Lecture 1 : Guidance system requirements

Gerard Leng, MDTS, NUS

MDTS 5705 : GuidanceLecture 1 : Guidance System Requirements


Course Admin

Instructor : Gerard Leng

Office : E2 -02 - 37

Contact : phone 6 874 6548

fax 6 779 1459

e-mail [email protected]

Consultation : Mon-Fri 12-2pm (happy hour)

Course Website : dynlab.mpe.nus.edu.sg/mpelsb


Course Outline

Topics

1 : Guidance System Requirements

2 : Line-of-sight Guidance

3 : Homing Guidance

4 : INS/GPS Guidance

Course Organisation

4 lectures/tutorial


Course Objectives & Requirements

1. Understand theoretical guidance concepts

2. Relate these concepts to practical weapon systems

Required Background

Basic engineering or science degree

( calculus, differential equations, particle dynamics )

Some programming experience ( eg : Matlab )


Text

P. Garnell & D.J. East, Guided Weapon Control Systems, Pergamon

Press, 1977

A.S. Locke, Guidance, Principles of Guided Missile Design, van

Nostrand, 1955

E. Fleeman, Tactical Missile Design, AIAA, 2006

P. Zarchan, Tactical and Strategic Missile Guidance , AIAA Progress in

Astronautics & Aeronautics, v239, (6th edition), 2012

Recommended references


Grading Policy

“Proposed” grading - Plan A

Project 40%

Final Exam 60%


1.0 What is a guided weapon ?

Guided Weapon = Sensors (Eyes & Ears)

+ Guidance Logic (Brain)

+ Control & Propulsion (Muscles)

+ Warhead

In other words ….

A guided weapon is a weapon system that can

correct its course to hit a target


Example : The earliest guided bomb

WWII German Fritz X

Specifications

• Weight 1300 kg, 270 kg AP warhead

• Wing span 1.6 m

• Guidance joy stick, radio link

• Range 5.6 km


Example : The earliest guided missile

WWII German HS 293

Specifications

Launch weight 1045kg, 295 kg HE warhead

Wing span 3.10m

Guidance joy stick, radio/wire link

Propulsion rocket

Range 18 km

../../movies/ASM/FritzX.mpg


Question : What can we observe & conclude from

these early guided weapons ?

A guided weapon doesn’t have to be really “high-tech” or even

autonomous

So can we build one with commercial-off-the-shelf (COTS)

components ?


1. 1 Mission profile of guided weapons

1.1.0 Guided weapons with different missions

• Anti Tank Guided Missile ATGM

• Air to Ground Missile AGM

• Anti-Ship Missile ASM

• Surface to Air Missile SAM

• Air Interdiction, Air-to-Air Missile AIM, AAM

• Anti-Missile Missile AMM

• Unmanned Combat Air Vehicles UCAV


1.1.1 Anti-Tank Missile Mission Profile

Question :Is a direct head on impact the most effective way for an ATGM

to destroy a tank ?

1. missile aligned with tank 2. head -on impact on the front hull


What is the best way to destroy a tank ?


Russian MBT T-72

Basic protection : 520mm - 590mm turret armour against HEAT

Main armament : 125-mm gun with range of 2000 m


Question : Where should the ATGM hit ?


ATGM flight trajectories

2. Elevated - Hellfire

1. Direct - Milan

3. Arched - Javelin

What’s this ?

../../movies/ATGM/ATGM trajectory3.mpg




1.1.2 Anti-tank missile guidance requirements

2. Attack armoured targets at the weakest point (top armour)

1. Additional protection eg : ERA (explosive reactive armour)

3. Guidance design implications :


1.2 What is the best way to destroy a ship ?

1.2.0 Warships can detect and defend against in-coming missiles

A : detection & launch

B : align with intercept plane

C : intercept course

D : target neutralised


1.2.1 Anti Ship Missile Mission Profile


1.2.2 Anti-ship missile guidance requirements

More complicated guidance design for different phases of mission

launch : dive/climb

mid-course : altitude hold

tactical maneuvers

terminal : pop-up


1.3 How to destroy an in-coming missile ?

1.3.0 Problems

Target can be as fast as your missile

Target may approach from any direction

Target can perform evasive maneuvers


1.3.1 Anti-Missile Missile Mission Profile


1.3.2 AMM guidance requirements

Vertical launch to “optimal” altitude

Tip-over to correct plane for interception

Mid course guidance to close with target.

Terminal guidance to counter evasive maneuvers


1.4 What are the guidance requirements for a UCAV

or a cruise missile ?

X45 X47

Hint : What kind of targets are suitable for UCAV or cruise missiles ?


1.4.1 UCAV/Cruise Missile Mission Profile


1.4.2 Cruise missile, UCAV guidance requirements

1. Long range, low-level terrain hugging flight

2. Best used against large stationary targets


1.5 The First Lesson of Guidance System Design

The design of the guidance system must suit the

mission profile and must function within the

limits of available sensors and controls

To paraphrase Sun Tze’s Art of War

Know your guided weapon, know your target.

In a 100 firings, you get a 100 hits (or close)


1.6 Basic Trajectory Analysis

q

g

R

V

a

OI

J

P

(1) Position of P

X = R cosq

Y = R sinq

1.6.0 Kinematics

(2) Velocity of P

X’ = V cosg

Y’ = V sing

X

Y


1.6.1 Turn rate and latax

1. Differentiate eqns (1)

X’ = cosq -sinq R’

Y’ sinq cosq Rq’

2. Substitute eqns (2)

Vcosg = cosq -sinq R’

Vsing sinq cosq Rq’


Inverting

R’ = V cos(g - q )

R q’ = V sin(g - q )

3. Conclusions :

a) The velocity component parallel to OP affects the rate of change of

OP

b) The velocity component perpendicular to OP affects the rotation rate

of OP


4. From the diagram, the lateral acceleration a = a { -sin g, cos g }

Differentiate eqns (2),

X’’ = cosg -sing V’

Y’’ sing cosg V g ’

5. Noting that the LHS is the lateral acceleration a …


We obtain

V’ = 0

V g ’ = a

6. Conclusion

The (applied) lateral acceleration (latax) changes the turn rate but not

the speed


Exercise : Getting a physical feel for the math

A fighter aircraft flying at 180 m/s (Mach 0.6) executes a 9g turn.

What is the turn rate ?

Noting that V g ’ = a

m V g ’ = ma = 9 mg

Hence g ’ =

=

=

=


Exercise : Estimating performance Aster 30 AMM

Reported : Dec 1997 test firing of the Aster 30 AMM

Intercepted target from above at Mach 2.68

miss distance < 4 m

max load = 60 g’s

What’s the turn rate ?

max turn rate =

=

Lecture 1 : Guidance system requirements

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