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Information about chapter5

Published on March 4, 2008

Author: Emma


Slide1:  5-1 Lesson objective – to discuss Concepts of operation including … Basic concepts Area coverage Combat air patrol Response time Example problem Slide2:  5-2 Review Concept of operations (ConOps) definition(s) How something is used or operated Typically associated with military systems but also applicable to commercial systems. The name of a document used to describe how a system should be operated, e.g. Which definition will we use? What is another way to describe it Slide3:  5-3 How UAVs are used Slide4:  5-4 Examples DarkStar Tom Cat Slide5:  5-5 Air operations Whether, manned or unmanned, there are two general types of missions, preplanned and on-demand Preplanned missions are scheduled well in advance On demand missions can be launched quickly (within minutes) if an aircraft is ready and a crew is on site - The military does “strip alert” and “standby alert” missions - Strip alert pilots are in the cockpit, ready to go There are two basic types of loiter missions - standoff and over flight (or “penetration”) Standoff missions generally are flown when over flight is not allowed or is considered too risky Exceptions are missions flown with sensors that do not look straight down such as synthetic aperture radar (SAR) Although missions can takeoff from one base and land at another, typically we design for single base operations Slide6:  5-6 Typical mission profile Slide7:  5-7 Target area coverage from base Platform only Ap = (p)*Rp^2 -Tan(p)*Db^2 (5.1) where p (radians) = ArcCos(Db/Rp) (5.2) Rp = Platform radius Db = Distance to border Slide8:  5-8 Coverage area example For Db = 250 nm Rp = 500 nm Platform only coverage p = ArcCos(250/500) = 60 deg Xmax = 433 nm Ap = (60*/180)*500^2-250*433 = 153549 nm^2 Slide9:  5-9 UAV vs. manned operations Military UAV missions can be planned and operated like manned aircraft if they stay in military air space Flights can be scheduled one day and flown the next or, in time critical situations, launched on demand But manned operations sometimes cease when they are unfamiliar with UAV launch and recovery operations If UAVs have to fly in civilian or international airspace, planning may have to be days to weeks in advance - To allow time for coordination with local civilian air traffic control and VFR traffic Most manned military missions are for training - Pilots need proficiency flying (20+ hrs/month) Reconnaissance UAVs operate differently, after initial training, most missions are operational UCAVs were to be even more different, keep them in storage until needed for combat (train on simulators) Slide10:  5-10 Sensor coverage Some sensors are fixed (called “staring” sensors) - Photo reconnaissance cameras are often fixed - Staring sensors also used for self defense Others are essentially fixed (e.g. “line-scanners”) - The sensor rotates, target coverage is in thin strips which can be integrated over time to form an “image” - They can provide horizon-to-horizon coverage Some sensors are fixed in one direction and can be “slewed” in another (e.g. side looking radar) - Horizontal coverage controlled by vehicle flight path, elevation controlled independently Other sensors can be slewed in azimuth and elevation but only within limits (e.g. SAR) The most flexible sensors are fully “gimbaled”in azimuth and elevation and can cover an entire hemisphere (or more) Slide11:  5-10a Platform + sensor coverage Example Db = 250 nm Rp = 500 nm Rs = 75 Platform + sensor pps = ArcCos(250/575) = 64.23 deg Xmax = 518 nm Ap = (1.121)*575^2-250*518 = 241139 nm^2 (vs 153549 nm^2 for platform only) Int’l waters Same logic as platform only except sensor (or weapon) can extend target area coverage Slide12:  5-11 Weapon coverage There are a wide variety of weapons types, both powered and unpowered - Powered weapons can extend target coverage from a little (free fall bombs) to a lot (cruise missiles) Almost all weapons are launched forward - Sonabouys and parachute delivered weapons are exceptions Guided weapons can attack targets well off of the flight patch axis Some weapons can be aimed like sensors - Machine guns and grenade launchers Some future weapons will also be aimed Lasers Slide13:  5-12 Loiter missions Manned military reconnaissance missions loiter over friendly territory - Sensors can look into neighboring territory without endangering the crew (in general) Manned strike missions are flown both ways - Stealth aircraft are designed for over flight but they seldom loiter over hostile territory Unmanned military reconnaissance (and strike) missions are also flown both ways - Global Hawk is designed to loiter over friendly territory - Dark Star was stealthy and designed to fly over hostile territory (UCAV will also operate this way) - Predator is not a stealthy design but often loiters over hostile territory - It takes a calculated risk (and is sometimes lost) Slide14:  5-13 Standoff vs. over flight Sensors - Sensors on penetrating platforms can look down and all around - Inherently, they can cover more target area than a standoff sensor Weapons - Weapons on penetrating platforms have the same advantages Sensor Coverage Capability Unusable sensor coverage Border Standoff distance Penetrate Standoff Border Slide15:  5-14 Loiter patterns Plus many others and combinations thereof Slide16:  5-15 Search area coverage Straight line coverage Area = SwathSpeedTime Equivalent range = Area/Swath Search pattern coverage KArea = SwathSpeedTime Typical factor (K) = 1.3? or Slide17:  5-16 Combat Air Patrol (CAP) Target area coverage (and response time) from a CAP type mission is a bit complex and not well understood In this type mission, the air vehicle loiters over an area until it receives and order to observe or attack an area of interest Assumed to be at maximum fly-out distance Upon arrival over the target area, the air vehicle performs its mission and then returns to base The flight path, therefore, is triangular consisting of: - An outbound segment to the CAP location - Another segment to maximum distance - A third segment back to base Typically the CAP location is over friendly territory and we will call it a loiter/penetrate mission Slide18:  5-17 Loiter/penetrate geometry - optional Definitions D1+D2+D3 = 2*R - LED = 2R’ (5.3) where D3 = Distance back to base R = Mission radius LED = Loiter equivalent distance 2max = ArcCos(Dso/D2max) (5.4) From geometry D1+ D2min = D3max (5.5) (D1-Dso)^2+Xmax^2 = D3min^2 (5.6) Dso^2+Xmax^2 = D2max^2 therefore (D1+Dso)^2- D3min^2 = Dso^2-D2max^2 and D2max = [Dso^2-(D1-Dso)^2+(2R’-D1)^2] 2(2R’-D1) (5.7) Slide19:  5-18 Platform only coverage Define LED Solve for D2min (10.9) Solve for D2max (10.11) Solve for 2max (10.8) Solve for D3min (10.10) Numerically integrate sector area from 2 = 0 to 2max where 2 = 2max/n n = number of integration steps note D2' + = 2*R -LED - D1 - D3’ (5.8) and D3’ can be solved using the same approach used to solve for D2max Subtract triangular area defined by Dso, Xmax and D2max Solution approach Optional topic Slide20:  5-19 Solve for maximum area coverage (LED = 300nm) where R = 650nm Db = 250 nm Dso = -125nm Solution steps D2min = 375nm D2max = 410.7nm 2max = 72.3 deg D3min = 464.3 nm Numerically integrate sector area from 2 = 0 to 72.3 deg (n=10) Sector area = 188767 sqnm Subtract triangular area defined by Dso, Xmax and D2max (48907sqnm) Total area = 139860 sqnm (vs 153549 nm^2 for conventional mission) Platform coverage example 2max Optional topic Slide21:  5-20 R = 650 nm LED = 300 nm Db = 250 nm Dso = -125nm therefore D2min = 375nm D2max = 410.7nm 2max = 72.3 deg D3min = 464.3 nm Circular sector area (2 = 0 to 72.3 deg) Average radius = 393 nm Sector area = 194895 sqnm Subtract triangular area defined by Dso, Xmax and D2max (48907sqnm) Approximate area = 146078 sqnm (+4.5%) Approximate solution The approximation is valid for loiter penetrate only 2max Optional topic Slide22:  5-21 Figures of merit During pre-concept and conceptual design, simple figures of merit are typically used Examples: Operational time on station - Global Hawk goal = 24 hours at a distance of 1200 nm from base Target area coverage per unit time - Global Hawk wide area search goal = 40,000 sq.nm/day - With 10 km sensor swath width at 343 kts at 10% overlap (Area = SwathSpeed24 0.9) Number of targets per unit time - Global Hawk goal target coverage = 1900 2Km x 2Km spot images/day But some ConOps require different metrics Increasingly the figure of merit of interest is area coverage within a given response time Slide23:  5-22 Response time example Platform response time On alert (pre-assigned) Tr = Tse+Ttto+Tcl+Tcr+Tpen where Tse = time to start engines (≈ 5 min) Ttto = time to taxi & takeoff (≈ 10 min) Tcl = time to climb = Dcl/Vcl Tcr = time to cruise = Db/Vcr-Tcl Tcr = time to penetrate = Dpe/Vpe Response time (Tr) - The time required to respond to a request or order such as: - Put platform overhead, put sensor on target or put weapon on target On standby (not assigned) Tr = Tr+Tprep where Tprep = additional preparation times including Aircraft prep (1-2 hrs) Crew transit (2-4 hours) Mission planning (15-60 min) Flight plan coordination (45 min) ≈ Tr + 3 to 6 hrs (@ minimum) Slide24:  5-23 Response time effects Sensors Sensors arrive on target before the platform (@ speed of light) - Target coverage is increased by the range of the sensor at any given time Weapons If a weapon is faster than the platform - the weapon will arrive over target first and response time improves If the weapon is slower – coverage area may increase but at a slower response time Slide25:  5-24 Figures of merit Platform only example For a specific missions with specific response time requirements, a calculation that includes all of the individual time increments and shows that the requirement can be met, will be the primary figure of merit. For more generalized missions, target coverage as a function of time, can be a good figure of merit - For example, Xsqnm target coverage within Y minutes Border Slide26:  5-25 Operating distance effects The closer an air vehicle loiters to its target area, the more efficiently it can employ its sensors and the quicker it can respond to assignments or requests It does, however, reduce target area coverage - It is a simple matter of geometry for a vehicle with a fixed range or radius Example Total mission radius = 650 nm LED = 300 nm Slide27:  5-26 Next subject Lesson objective – to discuss Concepts of operation including … Basic concepts Area coverage Combat air patrol Response time Example problem Slide28:  5-27 Surveillance UAV - review Predator follow-on type Land based with 3000 foot paved runway - Mission : provide continuous day/night/all weather, near real time, monitoring of 200 x 200 nm area - Basing : within 100 nm of surveillance area Able to resolve range of 10m sqm moving targets to 10m and transmit ground moving target (GMT) data to base in 2 minutes - Able to provide positive identification of selected 0.5m x 0.5 m ground resolved distance (GRD or “resolution”) targets within 30 minutes of detection - Ignore survivability effects Minimum required trades Communication architecture Sensor(s) required Control architecture Operating altitude(s) Time on station Loiter pattern and location Slide29:  5-28 Surveillance UAV Slide30:  5-29 Our example – how to start? Analyze the problem What is the customer really asking for? What information is missing? Look at some potential solutions What are the overall system design drivers? ConOps Communications Payload Pick an initial approach (or starting “baseline”) Define requirements Analyze it Estimate cost and effectiveness Analyze the other approaches Compare results Select a baseline approach Reasonable balance of cost, risk and effectiveness Today Slide31:  5-30 What is the customer asking for? A system that can monitor a large area of interest Conduct wide area search (WAS) for 10 sqm ground moving targets (GMTI), range resolution  10m. Send back data for analysis within 2 minutes A system that can provide more data on demand Based on analysis of wide area search information Based on other information A system that can provide positive identification of specific operator selected targets Within 30 minutes of request at a resolution of 0.5 m But what is positive identification (ID)? Does it require a picture or will a radar image suffice? …and what happens to search requirements while the UAV responds to a target identification request? …and how often does it respond? …and what is the definition of “all weather”? Slide32:  5-30a Example - WAS sensor data Typical high resolution spot time = 45 sec Slide33:  5-30b Example - ID sensor data Slide34:  5-31 Getting answers Ask the customer But don’t always expect a definitive answer Some typical responses – Positive identification : “Visual image required” Search while responding to target identification request: “interesting question, what are the options?” ID response frequency – Assume 1 per hour Weather definition : “Assume Clear day, unrestricted visibility (50% of the time) 10Kft ceiling, 10 nm visibility (30%) 5Kft ceiling, 5 nm visibility (15%) 1Kft ceiling, 1nm visibility (5%). Threshold target coverage = 80%; goal = 100%” Note: a measure of effectiveness just got defined! Slide35:  5-32 Sensor target coverage WAS all weather sensors Assume minimum look down angle () = 5 Assume maximum look down angle () = 60 ID sensors (against 2D ground target) Assume nominal maximum slant range = 30 nm For reasonable resolution against typical ground targets (with high resolution sensor) Assume minimum look down angle () = 20 Min range = Rmin h = altitude Slant range - min SLRmax = Max slant range    h(req’d) = RmaxTan() Strip width (w) Max range = Rmax GMTI coverage area  [h^2][1/Tan()^2-1/Tan()^2] Slide36:  And the image processing plus transmit time is held to 30 seconds or less 2. The WAS range is slightly larger than ½ the width of the surveillance area Area of circlesquare = /4 = 0.785 3. It has a 100% detection rate,100 % of the time 5-33 If a UAV loiters over a fixed point in the middle of a square surveillance area, it can meet an 80% coverage, 2 minute wide area surveillance (WAS) moving target detection requirement if It makes 2 minute turns (assuming a nominal 45 degree azimuthal field of regard or FOR) WAS ConOps Target FOR Min range effects ignored Slide37:  5-34 We have a threshold requirement for positive (visual image) target identification (ID) 80% of the time To design our baseline for the threshold requirement We have to be able to ID targets at or below 10 Kft what percentage of the time? 50% of the time we can stay at higher altitude and % of the time we won’t see a target unless we operate at even lower altitudes Positive ID ConOps Answer - at least 30% 20 Slide38:  5-35 ConOps assessment The WAS and ID mission requirements are in conflict 80% WAS coverage is required (at a minimum) Assuming a uniform distribution of targets This implies that minimum sensor range  100 nm for a single UAV WAS ConOps which drives the WAS sensor to operate at what altitude? Target ID, however, will be at 10Kft or less To meet the 80% visual ID requirement (weather) One option for reducing the mismatch is to go to a multi-UAV ConOps A four (4) UAV WAS ConOps would reduce the WAS range requirement to 50nm (at a minimum) A Sixteen (16) UAV WAS ConOps would reduce the range requirement to 25 nm h(req’d) = RmaxTan() = 100nmTan(5) = 8.75 nm = 53158 ft Slide39:  5-36 We can design one (1) air vehicle or two (2) A one air vehicle type solution will be a compromise Can’t optimize for both environments But only one development program, production line and support system will be required A two air vehicle type solution will require 2 development programs, 2 production lines and 2 support systems Cost will go through the roof We could do a trade study to determine which approach is most cost effective but historically a single, multi-capability design will be lower cost than 2 optimized single mission vehicles Therefore, we will try to find a single system design solution for both missions If that doesn’t work, we can always fall back to the other option Bottom line Slide40:  5-38 Intermission

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