TURTLE – Systems and technologies for Deep long term presence

Hugo Ferreira3,4, Alfredo Martins4,5, José Miguel Almeida4,5, António Valente6, António Figueiredo1, Batista da Cruz1, Maurício Camilo2, Victor Lobo2, Carlos Pinho4, Augustin Olivier4, Eduardo Silva4,5 1A Silva Matos – Metalomecanica S.A. 2CINAV (Portuguese Navy Research Center) 3ESEIG – School of Industrial Studies and Management, Porto Polytechnic Institute 4INESC TEC - Institute for Systems and Computer Engineering of Porto 5ISEP - School of Engineering, Porto Polytechnic Institute 6PLY Technologies (Engineering) {hugo.a.ferreira, alfredo.martins, jose.m.almeida, cpinho, aolivier, eduardo.silva}@inesctec.pt, {antonio valente}@ply.pt, {antoniofigueiredo, batistadacruz}@asilvamatos.pt, {mauricio.camilo, sousa.lobo}@marinha.pt

Abstract – This paper describes the TURTLE project that Autonomous Underwater Vehicles (AUV). These systems aim to develop sub-systems with the capability of deep- have found increased applications with emphasis on Mine long-term presence. Our motivation is to produce new robotic Countermeasures Operations in the military applications or in ascend and descend energy efficient technologies to be bathymetric surveying or oceanographic data gathering in incorporated in robotic vehicles used by civil and military civilian oriented tasks. stakeholders for underwater operations. TURTLE contribute This project will provide added value by developing new to the sustainable presence and operations in the sea bottom. structures, processes and systems allowing higher efficiency in Long term presence on sea bottom, increased awareness and autonomous and semi-autonomous operation on the ocean operation capabilities in underwater sea and in particular on floor. It will allow for lower transport and reduced logistics for benthic deeps can only be achieved through the use of cargo deployment and retrieval (energy efficiency) between advanced technologies, leading to automation of operation, surface and ocean floor. This is achieved through the coupling reducing operational costs and increasing efficiency of human of 3 key elements: new structural lightweight materials for activity. pressure vessel and immersed mechanical structures, versatile and high efficiency methods for surface-bottom transport (taking advantage of variable buoyancy systems and I. INTRODUCTION controlled deformable structures) and advanced control and Over the past decades, the underwater operations in deep guidance algorithms. sea are an attractive topic in the robotics community. However, most of the work related with deep ocean robotic TURTLE aim to develop a robotic benthic lander with operations is conducted by a few academic institutions, and autonomous capability of re-positioning and multiple ascend the oil and gas industry. and descend cycles without the need for human intervention. A benefit is that its efficiency capabilities will allow it to Current operations at full ocean depth are carried out by break through the barrier of UUV (Unmanned Underwater dedicated systems and for the most part with the use of ROVs Vehicles) long duration missions. Take in account that in (Remotely Operated Vehicles) operated from a support ship. nowadays economy people are starting to realize that this new These systems allow teleoperation on the bottom of the sea generation of ocean robots can often do what ships do at a and are used in a variety of tasks, from work and assembly in fraction of the operation cost. the offshore oil sector to inspection or information retrieval for TURTLE is envisioned to be a system with no need for wide range of activities. chains or umbilical cables. Its wireless characteristic Longer term moored instrumentation is often deployed is a major benefit in scenarios with crowded surface and mainly for information gathering either scientific data subsea systems. High traffic marine waterways or offshore oil collection or defence related information (such as monitoring and gas industry scenarios with drilling rigs and drilling ships, human activity on the sea for instance by acoustic signal geological survey vessels, floating production off-loading and monitoring). In addition, survey and mobile data gathering is storage units (FPSOs), crane and heavy lift vessels, shuttle performed, not only by surface driven methods such as ships tankers, cable and pipeline layers, and multipurpose vessels or submerged two-fish systems, but more recently by [1]. Underwater operational environments with work-class

978-1-4799-4918-2/14/$31.00 ©2014 IEEE operating ROVs, unmanned crawlers, dredging and drilling JASON ROV from WHOI, Quest4000 from MARUM, Venom vehicles, cable laying remote operated vehicles are scenarios from SMD, Ventana from MBARI, or the Portuguese LUSO were the TURTLE lander prototype cable-free capability is an ROV from the Mission Structure for the Extension of the important asset. Fig. 1 presents a scenario – Deepwater . Horizon disaster – were mobility and ship operations were C. Autonomous Underwater Vehicle confined to different distance radius. Numerous worldwide research and development II. TECHNOLOGIES - SEAFLOOR LANDERS activities have occurred in underwater robotics, especially in The bottom are the single largest geographic the area of autonomous underwater vehicles (AUVs). This feature in our Planet that, not only need to be mapped, but vehicles are commonly used for seafloor mapping, underwater explored. The general rise in resource materials procurement object searching, and pipeline tracking/inspections. Compared will increase the exploration of deep sea deposits. This will to ROVs the AUVs have more autonomous decision boost the need for marine technologies, with crucial economic capabilities and are un-tethered vehicles, but on the other and scientific role, for deep sea inspection and exploration hand, they have low operational capabilities to physically tasks. interact with deep sea structures/platforms. Deep sea technologies, such as, Remotely Operated Vehicles as the Bluefin21 from Bluefin Robotics, which Vehicle (ROV) and Autonomous Underwater Vehicle (AUV) was used in April 2014 for the search of the Malaysian Airline systems are utilized, in the oil and gas industry, for underwater flight MH370, is a torpedo shape with 5 meters and 800 surveys, underwater structure/pipeline inspections and kilograms capable of depth ranges of 4500 meters during 25 construction support, focused in performing repetitive and hour missions. Similar specifications are demonstrated by the arduous subsea tasks more efficient and consistent. REMUS 6000 AUV which allows 22 hours autonomous operations in up to 6000 meters depths, weighting 800kg and 4 A. Manned meters long. Kongsberg also develops the Hugin AUV capable The deep sea is also visited by manned vehicles capable of high speed surveys at operating depths of 3000 meters. of reaching depths of near 11km. A well-knowned project was developed by James Cameron and the National Geographic – the Deepsea Challenger. The manned lander was used in 2012 to go to the deepest place on Earth – the Marianas Trench. One of the most important vehicles in the oceanographic community is the ALVIN deep submergence vehicle (DSV) from WHOI. A 7 meters length and 16 tons weight that transports a crew of 3 elements till 4500 meters depths for a maximum of nine hours dive. The French IFREMER institute has the NAUTILE manned submersible capable of 6000 meters depths. The Russian II, battery powered and 3 person submersible, is also capable of achieving 6000 meters depths. This deep diving capabilities allows this vehicles to reach approximately 98% of the ocean floor. B. Remotely Operated Vehicle The biggest robotic tool for deep sea operations are the ROVs. Originally conceived as subsea “eyeballs”, ROVs are Fig. 1 – SENTRY AUV from WHOI close to the Deepwater Horizon disaster rapidly evolving into highly capable robotic machines. Work- site [2] class ROVs are powerful heavy tools, slow in speed due to the high drag on the vehicle and tether cable, but are dedicated to Nowadays, several non-torpedo shape vehicles have work via video or imaging sonar on site, with full control of appeared and proven to be design efficient. Normally movement along all axes. associated with hovering maneuvers or hybrid ROV/AUV Several vehicle are capable of 6000 meters dives: the capabilities. Tiburon and now the Doc Rickettes from MBARI, Keil6000 Fig. 1 presents the Sentry AUV from WHOI which is from GEOMAR, or Victor6000 from IFREMER. Used within designed to descend to 4500 meters and to carry a range of multidisciplinary scientific/industrial projects and for the devices to take samples, readings and pictures from the deep installation and maintenance of ocean observatories/networks. sea. Equipped with high definition video cameras, fiber optics DEPTHX AUV from Stone Aerospace [3] is an ellipsoid telemetry, hydraulic thrusters, variable buoyancy system and shape vehicle developed for exploration and mapping of deep payload mounting capabilities. hydrothermal springs (subterranean cavern) to sub-glacial lake For lower depths (<4000 meters) but with high usability exploration and science missions in Antarctica. Equipped with in the scientific/industry community are ROVs, such as, several directions sonars that allows it to create 3D maps and 1) Micro tripod open-frame landers implement 3D-SLAM [4]. Open frame tripod shape equipped with high definition MARUM Centre for Marine Environment Sciences is cameras for deep sea creatures’ image capture. Other missions developing a hybrid ROV for under-ice operations, near incorporate multiparametric water quality sensor probes. bottom work in harsh topography or hydrothermal vents. It is The ROBIO – Robust BIOdiversity lander [13] is a free- envisaged a flat shape design with 5x2 meters, capable of fall autonomous baited camera lander rated to 3000 meters and hovering maneuvers till 4000 meters depth [5]. has been used in several biodiversity surveys in the vicinity of The top of the art in deep sea unmanned vehicles was the sub sea oil extraction. The landers (presented in Fig. 3) carry WHOI hybrid ROV Nereus. It operates in two different the camera as well as other equipment which measure how modes. For broad-area survey, the vehicle can operate fast the current is moving, and in which direction, and it also untethered as an autonomous underwater vehicle (AUV) measures how salty the sea is (salinity). capable of exploring and mapping the sea floor with sonars and cameras. Nereus can be converted at sea to become a remotely operated vehicle (ROV) to enable close-up imaging and sampling [6]. The ROV configuration incorporates a lightweight fiber-optic tether for high-bandwidth, real-time video and data telemetry to the surface enabling high-quality teleoperation. A manipulator, lightweight hydraulic power unit, and sampling instruments are added to provide sampling capabilities [7]. Sadly, HROV Nereus was lost during a dive to 10,000 meters in the Kermadec Trench in May, 2014 [8].

Fig. 3 – The entire ROBIO lander with mooring and ready for deployment

The ISIT (Intensified Silicon Intensifier Target) lander has been designed to research spontaneous and stimulated bioluminescence in the and benthic boundary layer to depths in excess of 4000m [14].

Fig. 2 – HROV NEREUS from WHOI Fig. 4 –ISIT deep sea lander (left). Medusa modular lander (right).

D. Deepsea Benthic Landers MYRTLE – Multi-Year Return Level Equipment is a deep water free-fall lander used mainly for measuring sea Benthic landers are instrumented platforms that are pressure/depth. It is designed to stay in the for 5 years lowered and left in the seafloor to gather in situ physical, and gradually release data capsules. The new version is the chemical and biological variables over a period of time. They MYRTLE-X capable of ten years deployments. function autonomously without any connection to the surface The Medusa research lander system is a low cost for periods of a few days (for biological studies) to several modular system rated for 2000 meters depth (See figure Fig. years (for physical studies) [9], [10]. 4). Autonomous video and instrumentation lander with high They can be deployed in a free fall mode or, deployed in payload capacity, a modular frame, and an acoustically- a high precision location to measure geomorphological actuated sacrificial drop-weight release mechanism, allowing features using special design launching device connected to recovery from the surface. It can operate in three different the surface ship. Normally they are retrieved by an acoustic modes, as a lander, mooring, or drifter [15]. command that releases ballast weights. The WHOI HADAL-lander A and B are free-falling Benthic landers come in a variety of shapes and sizes baited landers equipped with high resolution video cameras depending upon the instrumentation they carry, and are and conductivity temperature and depth (CTD) sensor. typically capable of working at any ocean depth [11], [12].

2) Macro open-frame landers The BOBO Benthic Boundary Observatory [18] is a 4-m tall deep sea lander from the Netherlands Institute of Sea Longer term deployments and with a greater number of Research. This landers measure near-bottom temperature, equipment leads to landers growth in size. salinity, the amount of particles in the water column, current DOBO – is the Deep Ocean Benthic Observatory lander speeds, current directions, and are equipped with cameras. All from the Aberdeen Ocean Lab. Designed with a titanium data collected by the landers are stored on data disks The structure, capable of 10 month deployments at water depths of BoBo lander will be deployed either as free fall lander 2500 meters. It is fitted with bait release systems and stills (released at the sea surface) or, to get a defined and more cameras in time lapse mode. It released portions of bait at pre- accurate positioning, it will be lowered on a wire and dropped programmed time intervals. The bait will attract fish and approx. 50m above the bottom by using an acoustic releaser. invertebrates that are photographed by the lander cameras. The Netherlands Institute of Sea Research also uses the The lander presented in figure Fig. 5 was deployed for ALBEX lander that it is normally deployed in the Middle gather data on within-canyon water and sediment movement Atlantic deep-water canyons. to determine their impact on deep-sea corals and other biota. Other line of work are the landers for in situ measurements at the Sediment-Water Interface. Focused on the biogeochemical cycling of organic matter in the seafloor sediments. The SedOBs and NusOBS are two landers deployed to monitor the exchange process between sediments and water in Shelf (coastal areas). AMERIGO is another benthic lander for dissolved flux measurements at sediment- water interface. The lander is able to measure fluxes of nutrients such as ammonium, nitrites, nitrates, phosphates and silica, gases such as oxygen, carbon dioxide and methane, trace elements such as heavy metals and also other dissolved Fig. 5 –DOBO deep sea lander (left). Deep sea coral study lander (right). pollutants resulting from human activity. The German company KUM Kiel develops the K/MT NOAA (National Oceanic and Atmospheric lander. With 2 meters wide and possible titanium structure Administration) uses benthic landers to perform long term allows to descend them up to a depth of 6000m and attach a monitoring and data gathering in deep-sea habitats. Fig. 7 variety of instruments, e. g. benthic chamber, sediment trap, shows the triangular aluminum frame lander used to study syringe sampler. unique slope habitats, such as deep-sea coral reefs and deep Denmark KC-Denmark Company produces several canyons. custom made deep sea landers (See figure Fig. 6).

Fig. 7 – Univ. of North Carolina at Wilmington benthic lander

The ECOGIG landers are used for microbial methane and hydrocarbon observations on the seafloor. Have open- frame cubic structures equipped with instruments and collection chambers. Fig. 6 – K/MT deep sea lander (left). KC-Denmark lander (right). The above landers are normally deployed by a support GEOMAR develops and deploys several underwater vessel with dynamic positioning by lateral or A-frame cranes. landers [16]. Systems like the BIGO lander (autonomous Landers are lowered or guided to the seafloor and might need biogeochemical ocean floor observatories) monitor the Baltic the support of a medium or work-class ROV. The ROVs flow Sea floor. The GasQuant lander uses acoustic swath sonars to down to the location of the lander on the seafloor and using quantify the volume discharge through bubbles in underwater manipulator arms can grasp tools or actuators. vents [17]. 3) Flat shape landers (network nodes) The mission objective of each lander can be very Similar design is presented by OceansWorks influenced by their mechanical shape. Landers discussed International and their seafloor networks nodes [20]. above uses open-frames with low horizontal drag to minimize Implemented as nodes for an interconnected subsea the effects of sea currents and allow water to flow through the observatory that provides scientists with gathered data from instruments and sensors payload. Mooring weights in their sensor installations covering vast areas of the seafloor [19]. bases that are left behind after the seafloor release. This systems are typically underwater observatory nodes Other systems uses a flat shape structure (trawl resistant for fiber optic and power transfer. A tool in the field of frame) that seats in the bottom, presenting a low drag oceanographic real time data telemetry with cabled ocean exposure, and uses its hydrodynamic effect to act as free observatories for high power and virtually unlimited data downward forces that anchors the systems with the increase of bandwidth. Deployed in observatories, e.g., Neptune Canada seafloor currents. Fig. 8 presents a flat shape system of one of [21], Monterey Bay MARS observatory [22], offshore communications backbone TWERC node being Warning and Early Response (TWERC), VENUS network deployed/landing. (See Fig. 10).

Fig. 10 – The VENUS network node

A singular system was developed under the Km3NeT observatory project that allowed the creation of a deep-sea neutrino telescope. The Launching Optical Modules (LOM) is a spherical open-frame structure with several internal glass spheres with optical modules (sensitive photomultiplier tubes). The LOM is deployed in the sea bottom, two fiber optical and tension cables are connected to an anchor system, which releases the LOM sphere in a rotating movement. During the Fig. 8 – Photos from Node deployment and landing in the sea floor [19] upward movement it releases the internal optical glass sphere modules attached to the fiber cables [23]. Kongsberg Maritime presented their modular subsea monitoring (MSM) design to be deployed in any kind of III. TURTLE subsea operation for continuous monitoring of the surround environment. Created to act as a tool in the increasing In the scope of the TURTLE project two work segments are environmental awareness world as a subsea alert unit for planned: events such as oil and gas leakages from subsea installations, First, design and development of materials and structures pipelines and risers (See Fig. 9). for deep submergence. A key part to support demonstration of dual use (civil and military) deep sea applications. Secondly, develop a fully operational deep sea (under the project restrictions) multi-purpose vehicle capable of acting as a sea-bottom long and medium term permanence station (for observation and instrumentation) with autonomous re- positioning capabilities and multiple ascent and dive missions. The materials and systems developed in the first point will incorporate the second line of work – multipurpose deep sea lander vehicle – allowing energy efficiency and long term presence on the ocean floor.

Fig. 9 – Kongsberg Modular Subsea Monitoring A. Requirements maximum weight of 1500 Kg and be contained The TURTLE deep sea lander prototype is being design to approximately in a box of 2m x 2m x 2m. These restrictions allow multiple ascend and descend cycles without the need for are typically similar to other oceanographic equipment to be human intervention. Either in an autonomous pre-programmed deployed such as large oceanographic buoys or medium class mode were it will be collecting data from the water column, or ROVs. collecting data from the bottom and then re-surfacing for This size and weight limitation is compatible with the satellite data transfer. It is intend to adapt the vehicle with project objectives of developing systems with reduced logistic capabilities to harvest energy in the seafloor or to surface to and deployment requirements and still retaining deep ocean collect solar energy. operation characteristics and application functionalities. Another requirement is the functionality of working as a B. Basic Vehicle Design cargo transportation system. Be capable of carrying tools or For the first prototypes, see Fig. 12, the design of the lander material, to or from the seafloor, and collaborate with other was based on the energy efficiency principle and to fit the underwater systems/vehicles. dimensions and weight specified in the Requirements to be As a lander system, TURTLE should be able to maintain deployed from any ship-of-opportunity. moored to the ocean floor for long term operations (3 The demand for lighter structures with better performance months) withstanding maximum seafloor currents of 3 knots. has emphasized the importance of efficient structural During the lander state the vehicle is capable of acoustic arrangements. The vehicle will use metal sandwich panels as monitoring the environment, either in search for they offer a number of outstanding properties allowing the unappropriated ship crossing or harbor intrusion (military designer to develop light and efficient structural configuration. scenarios), or for marine mammals monitoring (civil scenario). The vehicle should be very hydrodynamic in long distance It will be used for register underwater seismic activities and vertical movements and (possible changing its shape) with a for other payload such as multiparametric probes or high flat design in the seafloor to minimize the energy spend to definition video logger/processing. moor it to the seafloor. A major differential functionality in the TURTLE lander is its capability for re-positioning itself in the seafloor. Underwater relocation in a radius of 500 meters without resurfacing. By means of electrical thrusters it is also capable of correcting is trajectory in the surface-bottom-surface movements. The TURTLE deep sea lander prototype should permit to be towed from shore to the deployment site, or transported on- board by a ship-of-opportunity with a crane and winch. The available hydrographic survey ships of the Portuguese Navy will be used as reference for the support ship to be used in the TURTLE prototype deployment. Since the TURTLE should be deployed at any possible point in the ocean, the ships from D. Carlos Class will be used as reference, as they are appropriate for missions in full ocean depths. In particular the – NRP Almirante Gago Coutinho [24] will be used in order to define prototype physical restrictions concerning deployment from cranes.

Fig. 11 – NRP Almirante Gago Coutinho [24]

Due to the available deck space and the convenience of use Fig. 12 – TURTLE lander – mechanical conceptual designs one of the lateral cranes at the stern, the prototype must have a

A. Housings The main drive and project objective is to develop new underwater structural elements based on Innovative Open Sandwich Panel Structures for application in Deep Sea solutions. Taking advantage of the advanced knowledge already gained on the development and production of this type of structures for aeronautics and space applications, it is envisioned the development of new lightweight high pressure resisting composite and lightweight metallic panels (See Fig. 14) leading to more cost effective underwater fixed systems and robotic solutions.

Fig. 13 – PLY Opencell™ lightweight metallic panels Fig. 14 – PLY OpenCell composite and lightweight metallic panels

Initial exploratory studies on housings are being developed to compare solid type with cellular and hybrid materials based designs. Maintaining the same structural strength but reducing the overall weight in 10-20%.

Another key point is the possibility, to combine metallic materials and casted syntactic foams, providing the capability to have positive buoyant designs. Normally, buoyancy is gained by adding syntactic foam or glass spheres that increases weight and external volume. Incorporating floatation TM material in the external Opencell structure gives structural Fig. 16 – Cylinder housing - linear buckling analysis robustness and lower drag. In case where electronics are fluid immerse other objectives as increased heat dissipation is also a very relevant aspect to be considered. Solutions where different materials are utilized, aspects like different modules, thermal expansion and corrosion must be taken into account. In alternative to conventional manufacturing methods such as 3D additive manufacturing is also being considered.

Fig. 15 – Underwater housings with internal or external OpencellTM B. Power and Propulsion System Aboard the lander will be installed LiFe4Po electrical In these models, a linear buckling analysis is being batteries. It is envisaged to place 10 kWh of battery source to performed for different designs with same external diameter operate the vehicle. The vehicle will operate in a low power or and weight. The result obtained demonstrates the potential to standby mode consumption when in seafloor lander mode. increase (+28%) linear buckling load factor for different type A key point is the use of atmospheric batteries and support of geometries (buckling analysis in Fig. 16). the extra weight of battery housing for deep sea pressures, or work in the path of batteries that withstand high pressures (pressure-compensated cells). Some pressure tests are being accumulate water volume. This way the energy required to conducted at A Silva Matos company to understand the move water around the system is reduced. batteries integrity strength to different pressures. D. Sensors and communications Future developments of the TURTLE lander will provide it with capabilities to harvest energy from currents, waves or TURTLE high operating depths present challenges for surface solar panels, which are an efficient and economic communications, positioning, and navigation sensing and mean of supplying electric power. This will extend the long- estimation. Externally mounted with acoustic USBL term deployments and even lead the vehicle to energetic auto- positioning, Doppler velocity logger (DVL), pressure sensor, sufficiency. altimeter, multibeam sonar, and acoustic pinger, will allow the Designed to act as an autonomous lander with seafloor vehicle to navigate and map in the deep sea. Internal inertial locomotion or vertical adjustments to its movements, the navigation system such as KVH 1750 fog IMU and GPS vehicle was designed to incorporate 6 electrical thrusters. antenna in the surface will improve the vehicle localization Solutions such as the Seaeye MCT1 or SM4, or even custom and mapping capabilities. made ring thruster to diminish power consumption. Iridium satellite and underwater acoustic modems are the main sources of communications with the vehicle. Custom C. Variable Buoyancy System made INESC-TEC underwater communications systems are An important point to the project is the creation of energy also being tested. efficient technologies and systems. The amount of energy During the project life-line, sub-system such as hydrophone available in the vehicle has a direct effect on its capabilities acoustic listeners and seabed seismographers systems are and long term endurance. Topics such as hydrodynamic intended to be developed. efficiency and battery technologies of nowadays underwater High definition video cameras, LED lights and line lasers vehicles have increased the amount of energy available are specified to perform oceanographic tasks and on-board onboard. But, the use of a variable buoyancy system (VBS) processing that allows visual odometry. will allow to save substantial energy. By changing the vehicle’s buoyancy, vertical motion can be achieved [25]– IV. CONCEPT OF OPERATIONS [27]. The different TURTLE lander operating modes are: 1) VBS will give us the capability for: dive the vehicle from Multiple ascend/descend movements Mode which consists the surface or lift off from the seafloor; controlling depth and of allowing the vehicle to surface or dive with changes in the rate of change of ascend/descend; assisting seafloor docking buoyancy/ballast system. Perform ocean floor long term and mooring; Trimming; Emergency release and recovery. deployments and surface if commanded or to exchange Ascend and descend vertical movement will be achieved by satellite data. 2) Transportation Mode which consists of the VBS and the help in the final stages, of electrical thrusters. transporting cargo/equipment to/from the ocean floor with The use of VBS will also be a challenge in the control autonomous precise positioning. Oil and Gas operational point-of-view. Maintain a position on the water column, scenarios were the use of TURTLE and a surface small boat is increase or decrease velocities, surface or seafloor landing easier and more cost effective then DP ships and extra work maneuvers are challenging tasks for the control unit. A control class ROVs 3) Seafloor re-positioning that consists in problem were the control variable, pump rate, is proportional missions were the vehicle for own decision or the command & to a constant rate of acceleration in the vertical, the sensed control order need to be re-positioned on the seafloor. Without variable is depth, and involves non-linear forces and delays. the need to re-surface, helped by electrical thrusters for Commonly, unmanned underwater vehicles (UUVs) need to horizontal locomotion and equipped with navigation sensors, maintain a positive buoyancy at working depth, requiring pre- allowing it to navigate and scan the new estimated position to mission buoyancy and trimming adjustments. Using an choose the best place to perform the new landing (See Fig. advanced VBS would eliminate this need and save time and 17). buoyancy failure risks. Our variable ballast system (VBS) is designed to pump in and out from a to the ambient so that buoyancy can be made variable. Option of a pressurized ballast tank to reduce structural weight and pressure difference between ambient and internal tank, thus reducing pump power consumption. The system components are main pressurized ballast tank and compressed gas reservoirs and electronic, pump, valves and drive motor. When increasing buoyancy a pump unit draws water from Fig. 17 – TURTLE concept of operations ballast tank where gas pressure maintain internal pressure to a minimum pressure level. In opposition when taking water into main ballast tank, pressure is increased as gas need to V. SEA OPERATIONAL TESTS These tests aim to 1) evaluate the easiness of deploy and To prove all concepts, and test the TURTLE prototype recover the lander in ships-of-opportunity cranes, 2) to lander vehicle, several progressive field tests will be perform underwater acoustic positioning and communications conducted in late 2014 and middle 2015. This tests will be tests, 3) the lander capability of scan the seafloor and chose divided in near shore and deep canyon deployments. the optimal landing zone, 4) variable buoyancy system tests, 5) multiple sub-systems operational and fail-safe tests, 6) A. Near shore field tests multiple seafloor re-positioning without surfacing. These first tests will occur in late 2014, in the Atlantic B. Deep sea canyon deployment Ocean coastal waters off Sesimbra, Portugal. The tests will be conducted with the support of the Portuguese Navy and An important test will be conducted in a 600-1000 meters particularly the Portuguese Naval Research Centre (CINAV). sea canyon. The Setubal canyon lies to the south of the Nazare These tests aim to 1) evaluate the towing motion canyon, presents a V-shape profile and reaches 2000 meters capabilities of the developed lander, 2) to evaluate and refine depths near Cabo Espichel, Portugal. the capability of the lander to be deployed with support of a This project demonstrator missions will be conducted in small vessel or rib boat, 3) the lander capability of be middle 2015 supported by the Portuguese Navy and on-board deployed in a specific position and maintain moored to the hydrographic ships. All systems and new technologies will be seafloor, 4) variable buoyancy system tests, 5) multiple sub- putted to the test in high pressure, harsh conditions, at remote systems operational and fail-safe tests, 6) multiple ascend and and inaccessible locations. descend maneuvers. For these purposes the Sesimbra shallow Fig. 19 shows the estimated landing and monitoring zone water operational scenario was chosen to allow an easy for the TURTLE prototype lander. The vehicle will carry out support by navy divers or small ROVs. It is planned to leave dive and ascend long distance movements, test the cargo the lander deployed at 20 meters depth from 1 to 7 days in an transportation capability to the ocean floor, and will be order endurance test (monitoring and data gathering). Fig. 18 shows to re-position in another spot to evaluate its autonomous the bathymetric line chart for the first operational sea trials. behaviors/maneuvers and acoustic communication positioning.

Fig. 19 – Setubal deep sea canyon. TURTLE canyon deployment

Fig. 18 – Atlantic Ocean coastal waters off Sesimbra, Portugal. VI. CONCLUSIONS AND FUTURE WORK A second set of dives will be performed near Sesimbra at This paper presents the TURTLE project systems and 100 meters depths. In this tests the lander will be transported technologies for Deep Sea long term presence. Describes the and deployed by the hydro-oceanographic ship Fig. 11 – NRP developed of platforms with new structural panels and Almirante Gago Coutinho [24]. housings that allow energy efficiency. Initial work concentrated on the development of a autonomous benthic lander capable of long term seafloor deployments, capable of Yoerger, “Navigation and control of the Nereus hybrid underwater navigating and transporting equipment to/from the seafloor, vehicle for global ocean science to 10,903 m depth: Preliminary results,” in 2010 IEEE ICRA, 2010. and deploying it in precise locations. 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