By Jim Haw
Originally published at ScientificAmerican.com
Note: Before we join the new group of students training for the 2012 Micronesia Expedition we will catch up with several of the USC scientific divers and see what they have been working on over the past year.
Ten years ago, Boeing built a robotic submarine and tested it in the Gulf of Mexico in support of offshore drilling projects. This submarine, Echo Ranger, was designed to be a flexible autonomous underwater vehicle (AUV) that could carry out missions to depths as great as 10,000 feet for days at a time entirely under on-board computer control. Equipped with powerful sonars and vast data storage, Echo Ranger was able to map the undersea environment with extraordinary resolution. But Echo Ranger was withdrawn from the Gulf during the slowdown following Hurricane Katrina. Recently, the US Navy has expressed a great deal of interest in AUVs that could function as the underwater equivalent of drone aircraft, performing tasks too dangerous or too extreme for existing manned submersibles, and Echo Ranger has come out of retirement to be evaluated for new missions.
Beginning in 2011 Boeing has been deploying Echo Ranger out of the USC facility at the Wrigley Marine Science Center at Two Harbors Catalina Island – the same facility at which we train our student science divers for the Micronesia Expedition. USC Dive Safety Officer Gerry Smith and I spent a number of weekends helping Boeing evaluate technologies and methods that might be used in the event that Echo Ranger become partially or completely disabled while in the Pacific Ocean. For example, if the AUV experienced a partial failure in the channel between Los Angeles and Catalina it would not do for the submarine to surface in front of a container ship – it would be better if Echo Ranger could phone home while circling safely below the keels of passing ships.
Gerry and I had the task of helping Boeing evaluate engineering prototypes for several add-on systems that will eventually let Echo Ranger make itself more secure in various situations. For the first phase of this work we had two large devices that we deployed in Big Fisherman’s Cove. The buoy canister assembly was constructed on a steel frame and was intended to test the reliability of a system for launching a communications buoy to the surface from a submerged AUV and recovering it even with fouling from kelp and other floating debris. To get the buoy canister assembly into place we craned it into the water off of our main dock and then suspended it using a 2000 lb. lift bag. We towed it out to near our floating dock above a bottom at 90 fsw, and carefully lowered it from the lift bag using block and tackle. Over the course of several months on the bottom we repeatedly had to do unplanned maintenance on this apparatus. When the April 2011 tsunami from the Japanese disaster reached Catalina it lifted our floating dock so high that it pulled the assembly off of the bottom and stood it up on its side. Gerry and I went down and set it right again. In spite of repeated challenges, Boeing engineers soon had the data they needed.
The other large device we worked with was a hydrodynamic simulator of the submarine, an empty shell matched to the buoyancy and drag characteristics of Echo Ranger. We used this simulator to test various anchors that the AUV could deploy to secure itself to a fixed bottom location while awaiting a signal to come to the surface. Because the current was strong in the part of the cove we deployed the simulator and the visibility was usually quite bad during that test period, diving on simulator always first involved searching the water column at 40 fsw for a massive object that would suddenly appear in front of us. We had the anchors set in 75 fsw, and changing anchors meant sending the old anchor up on a lift bag where it would hopefully remain near the surface and not fall back down while we were working.
A little later we had the opportunity to practice support and recovery methods on Echo Ranger itself, including a simulated recovery using a remotely operated vehicle (ROV) in deep water off of Catalina Island. Because the sea is sometimes quite rough in the channel, the procedure for an actual submarine recovery would call for a hold at a depth such that the sub would not start jumping with the swell (and snapping the recovery lines) while we attached one or more 2000 lb. lift bags and then floated Echo Ranger the rest of the way to the surface. This was also a good opportunity to do a little blue water diving (diving without a bottom that a diver can safely reach), something that is too advanced for most of our students, at least not without safety lines.
We are hoping that there will be time in Echo Ranger’s schedule for some environmental missions. As Echo Ranger undergoes a battery upgrade project we are looking at the possibility of circumnavigating Catalina and using its acoustic sensors for a variety of purposes including mapping of sensitive marine habitats. Working with the Boeing engineers has permitted us to do some things a bit beyond the ecosystem transects that will be the norm for our students in Micronesia.
About the Author: Dr. Jim Haw is Ray R. Irani Professor of Chemistry and Director of the Environmental Studies Program in the USC Dana and Dornsife College of Letters, Arts and Sciences. He is also a scientific, technical and recreational diver. Author photo by Ross Peterson.