LARS: Not Just a Simple Handling Tool
Launch and recovery are often the riskiest parts of a subsea operation, and as iDROP COO David Galbraith points out, with a payload of new data, subsea vehicles are more valuable on recovery than they were on launch.For iDrop, the challenge is how to launch and recover large numbers of its autonomous ocean bottom nodes (OBNs). The current method for laying OBNs, which catch reflected waves during seismic surveys, involves specialist vessels and crews. Instead, iDrop’s Oceanid™ drones are designed to self-steer to the seafloor without the need for ROV help or DP-capable mother vessels. They can then resurface back into simplified collection lines for easy recovery.All launch and recovery systems (LARS) aim for efficiency, but with swarms, the challenges are amplified. “We have all these bespoke launch and recovery solutions recovering our multi-million-dollar AUVs, but those solutions just don’t scale economically when you’re talking about a variety of different vehicles, or swarms,” says Seth McCammon, a scientist at Woods Hole Oceanographic Institution. “A LARS system for a swarm needs to be flexible and repeatable, since it will have to pick up many, and likely many different AUVs"The solution, he says, is to have two types of vehicles: larger, more capable autonomous platforms that can recover smaller, less capable ones. The smaller swarm members need to be able to navigate underwater but not necessarily localize globally underwater. They could just localize to where they last surfaced or descended.The recovering autonomous surface vessel needs to be a much more capable platform, perhaps with machine vision as well as GPS and the ability to detect acoustic signals. “You’re investing more in the autonomous systems on that vehicle, but you need significantly fewer of them,” he says. This lets the inexpensive AUVs benefit from the extra capability of the surface vessel, while still keeping each AUV low-cost.McCammon is currently developing a net system for an autonomous surface vessel to enable it to recover swarm AUVs. The system is scalable because the recovery onus is on the larger, more capable platform. When the swarming agents are done with their mission, the ASV uses use computer vision and acoustic tracking technology to locate and scoop them up.Exail has developed a modular LARS that can handle both AUVs and towed underwater vessels from an unmanned surface vessel. This reduces the number of LARS that are needed to be purchased, operated and maintained. The LARS can operate in heavy seas, because at the end of the mission, it puts a cable into water and unwinds it until its tip is well below the influence of waves. The AUV detects the cable using front-looking sonar and seizes it using specially designed clips. The LARS can then rewind the cable, bringing the vehicle onboard. Smart interactions between vehicle and surface vessel determine the best heading for launch or recovery. The surface vessel adopts the plan and so does the LARS.“We have many autonomous functions integrated into our systems,” says Peter Crocker, Kraken Robotics’ KATFISH and LARS Product Owner. Kraken Robotics offers the ISO20-LARS, which fits an ISO20 footprint, and a more compact LARS suitable for uncrewed surface vessels. While the ISO20-LARS integrates human-in-the-loop autonomy features, the USV-LARS is designed to allow for fully autonomous launch and recovery.Kraken Robotics offers the ISO20-LARS, which fits an ISO20 footprint (pictured), and a more compact LARS suitable for uncrewed surface vessels. Credit: Kraken RoboticsBoth systems include an intelligent, all electric winch that is software controlled and able to be remotely operated in a safe manner. The software continuously monitors cable tension, and in the event of a cable snag on the seabed, the winch will automatically pay out, keeping the system below the safe working load of the tow cable and system. Additionally, auto-tensioning of the winch ensures the KATFISH is securely held in the LARS docking head for safe recovery. It also ensures optimum spooling of the tow cable on the winch.“Video data and other sensor data can be monitored remotely by an operator,” says Crocker. “During towing operations, the winch is programmed with a safe-depth mode: when commanded in an emergency, the winch and KATFISH autopilot will bring the KATFISH up to a safe depth below the vessel. These autonomous safety features built into our LARS allow for safe remote operation of the systems over low bandwidth data links.”DeepOcean's patented LARS has been specifically developed for the 24-meter long USV Challenger. Unlike conventional moonpool or A-frame systems used on larger vessels, it launches and recovers a ROV over the stern while the vessel remains in motion. The LARS consists of an electrical winch, a sheave wheel trolley, kicker and rear hatch. When launching, the ROV is simply pushed in. When recovering, the ROV is pulled in like a trawl. The USV is also equipped with a gyro stabilizer that reduces vessel movements during launch and recovery operations.Recently delivered from the shipyard, the USV Challenger began commissioning and testing for uncrewed operations in June with promising results. The USV was built around the LARS to optimize the integration between the vessel, its remote systems and the ROV. This intentional, coordinated design improves the reliability and safety of launch and recovery operations.DeepOcean's patented LARS has been specifically developed for the 24-meter long USV Challenger. Credit: DeepOceanThere’s value in having a modular and flexible system. AXTech’s Smart Tower Solution is designed to launch and recover a range of pre-assembled subsea modules, such as subsea stack, including xmas trees and subsea modules. The solution provides multiple options, ranging from light well intervention operation and coil tubing operation to pulling tubulars out of the well. Despite these varied operational duties, it can be installed on any offshore construction vessel equipped with appropriate cranes and a moonpool. It typically operates through the moonpool, avoiding the need for hull modifications.AXTech’s Smart Tower Solution is designed to launch and recover a range of pre-assembled subsea modules, such as subsea stack, including xmas trees and subsea modules. Credit: AXTechResearchers at KTH are aiming to take platform flexibility in a new direction, up, and they’ve gained the attention of companies looking to launch both large and small vehicles. The aerial LARS project, underway in partnership with Saab, involves using autonomous aerial drones to carry and release underwater vehicles precisely to mission locations. A winch system will also allow the aerial drones to retrieve the vehicles from the water without requiring human intervention. The system leverages machine learning algorithms for object detection and dynamic stability during deployment and retrieval.Researchers at KTH are using autonomous aerial drones to carry and release underwater vehicles precisely to mission locations. Credit: KTHThe aim is to achieve faster and more flexible vehicle deployment and recovery, to reduce risk to human operators by eliminating manual handling and to enable multi-domain autonomy with real-time AI-powered decision-making. Prototype testing is advancing towards the goal of initiating operations simply with the push of a button.