MDTS 5705 : Guidance Lecture 1 : Guidance System Requirements
Course Admin Instructor : Gerard Leng Office : E2-02 - 37 Contact : phone 6 874 6548 fax 6 779 1459 e-mail mpelsb@nus.edu.sg Consultation : Mon-Fri 12-2pm (happy hour) Course Website : dynlab.mpe.nus.edu.sg/mpelsb
Course Outline Course Organisation 4 lectures/tutorial Topics 1 : Guidance System Requirements 2 : Line-of-sight Guidance 3 : Homing Guidance 4 : INS/GPS Guidance
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 E. Fleeman, Tactical Missile Design, AIAA, 2006 Recommended references P. Zarchan, Tactical and Strategic Missile Guidance, AIAA Progress in Astronautics & Aeronautics, v239, (6 th edition), 2012 P. Garnell & D.J. East, Guided Weapon Control Systems, Pergamon Press, 1977 A.S. Locke, Guidance, Principles of Guided Missile Design, van Nostrand, 1955
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 Wing span Guidance Range 1300 kg, 270 kg AP warhead 1.6 m joy stick, radio link 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
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 Air to Ground Missile Anti-Ship Missile Surface to Air Missile Air Interdiction, Air-to-Air Missile Anti-Missile Missile Unmanned Combat Air Vehicles ATGM AGM ASM SAM AIM, AAM AMM 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 1. Direct - Milan 2. Elevated - Hellfire 3. Arched - Javelin What s this?
1.1.2 Anti-tank missile guidance requirements 1. Additional protection eg : ERA (explosive reactive armour) 2. Attack armoured targets at the weakest point (top 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 V 1.6.0 Kinematics J g (1) Position of P a X = R cosq X Y = R sinq P R (2) Velocity of P Y X = V cosg q Y = V sing O I
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 = =