Depending on which maritime body you ask, there are somewhere between 50,000 and 100,000 large ships sailing the world’s oceans, with cargo vessels, passenger ships, and warships making up the bulk of this number. Commercial vessels are required to have their hulls inspected on an annual basis, and military vessels generally follow a similar inspection regimen. There are various global and national bodies which provide certification standards, such as ABS (American Bureau of Shipping) and Lloyds of London. The goal of inspecting large vessels is to protect the owners of the ships, the crews, the passengers, the companies using the ships, and the insurance industry.
There are a variety of different certification standards, but the standard ABS inspection regimen is fairly typical for the industry. The ABS regimen is known as HIMP, which stands for Hull Inspection and Maintenance Program. HIMP has a three-tiered system of inspections, with annual inspections, three-year inspections, and five-year inspections. The three- and five-year inspection tiers encompass all the inspection areas of the lower tiers, while adding further areas of the ship to the inspection list. HIMP inspections cover the entire vessel, but the underwater portion of the survey is the trickiest for ship owners. Underwater surveys can be conducted by human divers, but increasingly this job is being handled by remote-operated vehicles (ROVs).
On a commercial vessel, the diver or ROV must provide visual data on the stern and rudder bearings, the sea suctions and sea valves, the propellers, and – most time-consuming - the hull plating. The inspection must look at any markings on the hull, all inlets and discharges, the rudder, the propeller, and all other objects that protrude from the hull. Corroded or damaged areas must be examined closely, and although thickness testing is not automatically part of the HIMP, any area found to be damaged or corroded is likely to be examined internally and have the thickness tested at the affected spot(s).
Military vessels follow a similar inspection regimen, and many military vessels will also have stencil-marked areas of the hull which need to be looked at. Inspections will check the hull and other secondary areas of the vessel for biofouling, to assess the need for having the ship’s bottom scraped. Inspections generally involve several waterline-to-waterline underwater traversals of the vessel, following the seams of welded sections. Propellers need to be inspected on both their front and rear facings.
In the early years of ROVs, their use in underwater hull inspections was relatively rare because the low video quality of early vehicles made their results of marginal utility to inspectors. Today however, with true HD displays and cameras on even consumer-level ROVs, these useful vehicles are an integral tool for large hull inspections. Since inspection divers need to be ABS-certified, many surveying companies are finding that it is highly useful to conduct a pre-inspection using an ROV only. This pre-inspection can find any problems that already exist so that they can be mitigated before the actual inspection, preventing a time-consuming, and expensive, temporary suspension of the vehicle’s certification when the inspector finds significant problems.
It’s Olympic season again and the 2016 Summer Games in Rio are in full swing. More than 11 thousand athletes from over 200 countries around the world are pouring into the Brazilian metropolis for the thirty-first modern Olympiad, which runs from August 5 through 21, 2016. The International Olympic Committee expects half a million foreign tourists to visit Rio during the Games, along with a huge number of local Brazilians. Unfortunately, the lead-up to the Rio Games has been marked by controversies surrounding Brazil’s ability to successfully host this major international event. One of the most pressing issues has been the issue of the water quality in and around Rio.
Rio de Janeiro is an enormous metropolis, with more than 12 million inhabitants, and Guanabara Bay has served as the city’s cesspool and sewage dump for many years. Before the games, a large majority of the sewage generated in Rio was delivered untreated into the bay, along with considerable quantities of ordinary junk and garbage, and the bacterial and viral contamination level in the water were astronomically high. Local officials promised that they would take steps to increase the level of treatment so that 80% of the sewage entering the bay would go through a treatment plant, but it is thought that, at best, only 65% of the sewage is treated at the current writing.
Brazil made a number of promises about cleaning up the city when it won its bid to host the Games, but numerous reports indicate that the cleanup efforts fell well short of promises. Although reports from Olympic athletes indicate that the amount of visible debris and waste have been significantly reduced, it is thought that these have been mainly cosmetic measures. Data from water quality assessments backs up this pessimistic account; an Associated Press investigation done before the Games began showed viral levels 1.7 million times higher than what would be considered problematic in the United States.
The water in Guanabara Bay is contaminated, but how about the water along Rio’s famous beaches, some of which front the Atlantic Ocean? Unfortunately, the beaches may be even worse off than the deep water of the Bay. The beaches of Rio de Janeiro are connected to a criss-cross maze of canals and stormwater drains, which are in turn deeply contaminated with human waste. Most of the residents of the city’s favelas (slums) have no indoor plumbing and the minor waterways of the city are essentially communal sewers. As a result, the beaches always have high levels of coliform bacteria, a problem which worsens exponentially whenever one of Brazil’s torrential rains floods the drains and canals.
Although the water in Rio is dirty, experts do caution against apocalyptic rhetoric concerning the actual level of danger. The World Health Organization notes that the most likely outcome from ingestion of contaminated water is short-term gastroenteritis; not something anyone wants, but not a major life-threatening condition for people in good health otherwise. Olympic athletes are taking precautionary measures for their time in Rio, stocking up on antibacterial wipes and keeping water bottles inside of plastic bags to avoid splash contamination, for example. Some athletes expecting to swim in the most contaminated areas have received Hepatitis A vaccines as a prophylactic step. The athletes and tourists, however, will be going home in a few weeks. Those at most risk from Rio’s dark waters are the people who have been there all along, and it is they who are most in need of a sustained and meaningful effort to address the water pollution in Rio de Janeiro.
Remote Operated Vehicles (ROVs) are of great utility in conducting underwater surveillance, data collection, sonar mapping, and searches for underwater objects. However, information gathering is only one of the things these versatile underwater craft can accomplish. With the addition of manipulator and grabber arms, ROVs can perform a wide array of useful tasks. ROVs have used manipulator arms since the first ROVs were deployed by the US Navy in the 1960s to recover objects on the sea bottom (including, famously, a hydrogen bomb that sank to the bottom of the western Mediterranean following a B-52 crash in 1966). Today’s manipulator arms are considerably more advanced than those early grippers.
Generally, modern ROVs use a master-slave manipulation model, where a human operator based on a surface vessel controls the ROV’s arm(s) either with a control panel or with an actual miniature manipulator matching the manipulator on the ROV. Remote control techniques originally developed in the space program allow any operator to work the arm easily, without the need for specialized ‘crane operator’-type skills. This allows the operator to be a mission specialist or a scientist skilled in what the manipulator needs to be doing, rather than a specialist who can control the arm well but needs to be told what to do with it.
Manipulator arms can be deployed to use a wide variety of tools. These tools are often simple or complex grippers, but can also be power tools like drills, saws, cutters, wrenches, or others. The earliest ROVs were limited to very simple grippers, and it was a major step forward when ROVs became capable of doing simple jobs like opening or closing a valve handle on an underwater platform.
There are three broad general categories of manipulator use for ROVs: industrial, military/law enforcement, and scientific. Industrial ROVs can use manipulators to cut and lay pipe, make and break hydraulic connections, lay and retrieving cable, lubricate underwater machinery, carry heavy tools for human divers, conduct trenching operations, and operate machinery like valves and levers. Military/law enforcement ROVs can use manipulator arms to retrieve or tag items, to place charges (for example, to neutralize underwater mines), and to cut cables. Scientific ROVs can use manipulator arms to select samples, to gather materials for analysis, to drill into the sea bottom, to sieve lighter materials, to take core samples, and to deploy and retrieve sensors.
ROVs equipped with manipulating arms have successfully assisted in exploring sunken vessels, raising ships and objects from the ocean floor, finding victims of crimes and criminal evidence, operating oil and gas platforms, and conducting pure scientific research. The use of manipulators makes these useful tools even more effective.
In a recent entry we talked about the importance of monitoring aquatic environments. Today we are going to talk about the various ways in which that monitoring can be performed. Each way has advantages and disadvantages.
Perhaps the simplest method of monitoring is manual observation, either with measuring instruments or with the naked eye. An example of this type of monitoring is a marine biologist who manually counts the number of whales surfacing off the coast in a particular spot in a particular time. The advantages of this type of monitoring are that it requires little investment in equipment, and has the highest degree of flexibility – if the biologist sees something else of interest at the survey site, he or she can make direct, first-hand observations without the need to redesign or redeploy instrumentation. Human observers may also be able to fix errors in the monitoring protocol “on the fly” in a way that a more instrument-focused approach cannot. For example, if a site survey has a particular set of GPS coordinates and the human observer arrives at those coordinates and realizes that the site location is off, the observer can fix the mistake and carry out the survey. The primary disadvantages of manual observation are that recurring observations quickly become very expensive, and there may also be reliability issues. For example, a graduate student can forget to come in to conduct a set of observations. Manual observations may also be subject to greater biases and subjectivity effects.
Another fairly simple, though powerful, technique for monitoring is the deployment of fixed sensors, whether singly or as part of a sensor network. An example of this type of monitoring is the global network of fixed data collection buoys and shore stations maintained by the National Oceanic and Atmospheric Administration’s National Data Buoy Center. This network of more than 1300 stations collects ocean temperature, current, conductivity, wave height, and wave frequency data, along with meteorological data, for use in weather forecasting, tsunami detection and alerts, and scientific and commercial research. The advantages of a fixed sensor network are in the acquisition of historical data sets which can be continuously compared to new data, the relative ease of maintenance of a network of fixed sites, and the ability to develop a comprehensive network. Indeed, the NDBC’s network has achieved global reach, making it one of the most valuable and useful fixed sensor networks in existence. The disadvantage of fixed sensors is that, being fixed, they cannot easily be redeployed to cover a new area of the aquatic region being monitored.
A more flexible approach to sensor deployment is the use of drop sensors, or temporary sensors for a particular location, which are then collected for re-use or allowed to degrade in place. An example of this type of sensor deployment would be the temporary placement of water-quality sondes along a flooding river system; the data collected from the sondes would be used for a limited time and then the sondes would be picked up and put back into storage or used on a different project. The advantage of this type of deployment is that it is extremely flexible; the sensors can be placed at the specific points where data collection is most important, and easily relocated as needs shift or if the initial deployment was less than optimal. The disadvantages of a drop sensor approach are that the sensors are generally not in a hardened or protected structure and are subject to theft, vandalism, or damage or destruction from environmental causes, and there is also potential for data loss owing to the ad hoc nature of the network infrastructure. For example, a set of inexpensive temporary buoys might be deployed to record ocean currents over a period of time, with the data to be collected at the end of the study period, only to have a major storm hit the network on the last day before collection, sinking half of the buoys and compromising the entire project.
The most sophisticated approach to monitoring the aquatic environment is to place the survey instruments on a ship, boat, or other craft and take the desired measurements from that vessel. For example, an aquaculture facility might have small craft with water quality sensors mounted in the hull to patrol the edge of the fish pens, testing the level of contaminants in the water. This approach has the advantages of most of the other approaches described here; it is flexible, it is protected from the environment, it has human observers on-site to address problems or concerns, etc. The main disadvantage of this approach is that ships and boats tend to be very expensive. The NBDC would need a much larger budget if it wanted to keep 1300 crewed ships on station to watch for tsunamis!
One way of greatly reducing the costs of this approach is to utilize ROVs as the data collection platforms. As ROVs are small, often portable by just one person, they can be deployed very flexibly in any aquatic environment, from water tanks to the deep ocean. Since they are controlled by a human operator, they maintain great flexibility and ability to adapt on the spot to problems that may arise, and are also protected against theft or vandalism by the proximity of the operator. When adverse weather or environmental conditions arise, the ROVs can be pulled out of the water, reducing the risk of data loss or loss of the vehicle itself owing to those kinds of conditions. Most importantly, ROVs can be equipped with a very wide array of top-quality scientific sensors, enabling them to monitor aquatic conditions just as well as sensor buoys or shore stations.
Every data collection mission has its own objectives and special needs, and finding the right type of monitoring solution for the mission requires judgment. ROV-based data collection is one option among many, but it is an option that is very flexible and has the potential to keep costs low without compromising the data collection process.