1. Ballistics & Fire Control
Naval Weapons Systems

2. We Know: How the target is detected, How the target is tracked,
How the weapon is launched,
How the weapon is propelled,
How the weapon finds the target,
How the weapon knows when to detonate,
How the weapon detonates.
Go over graphic as a review.
What is missing????
Where do we aim the weapon to get a hit.
This is very important with a weapon that doesn’t know where it is and where the target is and continuously corrects, like a gun.
Its is even important for very smart weapons to keep from wasting time and fuel by shooting in the wrong direction.
For example: you don’t want to have a target on your right and shoot left, because then the missile will have to do a 180 and then may not have enough fuel to reach the target or give the target time to get away or destroy the weapon.
Solving the problem of where to aim is called solving the FIRE CONTROL PROBLEM.
The fire control problem begins when the target is assigned and ends when the target is destroyed.

3. The Fire Control Problem
Factors affecting the problem:
Effects of relative motion during flight
Effects of physical phenomena
(exterior ballistics)
The fire control problem would be easy if we could just point the weapon at the target and shoot and a magical beam of energy instantaneously got to the target and destroyed it. (The future of laser weaponry.)
It will take some period of time for the weapon to get from the launcher to the target. That time is call flight time. If the weapon is shot directly at the target and there is any movement of the target during the flight time, then the weapon will miss the target (unless its flight path is changed during the flight).
This motion will effect the fire control problem.
Other factors which effect the fire control problem are a result of the physical environment in which the weapon travels. We will divide these physical effects into to main categories
a. Consistent forces
b. Variable forces

4. Relative Motion Present target position Relative velocity Bearing rate
Own ship motion
Target motion
Bearing rate
Speed across line-of-sight
Future target position
Relative Motion is the apparent motion of another object when viewed from a location that is considered to be standing still.
Relative Motion will be a HUGE issue in Navigation I and II and eventually on your ship!!

5. Relative Motion
The apparent motion of an object when viewed from a point. C
20 mph
10 mph B
Use the diagram to ask students what the relative motion of each car is when viewed from standing on the curb or if they were in each car.
It doesn't matter if the target is moving or the launch platform is moving or if both are moving, under the relative motion the problem can be reduce down to the launch platform is not moving and the target is. Example:
Car A sees the man on the curb closing at 10mph.
The man on the curb sees car A closing at 10 mph.
Car A would see car B opening at 10mph.
Rather than solve the the fire control problem calculating the motion of both the target, weapon and launch platform we consider the relative motion as if the launch platform is standing still. Our frame of reference is from the launch platform.
a. This works out well because that’s where the radars, etc. are located which will track the weapon.
So our analysis of the motion will always be from the aspect of relative motion or movement of the target, viewed as if the launch platform was stationary.
10 mph A

6. Affects of Target Relative Motion on Range and Bearing
Present
Position
Future
Position
Ship’s
Heading
Present Range
Bearing
Change
Range Change
Go over diagram to show the geometry of the problem. Show
a. Development of Bearing Change
b. Development of Range Error
Goal is to determine the target’s course and speed so we can predict where the target will be at the time it takes the weapon to reach the target.
We are trying to solve a solution with respect to time:
ie. We want to adjust the aim point such that the target and the weapon arrive at the same point at the same time.
We then convert the Bearing change to a time reference by calling it a bearing rate. ie. how much the bearing changes with time. We do the same thing with range.
Getting this solution is just a little better than a trial and error process. It is a multiple step process when one solution is tried and the errors fed back to improve the next solution trial. This is called an iteration process.
Future Range
Present
Bearing

7. Solving the Relative Motion Problem
INPUT
Launch Platform Sensors
Output
Navigation Systems (location)
Gyrocompass (course)
Electromagnetic Log (speed)
Dead reckoning Analyzer
Depth indicator
Target Course
Target Speed
Target Range
Target Bearing
To summarize what has been presented:
Cover the graphic explaining the inputs that go into determining the target’s relative motion.
Target Position
Radar (search and fire control)
Sonar
Electronic warfare equipment
Data Systems (NTDS)

8. Exterior Ballistics Gravity Drag Wind Drift Coriolis Effect
If the flight path of the weapon was straight then we would have the problem solved. Unfortunately life isn’t that easy.
1. The environment effects the flight path of the weapon.
2. Go over list. The slides following also discuss the items in the list.
3. These items have the tendency to make the weapon’s flight path to curve.
4. This curved path will effect the weapon’s flight time and the aim point so they must taken into account.
5. Coriolis Effect has a very small effect on our weapons. The only one of consequence would be the Trident Warheads as they fall back to the earth.

9. Effects of Gravity Line of Fire Line of Sight
1. Gravity pulls an object down resulting in a curved flight path.
2. The longer the flight time the more the effect of gravity (more curve).
3. This means there is an entirely new flight path needs to be calculated each time the flight time is varied.

10. Effects of Drag Drag is loss of energy of a projectile during flight.
Energy is lost through:
a. Creation of air waves (function of projectile shape)
b. Creation of suction and eddy currents (shape)
c. Formation of heat (friction)
Cover the graphic.
Drag will change the speed of the projectile
- increased flight time
- increased curve caused by gravity
- changes intercept!

11. Effects of Drift Drift is caused by the rotation of a projectile.
Drift results in a lateral right displacement in flight path.
MAGNUS Effect.
Vertical Plane
Drift
Horizontal Plane
Line of Fire
Drift is caused by the rotation of the projectile.
a. Remember the barrel rifling (grooves) that cause the projectile to spin.
We did this to set up a gyroscopic motion to keep the projectile aligned
so it didn’t tumble.
b. A draw back to this spin is drift.
c. The physics of this effect is called the Magnus Effect but it will not be
covered. You can read more in the text (p556 – Old Book).
d. Just understand that drift is of concern and will cause the aim point to
be shifted.

12. Effects of Wind Horizontal Effects Vertical Effects Line of Fire
The wind has an effect on the performance of a projectile which may cause the projectile aim point to be moved.
Traverse (or crosswind) effect:
a. Can move the projectile either left or right horizontally.
b. Can also effect the vertical flight path of the projectile.
Range Wind effect:
a. Either retards or aids projectile speed and thus range.
b. Either pushes the projectile faster or slows it down varying the flight time
and the resulting aim point.
Horizontal Effects
Vertical Effects

13. Coriolis Effect Caused by the earth’s rotation. Results in apparent a
right curve in the northern hemisphere, left in southern.
10 mph
Coriolis Effect is because the earth is rotating.
1. A point on the equator is moving faster than a point near the pole (less distance to travel in one rotation).
2. If viewed from space watching the earth go by, a point on the equator will move from left to right at one speed and a point near the pole will be moving from left to right at a slower speed.
3. Now lets shift to two cars speeding along as shown on the graphic. One car
is moving faster faster than the other.
4. Looking at the slower car from the reference of the faster car, What is the
relative motion? Answer: The slow car would be moving to the left.
5. If at the exact time the fast car passes the slow car, you throw a ball straight
at the slow car aiming at the same window you through the ball through.
Would the ball hit the car?
Where would the ball hit? It would hit forward of the car.
Don’t for get the ball has the same for ward motion as the fast car
6. From the frame of reference of the the fast car you threw the ball straight the slow car was just moving to the left and that is why you missed.
7. From the frame of reference of the slow car the ball was aimed at the slow car but curved.
8. Now view the same thing from the curved surface of the earth.
EXTREMELY SMALL EFFECT ON MOST OF OUR WEAPONS.
20 mph

14. Fire Control Problem Input Computations Target data Own ship data
Relative motion procedure
Exterior ballistics procedure

15. Fire Control Problem Con’t.
Solutions
Weapons time of flight
Bearing rate
Line of Sight(LOS): The course the weapon must follow to intercept the target
Speed across LOS
Future target position
Launch angles
Launch azimuth
Launch elevation
Weapon positioning orders

16. The Iterative Process to the Fire Control Solution
Step 1
Step 2
The iterative process starts with an initial guess of the solution. The aiming point is put into the computer and the position of the target is computed at the time the weapon reaches the aim point. The error is fed back to refine the aim point. For example:
Step 1
a. The aim point is where the target is at the time of fire. At impact the target will move down its track.
Step 2
a. The bearing error is used to change the bearing of the aim point.
b. Note: If only used bearing error, the weapon would always fall short so
the range error is also used
The iterative process continues until the the weapon and the target’s solution intersect at the flight time of the weapon.
As a review:
What Information does the computer need to solve this problem?
1. Target position
2. Target data over a period of time to determine target course speed and range.
3. Weapons speed to compute time of flight
Step 3
Last Step

17. A 3-Dimensional Problem
Line of Sight
Present Range
1. In the previous examples we were concerned with two dimensions. The actual problem could be 3-dimensional.
2. The problem is essentially the same but have different names.
Target
Elevation
Gun
Elevation
Horizontal Reference Plane

18. GUNS, MOUNTS, TURRETS
Naval Weapons Systems

19. Gun Description Caliber: Measurements of Bore Diameter vs Bore Length
3 inch and larger guns
5 inch 54 caliber (5”/54)
5 inch bore
54 calibers bore length = 270 inches (54x5)

20. Uses of 5”/54 Shore Bombardment Close In firepower for surface action
Counter Small patrol craft
Political presence (shot across the bow!)

21. Basic Definitions Gun: Barrel or whole assembly
Mount: Fixates gun to ship’s structure
Houses Recoil/Counter recoil system
Train: Bearing position of the gun
Elevation: Upward angle from horizon

22. Rifling

24. Bore Deterioration Corrosion Dirt Erosion Copper Fouling
Corrosion: from the propellant powder
Dirt: Encourages corrosion – resistance to passing projectile
Erosion: Deterioration due to passing projectile – Friction, heat, cool
- Leads to lower pressures, less velocity
Constriction:
Copper Fouling

25. Questions?