Catapult Launcher for UAV by Nainesh

Part 2 Design case study Catapult launcher for Unmanned Air Vehicles (UAV) SESM2005: Engineering Design and Structural Analysis Methods Group 8 Nainesh Bumb; Xenofon Kalogeropoulos; Alex Kelday; Leong Wai Hou; Lin Xiao; Halil Portakalcioglu; James Tagg; Bugra Tarazi 16/05/2012

The following report follows the design process of a UAV launcher specifically from conception to final design. The design process includes identifying the customer requirements, researching existing designs and constraint & cost analysis. Finally a des

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Table of Contents Abstract ..................................................................................................................................................................... 3 Introduction ............................................................................................................................................................ 3 2.1 Overall Perspective ................................................................................................................................. 3 2.2 Literature Review .................................................................................................................................... 4 2.3 Critical Review of design alternatives ............................................................................................ 7 Engineering Calculations .................................................................................................................................. 9 3.1 Basic Calculations .................................................................................................................................... 9 3.11 Stiffness research .......................................................................................................................... 11 3.12 Winch requirements .................................................................................................................... 13 Engineering Design methods ....................................................................................................................... 14 4.1 Customer requirements .......................................................................................................................... 14 4.2 Design Concept Generation ................................................................................................................... 18 4.3 Design Concept Selection ....................................................................................................................... 27 4.31 The Launching system: ............................................................................................................... 27 4.32 The cradle: ........................................................................................................................................ 30 4.33 The support:..................................................................................................................................... 30 4.34 The Final Decision ......................................................................................................................... 35 4.5 Design Optimisation ................................................................................................................................. 37 4.6 Cost Analysis (Vanguard Studio) ........................................................................................................ 41 4.6.1 The Overall Model ............................................................................................................................. 41 4.6.2 Material Costs ..................................................................................................................................... 42 4.6.3 Fixed Costs ............................................................................................................................................ 43 4.6.4 Processes Costs .................................................................................................................................. 44 4.6.5 Logistics Costs ..................................................................................................................................... 45 4.6.6 Cost versus Merit Graph ............................................................................................................ 46 4.7 Finite Element Analysis .............................................................................................................................. 47 4.7.1 Simulation of the Trolley: ......................................................................................................... 47 4.7.2 Simulation of the Roll‐Bars ...................................................................................................... 52 4.7.3 Simulation of the winch assembly: ...................................................................................... 53 4.7.4 Summary for simulation analysis ......................................................................................... 56 4.7.5 Calculation of Factor of Safety for the tested parts. ..................................................... 57 Summary ................................................................................................................................................................ 59

Group 8 Conclusion ............................................................................................................................................................. 60 Future work ......................................................................................................................................................... 61 References ............................................................................................................................................................. 62 Appendices ........................................................................................................................................................... 65 Appendix A: Design Matrices .................................................................................................................. 65 A.1 Blank Binary Weighting Matrix ................................................................................................. 65 A.2 Completed Binary Weighting Matrices and Averaged Results ................................... 65 A.3 House of Quality ............................................................................................................................... 72 A.4 CODA ...................................................................................................................................................... 73 Appendix B: Production Drawings ....................................................................................................... 76 B.1 Base Connecting Bar ....................................................................................................................... 76 B.2 Cradle .................................................................................................................................................... 76 B.3 Winch Base ......................................................................................................................................... 77 B.4 End Link ............................................................................................................................................... 78 B.5 Ground Support ................................................................................................................................ 79 B.6 Leg Bar .................................................................................................................................................. 80 B.7 Link ......................................................................................................................................................... 81 B.8 Roll Bar ................................................................................................................................................. 82 B.9 Trolley ................................................................................................................................................... 84 B.10 Wheel .................................................................................................................................................. 84

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Abstract The following report follows the design process of a UAV launcher specifically from conception to final design. The design process includes identifying the customer requirements, researching existing designs and constraint & cost analysis. Finally a design is selected and then modelled in SolidWorks for finite element analysis.

Introduction

2.1 Overall Perspective UAVs (unmanned aerial vehicle) are aircrafts that are piloted without having a human on board. Usually, they are controlled remotely although autonomous use is increasing. As a result, the vehicles tend to be much smaller than their manned counterparts with typical wingspans of just a couple of meters being able to provide a sufficient enough lift force to keep the UAV airborne. Although predominately used by the military, UAV’s are becoming popular in a small number of civil applications.

Figure 1: Showing the wide range of UAV in term of wing span length. [1] 3

Group 8 Launchers allow the UAV to be launched in relatively short distances. This is desirable since it isn’t always possible to find open flat surfaces that can act as runways. UAV Launchers allow the user to launch the craft virtually anywhere. Although UAV’s are mainly used by military for various uses such as reconnaissance and combat, applications in the civil sector are increasing. The specification of the UAV depends on its purpose. Combat UAVs can have huge sizes where ones used for filming tend to be smaller. Figure 2: Showing the possible type of launcher used in military. [2]

2.2 Literature Review

Introduction The literature review has been done to find the importance and the outline the requirements for an Unmanned Air Vehicles (UAV) catapult launcher and to investigate some different methods of solving the engineering challenge used in different type of applications. 4

Group 8 Body Unmanned Air Vehicles (UAVs) are also known as drones, which are unmanned piloted aircraft. UAV are available in wide variety of sizes ranging from small to large scale of 50 feet wing spans or more. For instance, RQ‐7 Shadow has 10 feet wing span and MQ‐9 Reaper has 66 feet wing span[3]. UAV are widely used in all sort of areas, especially maritime as they allow the ships to defend themselves and detect enemy threats autonomously from aerial vantage points. Furthermore, since naval ships can be expected to operate in hostile environment and emergency situations, it is important that the aerial platforms are also capable of being operated under these conditions. For instance, the Manta UAV used to perform hyperspectral imaging can be launch from the upper deck of the combat vessel “Stiletto” and Silver Fox UAV mounted and launched from an 8m rigid hull inflatable boat (RHIB) boats while they are in motion[4]. UAVs can be further divided down into few different categories such short‐ range, close‐range, medium range and stratospheric. Each UAV is assigned to different type of mission depending on their endurance limit and payload capacity. For example, the MQ‐9 Reaper is used for combat mission due to its high endurance limit of 24 hour and high payload capacity of 3750 lb allowing it to carry 4 x 500lb weapons. However, this massive UAV has to be launch using a runway due to its weight. Furthermore, Scan Eagle is used in Marine Corps and Air Force for surveillance by attaching a stabilized camera on to it for Electro‐Optical/Infra‐Red imagery. Scan Eagle can be launched by a pneumatic catapult launcher which allows operations from ships or from remote, unimproved areas [5]. The importance of UAV launchers in successful operations has given rise to the challenges of designing and optimizing launchers for safety and operability in all sorts of conditions; cost reduction by using a simpler and more effective launching mechanism thus reduces the required manpower to operate and maintain. As a result, most manufacturers aim to improve their designs in order to accommodate what customer requires. For instance, the Pusher Prop launcher manufactured by BAE system can launch a UAV at up to 44.8mph, it takes less than 12 minutes to assemble and can be operated in remote locations with a battery pack. A more handy UAV launcher such as the Tractor Prop Launcher by BAE System (shown in 5

Group 8 Figure 3 below) weighs less than 18kg and can packaged in one small container 152cm X 35cm X 40cm in size. Engineered Arresting Systems Corporation have designed a expeditionary launcher which can mounted onto a HMMWV trailer for off road mobility and can launch a UAV in less than 10 minutes with only two personnel. These new types of launcher not only encourage all sectors to replace expensive manned aircraft for suitable small operations, but also show the convenience of using UAVs.

Figure 3: Launcher [6]

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2.3 Critical Review of design alternatives There are a various number of solutions for UAV launcher mechanisms that depend primarily on the size and function of the UAV. Smaller UAVs, of 50kg or less are suitable for bungee mechanisms. This is where a bungee cord is either winched or cranked mechanically. The potential energy is stored in the bungee cord itself and transferred to the mechanism cradling the UAV. They are used mainly in launchers that are required to propel small UAVs because there relatively cheap compared to other systems. The main drawback of a bungee launcher is the amount of potential energy required to launch UAVs of larger masses. This typically results in higher stiffness values that as are a function of the bungee’s cross sectional area. Hence UAVs with greater masses require the bungee cord to have a greater area or bungee’s arranged in parallel. However this affects efficiency and less energy can be transferred to the bungee.

Figure 4: Pneumatic launcher. [7] Pneumatics makes up the majority of the other launchers, usually used to propel loads of 100kg or higher. They are usually self‐contained, compressed air driven, stand‐off delivery systems capable of firing various projectiles to distances of greater than 500 ft. The system consists of an air chamber, barrel assembly, braking system, air compressor, and control panel. The air chamber is a cylindrical low pressure vessel capped by spherical ends with airtight seals. The chamber has two outlets: one provides inlet pressure to the air receiver, the other outlet links directly to the projectile (this outlet would be capped in a UAV application). A firing mechanism, air pressure equalizing tube, and barrel make up the barrel assembly. When the firing mechanism is actuated, air pressure forward of the projectile unseats the barrel cover and the resulting arterial force created helps pull the 7

Group 8 projectile along the barrel, while the air pressure behind the projectile simultaneously propels the unit through the barrel, assisting in a smooth overall acceleration due to a push‐pull effect. [8] They are very reliable and can deliver remarkably consistent results. Given the wide range of pneumatics available, it’s possible get the optimal sized pneumatics for your mechanism. Compared to the bungee mechanism, the cost of pneumatic cylinder is higher and mostly the pneumatic launcher comes in a huge size, thus creating problems in transportation.

Figure 5: Car top launcher. [9] Car launchers – A cradle is attached to an automotive vehicle and the UAV. The car then accelerates to the desired take off velocity at which point the UAV is airborne. The advantage of such a design is the launch design itself is simple as all the kinetic energy is provided by the car. The obvious draw back of the design however is that fact that both a car and large open space are required. Hydraulic Launch – The basic concept utilizes compressed gaseous nitrogen as the power source for launch. The oil side of an accumulator is connected to a launch cylinder, a piston connected to a moving crosshead of cable reeving with a 6:1 ratio. The cable is routed over the launch rail and back to a launch shuttle designed to "carry" the UAV. When proper launch pressure is reached, the release mechanism, an electro‐mechanical device, is actuated to start the launch sequence. The system's release mechanism is programmed with an actuation cycle which is designed to lessen the rate of onset of acceleration. After release the shuttle is accelerated up the launch rail at a near constant rate of acceleration. At the end of the launcher's power stroke (10 to 12 ft.), the shuttle engages a nylon arresting tape, connected to a water brake, the shuttle comes to rest and the UAV is launched. [10]

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Engineering Calculations

3.1 Basic Calculations After selecting the bungee catapult as a launching mechanism, the next step was to calculate the necessary power required to launch the UAV. The main variables to consider would be  Mass of UAV and launcher cradle  The aerodynamic drag  Resistance on wheel bearings  Angle of elevation  Stiffness of bungee R kx d μR mg θ Figure 3.1 Figure 3.1 shows the forces on the mass at point where the mechanism is released. As the UAV and cradle move vertically relative to the inclined ramp, the equilibrium equation can be shown to be: cos 0 cos Equation 3.1 At the point of release, the mass is accelerating and therefore equilibrium doesn’t exist. The force due to acceleration acting on the mass can be represented as f0. Using Delbert’s principle the dynamic problem therefore can be considered static. Equation 4.2 shows the forces acting parallel to the ramp. 9

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sin

cos –

sin

Equation 3.2

Where the symbols have their usual meanings, K represents the spring force of the bungee, d represents the aerodynamic drag, x is the bungee extension and μ is the co‐efficient of friction. Although the drag force varies with velocity (and therefore at the point of release will be zero), the maximum drag force has been calculated and assumed to be constant throughout to simplify the equations. The maximum drag force is worked out to be approximately 25 N as show in equation 3.3: 1 2 Equation 3.3 The resultant force that acts on the mass f0 can be equated to the change of energy in the system ΔU, by integrating over the distance x, in which it acts. The possible changes of energy are kinetic and potential, however since the equilibrium equations are considered parallel and perpendicular to the inclined surface, the potential energy changes are already accounted for in f0. Therefore the total energy change can be given by equation 3.4 ΔU

1 2

–

cos –

sin

cos –

sin

Rearranging for the bungee stiffness gives k to be

cos – sin

Equation 3.4 Using equation 3.4, a python based program was written to that plotted the extension in bungee length against the bungee stiffness k. 10

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Figure 3.2

From figure 3.2, we can see that the relationship between k and extension is inversely proportional. Hence the bigger the bungee extension, a smaller stiffness is required to propel to UAV. 3.11 Stiffness research Quick analysis from the graph shows that for an extension in the interval of 3‐ 5 meters, a bungee stiffness value is required in the range of approximately of 200‐ 550 N/m. After researching bungee stiffness values on the Internet, it became apparent that bungee cords are not sold by a specific k value. The reason is simple;

Where E is Young’s modulus, a material constant, A0 is the cross‐sectional area of the material and L0 is the initial length of the cord. Therefore the stiffness depends of the length of your bungee and that is likely to be the reason why bungee cords are not sold with given k values. Therefore, since k and E are constants, a linear relationship between the initial bungee length and cross‐sectional area develops. 11

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Equation 3.5

Since Young’s modulus is given as E

Stress Strain

percentage elongation

After contacting several retailers to find the Young’s modulus values, it was suggested that the best way to find the numbers was to test some samples. An experiment was devised to find the Young’s modulus of bungee rope by measuring the extension of a cord. Weights were attached to a bungee cord via a hanger and the extension measured. The results are shown below for a bungee with a diameter of 14mm. Mass (kg) Extension (ΔL/L0) Young’s modulus, E 7.5 6% 8.01 x 106 8.75 7% 8.00 x 106 9.75 7.4% 8.41 x 106 So the value on 107 Pa is a good approximation for the Young’s modulus. The number was checked and verified with Professor P. Reed. Rubber has a modulus value between 0.01 and 0.1 Gpa[11] so the value seems reasonable. As the design of launcher requires two bungees to extend in parallel, the total stiffness value is halved as for bungees acting in parallel; the total k is the sum the individual cords. With a given initial length it is now possible to determine the required stiffness value, k to launch the bungee at a velocity of 12 ms‐1. Thus for an extension of 4m and an initial length of 4m (8 meters when extended), the required k value required is approximately 360 Nm‐1. Rearranging equation 4.5 in 12

Group 8 terms of cross sectional area and substituting the values shows that an area of 1.4 x 10‐4 m2 is required. Thus the radius of each cord should be a minimum of 4.52 mm. Given that it’s unlikely to find a cord on the market with such a specific diameter (without having one especially made) a 5mm radius will be sufficient. This is equivalent to a value of 420N.

3.12 Winch requirements The tensional force acting on the winch will be equal to the extensional force on from the bungee. Hooke’s law as gives this force; 400 ∗ 4 1680 N Effectively this translates into a lifting force of approximately 170 kg. Electric winches available to buy on the market have much higher values for lifting loads. Therefore this gives room to maneuver in selecting a model which best suits the other customer requirements. The LT2000 ‘Superwinch’ was selected as the preferable mechanism. As well as having a higher lifting load value of a 907 kg, it has a mass of only 5.4 kg and therefore is extremely light. The equipment can be charged by connecting directly to a car battery. However this requires use of an nearby automobile, which may not be practicable in some environments. Therefore a 12V DC battery is supplied with the launcher.

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Engineering Design methods 4.1 Customer requirements

Based on the research, the most significant and important customer requirements for the UAV launcher were listed in the customer requirements shown below:                    

Compact size Minimum weight Setup quickly and easily Safety Low cost Weather resistant Suitable for special terrain Consistent launch characteristics Easy to operate Easy to handle Easy to repair Durable Reliable Optimum take off distance Optimum launch times Aesthetics Minimal personal requirement Adjustable launch direction Adjustable angle of launch Multiple launches per day

Group 8 Compact size As stated in the question sheet the size of the launcher needs to be small enough to fit into a van. Furthermore, the smaller the size the better as the storage and mobility is not a problem to any user. Minimum weight The weight will affects the stability and the ease of transport of the launcher from a launching area to other launching area. Setup quickly and easily The time is precious. In order to achieve a successful operation, the launching has to be fast and effective. Safety Safety is the most significant requirement of all customer requirements. This is because to prevent any injuries and harm to the customer as wells as the environment. Low cost Cost can manipulate the potential market of the launcher and the design as wells. Low cost can attract more customers. Weather resistant The launching of UAV area varies. It can be done in anywhere any place with varying weather and temperature. For example, the weather may change from time to time and the launcher needs to cope with the changes. Suitable for special terrain The base of the launcher determines the effectiveness of the launch. In this case, the launcher has to be flexible to fit for all kinds of terrain regardless of its place. For example, the launching of the similar UAV can be done on a desert and on top of the deck. 15

Group 8 Consistent launch characteristics The consistency could determine the planning and timing of the launching the UAV to the air thus affects the outcome of the operation. Easy to operate The use of a manual can be neglected if the operation for the launcher is user friendly and easy. This has the advantage of giving the operator a quick understanding of the launcher and encourages people with various machine operating skill levels to use it. Easy to handle This can make the transportation of the launcher easier and user friendly. Easy to repair Minimizing the need for repairing and servicing equipment is very important in business as it reduces manpower requirements and running costs. To ensure the durability and effectiveness of launching, the launcher has to be easy to repair as wells as service. Durable Durability determines the lifespan of the launcher. This can affect the customer choice as all customers want products to last as long as possible. Reliable Reliability implies the amount of responsibility that can put on the launcher. For example this will determine the amount of launches that can be performed on a daily basis. Optimum take off distance The launching distance has a large effect on the performance of the UAV and its successfulness in operation. Moreover, the distance available in which to launch a

Group 8 UAV is not always guaranteed to be the exact length a customer wants. So the take‐ off distance needs to be optimised in order to satisfy the customers. Optimum launch times The time taken to launch the UAV is considered fairly important as it determines how many launches can be done in a given length of time. Aesthetics Aesthetics can affect the customer choice. This is likely to be important in a military environment where camouflage is vital. Some customers may prefer a launcher to match the UAV if, for example, it is being used in a public arena, such as the demonstration of a UAV to potential customers. Minimal personal requirement The number of personnel required to launch a UAV can greatly influence cost and work force allocation for the customer. Adjustable launch direction The conditions the UAV is being launched in may vary considerably, and due to time or space constraints it may be impractical to relocate the launcher. For example, the wind direction can affect the preferred direction of launching. Adjustable angle of launch The angle of the launch will determine the effectiveness and the performance of the UAV. For example, 45 degree is the optimum launch angle to get the maximum projection. However, this may vary depending on the wind conditions Multiple launches per day As stated in the case study description, the launcher needs to be used several times in a day.

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4.2 Design Concept Generation

The launcher is intended for a UAV of 3 meters wide and 2 meters long. It has

maximum weight 25kg and takeoff speed requirement of 12ms‐1. Several primary concepts of the UAV launcher were generated based on the research and are shown :

This launcher contains a cylinder with a little gap on it. And for this piston, it uses a special piston which is fixed to the cradle so that when the compressor is connected to the cylinder, the air will pushes the piston and so the UAV.

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For this one, it is quite similar to the previous one. But this one is using a spring to accelerate the UAV and a motor is provided to pull the spring back to its origin position after each launching process. The spring stores maximum energy in the compressed position and its extension can be controlled by the motor. So when the motor is turned on, it pushes the UAV with the desired energy. The design is simple and user‐friendly. It can be produced cheaply. To meet the take‐off velocity, a large spring stiffness value is required increasing the cost of the system. Also, this design does not consider the positioning of the propeller of the UAV.

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A simple pulley block and cylinder is used in this case. The pulley block has an elongation ratio 2:1. This means when the cylinder is fully extended, the rope will pull the UAV to its critical position.

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This design is based on a crossbow design and it is using bungee to power the UAV. An electrical motor is attached at the end of the launcher to pull the bungee back to its initial position.

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A heavy mass is used in this design to store the potential energy. When it operates, the energy in the mass is transferred to kinetic energy. Alternatively the motor in the fulcrum could provide work.

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A big fly wheel is used in this design. In the preparation stage, the fly wheel is powered by an electric motor and rotates in very high speed. In the launch stage, the fly wheel is connected to a rope which pulls it.

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In this design, the UAV is accelerated by its gravity. The advantage of such a design is that no power requirement is needed and increases the reliability of the system. The main drawback is that by equating the required kinetic energy at the end of the ramp the potential at the top, the required energy needed to launch the UAV at 12 ms‐1 requires a vertical change in displacement of over 7 meters.

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The belt drive is used in this case. And when the rotator is driven by electric motor or gas engine, the UAV will reach its launch speed at the end. The whole design consists of only 4 parts. Hence it can be produced cheaply. The launcher would require a lot of force to meet the criteria of 12m/s take‐off speed i.e. it would require a large battery to power it increasing the cost. Another method to meet the criterion is to increase the distance between the gears. This would increase the length of the belt again increasing the cost.

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This is the launcher works like a rail gun. The UAV is sitting in the middle attachment which works like a clamp. And when the attachment is disconnected from the rail, it splits into two parts as there is no additional force on either side of the attachment and the releases the UAV.

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4.3 Design Concept Selection

For analysis, the UAV launcher is divided into three parts: the launching system, the cradle and the support. And each part has several choices.

4.31 The Launching system: The pneumatic system: The pneumatic system is quite powerful and it is quite stable and clean. However, it is relatively expensive and it is difficult to manufacture. Also the weight of the pneumatic system can be relatively large and the storage for the compressed air can be a problem. There are two different types of pneumatic design which have different emphasis:

(The normal type cylinder) This is a typical pneumatic system which using a pulley block. But this design is a bit long so that fracture may easily occur during the launching process as there will be more torque and momentum.

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(The cylinder with a gap) In this pneumatic system, there is a small gap in the middle of cylinder which allows the piston to push the cradle directly. This results in a shorter piston/cylinder and therefore a more compact design. A loss of energy will occur due to air escaping from the gap. This would need to be factored into the design or a seal would need to be designed to prevent/reduce the escape of air. This would increase the complexity and therefore the cost of the design as well as compromising its suitability to operate in adverse weather conditions and environments. The spring/bungee system: The spring/bungee system is very cheap, safe, easy to manufacture and relatively light‐weight. The spring and bungee contribute a decreasing force, not a constant force. This means the UAV has a maximum stress initially but very low acceleration at the end of the rail. Usually these require two winches to pull the system to its initial position.

(The spring launching system) (The bungee launching system)

(The crossbow bungee launching system) The gravity/mass system: Systems using the gravity to store energy are reliable. The gravity system is required to be quite large which means they are heavy, not a compact size and difficult to assemble. For the size of the UAV and the mass of the payload, a very large counterweight would be required. Also both of these systems have a low acceleration and low efficiency.

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(Self‐gravity launching system) (The mass launching system) The flywheel system: this system contains a flywheel to store kinetic energy. As a result of launching, the flywheel would keep rotating for a while, and the energy efficiency will be quite low. Also before the launching, the flywheel needs to reach a required velocity which may take a long time. For a large flywheel the machine will be massive.

(The launcher with a flywheel) The electric system: The major concern with an electrical system is the generation or storage of sufficient electricity while maintaining the light weight, compact design philosophy to facilitate transport and flexibility. The rail gun system especially requires prohibitively large currents. It is unlikely that a system with lower energy requirements would have sufficient power to accelerate the UAV to the required speed in an acceptable distance.

(The launcher with track) (The rail gun launching system)

Group 8 4.32 The cradle: The clamp cradle: this cradle will separate into two pieces so that it releases the UAV. It has a quite large friction due it needs force from both sides to maintain occlusion and it requires a high tolerance level in manufacturing. Due to its working function, the stability of that cradle is also an issue.

Clamp (before launching) Clamp (after launching) The holding cradle: this cradle holds the UAV and will have bump‐stops at the end. The holding cradle may cause the UAV to stick at the top surface due to the upwards force produced by the wings. There is a potential issue with collision with the tail of the UAV when the cradle hits the bump‐stops.

(The holding cradle)

4.33 The support: Three points support: this three point supporting system uses a ball rolling mechanism so that it can rotate 360 degrees and has multi launch angels. However, it is unstable due to the size of the launcher. In addition, all of the stress is concentrated on a single point which will require significant reinforcement to prevent failure. 30

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(The three points support) Multi‐points support: this is more stable than the three points support but it can’t rotate naturally due to its structure. This could potentially be overcome by mounting the system on wheel, but this would necessitate some method of locking the structure in place.

(Different types of multi points support)

In summary, for the launching system: Type of launching Benefits system Pneumatic Powerful, stable, clean.

Spring/bungee

Cheap, low weight, easy to operate, clean

Gravity/mass Electric

Relatively stable, clean Easy to operate, clean, high energy efficiency

Drawbacks Expensive, hard to manufacture, not assembled, difficult to store Property changes when contact chemicals/at critical temperature High weight/large size Low power

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a. b. c. d. e. f. g. h. i. j.

The normal pneumatic type cylinder The pistonless pneumatic type The spring launching system The bungee launching system The crossbow bungee launching system Self‐gravity launching system The mass launching system The launcher with a flywheel The launcher with track The rail gun launching system

For cradle: Type of cradle Clamp cradle

Benefits Simple structure

Holding cradle

Easy to operate

Drawbacks High friction, high manufacture tolerance level, unstable The structure may collide with the UAV

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a. The clamp cradle b. The holding cradle The support: Type of support Benefits Three points supporting 360 degrees launching, multi slope launching Multi points supporting Stable

Drawbacks Unstable Fixed degree of launching

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a. Three points supporting b. Multi points supporting

Group 8 4.34 The Final Decision In this case, the spring launching system, multi point supporting and a holding cradle is finally selected. And the design is shown below:

After evaluating all the designs, the bungee mechanism was selected as the mechanism launcher over a pneumatic design. For UAVs with a mass less than 50kg, the research suggested that this was the most widely used launcher for UAVs of this size. It’s generally accepted that the pneumatic launcher offers more reliability over bungee cords, however with an additional price increase. Pneumatics cylinders would require relatively large and expensive air compressors to generate to the necessary force to launch the UAV. Hence the bungee mechanism is more simple. Also the calculations required to work out the required take off velocity of the UAV are simple and easy to calculate. This makes it easier to determine the neutral points of such parameters as bungee stiffness, extension and initial length. The design also has minimal moving parts, increasing the reliability of the system and the decreasing the chances of system malfunctions.

Operation of the launcher The design of the mechanism is relativity simple, as explained in the concept generation. The principle of the mechanism is to transfer potential energy from the bungee cord to the UAV. Due to the Penguin B UAVs design, special consideration was given on how to then transfer the kinetic energy from the trolley (or cradle) to the UAV. Constraints such as propeller size and torque on the wheels had to be 35

Group 8 taken into account. The final design was to ‘cradle’ the wings above and below. The cradle itself has groves to position the wheels. A winch pulls the pulls a cable positioned on the undercarriage of the cradle such that it doesn’t interfere which the UAV propeller. The Cradle itself has a total of 6 wheel bearings that slide into the rails on the ramp. Wheel bearings are advantageous since they minimize the contact area and therefore friction with the rail. When the bungee is fully extended to a length of 4m, the lynch pin is pulled to release the winch from the cradle. The pin is connected to an inextensible cable and therefore can be pulled at distance to increase the safety.

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4.5 Design Optimisation

Having determined the customer requirements, a binary weighting matrix was constructed (appendix A.1). This was sent out to potential customers; the BBC; ITV; Army Air Corps; RAF; Boeing; Lockheed Martin; and BAE systems in the hopes we could obtain some input from potential users of UAV launchers. Unfortunately, we received no responses. In order to generate weighted requirements the group filled out the matrix individually and the resulting normalized scores were averaged to give a set of weighted requirements we could use to optimise the design

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From the combined customer requirements, it is clearly shown that the customer requirement of safety is the highest with 9.30%. The second highest requirement is reliability with 8.72% and third, consistent launch characteristics with 7.56%. The main reason for this is because safety plays an important role in everything that people do. Launching the UAV needs to be safe for the people operating the launcher and for people in the vicinity. On the other hand, reliable and consistent launch characteristics are very important in determining the outcome of the operation as it will determine the consistency of launching the UAV. Besides that, the requirement of optimum take off distance, and durability have the same percentage of 6.98%. Easy to repair, easy to operated and compact size, all have the slightly lower percentage of 4.65%. The least important customer requirement is the aesthetics which has a percentage is less than 1%. Having selected a concept design, a ‘House of Quality’ (HOQ) and ‘Concept Design Analysis’ (CODA) [12] were used in order to optimise the design. The basic engineering calculations above were used to determine both the feasibility of the design and the parameter that would affect the optimisation. These calculations also gave us baseline values for the relevant design parameters from which to start the optimisation. 38

Group 8 Initially the HOQ was constructed (see appendix A.3) in order to identify conflicting parameters. The HOQ shows that parameters which determine the characteristics of the bungee were found to conflict. These are fundamental properties and as such are not subject to change. Instead, a compromise between these parameters will have to be found which will give the desired characteristics. This will be done using the CODA. A further benefit of the house of quality is that it gives a very user friendly, graphical interface to determine the strength of the relationships between the customer requirements. This interface was utilized by connecting it to the CODA and using the strength relationships from the HOQ in the CODA. The CODA (appendix A.4) was constructed using some of the baseline parameters determined from the engineering calculations; for example bungee characteristics, the required winch power, ramp length etc. Others parameters, such as density of the ramp, were selected by common sense: for example ramp density was chosen to be between that for Aluminium (2700 kg m‐3) and stainless steel (7930 kg m‐3)[13]. The relationship functions were then considered individually and neutral points/tolerances determined by basic calculations, rudimentary costing and research as required. Once these elements were in place Solver was used to solve the CODA and find the optimum design. The highest overall design merit possible is 54.06% customer satisfaction. The design parameters to achieve this design are: 39

Group 8 Design Parameter

Value ‐3

Density of Ramp (kgm ) Length of ramp (m) Cross sectional area of ramp (m2) Initial bungee length (m) Bungee stiffness (Nm‐1) Bungee extension (m) Bungee Area (cm2) Take off velocity (ms‐1) Winch power (kg) Winch weight (kg) Ramp recoil Cradle density (kgm‐3) Cradle length (m) Launch times (s) Pin weight (kg) Launch angle (º) Pin size (m) Wire length (m) Co‐efficient of friction between ramp and cradle Co‐efficient of friction between bungee and trolley Number of bungees

2700 4.87 0.03 6 550 5 1.8 12 300 38.2143282 3.00 1600 0.01 10.65 0.005 45 0.5 1 0.0172672 0.6 2

An issue that the CODA raises is that one of the customer requirements ‘weather resistant’, is not addressed by these design parameters. However, the chosen design is inherently weather resistant. This will be improved by selection of weather/corrosion resistant materials where possible and, if necessary, a marginally increased maintenance schedule.

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4.6 Cost Analysis (Vanguard Studio)

The overall merit of the design was obtained using the CODA in the previous section. Even with a high merit, the launcher design could be rejected if it is very expensive to build. Hence, in order to evaluate the cost of manufacturing the UAV Launcher, Vanguard Studio software is used. The studio has a hierarchical tree interface which comprises of branches. Branches on the left are dependent on the ones to their right i.e. to solve a problem, the current branch is divided into two or more simpler components. The process is repeated until there is no further division of components. [14] The right most branches contains the design parameters used in the CODA and in this Vanguard can used in tandem with CODA to obtain the best value‐for‐money launcher by comparing the design merit to the cost.

4.6.1 The Overall Model For the UAV launcher, a cost analysis decision tree was designed to perform two tasks. The first task was to evaluate the optimum cost of the launcher by varying the design parameters and the second task was to relate the parameters with the overall merits. The basic Vanguard model of the UAV launcher is shown in figure 1.

Figure 1: Overall decision tree cost analysis of the UAV launcher.

Group 8 The model is a merger of two different modeling approaches: 1. Fixed Costs and Variable Costs: In this approach, the cost is split into fixed costs and variable costs. The fixed costs are independent with respect to the production. In this model the wheel bearings, bungee cord, tooling items and the winch contribute to the fixed costs. The variable costs depend on the manufacturing process of the material at hand and the number of components manufactured. The material cost branch contributes to the variable costs. 2. Costs associated with physical manufacturing processes:



The model is based on the costs associated with the different stages involved in manufacturing a launcher. These stages can be defined as: Processes costs



This branch includes the cost required to assemble the parts to make the product. It includes processes like fabrication and assembly costs. Logistics costs This branch describes the cost required to support the product. It includes the cost of transportation. It is a part of overhead cost as it is not directly related to the launcher itself.

4.6.2 Material Costs As mentioned before this section includes the cost required to manufacture individual parts. The components given in the table below were manufactured.

Manufactured Ramp Cradle Base Table 1: The table shows the components that were manufactured

The components to be manufactured have their cost depending on constraints such as the material of the part and its dimensions and so on. Consider the ramp for example. The cost of building an Aluminium ramp is broken 42

Group 8 down into the amount of Aluminium used for one ramp bar, the number of ramp bars and the cost of Aluminium per kg. The branch of the amount of Aluminium used for one ramp bar is broken down into the density of the bar and the volume of the bar which is further divided into the cross‐sectional area and the length of the ramp bar. It is convenient to build the ramp and cradle from the start as the prices of Aluminium and PVC are low for bulk quantities. [15][16]

Figure 2: Material Costs (variable) branch of the decision tree.

4.6.3 Fixed Costs This branch deals with the cost required to purchase a component.

Purchased Winch Wheel Bearings Tooling Bungee Cord Battery Table 2: The table shows the components that were purchased.

Group 8 The components in the above table make up the off‐the‐shelf purchases and hence have a direct cost associated with them. It is easier and more convenient to get these components from the market than manufacturing them. [17][18][19][20]

Figure 3: Fixed Costs branch of the decision tree.

4.6.4 Processes Costs The processes costs include all of the processes involved to assemble the launcher. These processes are:  Fabrication‐ The processes of cutting, bending and welding of Aluminium bars are included in fabrication. Each branch is further divided into the time required to perform these tasks, the number of labourers performing the task and the labour rate per hour.[21]  Assembly‐ It deals with the labour cost to assemble the product. [21]

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Figure 4: Processes Costs branch of the decision tree.

4.6.5 Logistics Costs For the launcher, logistics covers the transportation costs and packaging costs. The individual components of the model are going to be placed inside a Thermocole box. The Thermocole box is placed inside a wooden crate. The Thermocole is present to protect the launcher from damage in case of an accident.

Figure 5: Logistics Costs branch of the decision tree

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Merit %

4.6.6 Cost versus Merit Graph By varying the design parameters in the CODA matrix, several values of merits and costs are obtained. Then, by plotting those on an excel spread sheet, a visual representation of the merit versus cost is seen. Hence, from the various plots, the best merit versus cost solution is chosen. 57 56 55 54 53 52 51 50 49 48 47 46 0

1000

2000 Cost $

3000

Figure 6: Graph comparing the cost and the merit values.

4000

Out of all the different merit‐cost combinations, the best result is the one noted in red (see figure 6). It is the cheapest and has the one of the highest merit value. Some of the designs have a higher merit value, but compared to the red dot design the cost does not justify construction of those designs. Having decided the parameters that provide the best merit and cost, the SolidWorks model can be finalized with these optimized values.

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4.7 Finite Element Analysis

4.7.1 Simulation of the Trolley: Simulation of the trolley was made by defining the fixed geometry of the trolley when assembled to the rest of the construction. Afterwards, two pulling forces (1000N) were applied to the two sides of the trolley representing the pulling force of the bungee when the trolley is located in the extreme position ready for release. The material selected for the trolley bars was Aluminium 1060 alloy. After running the SolidWorks simulation with these parameters the following results were obtained:

Figure 1 ‐ Deformation of the trolley due to bungee pulling force (Scale x40)

From this simulation study the maximum displacement of the model was found to be 0.1487mm which is considered to be minimal. Furthermore, from SolidWorks simulation the stresses within the trolley structure due to the bungee pulling force when in the extreme position were plotted:

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Figure 2‐ Stress results plot due to bungee pulling force (scale x40)

From this simulation study the maximum stress within the trolley is about 21.879MPa and it occurs in the side bars of the trolley as predicted, so Aluminium bars are necessary for the trolley structure to maintain its structural rigidity during its stress cycles. It should be pointed out that Aluminium can contribute to a heavy weight construction if used solely even though it is considered one of the lightweight metals it is much heavier and denser than many plastics such as PVC. For those reasons it was decided that Aluminium should be used only in parts were the stresses are concentrated and large. For this reason it was decided to make the trolley form PVC material (which contributes to a lightweight construction) except for the side bars that will be made from Aluminium 1060 alloy due to high carrying load. To verify that PVC is a well suited material for the rest of the Trolley part some more simulations were conducted, which are displayed below. Firstly, the cradle was mounted on top of the Trolley and then another stress simulation was conducted. The aim of this simulation was to examine how the cradle responds to the reaction force applied to it from the UAV wings the moment when the Trolley is released and has its maximum acceleration. The material used for building the cradle was PVC, because it is a bulky part with complicated shape and 48

Group 8 building it out of a metallic alloy would be complicated as well as expensive and it would result in a very heavy‐weight construction. The results of the simulation test are shown below:

Figure 3‐Deformation of the cradle due to reaction force from the UAV wings when trolley released (scale x20)

From this simulation the results obtained state that the maximum displacement of the cradle compartment due to reaction from the UAV wings when having maximum forward acceleration is 1.52mm in the x direction. Such a displacement is satisfactory because it only occurs for a very short time. This is because as the trolley moves forwards, the extension of the bungee cords is minimised and so does the reaction force from the UAV wings to the cradle. Thus the 3.261 mm displacement will be occurring very rarely in the whole time‐span of a take‐off. Next, the stresses within the cradle and the frame were plotted:

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Figure 4 ‐ Stress of the cradle and the frame due to reaction from the UAV wings when trolley released. (True scale)

From the results obtained, it is visible that the highest stresses occur in the bars connecting the cradles with the trolley. The extreme stresses occur in the region of the two back supports (wheel) which are made out of Aluminium with a magnitude of 32.7MPa. After all, the choice of PVC for the cradle and the unstressed regions of the trolley is a reasonable choice of material. Furthermore another stress test for the trolley compartment was conducted. Its aim was to demonstrate how the lower free (cantilever) part of the trolley which supports the front wheel of the UAV responds if some of UAV’s is supported by this part. It should be pointed out that when designing the trolley part, this lower cantilever was designed just to support the UAV’s weight and not carry any of its weight. The weight of the UAV will be carried by the cradles. Although in case of slight possible movement of the UAV during take‐off some of its weight may be carried by the lower supporting part. Precautions should be taken against large displacement of this part which may result in resonant vibrations. The stress test was conducted with an arbitrary force of 100N was applied to the free lower cantilever (roughly 1/3 of the UAV’s weight). The results obtained were:

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Figure 5 ‐ Deformation of the lower cantilever part, supporting the front wheel of the UAV (scale x5) paint

The results show that if the supporting part in the take‐off process happens to carry about 30% of the UAV’s weight it will have a displacement of 8.7mm. It should be pointed out that this is an extreme scenario which rarely may happen in case of wrong attachment of the UAV on the cradles. Similarly the stresses carried by the cantilever in this worst case scenario are plotted:

Figure 6 – Stresses in the lower part cantilever support (scale x5)

Group 8 4.7.2 Simulation of the Roll‐Bars In this section, the simulation of the roll‐bars was carried out when the bungee cord wrapped around them is stretched fully by the winch. The Bars are made out of Aluminium since it is a light metal which high deformation resistance. The bars were hollowed in an attempt to minimize the structure weight. The simulation results and plots are displayed below:

Figure 7 ‐ Deformation of the roll‐bar due to buckling load from the bungee when stretched at its extreme position (scale x1000)

The results of the simulation show that the maximum displacement of the roll‐bar part is 0.0189mm which is minimal. This shows that the Aluminium is a good selection of material for the roll‐bar. It might be a heavier choice than a very expensive alloy or a plastic material but it is crucial that the skeleton of the design remains as rigid as possible when stressed. Next, the stresses in the roll‐bar were plotted:

Group 8

Figure 8 ‐ Stress within the roll bar when buckling load applied by the stretched bungee (scale x1000)

The maximum stress obtained from the simulation is 4.839MPa. Its location is close the point of application of the force. The maximum stress is very low compared to the yield stress (27.6MPa). Thus from the simulations of the roll‐bars the application of Aluminium material is justified. 4.7.3 Simulation of the winch assembly: The last simulation made was on the winch assembly. Its aim was to give an insight of how the winch assembly will respond when the winch stretches the bungee cord to its extreme position. The results of the simulation are shown below: Firstly, the stress plot was carried out so see the levels of stress in order to select a suitable material for the base flat plate of the winch assembly.

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Figure 9‐ Stress within the winch assembly when bungee is stretched to its extreme position (true scale)

It was shown that the maximum stresses are in the region of 70MPa located in the triangular bars connecting the base with the legs. Aluminium 1060 alloy has only 27MPa yield strength. Therefore Aluminium 1060‐H18 was decided to be used for those two bars which have much higher yield strength of 125MPa. The material selected for the base of the winch was selected to be PVC because of lightweight properties and because the base does not carry any high value stresses. After that the deformation plot was carried out:

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Figure 10‐ Deformation of the winch assembly when bungee is stretched to its maximum position (true scale)

From the simulation the largest displacement came out to be 2.125mm which is minimal.

Group 8 4.7.4 Summary for simulation analysis

Group 8

4.7.5 Calculation of Factor of Safety for the tested parts. Factor of safety (FoS), also known as (and used interchangeably with) safety factor (SF), is a term describing the structural capacity of a system beyond the expected loads or actual loads. Essentially, how much stronger the system is than it usually needs to be for an intended load.[22] A simple formula for the calculation of the Factor of Safety of a component is given from ℎ From the SolidWorks simulation we can work out the maximum stress that each component experiences and knowing the material properties (Yield strength) we can compute FoS for each stress tested part: 57

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Summary The final design is shown below: Its powered by bungee which runs from a winch to the UAV supporting trolley via blocks in the end of the rails. The trolley is constructed of Aluminium 1060 and is attached to a PVC cradle in which the UAV sits. The trolley runs on Aluminium 1060 C‐section which controls the launch trajectory of the UAV. Specific parts of the structure which are subject to greater stress are made of Aluminium 1060‐H18 which has a higher yield stress. The result is a minimum factor of safety of 1.2. This has been deemed acceptable as during all calculations the worst‐case scenario has been assumed so there is already an in‐built redundancy. In order to keep the design compact the structure collapses and the rails split into two so the largest piece is just over 2m in length, which will fit in a short wheel base Ford Transit [23]. To facilitate an adjustable launch angle, the supporting legs are adjustable. The construction is primarily of Aluminium and PVC so the design will be both light‐weight and weather resistant. The electric winch will add to the weight, especially if an additional 12V battery is required for remote use. These were included in the design to make the launcher easy to use and reduce launch times. If the launcher is required to be carried long distance or operate remote from an electrical supply, it would be a simple matter to substitute a hand‐winch into the design. In order to maximise reliability and minimise maintenance requirement we have adhered to CL (Kelly) Johnson’s principle of KISS [24].

Group 8 As alluded to previously, the design is a compromise between customer requirements, not least minimising cost. The design process that we have employed ensures that we have met the customer requirements as fully as possible, while minimising cost and ensuring safety and reliability.

Conclusion This report demonstrates the design engineering process involved in making an UAV launcher. Firstly the requirements of the customer were identified and then weighted such that most important design aspects were focused on. The safety of the user was identified as being the primary requirement with reliability being second. From this, preliminary concepts ideas were generated from which a final design was chosen. The design selected was a bungee catapult mechanism. The design works by winching two bungee cords back and simultaneously releasing them. The values for parameters such as bungee stiffness, extension and aerodynamic drag were determined. As safety was the top requirement, the quick release mechanism has designed to include a lynch pin that could be operated at distance. Analysis of the CODA matrix showed that the best merit design to be 56.25%. The Price of the final design is $870 which is relatively cheap when compared to commercially available launchers of this type. This could be due to extra overheads in the design process that have not been incurred in this process such as office rent, salaries and tax. The SolidWorks model is then built and a stress & displacement analysis preformed. The Finite elements analysis shows the stress acting on the launcher is at its maximum around at the point where the winch is attached to the ramp; the material at this point was strengthened with a tougher aluminium alloy. To minimize the weight and drag, the cradle was perforated. The lower stressed points such as the assembly supports between ramp links were changed to cheaper lower weight PVC.

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Future work Based on the customer requirements and further research into the optimization of the launcher, the current launcher can be modified to increase efficiency. Currently the angle of launch can be adjusted by varying the position of the feet of the base. This adds an additional weight and size requirement. The design would be better optimised if the back end on the rail could be adjusted and pivoted about the front. This technique not only can provide a launching angle by using the available space underneath the launcher, but also shows the flexibility of the launcher in terms of handling and operating. Besides that, the lowered ramp can provide a significant improved in the stability as the center of mass is lower assuming the mass of the ramp is larger than other parts of the launcher. On the other hand, the solid ramp could be redesign to hollow in order to save cost for the materials and weight. This is because the ramp does not generally carry much weight and stress from the UAV, but the leg and the cradle of the launcher.

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References 1. Summary, Policy Options for Unmanned Aircraft System (pdf), The Congress of the United States O Congressional Budget Office. Available on http://www.google.co.uk/url?sa=t&rct=j&q=policy%20options%20for% 20unmanned%20aircraft%20systems&source=web&cd=2&ved=0CGIQFj AB&url=http%3A%2F%2Fwww.cbo.gov%2Fsites%2Fdefault%2Ffiles%2 Fcbofiles%2Fftpdocs%2F121xx%2Fdoc12163%2F06‐08‐ uas.pdf&ei=HjCyT5iRBefW0QWeutmzAw&usg=AFQjCNGRa‐lojeSUyQ‐ YjLuBNHxjaKKhVg&cad=rja Accessed on 17/04/12 2. Light Weight Launcher development 1, Unmanned Air Vehicle (UAV) Requirements Meeting the need of the Warfighter (pdf), Advanced Ceramics Research. Available on http://www.google.co.uk/url?sa=t&rct=j&q=unmanned%20air%20vehicl e%20(uav)%20requirements&source=web&cd=1&ved=0CF4QFjAA&url= http%3A%2F%2Fwww.acrtucson.com%2FPresentations_n_Publications %2Fpdf%2FUAV_Requirements.pdf&ei=2TCyT7WmEuqd0AWn8bCfCQ& usg=AFQjCNHZ3qjNdQEE_IQiBssCkEEAVCZh0Q Accessed on 17/04/12 3. Existing Unmanned Aircraft Systems and Future Plans, Policy Options for Unmanned Aircraft System (pdf), The Congress of the United States O Congressional Budget Office. Available on http://www.google.co.uk/url?sa=t&rct=j&q=policy%20options%20for% 20unmanned%20aircraft%20systems&source=web&cd=2&ved=0CGIQFj AB&url=http%3A%2F%2Fwww.cbo.gov%2Fsites%2Fdefault%2Ffiles%2 Fcbofiles%2Fftpdocs%2F121xx%2Fdoc12163%2F06‐08‐ uas.pdf&ei=HjCyT5iRBefW0QWeutmzAw&usg=AFQjCNGRa‐lojeSUyQ‐ YjLuBNHxjaKKhVg&cad=rja Accessed on 17/04/12 4. Anthony Mulligan, Andrew M Osbrink and Mark C.L. Patterson, Lessons and Future Platforms, Precision Recovery Capability for small UAS, Advanced Ceramics Research (pdf). Available on http://www.google.co.uk/url?sa=t&rct=j&q=precision%20recovery%20c apability%20for%20small%20uas&source=web&cd=1&ved=0CFgQFjAA &url=http%3A%2F%2Fwww.acrtucson.com%2FPresentations_n_Publica tions%2Fpdf%2F23rd_Bristol_Precision_Recovery_Conf_07_Author_chan ge.pdf&ei=0TKyT4vpHaLB0QXUzYnBCQ&usg=AFQjCNHyRQaf3PXHPK9tb Xj9TCi71BHR_w&cad=rja Accessed on 20/04/12 5. Unmanned System Roadmap 2007‐2032 (pdf). Available on http://www.google.co.uk/url?sa=t&rct=j&q=unmanned%20system%20r oadmap%202007‐ 2032%20&source=web&cd=1&ved=0CFgQFjAA&url=http%3A%2F%2F www.fas.org%2Firp%2Fprogram%2Fcollect%2Fusroadmap2007.pdf&ei =QDOyT6DjN8Wn0QX73KXeDA&usg=AFQjCNF3onEJJYUMS3JMXxuZ0zLv b4zQKA&cad=rja Accessed on 20/04/12

Group 8 6. Tractor Prop Launcher (pdf), BAE System. Available on http://www.acrtucson.com/UAV/launcher/index.htm Accessed on 17/04/12. 7. Pneumatic Catapult Launcher (pdf), Robonic Ltd, UAV Launching Systems. Available on http://www.google.co.uk/url?sa=t&rct=j&q=pneumatics%20catapult%2 0launcher%20robonic&source=web&cd=2&ved=0CHAQFjAB&url=http% 3A%2F%2Fwww.epicos.com%2FWARoot%2FNews%2FLauncher_Robon ic.pdf&ei=IjWyT‐6jJMen0QXXq42QCQ&usg=AFQjCNFevd‐ PQ5jxwERhAZ5oFkwg1LOXRQ Accessed on 25/04/12. 8. Technology Option, Pneumatics, Launcher/Booster system Tradeoff Report (pdf), Jan 1995, Naval Research Laboratory. Available on http://www.google.co.uk/url?sa=t&rct=j&q=launcher%2Fbooster%20sy stem%20naval%20research%20lab&source=web&cd=1&ved=0CFkQFjA A&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi‐ bin%2FGetTRDoc%3FAD%3DADA290066&ei=djiyT‐ XwCImy0QXY_IyQCQ&usg=AFQjCNGI‐9YO2LPReZfq5PkYEh2T9cjRgg Accessed on 26/04/12. 9. UAV Car Top launcher (pdf), UAV Factory. Available on http://www.uavfactory.com/product/22 Accessed on 22/04/12. 10. Technology Option, Hydraulic, Launcher/Booster system Tradeoff Report (pdf), Jan 1995, Naval Research Laboratory. Available on http://www.google.co.uk/url?sa=t&rct=j&q=launcher%2Fbooster%20sy stem%20naval%20research%20lab&source=web&cd=1&ved=0CFkQFjA A&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi‐ bin%2FGetTRDoc%3FAD%3DADA290066&ei=djiyT‐ XwCImy0QXY_IyQCQ&usg=AFQjCNGI‐9YO2LPReZfq5PkYEh2T9cjRgg Accessed on 26/04/12. 11. The Engineering ToolBox (website). Available on http://www.engineeringtoolbox.com/young‐modulus‐d_417.html. Accessed on 03/05/12. 12. Calvert JR, Farrar RA, An Engineering Data Booki, 3rd edition.Palgrave Macmillan, 2008 ISBN: 978‐0‐230‐22033‐1 13. A Metric-based approach to Concept Design James Scanlan; Max Woolley; Hakki Eres; http://www.southampton.ac.uk/~jps7/Lecture%20notes/Student%20co py%20value%20based%20design.pdf 14. Visual Interface, Vanguard Studio, Vanguard Software Corporation. Available on http://www.vanguardsw.com/products/vanguard‐ system/components/vanguard‐studio/ Accessed on 13/05/2012 15. Aluminium, metalprices.com. Available on http://metalprices.com/FreeSite/metals/al/al.asp Accessed on 14/05/2012 16. Plastic Prices, Worldscrap. Available on http://www.worldscrap.com/modules/price/index.php Accessed on 14/05/2012 17. Superwinch 1220210 LT2000 Utility Winch, amazon.com. Available on

Group 8 http://www.amazon.com/Superwinch‐1220210‐LT2000‐Utility‐ Winch/dp/B0015U6VLQ/ref=sr_1_fkmr0_1?ie=UTF8&qid=1337111478& sr=8‐1‐fkmr0 Accessed on 14/05/2012 18. 2 Bearing 6203ZZ 17x40x12 Shielded Ball Bearings VXB Brand, amazon.com. Available on http://www.amazon.com/Bearing‐17x40x12‐Shielded‐ Bearings‐VXB/dp/B002BBOFG6/ref=pd_sbs_indust_5/191‐6039834‐ 3380561 Accessed on 14/05/2012 19. Bungee cord black (10mm), Bungee cord. Available on http://www.bungeecord.co.uk/bungeecordblack10mm.htm Accessed on 14/05/2012 20. Mobility battery 12v‐26Ah (AGM), Puredrive Batteries Limited. Available on http://www.puredrivebatteries.co.uk/golf‐trolley‐battery‐84‐12v‐26Ah‐ 7‐AGM‐Batteries.html Accessed on 15/05/2012 21. Wage and hour division (WHD), United States Department of Labor. Available on http://www.dol.gov/whd/minwage/america.htm#NewYork Accessed on 15/05/2012 22. Young, W: Roark's Formulas for Stress and Strain, 6th edition. McGraw‐Hill, 1989 ISBN:0‐07‐072542‐X 23. [23] Ford Transit Technical Specifications: http://www.fordtransitdirect.co.uk/newsales/newvans/transit/technicalspec. aspx Accessed 16/05/2012 24. 24. BIOGRAPHICAL MEMOIRS: CL (Kelly) Johnson The National Academies Press http://www.nap.edu/readingroom.php?book=biomems&page=cjohnson.htm l Accessed 16/05/2012

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Appendices Appendix A: Design Matrices A.1 Blank Binary Weighting Matrix

Group 8 A.2 Completed Binary Weighting Matrices and Averaged Results

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Group 8 A.3 House of Quality

Group 8 A.4 CODA

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Appendix B: Production Drawings B.1 Base Connecting Bar

Group 8 B.2 Cradle

Group 8 B.3 Winch Base

Group 8 B.4 End Link

Group 8 B.5 Ground Support

Group 8 B.6 Leg Bar

Group 8 B.7 Link

Group 8 B.8 Roll Bar

Group 8 B.9 Trolley

Group 8 B.10 Wheel