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Design of UAV Systems c 2004 LM Corporation Lesson objective - to discuss Requirements analysis including … Basing Operational radius Operational endurance Maximum range Speed Turn around time plus … Example problem Requirements analysis 8-1 Design of UAV Systems

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slide1

Design of UAV Systems

c 2004 LM Corporation

  • Lesson objective - to discuss
  • Requirements analysis
    • including …
      • Basing
      • Operational radius
      • Operational endurance
      • Maximum range
      • Speed
      • Turn around time
    • plus …
      • Example problem

Requirements analysis

8-1

slide2

Design of UAV Systems

c 2004 LM Corporation

Definition

  • Requirements analysis
    • Quantitative and qualitative engineering analysis to translate overall customer goals and objectives into a traceable set of “design-to” requirements
      • Provides the design team with a consistent set of numbers they can work to
    • Basically a form of “reverse engineering”
      • Working backwards to determine what combination of concepts, design and technology best meet customer expectations?
    • Usually a cost and risk-based analysis
      • What is the highest level of system performance achievable at the lowest cost and risk?
    • Air vehicle empty weight and payload weight are often used as cost surrogates

Requirements analysis

8-2

slide3

Design of UAV Systems

c 2004 LM Corporation

UAV system design drivers

  • Most top level UAV requirements focus on target area coverage, capability and time
    • Reconnaissance capabilitiesare typically defined in terms of types or numbers of targets and sensor resolution
    • Strike capabilitiestypically are defined in terms of types, numbers and distribution of targets
  • For the UAV air vehicle element this typically translates into derived requirements on
        • Basing
        • Operational radius
        • Operational endurance
  • Maximum range
  • Speed
  • Turn around time

Requirements analysis

8-3

slide4

Design of UAV Systems

c 2004 LM Corporation

Land Based Operations

  • The typical basing mode for aircraft
  • Other basing options impose penalties
    • Weight and complexity
    • …...and/or…..
    • Operational constraints
  • Land based operations are supported by over 45,000 airports world wide
    • Although most runways are short and unpaved
  • Very short fields penalize air vehicle design
    • Sophisticated high-lift systems are heavy and complex
  • Unpaved airfieldsincrease the penalty for takeoff, landing and ground operations
    • Landing gear, wheels and brakes comprise a significant percentage of air vehicle empty weight

Requirements analysis

8-4

slide5

(Total = 45,024)

Design of UAV Systems

What runway length do you design for?

Data Source -

c 2004 LM Corporation

Worldwide airport data

Requirements analysis

8-5

slide6

Design of UAV Systems

http://www.eden.com/~tomzap/b_apt.html

c 2004 LM Corporation

Typical unpaved field

What runway type do you design for?

Requirements analysis

8-6

slide7

Design of UAV Systems

c 2004 LM Corporation

It depends on the mission

  • Example - A Korean venture capitalist sees a market for overnight aerial delivery of small, high value products between Korean and Chinese commercial and industrial airports. An automated UAV delivery vehicle could have cost benefits compared to a manned aircraft.
    • - He wants to operate out of a hub in Sachon
    • - He is familiar with the runways in Korea and is confident that they will support his delivery concept
    • - He is not familiar with the runways in China
    • - He asks for an initial study to assess UAV takeoff and landing requirements

Requirements analysis

8-7

slide8

Design of UAV Systems

c 2004 LM Corporation

Analysis approach

  • - We log on to the internet and access the “World Fact Book” at www.odci/cia/publications/factbook/indexfld.hmtl and collect runaway data for China and Korea
  • - A spreadsheet is created to correlate runway length and type vs. the number of runways per country
  • The results are plotted and compared

Requirements analysis

8-8

slide9

Airports - China

Airports - ROK

100

100

90

90

Unpaved

Unpaved

Design of UAV Systems

80

80

Paved

Paved

70

70

60

60

Number (%)

50

Number (%)

50

40

40

30

30

20

20

10

10

0

0

> 10Kft

> 8Kft

> 5Kft

> 3Kft

Total

> 10Kft

> 8Kft

> 5Kft

> 3Kft

Total

Runway Length (Kft)

Runway Length (Kft)

c 2004 LM Corporation

Airport data

Requirements analysis

8-9

slide10

Design of UAV Systems

c 2004 LM Corporation

Assessment

  • Almost all ROK and Chinese airports with runways longer than 3000 feet are paved
    • - There is no real benefit to having a capability to operate from unpaved fields
  • 85% of the airports in China are 5000 feet or longer
    • - There is no real benefit to having a capability to operate from shorter fields in China
  • But only 33% of the airports in the ROK are 5000 feet or longer
    • Is this enough or should we serve shorter ones?
      • Answer: Korea is a small country with 54 airports with runways > 5000 feet

Requirements analysis

8-10

slide11

Design of UAV Systems

c 2004 LM Corporation

Vehicle Implications

  • A subsonic (low wing loading) jet powered UAV could operate from a 5000 foot runway in either country
  • A prop powered UAV could be able to operate from a 3000 foot runway in either country
    • - 3000 feet is possible for a jet it but requires a very low wing loading or a high thrust-to-weight (or both)
        • see Raymer, Figure 5.4
  • Bottom line
  • A jet powered UAV could operate from 85% of the runways in China and 1/3 of the runways in Korea
  • A prop powered UAV could operate from >90% of the runways in China and >40% of the runways in Korea

Requirements analysis

8-11

slide12

Design of UAV Systems

c 2004 LM Corporation

Jet UAV example

  • Note that takeoff and landing requirements are based on distance over a 50 foot obstacle
  • See Raymer, 5.3 through page 103 for more information

Requirements analysis

8-12

slide13

Design of UAV Systems

c 2004 LM Corporation

Unpaved fields

  • Unpaved fields are not as bad as they may sound
    • They are designed for aircraft operations
    • Typically they are reasonably smooth
      • - They may not, however, be level
      • - Nor particularly straight
    • And they cannot be cleaned
      • - This is a problem for jet aircraft with engine inlets located near the ground
    • They also are generally unusable in wet weather
    • And aircraft with high gross weight/tire contact area ratios can sink into the ground, whether wet or dry
      • - Runways and taxi ways generally have a LCN (load contact number) rating to indicate how much load/tire contact area can be handled

Requirements analysis

8-13

slide14

Design of UAV Systems

c 2004 LM Corporation

Unprepared fields

  • Unprepared fields are different from unpaved fields
    • An unprepared field can be anything from a soccer field to a muddy pasture
      • - A requirement to operate from such fields can impose severe penalties on fixed wing aircraft
        • Low takeoff and landing speeds
        • Heavy duty landing gear
        • High flotation tires, etc.
    • The requirement can be met with a fixed wing aircraft but the result is usually a slow vehicle with a low wing loading (like a Piper Super Cub) or a faster vehicle with powered lift (e.g. Short Take Off Vertical Landing)
      • - According to Raymer, STOVL weight penalties are 10-20% for fighters and 30-60% for transports
    • Rotary wing aircraft are often a better option for operations from unprepared fields

Requirements analysis

8-14

slide15

Design of UAV Systems

c 2004 LM Corporation

Operations at sea

  • Operating an air vehicle from a ship is complicated
    • Manned fighters and fighter bombers have been operating from aircraft carriers for years
      • - But deck and air operations are complex
        • Very high level of pilot proficiency required
        • Crowded deck space
        • High potential for accidents and injuries
    • Helicopters also have been operating from smaller ships for years. Operations are less complicated but still demanding
      • - STOVL aircraft can also operate from smaller ships
      • - Fixed wing UAVs have operated from smaller ships with mixed success
    • Cruise missiles have operated from smaller ships and submarines but they do not recover back to the ship
      • - UAV/UCAV operations from subs are being studied

Requirements analysis

8-15

slide16

Design of UAV Systems

c 2004 LM Corporation

Benefits

  • Ship based air operations
    • 70% of the surface of the earth is covered with water
    • Operating from ships frees operators from requirements to build or establish land bases
    • Well equipped ships have housing and provisions for crew members and facilities and spare parts for maintenance and overhaul
    • Global mobility is enhanced

But the cost is high and the ships involved are large and complex

Requirements analysis

8-16

slide17

Helicopters

8 SH-3 Sea King or..

8 SH-60 Seahawk

Fixed Wing Aircraft

14 F-14 Tomcat 4 EA-6 Prowler

36 F/A-18 Hornet 4 E-2 Hawkeye

6 S-3 Viking

CVN-68

Nimitz-class

Crew

5680

Design of UAV Systems

252 ft (77 m)

1092 ft (333 m)

http://www.fas.org/man/dod-101/sys/ship/cvn-68.htm

Aircraft designed for carrier operations typically pay a 10-15% weight penalty

c 2004 LM Corporation

Aircraft Carriers

Requirements analysis

8-17

slide18

Helicopters

Up to 42 CH-46

Sea Knight

Crew

1100 Sailors

1900 Marines

LHD-1

Wasp-class

Fixed Wing Aircraft

Up to 20 AV-8B Harriers

Design of UAV Systems

200 ft

(61m)

252 ft (77 m)

http://www.fas.org/man/dod-101/sys/ship/cvn-68.htm

  • Only Short Takeoff Vertical Landing (STOVL) aircraft and helicopters currently operate from assault ships
    • - A fixed wing UAV designed to operate from this class ship would probably use powered lift (10-20% weight penalty)

844 ft (253 m)

c 2004 LM Corporation

Assault Ships

Requirements analysis

8-18

slide19

Design of UAV Systems

http://sun00781.dn.net/man/dod-101/sys/ship/LHD12.JPG

Decks are crowded and space is limited

c 2004 LM Corporation

Typical assault ship

Requirements analysis

8-19

slide20

Other surface ships

  • Fixed wing aircraft have been launched from other types of ships
    • - Handling is complex and this is not widely used

Design of UAV Systems

www.wa3key.com/growler.html

http://www.fas.org/irp/program/collect/pioneer.htm

Regulus - 1950s

Pioneer - 1990s

c 2004 LM Corporation

Requirements analysis

8-20

slide21

The big problem is landing

    • - Current interest focuses on rotary wing UAVs but other concepts are being studied

Design of UAV Systems

http://www.fas.org/irp/program/collect/pioneer.htm

US Navy VTUAV

Replaces Pioneer

http://www.lmaeronautics.com/image_gallery/index.html

http://www.fas.org/irp/program/sources.htm

c 2004 LM Corporation

UAV ship operations

Requirements analysis

8-21

slide22

Design of UAV Systems

www.wa3key.com/growler.html

  • Cruise missiles have been launched from the decks of submarines
    • - Current concepts are torpedo tube launched

http://www.fas.org/man/dod-101/sys/smart/bgm-109.htm

c 2004 LM Corporation

Submarines

Requirements analysis

8-22

slide23

Design of UAV Systems

http://www.fas.org/irp/agency/daro/uav96/page32.html

http://www.lmaeronautics.com/image_gallery/index.html

Launching UAVs from subs is being studied

- Size and weight penalties are significant

Operating UAVs from subs has been demonstrated

c 2004 LM Corporation

UAV operations

Requirements analysis

8-23

slide24

Design of UAV Systems

c 2004 LM Corporation

Air launch

  • Launching UAVs from aircraft is straight forward
  • The UAV benefits are reduced size and weight
      • Carrier aircraft adds to operational range
      • Engine can be sized for cruise
      • Landing gear can be sized for landing weight
  • But there are limitations on size and weight
      • Under wing mounted (NB-52 with X-15A-2)
        • - Length = 52.5 ft, span = 22.5 ft, height = 14 ft
        • - Weight = 56.1 Klb
      • Upper fuselage mounted (B747 with Shuttle)
        • - Length = 122 ft, span = 57 ft, height = 57 ft
        • - Weight = 180 Klb
      • Under fuselage mounted (L1011 with Pegasus)
        • - Length = 55 ft, span = 22 ft, diam. = 4.2 ft
        • - Weight = 51 Klb

Requirements analysis

8-24

slide25

http://www.dfrc.nasa.gov/gallery/photo/index.html

Design of UAV Systems

Under wing carriage of large vehicles requires something like a B-52

http://www.dfrc.nasa.gov/gallery/photo/index.html

Upper fuselage loading and unloading is very complex

Unless your customer has such resources, carriage will be constrained to smaller aircraft

c 2004 LM Corporation

Practical constraints

Requirements analysis

8-25

slide26

Design of UAV Systems

http://www.spectrumwd.com/c130/dc130p1.htm

http://209.207.236.112/irp/program/collect/aqm-34n.htm

Orbital Sciences Pegasus

Span: 22 ft. Diameter: 4.2 ft.

Length: 55 ft. Weight: 51 Klb

Ryan AQM-34N

Span: 32 ft. Weight: 3,830 lbs.

Length: 30 ft. Speed: 420 mph

Height: 6.75 ft. Range: > 2000 NM

c 2004 LM Corporation

More reasonable sizes

Requirements analysis

8-26

slide27

Design of UAV Systems

c 2004 LM Corporation

Aerial recovery

  • AQM-34 reconnaissance drones were recovered in mid air during the Vietnam war
  • 65% of the drones were successfully recovered, many using a Mid Air Retrieval System (MARS) equipped helicopter which performed an aerial “snatch”
  • Despite past success, aerial recovery is complex and dangerous (for the helicopter)
  • I can find no pictures of the recovery system but take my word for it, aerial recovery of UAVs is very difficult

Requirements analysis

8-27

slide28

Design of UAV Systems

c 2004 LM Corporation

Next subject(s)

  • Lesson objective - to discuss
  • Requirements analysis
    • including …
      • Basing
      • Operational radius
      • Operational endurance
      • Maximum range
      • Speed
      • Turn around time

Requirements analysis

8-28

slide29

Design of UAV Systems

c 2004 LM Corporation

Operational radius and endurance

  • Why are they important?
  • Operating radius defines how far the UAV operates from base
    • - Typically sizes the system architecture (comms, etc.)
  • Endurance (time on station) and operating radius typically size the air vehicle
  • Example - Global Hawk (RQ-4A) early program goals

Requirements analysis

8-29

slide30

Design of UAV Systems

c 2004 LM Corporation

RQ-4A question

Where did 24 hours and 3000 nm come from?

  • They were driven by customer and crew considerations
    • - UAV products are generally needed around the clock (24 hours a day, 7 days a week)
    • - Air operations are planned in 24 hour cycles
    • - Crews operate on 8 or 12 hour cycles*
  • Original Global Hawk endurance would allow 2 air vehicles to provide 24/7 coverage at 3200 nm with fixed takeoff and recovery times.
  • 3200 nm would allow operations from secure bases far from a combat zone (Diego Garcia - Kuwait = 2640 nm)

* Civilian air crews operate on 8 to 14 hour cycles

Requirements analysis

8-30

slide31

Design of UAV Systems

c 2004 LM Corporation

Expanded explanation

  • Preflight checks and maintenance
    • - Nominal 1.5 hours (est.)
  • Time to taxi and takeoff
    • - 30 minutes (from NGC)
  • Time to climb
    • - 200 nm @ 225 kts (135 KEAS* average) = 1 hr
  • Time enroute
    • - 3000nm/350 kts = 8.6 hrs
  • Time on station
    • - 24 hours for single vehicle coverage
  • Enroute return = 8.6 hrs
  • Time to descend
    • - Nominal 1 hour (est.)
  • Landing loiter time
    • - 1 hour (from NGC)
  • Time to land and taxi
    • - Estimate 15 minutes
  • Post flight checks - Nominal 1.5 hours (est.)

Single vehicle nominal flight + ground time = 48 hours; i.e. one vehicle can launch every 24 hours

* See Chapter 17 for definition

Requirements analysis

8-31

slide32

Design of UAV Systems

c 2004 LM Corporation

Maximum range

  • Why is it important?
    • Defines how far the UAV can deploy from base
    • Establishes the support assets required to support deployment
  • Global Hawk 12500-13500 nm range permits self deployment anywhere in the world without aerial refueling

Requirements analysis

8-32

slide33

Design of UAV Systems

LOS

h

c 2004 LM Corporation

Range and endurance impact

  • Range and endurance drive system size, complexity and cost
    • Range - Communication architecture goes from simple to complicated when range exceeds line of sight (LOS)
      • LOS (nm) ≈ 0.87sqrt [2h(ft)] (see Chapter 9) 
        • LOS @ 10Kft = 123 nm
        • LOS @ 65Kft = 315 nm
        • - Beyond line of sight (BLOS) coverage requires comm relay (surface or airborne) or satellite*
    • Endurance (time on station) - 12 hour endurance (at 3200 nm) Global Hawk type air vehicle would be about 60% the empty weight at the same payload
      • - Range and endurance would also drop by 40%**
      • - Number of air vehicles for 24/7 would increase 50%h

Examples

* More about this in Chapter 9 (week 14) ** Explanation to come - Chapter 24

Requirements analysis

8-33

slide34

Design of UAV Systems

c 2004 LM Corporation

Fleet size

  • Number of air vehicles required driven by:
    • Time on station, operating radius and cruise speed, turn around and other times. Global Hawk example:
      • - Total ground time = 3.75 hrs, time to climb/descend/land = 3 hrs, time enroute = 2*[op’n radius]/speed =17.5 hrs
  • If time on station=24 hrs, 2 vehicles req’d, one launch every 24 hours
  • If time on station=12 hrs, 3 vehicles req’d, one launch every 12 hours
  • If time on station = 6 hrs, 5 vehicles req’d, one launch every 6 hours

24 hour coverage

Requirements analysis

8-34

slide35

If time on station = 2 hrs, 13 vehicles req’d, one launch every 2 hours

24 hour coverage

Design of UAV Systems

* Air vehicle cost excludes payload (which should be included) - more about this later

c 2004 LM Corporation

Time on station – cont’d

Notional example

Requirements analysis

8-35

slide36

Range analysis

  • Straight forward assessment of required or desired target area (commercial or military) coverage
    • Commercial and military considerations functionally similar
  • Military assessments driven by targets and “threat lay down”
    • Drive routing considerations (which impacts range req’d)
  • Commercial assessments driven by target markets and routing
  • Common considerations
    • Launch base(s)
    • Target(s)
    • Recovery base(s)
    • Deviations from most efficient routes (great circle)
  • Both types require geographic area analysis
    • Typically a problem for individual students

Design of UAV Systems

c 2004 LM Corporation

Requirements analysis

8-36

slide37

Geographic area analysis

  • Efficient assessment of geographic area coverage requires digital mapping software and data bases that are not typically available to students.
    • Example - A UAV operating out of Korea has an operating mission radius of 1200 nm
    • - How much of the Chinese land mass could it survey?
    • - How would coverage compare to a UAV with a 600nm operating radius?
    • - Assume that you do not have time to grid a map and manually count squares

Design of UAV Systems

c 2004 LM Corporation

Requirements analysis

8-37

slide38

Design of UAV Systems

600 nm

1200 nm

c 2004 LM Corporation

Geographic area coverage?

Requirements analysis

8-38

slide39

Simple solution

Internet databases are available on airports (numbers, types, and locations). You can use airports as surrogates for geographic area.

  • Example - A Korean venture capitalist sees a market for overnight aerial delivery of small, high value products between Korea and Chinese commercial and industrial airports. He believes an automated UAV delivery vehicle could have cost benefits compared to a manned aircraft.
    • - He wants to operate out of a hub in Sachon
    • - How would we do a requirements study to determine what UAV operating ranges, types and speeds would be required?

Design of UAV Systems

c 2004 LM Corporation

Requirements analysis

8-39

slide40

Design of UAV Systems

c 2004 LM Corporation

Analysis approach

  • We randomly select 25 Chinese ICAO airports with long runways
    • ICAO designations indicate the airports are used for commercial operations
    • Long runways identify major airports with significant airline operations
  • We log onto Worldwide Airport Path Finder and start to develop a database.

Requirements analysis

8-40

slide41

Unfortunately fallingrain.com

no longer maintains this site

Design of UAV Systems

c 2004 LM Corporation

Example

  • This is the output from WAPF at http://www2.fallingrain.com.air/
  • WAPF has a database of all known airports and allows a user to plan a flight between any airports with ICAO designators. This example is a 52 nm flight from Sachon (RKPS) to Pusan (RKPP).
  • A data set is created by calculating the distances between Sachon and each of the 25 Chinese airports
    • The data set is listed in order of distance, from shortest to longest and plotted

Requirements analysis

8-41

slide42

ICAO ID

Distance(nm)

zsqd

381.00

zytl

390.00

zsss

411.00

zshc

488.00

zsnj

499.00

zycc

545.00

zbtj

567.00

zsof

574.00

Design of UAV Systems

zsfz

700.00

zhcc

701.00

zhhh

743.00

zbyn

762.00

zsam

817.00

zbhh

841.00

zgha

863.00

zggg

1052.00

zgkl

1104.00

zuck

1130.00

zppp

1142.00

zuuu

1243.00

zgnn

1281.00

zghk

1302.00

zwww

1931.00

zwtn

2315.00

zwsh

2463.00

c 2004 LM Corporation

The data set

Requirements analysis

8-42

slide43

Design of UAV Systems

c 2004 LM Corporation

The plot

A UAV with an operating radius an 1300 nm can cover 90% of the airports studied. The radius has to double to cover the remaining 10%. Is this the result of the small data base used or does it indicates that a study is needed to determine if covering the last 10% is cost effective?

Requirements analysis

8-43

slide44

Does this help you answer?

Design of UAV Systems

c 2004 LM Corporation

  • China is a big country
    • Not many people live in the western half

Requirements analysis

8-44

slide45

Why is it important?

  • It has a major impact on the cost and complexity of the air vehicle - Speed costs!

Design of UAV Systems

Jet

Turboprop

Piston Engine

Data source - http://cessna.com/aircraft/

c 2004 LM Corporation

Speed

Requirements analysis

8-45

slide46

Design of UAV Systems

c 2004 LM Corporation

Block time

  • Why it is important?
  • It is what an aircraft gets paid for
    • Passenger or freight customers pay by the trip
    • Once an aircraft is loaded with freight or passengers, it doesn’t earn any more money until it is loaded again
  • But from a revenue standpoint, if an aircraft has to sit on the ground for long periods of time between flights, it almost doesn’t matter if it flies fast or slow.
    • Time on the ground (ground turn around time) is a key mission consideration

Block time = Mission distance/block speed

Requirements analysis

8-46

slide47

Block speed

  • What is it ?
    • The average speed for an entire mission including takeoff, climb, cruise, descent and landing
  • Why it is important?
    • It is the only speed that matters from a revenue stand point

Design of UAV Systems

c 2004 LM Corporation

Requirements analysis

8-47

slide48

ICAO ID

Distance(nm)

zsqd

381.00

zytl

390.00

zsss

411.00

zshc

488.00

zsnj

499.00

zycc

545.00

zbtj

567.00

zsof

574.00

Design of UAV Systems

zsfz

700.00

zhcc

701.00

zhhh

743.00

zbyn

762.00

zsam

817.00

zbhh

841.00

zgha

863.00

zggg

1052.00

zgkl

1104.00

zuck

1130.00

zppp

1142.00

zuuu

1243.00

zgnn

1281.00

zghk

1302.00

zwww

1931.00

zwtn

2315.00

zwsh

2463.00

c 2004 LM Corporation

Sortie length analysis

  • Sortie length
    • = time to service, taxi, load & unload + distance/(block speed)
  • Assumptions
    • - 1 hour to load and takeoff
    • - 1 hour to land and unload
    • - 40 knot headwind
  • Block speeds
    • 60,120 kts (piston engine)
    • 240 kts (turboprop)
    • 480 kts (subsonic jet)
    • 960 kts (supersonic jet)

Min. coverage

50% coverage

90% coverage

Requirements analysis

8-48

slide49

Design of UAV Systems

c 2004 LM Corporation

Analysis results

  • 60 & 120 kt UAVs cannot provide overnight service
  • A 240 kt UAV can make one (1) flight per night (90% coverage)
  • A 480 kt UAV can fly two (2) 90% coverage missions (one round trip) per night
    • Or 1 max. distance mission
  • A 960 kt UAV can fly 3 times per night (90% coverage)

Total time (hr)

Block speed (kts)

Questions

- Which speed is most cost effective?

- What are the sensitivities of the results to the assumption of a 2 hour turn-around time (international flight)?

Requirements analysis

8-49

slide50

Design of UAV Systems

c 2004 LM Corporation

Cost effectiveness

  • Best option = 240 kts
  • Lowest cost to meet requirements
  • Relative cost (assumption)
    • - 60 kt UAV = 1.00
    • - 120 kt UAV = 2.00
    • - 240 kt UAV = 4.00
    • - 480 kt UAV = 8.00
    • - 960 kt UAV = 16.00
  • Relative income
    • = 12hrsBlock time

Requirements analysis

8-50

slide51

China - 2 hour turnaround

China - 4 hour turnaround

Total time (hr)

Total time (hr)

Design of UAV Systems

Block speed (kts)

Block speed (kts)

c 2004 LM Corporation

Turn around time

  • A 240 kt UAV still provides 90% overnight coverage with 4 hours on the ground
  • With 4 hours on the ground, a 480 kt UAV can now make only one overnight flight with 90% coverage
  • A 960 kt UAV can make 2 flights per night (one round trip) with 2 hour turn around or 1 flight if ground time is 4 hours.

Requirements analysis

8-51

slide52

Design of UAV Systems

c 2004 LM Corporation

Expectations

  • You should now understand
    • How simple analysis can provide insight into basic customer requirements
        • Basing
        • Time
        • - Distance
    • How to develop airport and runway requirements to include length and type
    • The design implications of operating from unpaved fields, ships and air launch
    • That requirements analysis is iterative
      • - Many analyses raise as many questions as they answer
      • - It is important to explore these issues and to study sensitivities, especially to assumptions

- Area coverage

- Speed

- Turn around time

Requirements analysis

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slide53

Design of UAV Systems

c 2004 LM Corporation

Next subject

  • Lesson objective - to discuss
  • Requirements analysis
    • including …
      • Basing
      • Operational radius
      • Operational endurance
      • Maximum range
      • Speed
      • Turn around time
    • plus …
      • Example problem

Requirements analysis

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slide54

Design of UAV Systems

c 2004 LM Corporation

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

Requirements analysis

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slide55

200 nm

Surveillance area

Design of UAV Systems

200 nm

Loiter location(s)?

100 nm

c 2004 LM Corporation

Review cont’d

Requirements analysis

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slide56

Design of UAV Systems

c 2004 LM Corporation

Review - Customer asking for?

  • A system that can monitor a large area of interest
    • Conduct wide area search (WAS) for 10 sqm ground moving targets (GMT), 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?
    • 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”?

Requirements analysis

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slide57

Design of UAV Systems

c 2004 LM Corporation

Other inputs - review

  • Customer guidance
    • 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%”

Requirements analysis

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slide58

Design of UAV Systems

c 2004 LM Corporation

Our first decision

  • Will we give the customer a threshold capability or will we give them what we think they need?
    • The answer will drive system cost and risk
      • We bring our team together to discuss and decide
  • We decide to design our initial baseline for a threshold capability except we will provide a simultaneous wide area search and target identification capability
    • Our decision is based on subjective analysis
      • If the system gets one target identification request per hour, it will spend all of its time doing target identification
      • There will be no time left for wide area search
  • We can do trade studies to evaluate other options
    • i.e. goal performance capability, etc.
  • And we need to select a starting concept and document our decisions as “derived requirements”

Requirements analysis

8-58

slide59

Maximum WAS range = 202 nm (374 km); h > 100 Kft

Design of UAV Systems

Target 1 location

141 nm in 30 min. = 282 kts

to 512 kts

Loiter location

282 nm in 30 min.

= 564 kts

100 nm

Target 2 location

200 nm x 200 nm

Why 53.7 Kft ?

c 2004 LM Corporation

Candidate system solutions

  • One large UAV with long range WAS sensor
    • Minimum WAS range required for 80% target area coverage = 101nm (187km); h = 53.7 Kft
  • Communications ranges potentially very long
    • Up to 316 nm (h > 65 Kft)
  • Lots of climbs and descents
  • And high speed required
    • From 262 kts

Note – required distance calculations assume no ID sensor range extension

316 nm

Requirements analysis

8-59

slide60

Design of UAV Systems

Target 1 location

141 nm in 30 min. = 282 kts

c 2004 LM Corporation

Another approach

  • Two large UAVs, one provides wide area search, the other provides positive target identification
    • WAS range (80% coverage) = 101nm ; h = 53.7 Kft
  • One would need very long range communications
    • Unless the other also served as a communication relay
      • Comm. distance reduces to
      • 200 nm
  • Speed requirements could be
  • reduced if UAVs cooperate &
  • switch roles
    • ConOps complexity
  • And frequent climbs
  • and descents required
  • And UAVs have to operate
  • efficiently at both altitudes
    • - Although not impossible

WAS loiter location

200 nm

Target 2 location

200 nm x 200 nm

Requirements analysis

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slide61

Design of UAV Systems

158 nm

100 nm

200 nm x 200 nm

c 2004 LM Corporation

Third approach

  • Five medium size UAVs, four perform wide area search and ID, a fifth on stays on CAP as gap filler
    • WAS range (80% coverage) = 51nm (95km); h = 27 Kft
  • Communications relay distance reduced
    • To 158 nm
  • Speed requirement can be reduced to 141 kts if UAVs cooperate and switch
  • roles
    • Otherwise 282 kt speed
    • required
  • Climb and descent reqmn’ts
  • reduced
    • WAS and ID
    • altitudes closer
  • Air vehicle altitude
  • optimization a little
  • easier

Why?

10 Kft

27 Kft

27 Kft

Requirements analysis

8-61

slide62

Design of UAV Systems

127 nm

100 nm

200 nm x 200 nm

c 2004 LM Corporation

Yet another approach

  • Twenty small UAVs, sixteen provide wide area search, four provide positive target identification
    • WAS range (80% coverage) = 26nm (48km); h = 14 Kft
  • Communications relay distance reduced
    • To 127 nm
  • Speed requirement can be reduced to 70 kts if UAVs cooperate and switch roles
    • Otherwise 141 kt speed
    • required
  • Climb and descent reqmn’ts
  • eliminated
    • WAS and ID
    • altitudes similar
  • Air vehicle design
  • optimization easy
    • Use Predator
  • But large numbers required

Requirements analysis

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slide63

Five medium UAVs, four provide wide area search, a fifth provides positive target identification

    • WAS range required (95km) not a challenge
  • But only one UAV responds to target ID requests
    • No need to switch roles, simplifies ConOps
    • No need for frequent climbs and descents

Design of UAV Systems

27 Kft

27 Kft

10 Kft

  • Speed requirement = 282 kts
  • Air vehicle operating altitude differences reasonable
  • We can study the
  • other options as trades

27 Kft

27 Kft

158 nm

100 nm

200 nm x 200 nm

c 2004 LM Corporation

Our starting approach

  • WAS UAV(s) serve as Comm
  • relays

Requirements analysis

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slide64

Design of UAV Systems

Atmospheric conditions (customer defined)

Cloud ceiling/visibility

Clear day, unrestricted

10Kft ceiling, 10 nm

5Kft ceiling, 5 nm

1Kft ceiling, 1nm

  • Percent occurrence
  • 50%
  • 30%
  • 15%
  • 05%

c 2004 LM Corporation

Requirement summary

  • It is important to maintain an up to date list of requirements as they are defined or developed
  • Defined requirements (from the customer)
    • Continuous day/night/all weather surveillance of 200nm x 200nm operations area 100 nm from base
    • Detect 10 sqm moving targets (goal = 100%, threshold = 80%), transmit 10m resolution GMTI data in 2 min.
    • Provide 0.5 m resolution visual ID of 1 target per hour in 15 min (goal = 100%, threshold = 80%)
    • Operate from base with 3000ft paved runway

Requirements analysis

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slide65

Design of UAV Systems

c 2004 LM Corporation

Derived requirements

  • Derived requirements (from our assumptions or studies)
  • System element
    • Maintain continuous WAS/GMTI coverage at all times
    • Assume uniform area distribution of targets
    • Communications LOS range to airborne relay = 158 nm
    • LOS range from relay to surveillance UAV = 212 nm
  • Air vehicle element
    • Day/night/all weather operations, 100% availability
    • Takeoff and land from 3000 ft paved runway
    • Cruise/loiter altitudes = 10 – 27Kft
    • Loiter location = 158 nm (min) – 255 nm (max)
    • Loiter pattern – 2 minute turn
    • Dash performance =141 nm @ 282 kts @10 Kft
    • Payload weight and volume = TBD
    • Payload power required = TBD

Requirements analysis

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slide66

Design of UAV Systems

c 2004 LM Corporation

Derived requirements

  • Payload element
    • Installed weight/volume/power = TBD
    • WAS
      • Range/FOR /resolution/target speed = 95 km/45/10m/2mps
      • Uninstalled weight/volume/power = TBD
    • ID
      • Type/range/resolution = TBD/TBD/0.5m
      • Uninstalled weight/volume/power = TBD
    • Communications
      • Range/type = 212nm/air vehicle and payload C2I
        • Uninstalled weight/volume/power = TBD
      • Range/type = 158nm/communication relay
        • Uninstalled weight/volume/power = TBD
  • Control Station element
    • TBD
  • Support element and sortie rates
    • To be determined

C2I = Command Control and Intelligence

Requirements analysis

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slide67

Design of UAV Systems

c 2004 LM Corporation

Individual homework – due Thurs.

  • Do a first-order requirements analysis of team UAV system requirements and propose an initial system concept
    • How many vehicles are required? Explain why
    • What speeds and altitudes are required?

- Document the calculations that support your conclusions.

    • Develop an initial ConOps and list of defined and derived requirements

- Use the example problem as a guide

(4) Submit to your project team for consideration and turn in as homework assignment

  • Submit via Email by COB next Thursday

Requirements analysis

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slide68

Design of UAV Systems

c 2004 LM Corporation

MIETG requirements*

  • Minimum header information
    • Design project name
    • Student or team name
    • Homework lesson number
    • Homework problem number
  • Submit electronically by due date/time
  • Bring paper copy to class

* Make It Easy To Grade ….or….. how to get your homework graded

Requirements analysis

8-67a

slide69

Design of UAV Systems

c 2004 LM Corporation

Team assignment – During class

  • Select a team starting baseline system concept
    • Evaluate team inputs (from homework)
    • Discuss options
    • Assess pros and cons
    • Agree on one starting baseline ConOps
    • Develop an initial list of defined and derived requirements

- Use the example problem as a guide

(4) Present your project team decision and turn in as team homework

- Email submittal by COB Monday

Requirements analysis

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slide70

Design of UAV Systems

c 2004 LM Corporation

Recommended reading/review

  • Raymer - Aircraft Design - A Conceptual Approach
    • Chapter 3 : Sizing from a Conceptual Sketch
      • 3.1 - Introduction
      • 3.2 - Takeoff Weight Buildup
      • 3.3 - Empty Weight Estimation
      • 3.4 - Fuel Fraction Estimation
      • 3.5 - Takeoff Weight Calculation
    • Chapter 12 : Aerodynamics
      • 12.1 – Introduction
      • 12.3 – Aerodynamic Coefficients (subsonic only)
      • 12.4 – Lift (subsonic only)
      • 12.5 – Parasite (Zero-Lift) Drag (subsonic only)
      • 12.6 – Drag Due to Lift (subsonic only)

Requirements analysis

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slide71

Design of UAV Systems

c 2004 LM Corporation

Intermission

Requirements analysis

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