grains
Progressive Burning Grains:
Multi-Perforated
Rosette
{pg 460 – Old Book}
Progressive Burning Grains
- Surface area increases as it burns
- Produces an increasing amount of gases
- Used in guns with longer tubes.

18. Reaction Launch Compression of Liquids/Gasses

19. 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.

20. Liquid Fuels More powerful than solid fuels High volatility
Can’t be stored for long periods
High Volatility is a good thing in some cases, Space Shuttle?
- look at the containment problems associated. One theory has that this is what did the Challenger in. The O-ring on the liquid fuel cells was so cold, that it couldn’t maintain it’s seal.
Another problem with Liquid Fuels is that they tend to be very corrosive, eating away at the container holding it.
- This is what most of the earlier versions of ICBM’s that the Russians had in the Cold War, and even through the more recent versions.
- In addition to their ICBM’s, the Soviet SLBM’s were liquid fueled as well. They couldn’t lick the solid rocket thing for a long time.

21. 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

22. Reaction Propulsion Development of Thrust in a Rocket Motor:
Pressure is Balanced
Burning Propellant along the inside
of the casing exerts pressure in all
directions at once, until a nozzle is
fitted a one end.
Recall Newton’s Third Law!!!
Talk about the Booster and Sustainer part of a generic missile here.
Pressure is Un-Balanced
Forward Velocity
Thrust

23. Bernoulli’s Theory Pressure Increases Pressure Decreases
Convergent
Divergent
Pressure Increases
Velocity Decreases
Pressure Decreases
Velocity Increases

24. Gas Turbine Engine

25. Turbojet LM2500 DC 10 TURBOJET – Exhaust operates a turbine.
- Axial flow comressor
- Air flow must be subsonic
TURBOFAN – with propellor

26. Turboprop

27. Ramjet Low-Supersonic Mach 3 to Mach 5 JP-4 RAMJET- No moving parts
- RAM Air in the front – convert high speed low pressure air to low speed high pressure air, Bernoulli’s Theory
- Pressure barrier prevents frontal escape
- Flameholder keeps combustion chamber high temp
- exhaust
- Mach 5 due to frictional forces
- DISADVANTAGE – no thrust at rest!
- <90k feet, needs air!

28. Scramjet
Hydrogen
Hypersonic Mach 5 to Mach 20

30. 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

31. LIQUID FUEL Advantages Disadvantages Restartable Many moving parts
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

32. TURBOJET Advantages Disadvantages Large static thrust Oxygen from air
Common fuels (JP-4,5,&8)
Thrust independent of speed
Disadvantages
Basic design lacks improvements in efficiency and power

33. TURBOFAN Advantages Disadvantages 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

34. TURBOPROP Advantages Disadvantages
Very high fuel efficiency at slow speeds
High shaft power to weight ratio
Disadvantages
Limited top speeds
Noisy
Complex prop driveshaft

35. RAMJET/SCRAMJET Advantages Disadvantages 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
Ramjets typically need to be moving faster than Mach 1 before they can be engaged.
Compared to the turbojet, ramjets are also usually much less efficient until around Mach 3 or so.
ADVANTAGE: hydrogen is extremely flammable
DISADVANTAGE: the cost and safety issues involved in manufacturing and storing cryogenically-cooled hydrogen fuel is another major drawback
- hydrogen is still very expensive to produce when compared to conventional hydrocarbon fuels.

36. Questions?