Maritime SAR: The Bluefin-21

The Bluefin-21 is an Autonomous Underwater Vehicle (AUV) that has been deployed to assist in several maritime Search and Rescue (SAR) operations.  On May 22nd, 2014, NBC News reported that a Bluefin-21 assisted in the search for the missing Malaysian Airlines Flight 370.  The Bluefin-21 is 16.2 feet long, has a diameter of 21 inches, and a dry weight of 1,650 pounds.  The AUV was built for a wide variety of applications ranging from offshore survey, search and salvage, archaeology, oceanography, to mine countermeasures.

The Bluefin-21 is built around the idea of payload flexibility and sensor integration.  According to the company, “Bluefin has integrated more than seventy different sensors from major suppliers throughout our AUV product line, building an extensive portfolio of payload flexibility” (Bluefin, 2015).  The standard Bluefin-21 sensors are divided into the categories of imaging, navigation, and scientific.

The Bluefin-21 has many Proprioceptive (PC) and Exteroceptive (EC) sensors designed for the maritime environment.  Imaging sensors include side scan sonar (EC), synthetic aperture sonar (EC), multi-beam echo-sounders (EC), imaging sonar (EC), sub-bottom profiler (EC), and a CCD camera (EC).  Navigation sensors include a USBL system (EC), an LBL system (EC), a Doppler velocity logger (PC), altimeter (PC), pressure sensor (PC), inertial navigation sensor (PC), inertial measurement unit (PC), acoustic tracking transponder (EC), and a compass GPS (EC).

The Bluefin-21 is an extremely capable remote sensing platform.  A major drawback with the Bluefin is a lack real-time data transmitting to the surface.  The Bluefin-21’s sensing data is recorded onboard and then downloaded after the craft surfaces.  In order to improve the SAR capabilities of the  Bluefin-21, better methods of transmitting data through water are needed.  Extremely Low Frequencies (ELFs) are known to be somewhat effective in water.  ELFs range from 3 to 30 hertz.  An ELF transmitter on the Bluefin-21 may be able to relay information to a buoy equipped with a receiver transmitter to rebroadcast the signal to a ship.        

A UAS can work in conjunction with a AUV during SAR operations to improve the search.  A UAS equipped with a bathymetric lidar system (mentioned last week) and a thermal camera can scan large areas quickly, and subsequently relay points of interest to the Bluefin-21 operators.  This type of collaboration can be valuable in time sensitive operations.    

The main advantage the Bluefin-21 has over a manned submarine is cost.  It is cheaper using an AUV over a manned submarine.  The unit price of a US Navy Los Angeles class submarine is $900 million.  The unit price of a manned NR-1 research submarine is approximately $67 million. The main advantage of using the Bluefin-21 over competing AUVs is depth; the Bluefin-21 has reached depths of over 4,695 meters.