They are designed like air vehicles. They have to meet flight critical air vehicle requirements. You need to know how to integrate complex, multi-disciplinary systems. You need to understand the environment, the requirements and the design challenges.
A UAV system is much more than a reusable air vehicle or vehicles. The UAV system includes five basic elements: (1) the Environment in which the UAV(s) or the Systems Element operates (e.g., the airspace, the data links, relay UAV, etc.); (2) the air vehicle(s) or the Air Vehicle Element; (3) the control station(s) or the Mission Control Element; (4) the payload(s) or the Payload Element; and (5) the maintenance and support system or the Support Element.
The design of manned UAV and the design of UAVs have some similarities; and some differences such as: design process; constraints (e.g., g-load, pressurization); and UAV main components (autopilot, ground station, communication system, sensors, payload). A UAV designer must be aware of the: (1) latest UAV developments; (2) current technologies; and (3) known lessons learned from past failures. Designers should appreciate breadth of UAV design options.
UAV are not new, they have a long history in aviation. Their history stretches back to the First World War (1920s), Cold War, Korean War, Vietnam War (RPV), Yugoslavia, Afghanistan, First and Second Persian Gulf war, and other wars (e.g., Pakistan, Yemen, Syria, and Africa). At least 20 countries are using or developing over 76 different types of UAVs. The contributions of unmanned UAV in sorties, hours, and expanded roles continue to increase. As of September 2004, some 20 types of coalition UAVs, large and small, have flown over 100,000 total flight hours in support of Operation Enduring Freedom and Operation Iraqi Freedom. Their once reconnaissance-only role is now shared with strike, force protection, and signals collection.
In this chapter, definitions, design process, UAV classifications, current UAVs, and challenges will be covered. In addition, conceptual design, preliminary design, and detail design of a UAV based on systems engineering approach are introduced. In each stage, application of this approach is described by presenting the design flow chart and practical steps of design.
1.2 UAV CLASSIFICATIONS
It is a must for a UAV designer to be aware of classifications of UAVs which is based on various parameters such as cost, size, weight, mission, and the user. For instance, UAV ranges in weight from Micro Air Vehicles (MAV) weighing less than 1 pound to UAV weighing over 40,000 lb. Moreover, these diverse systems range in cost from a few hundred dollars (Amazon sells varieties) to tens of millions of dollars (e.g., Global Hawk). In addition, UAV missions ranges from reconnaissance, combat, target acquisition, electronic warfare, surveillance, special purpose UAV, target and decoy, relay, logistics, research and development, and civil and commercial UAVs, to environmental application (e.g., University of Kansas North Pole UAV for measuring ice thickness).
The early classification includes target drones and remotely piloted vehicles (RPVs). The current classification ranges from Micro UAVs (less than 15 cm long, or 1 lb); to High-altitude Long Endurance (HALE); to tactical and combat UAVs. In this section, characteristics of various classifications are briefly presented.
The Micro Unmanned Aerial Vehicles (MAV) was originally a DARPA program to explore the military relevance of Micro Air Vehicles for future military operations, and to develop and demonstrate flight enabling technologies for very small UAV (less than 15 cm/6 in. in any dimension). The Tactical UAV (e.g., Outrider) is designed to support tactical commanders with near-realtime imagery intelligence at ranges up to 200 km. The Joint Tactical UAV (Hunter) was developed to provide ground and maritime forces with near-real-time imagery intelligence at ranges up to 200 km. The Medium Altitude Endurance UAV (Predator) provides imagery intelligence to satisfy Joint Task Force and Theater Commanders at ranges out to 500 nautical miles. The High Altitude Endurance UAV (Global Hawk) is intended for missions requiring long-range deployment and wide-area surveillance or long sensor dwell over the target area. Table 1.1 shows the UAV classifications from a few aspects including size, mass, and mission. The MLB Bat 4, a mini-UAV (Figure 2.7) with a length of 2.4 m, a wingspan of 3.9 m, and a maximum takeoff mass of 45 kg has a maximum cruising speed [54] of 120 knot.
In the U.S. military, the classification is mainly based on a tier system. For instance, in the U.S. Air Force the Tier I is for low altitude, long endurance missions, while Tier II is for medium altitude; long endurance (MALE) missions (e.g., Predator). Moreover, Tier II+ is for high-altitude, long-endurance (HALE) missions and Tier III- denotes HALE low observable. For other military forces, the following is the classification. Marine Corp: Tier I: Mini UAV; (e.g., Wasp, and MLB Bat); Tier II: (e.g., Pioneer); and Tier III: Medium range, (e.g., Shadow). Army: Tier I: Small UAV, (e.g., Raven); Tier II: Short range, tactical UAV, (e.g., Shadow 200); and Tier III: Medium range, tactical UAV.
Table 1.1: UAV classification
Another basis for UAVs classifications in military is echelon: Class 1 supports platoon echelon, (e.g., Raven), micro air vehicle (MAV), and small UAV; Class 2 supports company echelon, (e.g., Interim Class 1 and 2 UAV); Class 3 supports battalion echelon, (e.g., Shadow 200 Tactical UAV); and Class 4 supports unit of action (brigade), (e.g., Hunter), Extended Range/Multipurpose (ER/MP) UAV.
Some current U.S. UAVs [46] are listed here: (1) Army UAV Systems: RQ-1L I-GNAT Organization; RQ-5/MQ-5 Hunter Aerial Reconnaissance Company; RQ-7 Shadow Aerial Reconnaissance Platoon; RQ-11 Raven Team. (2) Air Force UAV Systems: RQ-4 Global Hawk; RQ/MQ-1 Predator; MQ-9 Predator B; Force Protection Aerial Surveillance System, Desert Hawk (Figure 8.3). (3) Navy UAV Systems: RQ-2 Pioneer; RQ-8B Fire Scout. (4) Marine Corps UAV Systems: FQM-151 Pointer; Dragon Eye; Silver Fox; Scan Eagle. (5) Coast Guard UAV Systems: Eagle Eye. (6) Special Operations Command UAV Systems: CQ-10 SnowGoose; FQM-151 Pointer; RQ-11 Raven; Dragon Eye.
It will be very helpful to know the features of some old and current UAVs. Hunter (RQ-5): Range: 125 km; Max speed: 110 knots; Dimensions: length: 22.6 ft; span: 29.2 ft; Endurance: 10 hr; Weights: Max Takeoff: 1600 lb; Ceiling: 16,000 ft. Hunter, was cancelled in January 1996 after some 20 air vehicle crashes. Pioneer RQ-2A: First flight: 1985; Dimensions: length: 14 ft span: 16.9 ft; Max. TO Weight: 450 lb; Speeds: cruise: 65 knots; dash: 110 knots; it was used extensively in Falujeh, Iraq, 2006. During Operations Desert Shield, the U.S. deployed 43 Pioneers that flew 330 sorties, completing over 1,000 flight hours. In 10 years, Pioneer system has flown nearly 14,000 flight hours. Since 1994, it has flown over Bosnia, Haiti, and Somalia.
Outrider: First flight: 2,000; Range: 200 km; Wing span: 11.1 ft; MTOW: 385 lb; Ceiling: 15,000 ft; Max speed: 110 knot; Endurance: 7.2 hr. Predator RQ-1A (Figure 5.4): First flight: 1994; Endurance: 25 hr; Ceiling: 26,000; Payload: 450 lb; Cruise Speed: 90 knots; MTOW: 2100 lb; Wing span: 48.4 ft. Extensively employed in Iraq, Afghanistan, Pakistan, … Predator RQ-1B (Figure 4.10): Honeywell TPE-331-10T, flat-rated to 750 shp; 4,500 kg take-off gross weight; Max speed/altitude: 210 knot/50Kft; - 20 m wingspan; Triplex systems; 1,360 kg fuel; 340 kg internal payload; 1360 kg external payload; 6 store stations/14 Hellfire missiles.
Figure 1.1: Northrop Grumman RQ-4 Global Hawk.
• Global Hawk RQ-4 (Figure 1.1): First flight was in 1998; Endurance: 41 hr; Ceiling: 65,000; Payload: 2,000 lb; Ranges: 14,000 nm; Cruise Speed: 345 knots; MTOW: 25,500 lb; Wing span: 116 ft. The Defense Advanced Research Projects Agency (DARPA) developed Global Hawk to provide military field commanders with a high-altitude, long-endurance system that can obtain high-resolution, near-real-time imagery of large geographic areas. Flew for the first time at Edwards Air Force
