Impact-9’s pressure adaptive collars require only a single seawater pump to affect stable submersion. Internal buoyancy is provided by compressible, cellularised foam or bladders that compress under pressure of introduced water. As these are secured in position, they ensure stability of ballast for equal, buoyancy control around the perimeter of the collar, with just a single water pressure umbilical. As water is the control fluid, there is fine control over the amount of ballast introduced to the collar and the system is isolated from any de-stabilising effects of external ambient pressure as depth varies.

The pressure-adaptive submersion allows for the integration of wave-activated pumps in the mooring connections, that pump high pressure water in response to dynamic mooring loads. When this in-flow exceeds a threshold it will cause the system to submerge autonomously, reducing the mooring loads. This self-regulating response protects the structure and contained stock from excessive dynamic loading in storms, without requiring any on-site intervention by the operator.

“Sinker Rings” are now used ubiquitously in fish pen design to improve the volumetric stability of the net barrier system in response to current flows and waves. These are normally formed by rigid HDPE pipe with steel weight inside, suspended from the floating collar with winched cables. By replacing the HDPE pipe with inflatable SeaStrut elements, IMpact-9 can provide a variable weight sinker ring that can also be depressurised to its most buoyant condition and collapsed for easier handling. By integrating numerous such elements in net barrier design, it is possible to control the net pre-tension and buoyancy in response to simple application of water pressure.

The above design approach increases fish farm resilience in a number of subtle but important ways:

• passive submergence response to storms with regulation and damping of mooring attachment loads

• high pressure submergence state means that in a leakage event, teh system fails to a positively buoyant condition

• high pressure supports pipe structures against collapse under pressure at depth, without needing to thicken pipe walls

• Collapsible SeaStrut elements are more flexible in dynamic conditions, with over-loading resulting in temporary collapse but recovery of the structure once the load is removed.

When the ocean moves, fish move with it. Conventional offshore structures are designed to attenuate or resist wave-induced motions. This results in relative motions between the structure and the ocean. In aquaculture, this may have consequences for fish health in storms.  From the fish’s frame of reference, nets and structures will be accelerating through their habitat requiring them to swim against accelerating flows to avoid impacts. In open ocean aquaculture, where waves can reach heights of 35m, providing a fish-friendly containment structure is not easy using a conventional steel structure. Equally, providing a safe operating platform is not possible using conventional pens or feed barges.