UNSY 605, Assignment 2.5, Unmanned Systems Maritime Search and Rescue

     Teledyne Gavia ehf has produced the Gavia autonomous underwater vehicle (AUV) for a variety of roles to include maritime survey, salvage, defense, and search and rescue (SAR) missions.  This underwater platform provides useful capabilities for operators to conduct searches for stricken vessels, aircraft, and victims.  The Gavia was recently deployed in such a role in the December 2014 international effort to locate Indonesia AirAsia Flight 8501 (Rossi, 2015).

     A prioproceptive sensor suite specifically designed for the maritime environment that is fielded on the Gavia AUV is an inertial navigation system (INS) aided by Doppler velocity log (DVL) technology (Teledyne Gavia ehf, 2015).  An INS navigates by starting from a known position, orientation, and velocity.  Instruments track the position and orientation of the vehicle from the known starting point.  However, INS become more inaccurate over time and distance due to noise perturbing signals in instruments, such as gyroscopes, inducing drift (Woodman, 2007, p. 3-5).  A DVL uses bottom tracking algorithms to provide high rate, high precision data to supplement the INS and significantly reduce the errors caused by drift (Teledyne RDI, 2013).  An exteroceptive sensor specifically designed for the maritime environment that is fielded on the Gavia AUV is a side-scan sonar system.  This sonar system is specifically designed to use higher frequencies to produce high resolution images.  The imagery resolution is sufficient to identify details such as vessel shapes or human forms (NOAA, 2015).  This capability would be very useful in SAR operations.

     An improvement that would make the Gavia AUV more successful in SAR missions would be a higher capacity battery module.  Currently, two battery modules are used on the vehicle to provide an endurance of approximately eight hours (Teledyne Gavia ehf, 2015).  The ability to provide continuous operation during a SAR mission is extremely useful.  Ocean currents can move wreckages of vessels or aircraft far from the point at which they initially foundered or crashed.  An increased endurance time will increase the probability of the AUV to locate wreckage sooner before it can drift further and increase the difficulty of search operations.  The probability of locating living victims also decreases as time passes.  The ability to remain on station for longer periods would provide increased probability of locating victims in time for rescue and medical aid.  An improved battery module featuring increased endurance would greatly assist these efforts.

    An unmanned aerial system (UAS) could be deployed in conjunction with an AUV to aid in a SAR mission.  An aerial platform can search a large area in a relatively short period of time traveling at higher speeds and scanning from a higher vantage point.    A UAS such as the Boeing/Insitu ScanEagle has a service ceiling of 15,000 feet, cruising speed of 50 knots, and an endurance of 24 hours (Insitu, 2013).  By comparison, the Gavia AUV has an endurance of approximately 8 hours and a speed of approximately 5.5 knots.  The side-scan sonar on the AUV has a range between 6.5 to 131 feet (Teledyne Gavia ehf, 2015).  The ScanEagle would be able to search a wide area but cannot search beneath the sea surface.  The Gavia can detect minute details but cannot feasibly search a wide area due to the limitations of its speed and range of its sensors.  A UAS and AUV operating in conjunction could be applied to the example of the search and recovery efforts for Air France Flight 447.  The debris field of the aircraft was spotted on the ocean surface, leading search teams to eventually locate the wreckage on the sea floor (Associated Press Staff, 2009).  A UAS would search a wide area for clues such as a debris field.  Once located, an AUV would be deployed for a closer inspection.

     AUVs also possess some advantages over their manned counterparts.  A manned submersible must include accommodations for crewmembers and associated support equipment in its design.  These requirements increase the dimensions and weight of the vehicle and reduce the capacity for payload and fuel.  A manned submersible is also limited in endurance by the oxygen supply available for its crew.  An AUV can devote space, that otherwise would be used to accommodate crewmembers, to additional payload and fuel/power supply.  An AUV can also be designed in a smaller, compact overall size that would facilitate transportability to operating areas.  A smaller vehicle would also be more maneuverable in tighter spaces, such as underwater caverns or inside a shipwreck.  An AUV would also not be limited by oxygen supply for crewmembers.  The limitations on an unmanned vehicle’s endurance would be determined by fuel or power supply.  The equipment dedicated to supporting crewmembers on manned platforms can also cause interference with sensors such as sonar (Vexilar, 2015).  An AUV, lacking such equipment, would be less prone to be affected by such interference to its sensors. 

     The Teledyne Gravia ehf Gravia AUV is a suitable platform to conduct SAR and search and recovery missions.  The performance specifications and sensor suites of the platform provide extremely useful capabilities to search teams.  Manned platforms still have a role in SAR missions.  However, unmanned platforms provide a powerful resource to augment this important mission.

References:

Associated Press Staff.  (2009, June 2).  Debris Confirms Crash of Air France Flight 447.  NBC News.  Retrieved from http://www.nbcnews.com/id/31057560/ns/world_news-americas/t/debris-confirms-crash-air-france-flight/#.VjaOEG5cTkM

Insitu.  (2013).  ScanEagle System [Fact Sheet].  Retrieved from http://www.insitu.com/systems/scaneagle

National Oceanographic and Atmospheric Administration (NOAA).  (2015).  Side Scanning Sonar [Fact Sheet].  Retrieved from http://www.nauticalcharts.noaa.gov/hsd/SSS.html

Rossi, M.  (2015, January 6).  Teledyne Gavia AUV to Aid in Search for AirAsia Flight QZ8501

[Press Release].  Retrieved from https://teledynemarinesystems.com/news_and_events/press_release_view/teledyne-gavia-auv-to-aid-in-search-for-airasia-flight-qz8501

Teledyne Gavia ehf.  (2015).  Gavia AUV [Fact Sheet].  Retrieved from http://www.teledynegavia.com/product_dashboard/auvs

Teledyne RD Instruments.  (2013).  Workhorse Navigator Doppler Velocity Log [Fact Sheet].  Retrieved from http://www.rdinstruments.com/navigator.aspx

Vexilar Inc.  (2015).  Solving Sonar Interference [Fact Sheet].  Retrieved from http://www.vexilar.com/blog/2014/08/28/solving-sonar-interference

Woodman, O.  (2007).  An Introduction to Inertial Navigation (ISSN 1476-2986).  Retrieved from University of Cambridge Computer Laboratory website: https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-696.pdf