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Aerotecnica Missili & Spazio, The Journal of Aerospace Science, Technology and Systems

First Flight of Scaled Electric Solar Powered UAV for

Mediterranean Sea Border Surveillance Forest and Fire Monitoring

G. Romeoa, M. Pacinoa, F. Borello a

a Politecnico di TorinoDipartimento di Ingegneria Aerospaziale

Abstract

Research is being carried out (as part of several EC funded projects) with the aim of designing Very-Long EnduranceSolar Powered Autonomous Stratospheric UAV (VESPAS-UAV) and manufacturing a solar powered prototype. This Itcould play the role of a pseudo satellite, with the advantage of allowing a more detailed land vision due to the relativecloseness to the land and at a much lower cost than a real satellite. 300km diameter area could be monitored by eachof these platforms. The full scale HELIPLAT R© UAV and SHAMPO UAV were designed using the most advanced toolsto obtain an endurance of 4-6 months and to be operable in almost all typical environmental conditions (jet stream upto 180km/h) at stratospheric altitude (17-20 km). During the day it will fly with 8 brushless electric motors in whichpower is generated by thin high-efficiency solar cells that cover the aircraft’s wing and horizontal tail. At night it will bepowered by a fuel cell system fed by gaseous hydrogen and oxygen stored in pressurized tanks. A payload of up to 150kg,with available power of up to 1500W, could be installed on board for several kinds of global monitoring of environmentaland security applications (GMES). A scaled size prototype (wing span 24 m , length 7 m) has been built in order toshow the technological feasibility of the project. The Small Electric Solar Unmanned Airplane (SESA) flying model wasbuilt to carry out several experimental flight tests with a small solar powered UAV and to demonstrate some criticaltechnologies and applications. The brushless electric motor was powered by high efficiency (21%) mono-crystalline siliconarrays and LiPo batteries. The structure was made entirely of fibreglass reinforced plastic, except for the wing box, forwhich carbon-fibre composite materials were also used. A wing with span of 7m was manufactured and 2 m2 of solarcells were bonded over the wing skin, in this way obtaining a far higher endurance of up to 8-10 hours in June and Julyin a level flight. With a total gross weight of 35 kg, the payload capabilities are of the order of 5 kg. The experimentaltests validated several critical technologies for high altitude very long endurance flight: high efficiency solar cells, anelectric brushless motor, controllers, video and thermo camera image transmission, telemetry system, autopilot.

1. Introduction

UAV technology has advanced sufficiently for theaeronautical industry to be ready to expand into anew ’added value’ Commercial industry - the youngand growing Civilian Unmanned Air Vehicle (CUAV)industry. The total UAV market is growing at a rapidpace and it is imperative that the European commu-nity should make a serious effort to attain a significantsegment of this market. The wide range of applicationsfor civilian UAVs, will open up a variety of marketsfor potential sales and economic growth. Competi-tiveness in Aerospace is strategically important andthe primary competition for the European communitycomes from the United States. As the civilian market

c©Copyright 2009 by G. Romeo. Published by AIDAA withpermission.

All information regarding HeliPlat R©, Shampo & SESA SolarPowered UAV is the Propriety of Prof. G. Romeo, the Politec-nico di Torino and cannot be reproduced without his authoriza-tion. All rights reserved.

for UAVs increases, a great potential will be createdto maintain and strengthen the competitiveness of theEuropean aerospace industry in a new technology area,which will guarantee and create highly qualified jobsfor the future. In a recent business market study car-ried out by Frost and Sullivan, the global market forUAVs in civil and commercial applications was esti-mated to be close to $2bn by 2014 [?] . The largestmarket shares are expected to pertain to Coastguardand Maritime Surveillance operations, Border Securityand Forest Fire Management. The Scientific Commu-nity could benefit in many ways from employing UAVsin the civilian sphere. The utilisation of UAVs forborder and costal patrol, homeland security, maritimesurveillance, ”Eye-in-the-sky” surveillance, will allowbetter law-enforcement for the protection of citizensand the integrity of the borders. The utilisation ofUAVs for forest fire mapping, real-time monitoring ofseismic-risk areas, air turbulence, vol-canoe eruptionsand other natural phenomena will ensure that the pub-lic is aware of imminent disasters and can therefore

8

First Flight of Scaled Electric Solar Powered UAV for Mediterranean Sea Border Surveillance Forest and Fire Monitoring 9

prepare for their occurrence. Under the coordinationof the first author, a research is being carried out (aspart of several EC funded projects) ( [?] , [?] , [?] , [?] )with the aim of designing Very-Long Endurance SolarPowered Autonomous Stratospheric UAV (VESPAS-UAV) and manufacturing a solar powered prototype.This could play the role of pseudo-satellite, with theadvantage of allowing more detailed land vision, dueto the relative closeness to the land, with continuousearth observation and at a much lower cost than realsatellites. Satellite sensors can offer good accuracy- spatial area trade-off, especially when modern highresolution satellites are taken into account - but suchhigh accuracy data are quite expensive today. Severalsatellite systems used for earth observation are uselessfor continuous real-time border surveillance because oftheir limited spatial resolution. All the MediterraneanSea border, from Turkey to Spain and the Canary Is-lands could be electronically controlled by 9-10 plat-forms from a high altitude (17-20 km), with very-longendurance (several months) stratospheric UAV (pay-load up to 150 kg, power available for payload up to1500 W). It is essential to control who and what entersEuropean countries in order to prevent the admissionof terrorists and instruments of terror across borders,along coastlines and harbours. Continuous (24h by24h) border monitoring would be guaranteed and insuch a way would drastically reduce service costs andtedious work (Fig. 1). A 300km diameter area wouldbe monitored by each of these plat-forms. No spe-cial projects are at moment known to be underwayon border surveillance of the Mediterranean Sea. Thisservice is at present made by several military shipsor piloted airplanes with several people on board andit is therefore a costly business. Furthermore, onlyspot controls are made, because of the large exten-sion of the border. In Spain, the coast from Moroccois controlled (limited to 50-60 km) by a radar system(SIVE) at a cost of 145 MEuro. Similar, very expen-sive systems are being installed all along the Italiancoast (more than 2000 km). At which cost? The Ital-ian Coast Guards have high costs for their ATR 42MPequipped for border surveillance. With minimum crewof 7 the cost of the aircraft is around Euro 7000-8000for a hour of flight. The VESPAS platform could alsobe conveniently used, with proper fire sensing tools,for forest fire monitoring (Fig. 1). This service is fre-quently requested in all Southern Europe (Spain, Italy,the South of France, Greece, etc.) for airborne imag-ing of uncultivated land fires and other natural andhuman-induced disasters. Several payloads are avail-able and most of them are used from satellites; theexisting and planned operational space-borne sensors,because of the very high altitude at which they oper-ate (500-600 km), show serious limitations if accurateparameters have to be obtained. As a result, theyonly allow detection of very large fires, and not in a

continuous matter. Higher performances are availablefrom electro-optic or infrared sensor airborne installa-tion and flight altitudes of 17-20 km and it is possibleto detect shorter flame lengths than one meter. Just4-5 VESPAS stratospheric platform could cover Italyfrom North to South.

Figure 1. Sea and terrestrial border monitoring andfire monitoring.

Electronic surveillance all over the South of Europecould clearly be obtained with a good HeliPlat Net-work. Early forest fire mapping could be realised withinfrared remote fire sensing tools. The maximum inthe spectral radiance distribution of vegetation firesoccurs in the mid wave infrared (MWIR) region at3-5 µm. Therefore, the mid wave infrared spectralrange is commonly recognized as the optimal spectralrange for fire detection. In order to reduce the highflight costs of piloted aircraft, it is necessary to haveunmanned vehicles with very long endurance (severalweeks or months) to obtain an efficient service. UAVsare less expensive than other manned aircraft usedfor border surveillance. With an UAV flying at an

Aerotecnica Vol.88, No.1/2, January-June 2009

10 G. Romeo, M. Pacino, F. Borello

altitude of 15-18 km and with proper sensors, it ispossible to detect illegal boats or people along bor-ders and with Total Life Cycle Costs of around 900-1000 Euro/hour of flight [?] . The main advantage ofVESPAS is that this system has less climbing and de-scending events, which is important when consideringinterference with aviation traffic. Other HALE-UAVconfigurations offer a very limited endurance (24-36hours), which would drastically increase any poten-tial collision risk with civil aviation traffic. Doublethe number of UAVs would be necessary to continu-ously guarantee the surveillance service, thus the To-tal Life Cycle Cost System would be increased to agreat extent. Other Medium Altitude Long Endurance(MALE) - UAVs offer a further disadvantage; a muchhigher number of UAVs are necessary to continuouslycover the entire Mediterranean Sea, since the coveredarea decreases with the square value of the flying alti-tude (Fig 2); the Total Life Cycle Cost system wouldincrease remarkably with a MALE configuration. Veryhigh endurance, in fact, calls for high mission reliabil-ity requirements of the air vehicle, its systems and itspayload.

Figure 2. HALE monitoring application advantages

An integrated, multi-sensor, interoperable system,based on the use of remote and local means of surveil-lance (e.g. UAV, satellite, etc..) and multiple sensorconcepts (e.g. I/R and E/O sensors, SAR, hyper spec-tral, sensor fusion, processing, etc.) for border surveil-lance from a stratospheric altitude is being studied todetect, even in adverse climatic weather, boats withillegal migrants or terrorists reaching the south Eu-ropean coasts from North Africa or Middle Easterncountries or illegal fishing boats. The information ob-tained will be transmitted to the control station and

from here to a network where Maritime Traffic Centredata are exchanged through Internet. It also providesa powerful tool to characterise the marine environmentfor habitat monitoring. All those features lead to:

• Reduced costs per Flight Hour through an ex-tensive increase in endurance flight hours.

• Potentially increased acquisition costs, but re-duced maintenance and spare part cost.

• Reduced costs - larger area coverage per aircraft,requiring fewer aircraft per area.

• Improved operational safety - due to the flightsbeing above aviation traffic and above adverseweather conditions, resulting in limited interfer-ence with aviation traffic.

Not even one real very-long endurance stratosphericplatform is actually available in Europe. A few are al-ready available in the USA. Several types of high al-titude solar powered platforms (HASP) were designedin the past. At the end of 1994, NASA started theERAST (Environmental Research Aircraft and SensorTechnology) program [?] ; one of the four drones isthe solar platform Pathfinder that exceeded 24 km ofaltitude in a 15 hour flight. In the summer of 2001,the Helios solar-powered platform sets a new worldrecord of 29350 metres, aiming at a flight of severaldays in year 2003. A solar-powered, unmanned air-craft is being developed by Boeing and QinetiQ forthe US Government (US Defence Advanced ResearchProjects Agency) for use in military and civil tasks [?].Unmanned long endurance (years) air vehicles couldbe used to replace conventional satellites. POLITO(under the scientific guidance of Prof. G. Romeo)has been working on one of the three existing worldprojects on solar powered aerodynamic stratosphericplatforms for several years. After preliminary fund-ing by the Italian Space Agency, a very great pushto the project was obtained by the financial supportreceived from the European Commission in the fieldof stratospheric platforms (HeliNet, Capecon, En-fica-FC, Tango) ( [?], [?] , [?], [?]). The possibility ofmedium-long endurance (4-6 months) for a strato-spheric platform can be obtained through the appli-cation of an integrated Hydrogen-based energy sys-tem. This is a closed-loop system: during daytime,the power generated by thin high efficiency solar cellsthat cover the aircraft’s wing and horizontal tail supplypower to the electric motors for flying and to an elec-trolyser which splits water into its two components,hydrogen and oxygen. The gases are stored in pressur-ized tanks and then, during night-time, used as inletgases for the fuel cell stack in order to produce electricDC power and water which is supplied to the elec-trolyser. Since fuel cells represent clean and efficient



power generation, they are a suitable alternative tocon-ventional energy sources. POLITO will capitalizeon the results and findings that are being obtained inthe on-going EU funded project ENFICA-FC (ENvi-ronmentally Friendly Inter City Aircraft powered byFuel Cells) co-ordinated by Prof. G. Romeo. A two-seater electric-motor-driven airplane powered by fuelcells is being developed by converting a high efficiencyexisting aircraft and it will be validate by a flight-testwhich is planned for October 2009, ( [?], [?]). The He-liplat/Shampo UAVs are being analysed as part of theEC funded project TANGO [?] (under the scientificguidance of Prof. G. Romeo for Polito) in coopera-tion with several satellite systems for a few civil appli-cations of GMES (Global Monitoring Environmentaland Security). Demonstrations will integrate satellitetelecommunication solutions with on-going GMES de-velopments in the framework of fishery management.Inclusion of UAVs in the global relay infrastructureenables quasi real time and continuous access to dedi-cated zones for monitoring or surveillance. A flight testis being prepared with a scaled solar powered UAV fora final integration with on-going GMES developmentsin the framework of fishery man-agement.

2. HELIPLAT R© VESPAS

The full scale HELIPLAT R© (HELIos PLATform)UAV (Fig. 3) was designed using the most advancedtools to obtain an endurance of several months (4-6)and to operate in almost all typical environment con-ditions (jet stream up to 180km/h) at stratosphericaltitude (17-20 km). ( [?]- [?]). The vehicle shouldclimb to 17-20 km by mainly taking advantage of directsun radiation and thereafter maintaining a level flight;the electrical energy that is not required for propul-sion and payload operation is pumped back into thefuel cell energy storage system and, during the night,the platform would maintain altitude through use ofthe stored (solar) energy; the geostationary positionwould be maintained by a level turning flight. A com-puter programme was developed to design a platformthat is capable of remaining aloft for a very long pe-riod of time and to gain a thorough understanding ofthe feasibility of a near term aerodynamic high alti-tude concept, electric motor, solar and fuel cell tech-nology, with special attention to stratospheric plat-forms. The solar radiation changes over one year, thealtitude, wind profiles with altitude, masses and effi-ciencies of the solar cells and fuel cells, aerodynamicperformances, structural mass, etc were taken into ac-count. Extensive use of high modulus Carbon-fibrewas made in designing the structure to minimize theairframe weight. The platform project was completedup to a quasi-final design stage. A numerical aero-dynamic analysis was performed to obtain the highestefficiencies of the whole wing and airplane. Several ex-

perimental tests were carried out in a Low-Speed-Low-Turbulence Wind-tunnel and a very good correlationwas obtained between the analytical and experimentalresults. A first HELIPLAT R© configuration (Fig. 3)was worked out, as a result of the preliminary designstudy. The platform is a monoplane with 8 brushlessmotors, a twin-boom tail type, horizontal stabilizerand two rudders. The design procedure followed inthe analysis was based on the energy balance equi-librium between the available solar power and the re-quired power for flying; the endurance parameter wasin particular fulfilled to minimise the power requiredfor a horizontal flight. The main characteristics for aflight at 38?N latitude and a design altitude of 17 kmare:

• Total weight: 8500N; Wing Area:176m2;Span:73m; Required Power:7500W; Aspect ra-tio=33; Cruise Speed = 71 km/h.

A payload of up to 130kg, with available power ofup to 1300W, will be installed on board for severalkinds of global monitoring of environmental and secu-rity applications (GMES). A numerical aerodynamicanalysis was performed to obtain the highest efficien-cies of the wing and airplane including the propellers(Fig. 3), by using the VSAERO software, at theReynolds numbers flight. Advanced design tools (suchas CATIA) (Fig. 3) and FEM structural analysis(MSC/ PATRAN/ NASTRAN) were used to designthe advanced composite wing (about 75m long), pay-load housing, booms and tail structures, and to ob-tain the highest structural efficiencies. Extensive useof high modulus graphite/epoxy material was madeto obtain a very light-high stiffened structure. A 1:3scaled size prototype (wing span 24m, horizontal tailspan 10m, length 7m) was built in advanced compos-ite material (high modulus CFRP) in order to showthe technological feasibility (Fig. 4). EADS - CASASpace manufactured the single CFRP elements: tubu-lar wing spars and ribs, horizontal and vertical tubu-lar tail spars and ribs, booms and the metal fittings.The POLITECNICO-DIASP, and ARCHEMIDE Ad-vanced Composite, assembled the different parts of theaircraft (wing, horizontal and vertical tails, booms)and the whole aircraft.

Several shear/bending/torsion static tests (Fig. 4)were performed in our laboratory on the completemanufactured scaled-size prototype and a very goodcorrelation was found between the in-house developednumerical analysis and the FEM analysis. Mechanicalequipment was designed and manufactured to performthe test; a steel supporting structure to sustain thescaled prototype and the tree-beam systems and thehydraulic jack to apply the load. Two trolleys wereused to support the tree-beam system in such a waythat the system adapts to the prototype’s deflectionbehaviour. A dummy fuselage was designed to apply



Figure 3. HeliPlat R© Configuration, Aerodynamic Re-sults and 3D details.

the expected loads to the centre of the model.Strain gauges and transducers were mounted along

the main spar of the wing in order to estimate de-formations and wing deflection. The strain resultsalong the wing, for flight conditions corresponding toa cruising flight of the n-V diagram (maximum limitload n = 3), as well as the wing deflection are re-ported in figure 5; a maximum wing tip deflectionof 500mm (left) and a maximum wing strain of 650microns were recorded. A very good correlation wasobtained between the analytical (in-house developed

Figure 4. 1:3 Scaled-size HeliPlat R© UAV.

theory) [?], numerical (Nastran) and the experimentalresults. The maximum limit load (n = 3) was reachedwithout any residual detrimental effect. The prototypewas than subjected to the ultimate load (n=4.5) to ob-tain the structural safety margin; again in this case,no detrimental effects were recorded. A static test upto failure load was carried out up to more than twicethe limit load (N = 7.5) obtaining a very good corre-lation between the analytical and experimental failureresults. A lighter structure shall be designed for thefinal project, based on this experimental results.

The results obtained in the CAPECON project [?],confirm the feasibility of a solar powered stratosphericUAV (SHAMPO satisfying the requirements of a longendurance stationary flight). A detailed aerodynamicand structural design, the flight mechanics and theelectric systems was completed by the Politecnico diTorino up to a quasi-final design. A greater aerody-namic and structural efficiency was obtained allowings higher payload mass (150 kg) and power (1.5 kW).(Fig. 6)

3. Small Electric Solar Unmanned Airplane

The flying model of the Electric-Plane was built, aspart of the EC funded project CAPECON, to carryout several experimental flight tests with a small UAVin order to demonstrate some critical technologies andapplications. The starting model (1:2.8 scale replica



Figure 5. 1:3 Scaled-size HeliPlat R© UAV andShear/Bending and Torsion Tests and Results.

of the Super Dimona (wing span 5.8m, weight 20kg,efficiency 24, minimum cruise speed of 15m/s) wasmodified by replacing its combustion propulsion sys-tem with an electric which included a single brushlessmotor and a NiMh battery system. The structure was

Figure 6. CAPECON SHAMPO Configuration, Aero-dynamic Analysis and 3D details.

realized using fibreglass reinforced plastic and carbon-fibre composite materials for the wing spar. The pay-load capabilities are of the order of 5-6 kg. As partof the EC funded project TANGO, the NiMh batter-ies were substituted by rechargeable LiPo batteries,which are mainly utilized during the take-off phase.A new 7m wing span was manufactured and 2 squaremeters of thin high efficiency (21%) mono-crystallinesilicon arrays were bonded over the wing skin (Fig.7); during the level flight the necessary power is ob-tained from the solar cell system covering the wing,and in this way a far higher endurance of up to 10hours can be obtained during June and July. All thestructures were designed according to EASA-VLA towithstand a limit load of 3.8. The power producedby the SESA solar cell during the day hours and fordifferent months is reported in Fig. 8. The main char-acteristics of the Small Electric Solar Unmanned Air-plane (SESA), are: Wing span: 7m; Wing area: 2.2m2; Total gross weight: 35kg; Max Solar Power: 370-



395 W (45◦-36◦N, June); Max power brushless Motor:3000W; Horizontal Flight Power: 350 W; MinimumSpeed: 36 km/h.

Figure 7. Small Electric Solar Unmanned AirplaneSESA.

Figure 8. Daily SESA Power for several months.

SESA made its first flight powered by solar energyin October 2007, near Turin (45◦ latitude North) at analtitude of about 300m [?]. The plane is the first Euro-pean Solar powered light UAV to fly in Europe. In the90’s, DLR (German Aerospace Centre) manufacturedand flew the ”Solitair” UAV scaled solar model but

this model is no longer active. In September 2007,the ”Zephir”, UAV solar model by Qinetiq, was flownin New Mexico. The experimental tests carried outup to now have validated a few critical technologiesfor high altitude very long endurance flight: high effi-ciency solar cells, electric brushless motor, controllers,video and thermo camera images transmission, teleme-try system, etc. These results shall be very useful toour group for the future projects.

3.1. Power electronic system

The flight management electronic power system isreported in Fig. 9.

Figure 9. SESA Power electronic system.

The power produced by the solar cells is directlysupplied to the brushless electric motor for level flight.During take-off and climbing, or for some particularmanoeuvres requiring more power, the power is alsosupplied by the LiPo batteries. The solar panel is com-posed of a parallel circuit series of 130 solar cells eachwith efficiency of 21.5% (@1000 W/m2 and 25◦C). Themaximum solar panel voltage is 43.5V. The develop-ment of the MPPT electronic device (Maximum PointPower Tracking) was of particular importance for thesuccess of the flight mission in order to optimize themaximum power that could be obtained by the so-lar cells and to improve endurance (Fig. 10). Theinverter will supply power (also more than 3kW) tothe brushless electric motor. The cooling of the in-verter, to avoid shut-off of the system as a maximumallowable temperature is reached, is also an importantfeature. Any solar cell power exceeding the requiredflight power will be used to recharge the battery.

3.2. Payload system

In order to show the opportunism of introducingsuch platforms in surveillance or monitoring systems,the model has been equipped with a wireless colour



CCD camera (40x, resolution 720x576 pixel) and withan infra-red thermo-camera (160x120 pixel); the videocamera zoom can be remotely controlled by an RS-485. Both cameras can transmit directly (at 1.2GHz),in a range of about 1-1.5 km in open air and throughan appropriate capturing peripheral device, to a PC(Fig. 11).

Figure 10. SESA solar cell curve and MPPT.

The PC could be used to analyze images in real-time, for example, to automatically detect small forestfires.

3.3. Remote control and telemetry system

At present the UAV is remotely controlled by a ra-dio modem. Up to 12 servo-actuators can be controlledfor the UAV flight. The elements actually controlledare: rudder and tail gear, 2 elevators, 2 ailerons, mo-tor rpm. A telemetry system (Fig. 12) has also beeninstalled on board to transmit in real time all the mostcritical data for the safety of the flight to the groundcontrol station. The following data are recorded andsent on wireless to the Ground Control Station in or-der to continuously have the real flight conditions ofthe aircraft:

1. True Air Speed

2. Voltage and Current of the brushless motor

3. Voltage, Current and consumption of the mainmotor battery

4. Temperature Service of the motor and inverter.

3.4. Autopilot system and mission architecture

An autopilot has been acquired and is being in-stalled on board for an autonomous flight of up to50km through the use of a highly integrated data ac-quisition, processing and control system; this includesall the necessary components for aircraft control. TheAutopilot system (designed and built by MavionicsGmbH,D) consists of three main parts: 1) The TrIMUSensor Block contains a complete 3-axis Inertia Mea-surement Unit (IMU) and two pressure sensors forbarometric altitude and airspeed determination. Itgener-ates up to 12 independent servo control signals.2) The Navigation Core hosts a sophisticated navi-gation filter for GPS/IMU data fusion which enablesprecise and long-term stable determination of the po-sition, velocity and the Eulerian angles and to obtaina reliable attitude determination. 3) a Satellite Nav-igation Receiver. 16 channel GPS receiver with highsensitivity and integrated ceramic patch antenna. Theconnection between the Core and Satellite NavigationReceiver is only through power and digital lines thussignificantly reducing interference. The on-board au-topilot system communicates with Ground Control viaa dedicated, direct bidirectional data link, using a ra-dio modem which operates in the European 868 MHzband. The A/P periodically sends data (GPS time,position, Eulerian angles, flight speed, etc.) to the GCat a rate of 4 Hz, and health monitoring data (batteryvoltage, electric motor current but with a lower datarate. Direct control through the radio modem doesnot lead to any latency problems; however, when weswitch to the Iridium L-Band Transceiver, the amountof data per Status Message (80bytes per data packet)from the aircraft does not seem to be a problem butthe update frequency and latency could be critical.No real problem is foreseen when using the L-BandTransceiver (weight 650g, latency less than 1 sec).However, a latency of 5 to 20 seconds could be pos-sible for a Short Burst Data communication (weight170g). Since the autopilot operat-es even without con-nection to the GC, latency is not a direct safety issuefor the automatic flight itself; once sent to the au-topilot, the A/P will follow the splines even withoutassistance from the GC. Therefore, latency is not a se-rious issue for the safety of the automatic flight itself,but latency is important for any kind of manual inter-vention and hence also becomes a safety issue. Fur-thermore, frequent losses of connection means a loss



of telemetry data and information concerning batteryconsumption and loss of the Endurance control. More-over, a delay in transmitting the picture of a ship, forexample, taken by the onboard camera could causesome problems in detecting the illegal boat. The smallsize of the demo scaled UAV precludes the use of highbandwidth geo satellite systems. The only systemscapable of being installed are those which have smallantennas, and thus Low Earth Orbit (LEO) systems(Iridium/Globalstar). Satellite based CommunicationSystem is being installed onboard for Iridium c© or asimi-lar network (Fig. 14). A complete separation be-tween the autopilot system and the payload systemwas adopted to obtain a Safe Flight configuration.

A direct radio connection will be used during thecritical flight phases (take-off and landing) and for sys-tem integration and testing, and an Iridium satellite-based system for longer flights off-shore. The signalfrom the 2.4GHz on-board R/C receiver is connectedto the autopilot and a special switching mechanism in-side the autopilot will allow the autopilot to be over-ridden by the remote control at any time, as long asthe remote control transmitter is within range of theaircraft. The range of this system will be 1 to 2 km,which is suitable for the visibility range of the man-ual pilot. In this way, any possible malfunction of theautopilot or telemetry system is overcome and flightsafety is increased to great extent. The same teleme-try transceiver (radio modem) system is needed forthe ground segment. In addition, a directional an-tenna can be used thus greatly increasing range andreliability of the data connection. The ground controlstation is basically composed of a PC and ground con-trol software which is the user interface to the SESAUAV system for mission planning and runtime control.All the mission planning work is done intuitionally onan underlying map. This allows a very flexible andsafe flight path design. A check with respect to theaircraft performance is done automatically to ensure arealistic and safe flight of the UAV

4. UAV Flight Demonstration for Fishery

The SESA flight demo has the following character-istics: the UAV will take off from the Italian shores.(Fig. 14).

1. The UAV will be manually controlled for takeoff.

2. Once in the air, it will be switched to auto pilotmode until it reaches its destination.

3. The ship positions are sent to the local authori-ties which will programme the UAV to reach theship coordinates

4. The target boat will be beyond line of sight andreach of RF waves, ie 20nm

5. The flying altitude will be between 150m and300m high.

6. The flight will be entirely above water and as faras possible from the Italian coastline but withinthe Italian EEZ

7. The images will be transmitted continuously tothe operation room (most likely a PC and an-tenna in a vehicle) at the take-off site. The targetcoordinates for the auto pilot might be updatedduring the flight if the ship has moved.

8. When it arrives at the ship location, the UAVwill take some high resolution pictures.

9. Once the mission has been accomplished, theUAV will be reprogrammed to automatically flyback to the take-off site.

10. When the plane reaches remote control and iswithin the line of sight of the operator, the UAVis switched back to manual mode to be safelylanded. When the UAV is at a distance of lessthan 5km from the GCS, a double redundancy oftransmission is expected for safety reasons (bothdirect radio link and satellite transmission arepossible for UAV control ).

11. The total duration of the flight should be around3h, depending on the distance to shore. Twohours to take off, to get into position and to takepicture and one hour to get back and land havebeen estimated.

Talks with the Italian CAA authorities concerningflying the UAV are at present underway to obtain thePermit to Fly. Since the SESA weight is just 30kgand since it shall be used for research and scientificpurposes, an EASA certificate is not necessary. Nev-ertheless, the following items shall be pursed:

• See and Avoid system on board;

• Flight over a non populated area (although theMaximum kinetic energy of 95 KJ shall not bereached);

• Direct visual manual control is necessary to ob-tain a safe flight and to avoid double-triple re-dundancy. The SESA shall be followed duringthe demo flight by a boat with the pilot on boardfor any UAV emergency remote control. If nec-essary the R/C can override the A/P control atany moment.

• No catastrophic failure condition shall resultfrom the failure of a single component; the al-lowable Quantitative Probabilities (per 1 flighthour) is less than 106.



5. New fuselage sructure

A new fuselage structure has been designed for abetter positioning of the masses inside the fuselage andfor a better centre of gravity excursion. The structurewas designed to withstand the limit load of 3.8. Thestructure has been built by the ”Archemide AdvancedComposite” company using fibreglass rein-forced plas-tic for the fuse skin and carbon-fibre composite mate-rials for a few frames, especially in the connection withthe wing spar. A mould was realized for the proper lay-out of the fuse. The boom that connect the fuse andtails has been manufactured in carbon-fibre. The newlanding gear has also been manufactured by CFRP.The new fuselage has been assembled and reported inFig. 15.

6. Conclusions

The following conclusion can be made as a result ofthe many years of research in the field of solar poweredUAV:

• HAVE-UAV can be used at least for low latitudesites in Europe and for 4-6 months continuousflight.

• Early Forest Fire detection, Border Patrol andFishery monitoring would be possible at muchcheaper costs and at a higher resolution than thecurrent systems offer, and it would be obtainedcontinuously.

• The very light CFRP structural elements are fea-sible. Good correspondence has been verifiedbetween the experimental, analytical and FEManalysis.

• The brushless electric motors and fuel cell sys-tems are feasible.

• The preliminary flight tests of a few critical itemswere successively carried out, verifying the cor-rect functioning of the new critical technologiesinvolved in the flight: solar power production,electric system, telemetry system, flight control.

7. Acknowledggements

The authors acknowledge the important contribu-tion of European Commission by the funding pro-grammes [?], [?], [?] and [?]. The authors acknowl-edge the important contribution given by M. France-setti and G. Correa. And of A. Motto (ArchemideAdvanced Composite).

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Figure 11. Video and Thermo camera wireless systemand acquisition examples.

Figure 12. Telemetry wireless system and data logger.

Figure 13. Telemetry wireless data display.

Figure 14. Possible Flight area and mission architec-ture.



Figure 15. New SESA Fuselage


first flight of scaled electric solar powered uav for … · 2010-02-24 · ried out by frost and...

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