Makai Ocean Engineering, Inc. and the University of Hawaii (UH) have jointly developed a novel autonomous underwater vehicle (AUV) that can effectively deploy seafloor sensing equipment by combining features of a free-swimming AUV and those of a bottom crawling vehicle. This ‘hybrid’ autonomous underwater vehicle is called the Bottom-Skimming AUV, or B-SAUV. The B-SAUV is propelled by thrusters but can touch, glide along, and interact with the seafloor. The B-SAUV is unique in that it autonomously adjusts its wet weight (by dynamically controlling its buoyancy) in order to control how it interacts with the ocean floor. The B-SAUV moves through the ocean using its thrusters and operating in three different buoyancy modes:
- Low Buoyancy: the B-SAUV presses on the seafloor with its full wet weight
- Medium Buoyancy: the B-SAUV lightly ‘skims’ along the bottom at a desired wet weight (to adjust for existing bottom conditions),
- High Buoyancy: the B-SAUV ‘flies’ temporarily above the bottom in the water column in order to overcome obstacles
The B-SAUV is controlled by a computer hardware and software system that, in addition to autonomously controlling buoyancy, enables it to navigate autonomously to a predefined location and install (and log data from) oceanographic sensors in the seafloor. These sensors are carried as a payload within the body of the B-SAUV and can be used for environmental monitoring or remote sensing.
Makai and UH have been working on the concept, designs, fabrication, and testing of the prototype B-SAUV since 2011. Most recently in November 2014, Makai and UH finished a successful at-sea test and demonstration of the complete prototype vehicle. The test validated operation of all critical subsystems and vehicle controls.
Submersible Pipeline Repair Vehicle
Makai was involved in a long-term design project with Shell Development in Houston for a large submersible pipeline repair vehicle (SPRV). Makai was chosen for its capability in designing large, buoyancy-controlled structures. The initial design for this remote-controlled vehicle was for 3000′ depths and payloads of 100,000 pounds. The final goals for the first vehicle were changed to allow for considerably heavier payloads, shallower water, and deployment in the North Sea. Makai’s responsibilities for the 700-ton, all-aluminum submersible included the ballasting, propulsion, docking, surface handling, and vehicle structure design around the tooling and electronics. Extensive model testing was conducted in Hawaiian waters for surface and subsurface handling characteristics and strain tests. A model was also taken to Marietta, Georgia, for wind tunnel testing of submerged drag characteristics.
High Sea State Recovery
Makai analyzed and studied the feasibility of recovering a 40-ton oil service maintenance capsule in Sea States 5 and 6 for Lockheed Petroleum Services, Ltd. Models were built to one-twelfth scale and a system design was successfully developed and tested.
Submersible Launch, Recovery, & Transport Vehicle
The Submersible Launch, Recovery, & Transport (LRT) Vehicle is a unique, manned submersible recovery system designed by Makai Ocean Engineering. This economical vehicle has been developed to safely and reliably launch and recover manned submersibles in rough seas and to provide a platform for their speedy transport over long, open ocean distances. The LRT is a twin-hulled, submersible platform upon which a submarine is placed and secured. It is towed on the surface by a support vessel to a selected dive site. The LRT and the submarine are both submerged under the control of the diver pilot and then accurately maintained in a stable hover at a depth of 50-60′. With the assistance of the deck crew, the submarine is released from the LRT and begins its dive and the LRT returns to the surface.
Makai’s first LRT was designed to transport and deploy the STAR II research submarine in rough Hawaiian waters. This LRT was operated for 12 years, with over 1400 successful dives, by the Hawaii Undersea Research Laboratory of Hawaii. A larger LRT was designed, fabricated and ABS certified to support the 13 ton PISCES V manned submersible for the University of Hawaii. After a series of successful tests, this LRT was used for regular operations.
From the viewpoint of the submarine operator, he sees the submerged LRT hovering in the depths much like an airplane pilot does when approaching an aircraft carrier, but with a far easier and safer landing to perform. The submarine pilot guides his vessel onto the LRT and, with the assistance of scuba divers, it is secured to the LRT and then the LRT surfaces. A launch or recovery sequence will take from 5 to 10 minutes.
The LRT is a highly reliable, safe, and inexpensive method of handling a massive, awkward and delicate vehicle in rough seas. Mating of the two vehicles occurs below the surface where the LRT and the submersible’s wave responses are nearly identical, the relative motion is extremely small and safe. The LRT configuration provides a high degree of stability both below water, on the surface, and through the interface. The ABS-certified aluminum LRT was also economical since no large support vessel with a large crane was required.
Makai consulted for a Great Lakes diving company, Deep Diving Systems, for the salvage of a 700-ton schooner that sank in 1911. A design for a combination dry dock and salvage vehicle was provided, utilizing scrap steel tank cars.
Underwater Oxygen Extraction Vehicle
Makai has worked closely with researchers from Aquanautics Corporation to evaluate the potential of developing a proprietary system for the extraction of dissolved oxygen from seawater for use in submersible vehicle power systems. This was a U.S. Navy DARPA funded project. It had as its goal, designing, constructing and demonstrating a self-sufficient, oxygen extraction submersible vehicle. Makai was responsible for the ocean engineering on the project, fabrication of the vehicle and vehicle testing at Makai’s ocean facilities
Although this aspect of work has been discussed relative to specific contracts, it deserves special emphasis relative to Makai’s overall capabilities. Makai has realized the limitations of wave tank testing, especially for high sea state systems and systems which must be tested underway at various angles to the waves. The basic problems with wave tanks are cost, the limited size of waves which can be generated and the distortion of these waves due to shallow tank depths available. To develop a representative deep ocean wave, the water depth should be ten times the wave height. We have, therefore, developed considerable experience in economically testing large, scale models both underway and stationary in deep water and can test in bi-directional and/or breaking waves. In addition, our unique location at the Makai Research Pier allows for convenient testing in actual ocean conditions. Both surface and underwater testing can be done either in our harbor or offshore.